cti journal, vol. 37, no. 2 · 1934 - 2016 arthur frederick brunn, jr., 81, of beaumont, died...

CTI Journal, Vol. 37, No. 2 1

The CTI Journal(ISSN: 0273-3250)

published semi-annuallyCopyright 2015 by The Cooling Tech-nology Institute, PO Box #681807 Houston, Texas 77268. Periodicals postage paid at Houston, Texas.

mission statementIt is CTI’s objective to: 1) Maintain and expand a broad base member-ship of individuals and organizations interested in Evaporative Heat Transfer Systems (EHTS), 2) Identify and ad-dress emerging and evolving issues concerning EHTS, 3) Encourage and support educational programs in vari-ous formats to enhance the capabili-ties and competence of the industry to realize the maximum benefit of EHTS, 4) Encourge and support cooperative research to improve EHTS Technol-ogy and efficiency for the long-term benefit of the environment, 5) Assure acceptable minimum quality levels and performance of EHTS and their compo-nents by establishing standard speci-fications, guidelines, and certification programs, 6) Establish standard test-ing and performance analysis systems and prcedures for EHTS, 7) Communi-cate with and influence governmental entities regarding the environmentally responsible technologies, benefits, and issues associated with EHTS, and 8) Encourage and support forums and methods for exchanging technical information on EHTS.

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publication disclaimerCTI has compiled this publication with care, but CTI has not Investigated, and CTI expressly disclaims any duty to investigate, any product, service process, procedure, design, or the like that may be described herein. The appearance of any technical data, editorial material, or advertisement in this publication does not constitute en-dorsement, warranty, or guarantee by CTI of any product, service process, procedure, design, or the like. CTI does not warranty that the information in this publication is free of errors, and CTI does not necessarily agree with any statement or opinion in this pub-lication. The entire risk of the use of any information in this publication is assumed by the user. Copyright 2016 by the CTI Journal. All rights reserved.

ContentsFeature Articles8 Hope Creek Circulating 144-inch Water Pipeline Carbon Fiber

Upgrade Anna Pridmore, Ph.D. & Jim Melchionna

18 Proposed Methodology For CTI ATC-128 Sound Certificaiton of Factory Assembled Towers

John Dalton & Larry Burdick

30 Safety In Cooling Tower Maintenance Magose Abraham Eju

36 Advancements in Cleaning and Passivation of Cooling Water Systems Raymond M. Post, P.E., Prasad Kalakodimi, Ph.D., Je"rey O’Brien & Richard H. Tribble

48 Mechanical Behavior of Polymer Fills Nina Woicke, Ph.D., & Daniel Dierenfeld

58 ASHRAE Legionella Standard 188: Evidence-Based Interpretation and Application Janet E. Stout, Ph.D.

60 New York Legionella Regulations: Are They Missing The Boat? Sarah Ferrari

Special Sections74 CTI Certified Towers80 CTI Licensed Testing Agencies82 CTI ToolKit

Departments2 Multi Agency Press Release2 Meeting Calendar4 View From the Tower6 Editor’s Corner

...see page 17

...see page 26

...see page 34

...see page 54

...see page 44

2 CTI Journal, Vol. 37, No. 2

CTI JournalThe Official Publication of The Cooling Technology Institute

Vol. 37 No. 2 Summer 2016

Journal Committee

Paul Lindahl, Editor-in-ChiefVirginia Manser, Managing Director/Advertising ManagerDonna Jones, Administrative AssistantAndrew Manser, Administrative AssistantAngie Montes, Administrative AssistantGraphics by Sarita Graphics

Board of DirectorsBill Howard, PresidentAnthony DePalma, Vice PresidentBrandon Rees, SecretaryFrank Michell, TreasurerJon Cohen, DirectorJames W. (Jim) Cuchens, DirectorNarendra Gosain, DirectorBrian Hanel, DirectorJean-Pierre Libert, DirectorHelene Troncin, Directorr

Address all communications to:Virginia A. Manser, CTI AdministratorCooling Technology InstitutePO Box #681807Houston, Texas 77268281.583.4087281.537.1721 (Fax)

Internet Address:http://www.cti.org

E-mail:[email protected]

Future MeetINg DateS Committee annual Workshop Conference

July 10-16, 2016 February 5-9, 2017 Pointe Hilton Tapatio Cliffs Sheraton New Orleans Phoenix, AZ New Orleans, LA

July 16-19, 2017 February 4-8, 2018 Hilton Orlando – Lake Buena Vista Hilton Houston North Lake Buena Vista, FL Houston, TX

July 15-18, 2018 February 10-14, 2019 La Cantera Sheraton New Orleans San Antonio, TX New Orleans, LA

For Immediate releaseContact: Chairman, CtI

Multi-agency testing Committee

Houston, texas2-September-2016

Cooling technology Institute, PO Box 681807, Houston, texas 77268 – the Cooling technology Institute announces its annual invitation for interested ther-mal testing agencies to apply for poten-tial Licensing as CtI thermal testing agencies. CtI provides an independent third party thermal testing program to service the industry. Interested agencies are required to declare their interest by March 1, 2017, at the CtI address listed.


View From The Tower Sixty six years of education. Sixty six years of growth. Sixty six years of commitment. Sixty six years of setting the industry standards. Sixty six years of fun. All this due to, sixty six years of CTI. Without the participation by all the attendees over the many years, CTI would never be what it is today. But let’s face it, without ACTIVE participa-tion, CTI would be even less than it is today. I would like to thank the many ACTIVE volunteers of CTI including all our board members over the years, all the presidents over the years and all the committee chairs and task group chairs and certainly even all the task group participants over the years that have helped create and update all our codes, standards and guidelines. By taking an ACTIVE role, both you and your company are providing a valuable service to CTI, but equally important is the impact we are having on the world. CTI has numer-ous international members which we embrace and welcome to our CTI family. Over the past several years, this number has continued to grow and as can be seen by the attendance at our meetings, these members are committing their time and efforts in helping to make CTI the world class technical organization that it is. The CTI staff continues to deliver the excellence that we all have come to ap-preciate and a special thanks goes out to Vicki and her entire staff.A technical organization is only as good as the documents and in-formation they contain as well as the people within the organization.

These are what creates CTI’s solid foundation. So while at the summer workshop meeting in beautiful Phoenix AZ, please join in, and take an ACTIVE role in ensuring that CTI remains the fore-font leading technical organization when it comes to all types of cooling technologies. It will be a time for a ton of fun in the hot hot sun! It will be a time to golf (Sunday only though, time to roll up those sleeves for the balance of the meeting! ), a time to see old friends, meet new friends and have a drink or two in the hospitality suite after a long days work.It will be a time when owner operators can network with other owner operators on trends and cooling technology specific to their plants and applications. It will be a time when direct competitors can join

hands (certainly not literally!) and be friends in the quest for a better organization mostly it will be a time to:“Ask not what CTI can do for you, rather ask what you can do for CTI.” CtI, “Join in, get involved, learn, educate others, par-ticipate and thrive!” Sincerely and respectfully,Bill W. Howard, P.E.CtI President

Bill Howard


CTI loses two of their best in 2016arthur “art” Brunn Jr.

1934 - 2016 Arthur Frederick Brunn, Jr., 81, of Beaumont, died Monday, March 21, 2016, at Harbor Hospice, Beaumont. He was born June 27, 1934, in Richmond Heights, Missouri, to Arthur Frederick Brunn, Sr. and Aileen Dorothy Rummel Brunn. They lived in Webster Groves, Missouri until 1939, when they moved to Kansas City, Missouri. The Brunn family moved to Memphis, Tennessee in 1950. Art graduated from Treadwell High School, where he was a member and president of the Key Club and a member of the National Honor Society. Art went to the University of Tennessee in Knoxville where he met Clarice Marie Tallent. They were married December 18, 1955. Art graduated with a Bachelor of Science degree in chemical engineering in August, 1956. Art and Marie moved to Milwaukee, Wisconsin where Art worked for Allis-Chalmers Manufacturing Company. Their first son, David Arthur, was born December 15, 1957. In February, 1958, Art, Marie and David moved to Houston, Texas, where Art did

sales and service work for Allis-Chalmers in the field of water treatment. Their second son, Michael Charles was born April 13, 1960 in Houston. In 1967 the family moved to Beaumont, Texas when Art started working for DuPont as a consultant in the field of industrial water treatment. Art was active with N.A.C.E., an international technical organization covering all phases of corrosion. He became chairman of the Technical Practices Committee of N.A.C.E., a member of their Board of Directors, and received the Brannon Award for service to the organization. He was also active in the Cooling Tower Institute, where he was on the Board of Directors, treasurer, and president. Art was named an Honorary Life Member of CTI and remained active after retirement from DuPont. Art was an active member of Redeemer Lutheran Church. He held the office of treasurer, chairman of the Voter’s Assembly, Chairman of the Children’s Center Board, and was active in many other phases of the church. Survivors include his wife, Clarice Marie Tallent Brunn of Beaumont; sons, David Brunn and his wife, Arlene; Michael Brunn and his wife, Stacey, both of Houston; sister, Julie Mochnak of Livonia, Michigan; five grandchildren; and four great-grandchildren.

Bruce Byron BrandBruce Byron Brand, 88, passed away peacefully at home on Sunday, May 15, 2016, in Fort Worth. Bruce was born Sept. 27, 1927, in Kansas City, Missouri to Ella and Carl Brand. He graduated from high school at the age of 16, attended Virginia Military Institute for one year, spent time in the U.S. Army teaching cadets at West Point, then went on to the University of Missouri and graduated with a Bachelor of Science in Chemical I, Engineering. He was a lifetime member of Sigma Alpha Epsilon Fraternity. He married Ellie, his neighbor and sweetheart, in 1953. The couple began their life in Kan-sas City, Kansas and Prairie Village, Kansas. Over the next 11 years, the couple welcomed their four children into their home. His children remember him as a kind, gentle, smart but stubborn father who encouraged and aided them to pursue their goals. Bruce was an accomplished cooling tower engineer.

He spent his early career with Havens Cooling Towers in Kansas City, Missouri. In 1973, he and Ellie picked up their four children and moved to Fort Worth were he started his new job at Ceramic Cooling Tower and remained there until he retired. Retirement did not slow him down, though; he became a consultant with Tower Engineering in Fort Worth and continued to “work” until just a few months before his passing. Outside of his work, he, Ellie and his children were avid sailors and members of the Fort Worth Boat club for many, many years. During this time, he amassed a room full of sailing trophies in-cluding some from the Lightning and Catalina 22 Nationals. When his children (crew) grew up and moved away, Bruce took up golf in his 50s and was an active member of the Ridglea Men’s Golf Association where he played up to three rounds per week until he was age 87 and continued to play, when he could, until just a few months before his passing. He was an active member of Ridglea Country Club since 1975, and he and Ellie could be seen there almost every night enjoying dinner and friends. Bruce was preceded in death by his parents, Ella and Carl Brand of Kansas City, Missouri; and his daughter, Mary Elizabeth Tracy of Syracuse, Kansas. Survivors: Loving wife of 62 years, Eleanor Arnold Brand; children, Melanie Brand Tracy and her husband, Timothy Allen Tracy of Syracuse, Kansas, Thomas Marshall Brand of Forth Worth, Jeffrey Douglas Brand and his wife, Lindy Denise Brand of Austin, Texas; grandchildren, Liz and husband, Josh Porter of Ambridge, Penn-sylvania, James Tracy of Wichita, Kansas, Whitney Tracy of Syracuse, Kansas, Jeffrey Brand Jr., Haley Rojas, Harper Brand and Matt Brand of Austin, Texas; and two great-grandchildren, Gabe Hrustic and Laney Porter of Ambridge, Pennsylvania.


Editor’s CornerDear Journal Reader,A new year for CTI started after the CTI An-nual Meeting in February, 2016. Bill Howard of CTD,Inc., has started his two year term as President of CTI. Several outside influences have had an im-pact on CTI, and some new activities are moving, so the next few years should be interesting.

Outside Influences:DOe Fan rule: My last Editor’s Corner made CTI Members aware that a Department of Energy rulemaking is in progress with regard to fans, which could include any of the products of interest to CTI that move air with a fan or blower. CTI has asked for exemption of heat rejection equipment from the rule, and have been successful in gaining the exemption in the term sheet agreed upon by the working group. The DOE is writing the final rule, which is expected in 2016, so we will need to continue to watch this closely. CTI members who produce fans for any purpose should be aware that they could be affected by this rulemaking, which will set minimum fan efficiencies by equipment types. For more information, contact Larry Burdick, Frank Morrison, or me.Legionnaires Disease: Outbreaks in New York City and Flint, MI, have brought media attention to the issue, and in the case of NYC/NYS have focused on cooling towers. Since then, the CDC has become vocal about the need for a whole building approach to Legionnaires Disease risk, and has published a nicely done Toolkit to supplement ASHRAE STD-188 (2015) Legionella: Risk Management for Build-ing Water Systems. CTI’s GDL-159 is expected to be a useful tool with this standard when completed, hopefully, this year. The CDC toolkit and the ASHRAE standard are available on their websites.

China Cooling tower Institute: This organization has been growing in China, and has reached out to CTI to explore ways the two organizations can work together. Several meetings have occurred between the organizations, and we continue to work toward future cooperation.

emerging activities:CtI research update: A research grant was award-ed to CleanAir to complete Pitot tip investigations to find a replacement for the (no longer commercially available) Simplex tip, which has been the CTI water flow measurement standard. CleanAir is currently proceeding with this, the first research project de-veloped under the relatively new CTI Research and Development Committee.Projects are proposed via

the standing technical committees, and proceed through a process administered by the R&D committee.Funding is raised and admin-istered via the CTI Finance Committee. Other projects are under consideration, and new ones may be proposed within the standing technical committees at any time.Licensed Sound testing: Licensed sound testing is in its first full year of operation in 2016. We look forward to growth in this test-ing service by CTI.There is much happening with our very active CTI volunteer tech-nical organization; we again encourage you to get involved in the CTI technical committees.Respectfully,

Paul Lindahl, CTI Journal Editor

Paul Lindahl Editor-In-Chief


Hope Creek Circulating 144-inch Water Pipeline Carbon Fiber Upgrade

Jim Melchionna, Corporate Program Manager - engi-neering Services, Piping, PSeg Nuclear –Salem & Hope Creek generating Stationsanna Pridmore, Ph.D., Vice President-Pipeline Solu-tions, Structural technologies

abstractHope Creek Nuclear Generating Station has a comprehensive asset management program to address their cooling tower in addition to their cir-culating water pipelines. Results from condition assessment of their circulating water pipelines in recent years indicated the need for repair of seven (7) distressed segments. The plant elected to repair the segments of 144-inch pre-stressed concrete cylinder pipe (PCCP) of the circulating water pipelines during an outage taking place in October 2013. Carbon fiber-reinforced polymer (CFRP), a trenchless structural repair system, was selected to strengthen the damaged PCCP. CFRP is a repair material used to provide targeted structural upgrades within distressed or damaged pipeline sections. This paper will discuss all aspects of design and implementation of the repair.

Background On Hope Creek generating Sta-tionIn 1974, construction began on the Hope Creek Nuclear Generating Station. In operation since 1986, Hope Creek Nuclear Generat-ing Station is owned and operated by PSEG Nuclear LLC. It is a single unit boiling water reactor with a total generating capacity of 1,178 megawatts net. As one of four licensed nuclear power reactors in New Jersey, whose combined output supplies over one half the electrical power to the state, Hope Creek generates enough electricity to power approximately one million homes each day. Hope Creek shares a 700 acre man-made island with its sister plant, Salem Nuclear Generating Station. Several years ago external distress was observed on the 144-inch PCCP circulating water system. Due the observed distress and due to its location directly adjacent to the natural draft cooling tower, Hope Creek management implemented a condition assessment pro-gram for the large diameter pipelines. It was through this program that seven (7) segments were identified for repair in 2013, and a proactive upgrade project was launched, budgeted and executed.

Background On Circulating Water System and Condition assessment Program The 144-inch diameter sections of the circulating water system for Hope Creek are comprised of embedded-cylinder type (ECP-type) PCCP, which is composed of an inner concrete core, a steel cylinder, an outer core, high strength wires under tension that are wound over the outer core, and a protective mortar coating (Figure 1). PCCP is generally a segmental pipe install in sections ranging

from 5 to 20 lineal feet. A common failure mode of PCCP is breakage of the prestressing wires within individual PCCP sections. Once enough prestressing wires break on an individual segment of PCCP, the concrete core in the region near the broken wires is no longer in compression and can crack, exposing the steel cylinder to ground water, causing corrosion. De-pending on the nature of the wire break, number of broken wires and other factors, the process of pipe failure can take from days or weeks to years to complete the process. Because of the segmental construction of PCCP and the predictability of failure following a large number of wire breaks, technology was invented

to inspect it with an objective of identifying broken wires. Elec-tromagnetic inspection technologies assist owners by allowing them to locate, with precision and accuracy, individual sections in need of replacement or repair. An electromagnetic inspection was performed and led to identifying the areas of broken wires – and ultimately the distressed segments – which Hope Creek selected for upgrade during the fall 2013 refueling outage.

Options analysis Once the segments were identified, Hope Creek then had to pri-oritize and discuss options for how to best proactively address the pipeline system. To immediately mitigate further distress to the above-ground portions of the circulating water pipelines, an external concrete encasement was installed. Beyond this stopgap measure the pipes either needed to be replaced or undergo a full structural repair in place. Due to their size, location and outage duration, replacement of the pipe segments was ruled out as an option. Hope Creek opted for a trenchless, fully structural repair utilizing a CFRP liner to address the distressed sections. The benefits of this option included completion of the repairs with no excavation required, the ability to perform the repair within the outage window and nearly no hydraulic loss because of the low-profile finish of CFRP liners. Unlike most lining systems, CFRP liners, which are hand laid into place, can be engineered and installed on the specific pipe segments requiring structural upgrade.

Design Of the Cfrp SystemGiven that the CFRP repair method needed to provide a fully structural repair, the design process was an important phase of the project. PSEG worked directly with the CFRP designer, Simpson Gumpertz & Heger, to make sure all design requirements were met. The CFRP lining system was designed as a standalone structural system where the CFRP system resists all internal and external structural demands without reliance on the host pipe.

Anna Pridmore


The CFRP design process involves collection of the design infor-mation, including as-built drawings, lay schedules, pipe specifica-tions, and pipe inspection reports. Typical parameters accounted for in the CFRP system design include: working pressure, transient (surge) pressure, vacuum pressure, temperature differential, soil cover, height of the water table soil material properties, and any vehicular traffic running on the ground above the pipe. CFRP systems are typically designed using a Load and Resistance Factor Design (LFRD) approach, where factors are applied to loads combinations and material properties to account for uncertainties within the design assumptions. As part of this design approach, design limit states are analyzed separately and the CFRP lining design is governed by the limit state that has the lowest demand to capacity ratio for the particular design scenario. From this process it is determined how many layers of unidirectional CFRP will be applied both longitudinally and circumferentially within the designated pipe segment. Typically longitudinal layers provide resistance to thrust, thermal changes, and Poisson’s ratio, while the circumferential layers provide strength in the hoop direction for internal pressure and external loads.

PreplanningThe 144-inch pipeline upgrade was a high profile project at Hope Creek during the fall 2013 outage, with an aggressive schedule and challenging working conditions. In order to ensure successful implementation, an extensive preplanning process was put in place and soft mobilization to the site was scheduled well ahead of the outage. To drive the preplanning process, the contractor and Hope Creek initiated planning conference calls twice a week for the 6 months leading up to the outage. These planning sessions included a wide variety of topics includ-ing coordination of roles and responsibilities and creation of extensive contingency plans for all aspects of the project. The contingency plans helped to insure all team members were aware of the processes for dealing with potential unforeseen develop-ments or conditions.

Cfrp Installation ProcessThe CFRP liner installation process consists of several typical steps which are broken down into five (5) task stages below. The task stages are as follows:

1. Mobilization to surface preparation2. Material preparation (saturation)3. Application of the CFRP system and top coat4. CFRP repair system termination details 5. Final curing of the system.

The Hope Creek project consisted of some unique challenges which are discussed in a separate section of the paper. Following is a description of the task stages for Hope Creek:

task Stage 1: Mobilization to surface preparation. Following mobilization of all personnel, materials and equipment to the Hope Creek site, an extensive amount of safety protocols were reviewed and put into place prior to entry into the pipe. All confined space entry was performed in compliance with the Con-tractor, Hope Creek and OSHA regulations. Given the schedule constraints at the Hope Creek project, environmental controls

were an important element of successful project completion. In all CFRP pipeline projects, the environment within the interior of the pipe repair area needs to have the temperature and humidity controlled to meet specifications of the CFRP manufacturer. For Hope Creek, and all projects requiring an expedited schedule, the pipe interior is heated to aid the curing process. Surface preparation was performed using sponge blasting as shown in Figure 2. Sponge blasting is a unique abrasive blasting media consisting of abrasive embedded within a polymer. The sponge component helps to minimize airborne particulate and is recyclable, which reduces the quantity of overall blasting media used on the project. It is much more environmentally friendly than typical sand blasting operations. PCCP has is an inner concrete substrate and surface preparation is a critical component to the successful long term performance of the CFRP liner. Proper bond to the sound concrete substrate is achieved by preparing the surface to ICRI CSP3 finish, removing laitance from the surface of the concrete, and exposing the aggre-gate. This allows for a mechanical bond to the pipe surface. Joint detailing for the CFRP system requires carefully chipping down to the steel cylinder at the end joints and preparing the exposed steel to SSPC-SP10 near white metal finish. Following surface preparation, bond tests were completed to insure proper adhesion of the CFRP system. These tests are discussed in the Quality Control section of the paper.

task Stage 2: Material preparation (saturation). CFRP systems are comprised of fabrics, glass and carbon, along with a 2-part 100% solids epoxy system. The carbon and glass fiber are dry rolls of fabric which are saturated in the field. The first step in material preparation is mixing of the 2-part epoxy, Part A and Part B. The Part A and Part B arrive at the jobsite in premeasured 5-gallon buckets and are poured together per the manufacturer specifications and mixed thoroughly to activate the epoxy. The epoxy system is used for multiple purposes throughout the installation process including saturation of the material and prim-ing of the pipe substrate. A thickened version of the epoxy system is also created using fumed silica. This thickened epoxy is used to fill imperfections in the pipe surface and as a coating between layers of CFRP. Prior to installation, the fabric is wet out in a mechanical saturation machine used which has two (2) baths of epoxy and a calibrated rolling system. The fabric is fed through the saturation machine, and through the roller system the proper amount of epoxy is com-pressed into the fabric.See figure 3 for example of mechanical saturation machine. The materials preparation process takes place in a tent to eliminate the chance for contamination and to reduce airborne particulate during the use of fumed silica. To insure the long term durability of the CFRP system, the materials preparation process has quality control procedures which are discussed later in the paper.

task Stage 3: application of the CFrP system and top coat. As the material and surface preparation were completed at the Hope Creek project site, installing the CFRP system began within the pipe. The first step within the pipe interior, following surface


preparation, was application of the primer coat of epoxy. Following the primer coat, a layer of thickened epoxy is placed on the concrete substrate, which is meant to infill imperfections and create a layer of epoxy for proper bonding of the first layer of CFRP. The saturated carbon fiber was then applied to the inside surface of the host pipe in what is referred to as a wet lay-up process. The wet-out fabric was pressed to the inside surface of the host pipe to achieve intimate contact. Any entrapped air between layers was released or rolled out without wrinkling of carbon fibers. When the CFRP was not properly aligned, the affected layer of the CFRP system was removed and replaced prior to curing. If the CFRP layer cannot be removed without affecting the integrity of the surrounding carbon fiber, an additional layer was overlaid onto the off-axis fibers to restore the laminate structure to its intended axial-strength requirements.For Hope Creek, unidirectional carbon fiber fabric was manually installed in both longitudinal (see figure 4) and circumferential layers (see figure 5) to meet design requirements as presented in the project drawings.Following installation of the prescribed number of layers on the Hope Creek repair segments, a final top coat of epoxy was installed. The top coat installed over CFRP repairs adds to the long term durability of the CFRP system, by providing protection from wear. In cases where water constituents require chemical resistance, the top coat can be engineered to meet project requirements.

task Stage 4: CFrP repair system termination details. One of the most important individual components of the design and implementation process for CFRP pipeline repairs, including the Hope Creek project, is the water tightness of the system. Water infiltration behind the CFRP repair system is a mode of failure, and this places a special importance on the points of termination, most often at the joint regions on each end of the repair. The best practice for design of these “end details”, as they are referred to, includes removal of the concrete at the joints down to the steel cylinder. A glass fiber is then installed directly onto the steel cyl-inder and tied into the CFRP repair system. Glass fiber is used as a dielectric barrier between the steel and the CFRP. After the glass fiber is installed and tied in, the joint is filled with an epoxy mortar to create a natural, sloped transition (see figure 6). The end detail is finished with layers of CFRP, per the design, and this process as completed at Hope Creek is shown in figure 7.

Step 5: Final CureAfter top coat was installed at Hope Creek, the final cure of CFRP system took place under monitored conditions. See figure 8. In general, CFRP systems are to have a minimum 80% cure before the pipe is returned to service. Durability of CFRP is affected by the degree of cure at the time the pipe is returned to full service. As discussed previously, the schedule at Hope Creek was expe-dited so the air temperature inside the pipe was elevated to over 100 degrees F to help accelerate cure. Testing has shown that the CFRP system cures faster at higher temperatures.

unique Project ChallengesFrom the onset of the project at Hope Creek there were several unique project challenges which were evaluated and addressed. These issues are discussed below:

1. removal of cooling tower muck Before access to the repair site could be established, the cooling water tower basin needed to be cleared of the muck seen in Figure 8. This situation was challenging in that the quantity of muck was an unknown at the outset of the project. The CFRP contractor was required to set up a system to remove the muck as rapidly as possible to gain access to the pipe (s) to be repaired.

2. two-tiered scaffolding system with multiple vertical slopes On typical CFRP projects, following the surface preparation and prior to CFRP installation, portable scaffolding is erected, as needed, spanning the pipe section to be lined. This is to give the installation crew the ability to apply the CFRP liner to all areas of the pipe section without the need to walk on the pipe. Best industry practice to ensure a successful installation is that the application takes place continuously in a manner that avoids contact with the CFRP after installation and until cured. The pipe sections being repaired required scaffolding for the 144-inch diameter pipe seg-ments to be built on a vertical slope and span over an area which had a vertical bend within the scaffold span. This required a specialized access system to be engineered and built in-place, as shown in figure 10.

3. Single point of entry for repairs On typical CFRP pipeline repair projects, two (2) points of entry are established within the repair area for safety and ventilation needs. As shown in figure 11, at Hope Creek the project had to be completed through a single entry point, with a butterfly valve as an obstruction. This presented several challenges for project execution; these challenges were addressed in the pre-planning process and steps to overcome were put in place and successfully implemented.

4. removal of existing epoxy system during surface preparation At the pipeline segments to be repaired at Hope Creek there was a build-up of epoxy on the pipe substrate, from previous repairs performed by others, which had to be removed during surface preparation. This is shown in figure 12. There were several com-ponents to this unknown condition including the amount of pipe which had adhered epoxy, the thickness of the epoxy (up to ¼”) and the condition the pipe substrate would be in following removal of the epoxy. As with other unknowns, contingency plans were put in place to address a variety of scenarios which might be present.

5. Special details and substrate pitting Once the substrate was sufficiently prepared at Hope Creek, and epoxy removed, extensive pitting, concrete patches, and other de-tails such as penetrations by the temperature probe shown in figure 13 were evident. The surfaces with pitting needed to be repaired and for areas of penetration, such as the temperature probe, special details such as shown in figure 14, were put in place.

Qa/Qc ProgramThe pipeline repair project at Hope Creek included a compre-hensive Quality Assurance / Quality Control (QA/QC) program that involved multiple owner representatives, a fulltime quality assurance manager and a third party quality control inspector in a rigorous system of tracking. Up to nine (9) data points were


captured during each phase of the project. From environmental conditions where the materials were stored through to curing of the installed system, each phase and step was documented and signed off throughout construction. QA/QC documentation recorded each stage of repair implemen-tation, beginning with receipt of materials. Material lot numbers were verified and recorded for all products shipped to the site.

Qa/QC - surface preparation. For surface preparation, all prepared concrete substrate achieved a minimum surface profile of ICRI CSP-3 (figure 15). All prepared steel surfaces where verified to have a near white metal blast of SSPC-SP10, with a minimum roughness of 2 mils. The representa-tive steel preparation is shown in figure 16. Once surface prepara-tion is completed, the substrate was verified to be all cleaned and dry prior to CFRP installation process begins.

Qa/QC – mixing and saturation. For mixing and saturation, lot numbers of fabrics and epoxies are recorded as a starting point. A sample of the fabric is cut and weighed prior to saturation in the mechanical saturation machine. (Weight test shown in figure 17) Following this the sample is satu-rated and weighed again. This weight test verifies ratio of fabric to epoxy is within tolerance (1:1 for carbon fiber fabric, 0.8:1 for glass fiber fabric ±10%). In addition, the gap between saturator rollers is measured and calibrated using weigh test.

Qa/QC – CFrP liner installation. During the installation process at Hope Creek there were several check points for the pipe interior throughout the installation and curing process. The environmental conditions monitored and re-corded periodically included air temperature, surface temperature, and humidity. In addition the physical installation is observed and misalignment of over 5 degrees is addressed. One additional instal-lation observation is development length of the installed fiber. For Hope Creek, the design called for a minimum development length of 12 inches in the fiber direction.

Qa/QC – terminations and Special Detailing. Along with other data points collected throughout the pipe (envi-ronmental), the termination points, joint details, have the epoxy mortar verified to insure a 2:1 slope.

QA/QC – cure and final walk-through. During the final cure process at Hope Creek the environmental conditions were monitored closely including air temperature, surface temperature and humidity. In addition, Shore D hardness values were recorded to assist in monitoring the progression of cure of the CFRP system. A final check on cure time is verification of testing in place to verify the degree of cure as determined by time and temperature. Following cure of the CFRP system at Hope Creek a final QA/QC walk-through took place, as seen in figure 18.

ConclusionThe use of CFRP at Hope Creek Nuclear Station provided a trench-less, fully structural repair of the distressed 144-inch diameter pipeline segments. Through the use of well-tested materials, a conservative design, experienced installers and a rigorous QA/QC program, the project was safely and successfully implemented.

The extensive pre-planning process contributed significantly to the project’s success and as well. The reliability of the cooling water system at Hope Creek was upgraded to meet long term requirements.

Figures

Figure 1. Components of an ECP-type Prestressed Concrete Cylinder Pipe Section.

Figure 2. Pipe segment during surface preparation.

Figure 3. Mechanical saturation machine.


Figure 4. Installation of longitudinal layers of CFRP at Hope Creek.

Figure 5. Installation of circumferential layers of CFRP at Hope Creek.

Figure 6. Joint region following surface preparation and installation of epoxymortar.

Figure 7. Joint region showing installation of CFRP layers.

Figure 8. Final curing preocss being monitored

Figure 9. Muck in the cooling tower basin that served as primary access into the pipeline. Muck removed prior to installation.

Figure 10. Two-tiered scaffolding system.


Figure 11. Single point-of-entry for pipeline repair project at Hope Creek.

Figure 12. Epoxy build-up on pipeline interior.

Figure 13. Pitting of concrete and temperature probe penetration requiring special detailing.

Figure 14. Detailing of CFRP repair at location of protruding temperature probe.

Figure 15. Verification of concrete surface preparation utilizing ICRI CSP profile sample.

Figure 16. Verification of steel surface preparation t o near white metal SP-10.

Figure 17. Weighing of fabric prior to saturation process.


Figure 18. QA/QC final walk-through.

referencesASTM D3039, Standard test method for tensile properties of polymer matrix composite materials. American Standard for Testing and Materi-als (ASTM)ASTM D4541, Standard test method for pull-off strength of coat-ings using portable adhesion: American Standard for Testing and Materials (ASTM)ICRI Guideline No. 310.2, Selecting and specifying concrete surface preparation for sealers, coatings and polymer overlays. International Concrete Repair Institute (ICRI)SSPC-SP No.10 / NACE 2 Near-White Blast Cleaning. Society for Protective Coatings (SSPC) and the National Association of Corrosion Engineers International (NACE)


Proposed Methodology For CTI ATC-128 Sound Certification Of Factory Assembled Towers

John Dalton and Larry BurdickSpx Cooling technologies

The Cooling Technology Institute has a very successful, long standing program for thermal capability certification of factory assembled towers, but this type of confidence or 3rd party validation for published sound levels does not exist within the industry. This paper discusses an approach taken, with its successes and challenges, to establish a sound data set for an entire pack-aged product model line that accurately reflects sound emission of all models within the line, and proposes basic ATC-128 certification requirements and guidelines.Methodology for model selection, testing, and data analysis is provided to facilitate the breadth of data and the considerations needed to establish information suitable for cooling tower site design and certification.

Sound Data QualityIdeally, sound measurements are made for each model in a qualified test chamber and meet very high standards for testing, but this type of testing is typically reserved for equipment in sound-sensitive areas such as indoor office spaces. Even then, it is often impracti-cal to test every product line variation, so good estimates based on empirical data are applied. Table 1 describes some of the different ways sound data may be determined with progressively more er-ror from left to right. Ambiguous data can often be recognized by vague descriptions and lack of units.

Table 1: Data Acquisition & Quality of Results

Pragmatic cooling tower and large industrial product testing best practice usually blends “Ideal” and “Good Estimates” categories to produce sound data. For example:

• The outdoor location is a compromise, so ef-forts such as testing at night are made to minimize background sound levels and to monitor the levels during testing. ATC-128 provides limits.• The test pad is a reflective plane most suitable for this type of equipment. No adjustments are made to the measured sound levels due to the reflective plane.• Personnel are trained in equipment use, setup, and testing.• The products being tested are part of a CTI ATC-201 certified product line.• The sound equipment meets requirements for accuracy per CTI ATC-128, e.g. Type 1 equipment.• Sound equipment calibrations are current per CTI ATC-128 requirements.

• An adequate sampling of models in the product line must be initially tested in order to apply the trends with small adjustments to the remaining untested variations.

• The manufacturer and a 3rd party CTI licensed Test Agency witness and take part in the sound measurements.

• The manufacturer uses the measured trends and applies small adjustments to closely estimate sound levels for the product line.

• The data is reviewed and must be approved by a 3rd party CTI licensed Test Agency.

adjustments:A key factor in judging how many units and variations must be tested is the determination of how far test data can be reliably ex-trapolated. Howden [2] developed equation 1 to calculate fan sound power and presented it as part of CTI Technical Paper TP93-03 on fan noise reduction. Equation 1 states that sound power can be calculated by combining empirical data, C, with adjustments for tip speed, net power delivered to the air by the fan (not including efficiency losses), fan diameter, and adjustments for variances such as inlet and outlet obstructions, tip clearance, fan guards, and beams located near the fan. The equations below are used to adjust data from test conditions to published design conditions with good success. The adjustments are applied uniformly across all octave bands.

John Dalton


PWL = the sound power level, WC = fan characteristic value, dB(A)utip = fan tip speed, m/sq = fan air flow, m3/sPtot = total pressure = static pressure + velocity pressure, PaDfan = fan diameter, m∆dB = correction terms, dB(A)

Based on sound radiating spherically from the source, sound power is directly related to sound pressure by equation 2, [2], so it fol-lows in equation 3 that changes in tip speed and / or a change in fan power directly correlate to sound pressure level.Eq. 2: PWL = SPL + 10 LOG (S / SREF) dB

PWL = sound power level, dB (re 10-12 W) SPL = sound pressure level, dB (re 20x10-6 Pa)S = surface area of a sphere, 4 π r2, m2

SREF = reference area, 1m2

C = test data, sound pressure at a specific operating condition, distance,

and location, dB (re 20x10-6 Pa)TSdesign = tip speed of the fan whose sound level is being determinedTStest = tip speed of the test fanBkWdesign = fan motor power of the fan whose sound level is being

determinedBkWtest = fan motor power of the test fan

Note that the correction for environment disappears. This is because the basis data, C, is test data of the fan in the tower environment, not a set of additions and subtractions based on theory. It includes how the fan and unit actually respond acoustically at the tested operat-ing conditions. Likewise, the fan diameter term disappears as it is absorbed in the adjustment for the ratio of fan speeds. Finally, the adjustment for power includes the fan and drive efficiency losses, all of which contribute to the sound characteristics of the system.

Comparison Of Overall Sound Pressure Level adjustments to test DataTables and charts 2a-2d compare overall A-weighted SPL test averages to A-weighted SPL predictions using equation 3: Table 2a shows base case measurements used for equation 3 predictions; tables 2c-2d compare predictions to actual measurements. The dif-ference between tested sound pressure levels at various conditions and predicted sound pressure levels is a simple subtraction, rounded to 0.1 dB. The example test data is from a large double-flow modu-lar crossflow package cooling tower nominally 14’long x 20’high x 22.4’wide and with a 3658mm (12’) fan. Four fan speeds and respective flow rates associated with the towers’ capacity at 35°C hot water – 29.4°C cold water – 25.6°C wet bulb conditions, (95-85-78°F) are considered. Sound pressure levels were measured at locations 5’ and 50’ from the louver face (LF), the cased face (CF), and above the fan (AF), as depicted in Chart 1.

Chart 1: Measurement locations at 1.5m (5’) and 15.2m (50’) from unit.

Photo 1: Microphone stationed at 1.5m (5’) from a tower Louver Face (LF).

Tables 2a-2d show examples of equation 3 predicting overall sound levels to within 0.9 dB when the fan rpm is within +/- 20% of the tested fan rpm, but when fan speed is different from the test con-dition beyond 25%, error increases rapidly to as much as 1.8 dB. The increasing error occurs because equation 3 models changes in magnitude and does not capture changes in frequency.


Table 2e, below, is another example illustrating the closeness of predictive results. The tower is a modular doubleflow with a 3658mm (12’) 8-blade fan tested in 1998 at various speeds. Predictions yield accuracy within 2 dB of actual at fan speeds as high as 120% of the base 214 rpm conditionTable 2e: Example of predicting sound at faster than tested fan speeds.

Predicted Individualoctave Band Sound Pres-sure Levels Versus actual test DataMechanical equipment operating frequencies create sympathetic vibrations in the tower structure and accessories. Consequently, resonances show up as octave bands variations that occur at dif-ferent fan speeds. Tables 3 - 5 compare the predictive model using equation 3 to the octave bands that make up the overall sound pressure levels shown in Appendix B.When limited to +/-20% of tested fan speed, it is evident from tables 3-5 that equation 3 often predicts the middle frequencies reasonably well, but does not account for frequency variations at different conditions. The lower frequencies are also close most of the time, yet the most pronounced error is at the low end in the 63Hz band due to fan speed. Since water noise dominates the upper frequencies, separating water and fan noise contributions, applying equation 3 to the fan portion to make predictions and recombining with water noise may yield the least error. In fact the data shows that the sound pressure level remains essentially constant at 8000 Hz across all four fan speeds at the 1.5m (5’) louver face location. Therefore the predicted sound level becomes more accurate if no adjustment is made to the base data at 8000 Hz for the 1.5m (5’) louver face location; the absolute error is reduced from 4.5 dB to 0.9 dB at 1.5m (5’) louver face in table 4.

A-weighting (dBA) reflects human sensitivity to sound at differ-ent octave band frequencies, so the overall sound pressure level is usually listed in dBA. Octave bands are typically communicated as “linear,” or unweighted (dB) sound levels. The large adjustments

between linear and A-weighted SPL at low frequencies shown in Table 6 minimize the impact of error at these frequencies on overall SPL. However, octave bands are important in predictive sound modeling, and low frequencies such as 63Hz are also the most difficult to attenuate. One of the reasons ultra-quiet fans have low overall sound pressure levels is A-weighting; another is that blade pass frequencies are often shifted to the 31.5 Hz band which we currently do not report.

Chart Group 4: Comparison of sound test data at 242 rpm


Predictions When The Fan Profile Is Constant and the Fan Size ChangesTable 7 contains overall tested SPL’s for a small and a medium sized crossflow package tower having different fan diameters. The smaller tower is nominally 8.5’ long x 18’wide x 11’high. The larger tower is nominally 12’long x 22.4’wide x 11’high.

Using the data in table 7 and equation 3, adjustments are made to the small box (S) test data to predict medium sized box (M) sound levels.


Chart 6 and table 9 show that: extrapolations of fan size by 40% yielded 4 dB errors. (Values rounded to 0.1)A second case of predicting sound levels of one tower size using test data from a tower of another size considers five fan speeds. The mid-size box (M) was nominally 12’long x 11’high x 22.4’wide and utilized a 3353mm (11’) diameter fan. The larger box (L) was nominally 14’long x 11’high x 22.4’wide and utilized a 3658mm (12’) diameter fan. The data includes five fan speed and cor-responding fan power increments. The comparison of 50’ above fan is not included as these two boxes were tested at 24’ and 33’ above fan, respectively and adjustments could introduce error into this comparison.

Predictions across Both Cabinet Size and Fan Size

Charts 7a-e and table 11 depict how much even incremental varia-tions in box and fan size can affect predictions.

application For Quiet Fans at Low Fan Power and rpmUse of the coefficients in equation 3 will under-predict the unit sound level when applied to very quiet fans, especially at low power and rpm. As fan induced sound fades off with lower and lower power, falling water noise stays relatively constant and mechanical noise from the motor and gear reducer or belt drive becomes audible. Changes in fan induced noise become so quiet that they are inconsequential, so continuing to predict quieter op-eration using equation 3 (generic black curve in chart 8) results in


unrealistic sound levels. Water noise is a good sound level floor for an operating cooling tower.

Chart 8: Tower sound levels become asymptotic as air noise lessons. Limits are relatively constant mechanical noise and water noise. Large crossflow package tower, 3658mm (12’) diameter very low noise fan.

Choosing units to Sound testExtrapolating test data far from the test points can quickly lead to differences between the predicted and actual sound levels, there-fore testing multiple configurations in many box sizes is necessary to provide high quality data. Minimizing both the number of boxes that need to be tested initially while at the same time minimizing how far data is extrapolated quickly reduces the number of test candidates a manufacturer may consider. Additionally, test data may already exist for a unit and this can further narrow the selec-tion process.Exceptions arise for large, low blade count fans operated at fan blade tip speeds near 61m/s (12,000 fpm) under difficult condi-tions. In this case, pulsing and unit vibration occur yielding sound levels that do not trend with higher blade count variations. Addi-tionally, if beams or obstructions are near the fan, a pulse frequency is more likely to be generated with a small blade count or a blade count coincidental with the number of obstructions.

• Once towers are selected, test as many models as pos-sible within that unit size. Recommend testing additional points that aid trending and closely align with points of adjacent box sizes that may not be tested at this time. A variable frequency drive (VFD) allows many fan speed changes in a short time. Model selection within the box size can be determined by mapping in a spreadsheet the motor speed, motor power, fan speed, drive ratio, and blade count. .

• Based on utilizing a VFD, use affinity laws to predict power draw as a function of fan rpm for each drive ratio, motor rpm divided by fan rpm, at a given fan pitch.

• For each rpm associated with a different model, check that the motor power is close to the design power, per CTI-ATC-128.

• The goal is to be able to mimic several models without major mechanical changes.

• Change the fan pitch between test points as needed during the test period to extend the number of test models.

Counterflow towers present a few other challenges including determination of adjustments for falling water height variations, air inlet height variations, and fill height variations.

Setup and testingSet up in a free-field area with a reflective plane per CTI ATC-128. Measure fan rpm with a calibrated strobe light or other means to match actual fan speeds with VFD settings. Measure fan power with a calibrated power meter for each condition, then calculate motor output power based on the motor nameplate efficiency. Measure water flow initially using a pitot tube to validate flow meter read-ings, then set the flow to match tower capacity at 95-85-78°F for each model being tested. Measure sound pressure level at 1.5m (5’) and 15.2m (50’) distances from the louver face, cased face, and above the fan. Above fan measurements can be facilitated with a pneumatic mast at the 1.5m elevation, or by mounting the microphone to an extension mounted to a man-lift basket. Ensure that background levels are adequately low and record two measure-ments of each point to eliminate occasional anomalies. Test with a 3rd Party CTI licensed Test Agency witness. Compare and affirm collected data with the Test Agency witness.

Photo 2: Sound test setup.

analysisApply equation 3 or other adjustments that fit test data trends, and test data nearest the design conditions for published literature. Trend data for very low sound models as mechanical equipment and water noise become predominant. Gain approval through the 3rd Party CTI licensed Test Agency.

ConclusionIt is clear that making adjustments to test data with the goal of predicting sound levels of different, untested configurations is imperfect, and therefore a variety of models in many cabinet sizes need to be tested to arrive at published overall sound levels with an accuracy of +/- 3 dB at all locations. Testing of an initial group of towers coupled with use of existing sound test data yields some sound predictions that are quite accurate while others are “ball-park” estimates. ATC-201 thermal certification provides customer confidence that the towers they purchase perform at the published levels claimed by manufactures. This paper provides justification for the concept of a parallel ATC-128 sound certification program, summarized in table 11, and targeted at achieving the same goal. The process begins with testing an initial group of towers and transforms “ballpark” sound data into “good estimates” gradually, by using adjustments based on annual recertification testing.


appendix a: references[1] Table adopted from TRANE training video, Evaluating Sound Data, video @ t =14:25/51:00 minutes. http://www.trane.com/com-mercial/north-america/us/en/products-systems/education-training/educational-resources-by-type/continuing-education/Evaluating-Sound-Data-HVAC-Acoustics.html[2] Reduction of Noise Generation by Cooling Fans, CTI 1993 Annual Meeting, TP93-03, Ir. Henk F. van der Spek, Ventilatoren Sirocco Howden B.V., Hengelo, The Netherlands[3] CTI ATC-128 (14), February 2014, Equation 4.

appendix B: Octave band data, test, Predictions, errors.


Safety In Cooling Tower MaintenanceMagose abraham ejuenergy Business total Solutions, Ltd

Magose Abraham Eju

abstractMaintenance of Cooling Towers usually poses quite a number of occupational / personal safety challenges. For example, the process of removing and replac-ing packing (fill) in a cooling tower involves working at height in most cases. If not well man-aged, this exercise can result to accident of falling; leading to injury and/or fatality. In order to avert such safety incidences during Cooling Tower Maintenance, a robust safety management system needs to be developed for every maintenance work.This paper uses a case study to show the various safety hazards that can be associated with maintenance of Cooling Towers, as well as, suggest ways that these hazards / risks could be mitigated.

IntroductionA major maintenance activity was carried out at one of the 9-cell cooling tower of the Nigeria Liquefied Natural Gas Company. The work scope include the production of new cooling water packing (fill), removal and replacement of the old fill, the revamp of the cooling water tower demister, cooling fan refurbishment, water basin draining / cleaning / refilling and the cleaning of associated heat exchanger tubes.Gas liquefaction in this plant is performed with the aid of three cooling circuits: the cooling-water circuit, the propane refrigerant circuit and the mixed refrigerant circuit. The mixed refrigerant (which is a mixture of Nitrogen, Methane, Ethane and Propane gases) liquefies the natural gas by refrigerating it down to a tem-perature of -160oC. The propane refrigerant circuit pre-cools the natural gas and partially condenses the mixed refrigerant. The cooling water circuit condenses and sub-cools the propane. The entire liquefaction circuit is a complete refrigeration cycle consist-ing of condensers, compressors, expanders and Joule-Thompson valves, in addition to a cryogenic heat exchanger, which acts as the evaporator where the actual liquefaction of the natural gas oc-curs. The cooling tower provides cooling water to both process and equipment heat exchangers using water for cooling or condensing within the Liquefied Natural Gas (LNG) Plant. A picture of the 9-cell cooling tower is shown in Figure 1.1 while, Figure 1.2 is a line diagram of the cooling tower system at NLNG plant. Each of three LNG Plant Production Train is equipped with an independent open re-circulation water-cooling system.

Figure 1.1: Picture of the 9-Cell Cooling Tower

Figure 1.2: Line Diagram of NLNG Cooling Tower System (Courtesy of NLNG Operating Manual)

Cooling is achieved by pumping treated fresh water to process exchangers and other equipment (“users” in Figure 1.2) and then back to the induced draught film type counter-flow cooling towers. The water to be cooled is fed into the top of the cells and the air and water streams come into intimate contact as the water falls by gravity into the three cooling water basins that feed the cooling water pump basin. Within the cells, the water is distributed to the spray nozzles which spray the water evenly unto the PVC pack-ing (see Figure 1.3 below for cooling tower cell schematic). This packing ensures that there is proper heat exchange between the air and water by breaking up the water into fine particles.In March 2012, a comprehensive revamp maintenance of the cool-ing tower system was done. The scope of work included:

• Changing defective/damaged nozzles.• Replacing fill packs (PVC packing): This was the major

part of the job requiring a large number of personnel working at height. All safety precautions were taken as directed in the Job Hazard Analysis. 3,000 cubic meters of fill packs were removed and replaced with new ones in a specified arrangement.

• Flushing of the drift eliminators: The drift eliminators were removed and washed with high pressure water to clear the algae on it.


• Cleaning the cooling water cells and pump basin (water jets were used to flush the cooling water cell walls and fan blades. Shovels and water jets were then used to clean the basin into which all the dirt from the top had fallen).

• Cleaning the trash screens at the pump inlet.• Back-flushing of piping

Maintenance work such as this usually poses a number of occu-pational / personal safety challenges and hence requires a robust safety program in order to avert the hazards resulting in accidents / incidence. This discourse shall highlight some of these safety issues that were highlighted / considered during this particular cooling tower maintenance by reviewing the activity of removing the old (fouled / damaged) packing (fill) of the NLNG cooling tower and replacing them with new ones.

Figure 1.3: Cooling Tower Cell Schematic (Courtesy of NLNG Operating Manual)

removal Of Old Packing / Fill From the Cooling towerThe removal of the old fill was a labour-intensive job because of the volume of material involved. The workers / personnel were arranged in chain across the cell and out of it so that the old packs could be moved in an organized way. Two 40-tonne cranes with man-baskets were used to move the removed packs to the ground floor from the top of the tower (33 feet / 10 meters height).

Safety and Job Hazard analysisThe job hazard analysis was conducted with the lead men on the job, safety professionals and the occupational hygienist. The prepared document is shown below and was discussed with the workers at the beginning of each 12 hour shift on the job. The analysis was done with the Materials Safety Data Sheet (MSDS) and all hazards were examined with recommended mitigation measures proposed.

Figure 2.1: Work Hazard Analysis Sheet for Removal of Old Fill

Production Of Pvc Packing / Fill Each cooling water cell contains 2,058 (1800 X 300 X 300mm) packs and 126 (600 X 300 X 300mm). Since there are 9 cells, the target production of the packs was as follows:

• 20,000 packs (1800 X 600 X 600mm)• 2,000 packs (600 X 300 X 300mm)

The raw materials come in sheets and 15 sheets make up a pack. The sheets are held together by an adhesive produced from a mixture of chemicals.The fill packs were produced on site with 3 production lines each with 4 men working 30 minute shifts. The work steps were as follows:1. A valid permit to work is obtained from Operations Depart-

ment2. The Job Hazard Analysis (see Figure 3.1 below) is discussed

with the men at the beginning of every 12 hour shift.3. Mixing of the chemicals was done in a mixer in the following

proportion:• Cyclohexanone 100% weight• Tetrahydrofuran 1-3% weight• PVC powder 4-5% weight

4. Stir the mixture for about 5 minutes5. Charge the rolling machines with the solution6. Run the PVC sheets through the machine ensuring that the

joining points adequately make contact with the solution.7. Stack 15 sheets together to make one pack.


Safety and Job Hazard analysisThe job hazard analysis was conducted with the lead men on the job, safety professionals and the occupational hygienist. The prepared document is shown below and was discussed with the workers at the beginning of each 12 hour shift on the job. The analysis was done with the Materials Safety Data sheet (MSDS) and all hazards were examined with recommended mitigating measures proposed.

Figure 3.1: Work Hazard Analysis Sheet for On-Site Production of New Fill

The pictures below show some of the work activities, the hazards and the safety precautions that were applied:

Picture 1: Damaged Fill of the Cooling Tower

Picture 2: Fouled Fill of the Cooling Tower

Picture 3: Cooling Tower after Removal of Old Fill


Picture 4: Cooling Tower Removal of Old Fill

Picture 5: Old Fill Removed from Cooling Tower

Picture 6: Lighting inside the Cooling Tower

Picture 7: Height of the Cooling Tower – 33 feet

Picture 8: Workers Installing Fan Blade

Picture 9: Flushing of Pump Suction Pipe – 72-inch


Picture 10: New Fill Installed in Cooling Tower

ConclusionCooling Tower maintenance work usually involves personnel from different fields of engineering, and sometimes, from different companies / organizations. In order to avoid downtime / loss time injuries due to accidents, it is essential that a Job Hazard Analysis is carried out prior to commencement of work to identify all the possible hazards and recommend / develop mitigating measures that will have to be put in place. Also, proper safety orientation of the various personnel on the work site has to be ensured. For example, it is necessary to have a safety brief / tool box session between supervisors and workers before the start of work. At this safety brief, all the work for that day, the possible hazards and the necessary precautions will be discussed in details. Finally, it is recommended that CTI develop a “Cooling Tower Maintenance Safety Guide” that will outline minimum safety requirements, based on best practices, for different types of main-tenance work on Cooling Towers.

references Atuchukwu, C. (2013), Cooling Tower Revamp. In: Nigeria

Society of Engineers Projects Report, Nigeria. British Standards Institute (1988), Specification for Water

Cooling Towers, BS 4485, Part 2 and Part 3. Nigeria Liquefied Natural Gas Plant Operating Manual, (2002).


Advancements in Cleaning and Passivation of Cooling Water Systems

Raymond M. Post

raymond M. Post, P.e., Prasad Kalakodimi, Ph.D. Jeffrey O’Brien, and richard H. tribble, Chemtreat

abstractNewly installed piping and heat exchangers should be pre-cleaned to remove surface rust and pas-sivated to protect against initial corrosion prior to entering service. Traditionally, high levels of polyphosphate [1], organic phosphate [2], ortho phosphate, and combinations have been used to both preclean and passivate in one step. Both poly-phosphate and organic phosphate have good iron se-questering and rust removal properties. Chromate and zinc are effective at forming a protective film, but have fallen out of favor due to environmental restrictions. Nitrite is an effective passivator in closed cooling loops, but promotes microbiological activity in open cooling tower systems and does not become incorporated into a durable, protective film. High levels of molybdate are also used for pretreatment, but molybdate is expensive for large systems and increasingly subject to environmental restrictions.Periodically it may also be necessary to clean equipment to remove accumulated corrosion products and deposits in order to restore thermal performance. Traditional cleaning methods include mechanical brushes and scrapers, acid cleaning, or neutral pH cleaning using high levels of sequestrants or chelants. Regardless of whether a mechanical or chemical cleaning method is used, the freshly cleaned steel surfaces should also be passivated im-mediately following cleaning to protect against flash rust until the normal treatment program is established. Proper initial passivation has been reported to approximately double the life expectancy of mild steel heat exchangers [3].This paper describes the development and application of a new non-phosphate pre-treatment chemistry that forms a truly passive film on steel surfaces. This passivation treatment can be used in combination with either mildly acidic or neutral pH solutions to provide a one-step cleaning and passivation. The use of electro-chemical techniques in the development and evaluation of the chemistry, including cyclic polarization and electrochemical im-pedance spectroscopy, are discussed. A case history is provided to illustrate the effectiveness of this technology for cleaning and passivation as part of a comprehensive program for protecting industrial cooling systems from corrosion.

IntroductionIndustrial cooling systems rapidly form iron oxide deposits which reduce their heat transfer efficiency. It is common to mechanically clean these systems when the iron oxide deposits become excessive. Mechanical means such as scraping, brushing, sand blasting, and high pressure water washing are few of the well-known mechanical cleaning methods. Mechanical cleaning, while effective in many cases, is time-consuming, laborious and expensive. Also, it is not always possible for the physical removal methods to access

all the areas of the system where the deposits are located. Chemical cleaning is more versatile in being able to reach all areas of the system and more effective in terms of removing all traces of rust and deposition.Traditional methods employed for chemically removing corrosion products relied upon strong acids and required special precautionary measures for handling and application. Additionally, the extreme pH risked excessive loss of the base metal, particularly in systems with mixed metallurgy. More recently, considerably safer neutral pH clean-ing programs for rust removal were introduced. These formulations essentially consist of (1) a

strong reducing agent to reduce ferric (Fe3+) iron oxide deposits into a soluble ferrous (Fe2+) form, and (2) an organic phosphate chelant to complex the dissolved iron. The system is thoroughly flushed after this process to remove the dissolved iron. Though safer to handle, neutral pH cleaners still can still be very aggressive to carbon steel base metal. Provided that the final pH of the solu-tion is greater than approximately 6.0, these neutral pH cleaners can provide some degree of passivation.Regardless of whether the cleaning is performed mechanically or chemically, freshly cleaned steel surfaces are extremely vulner-able to flash rust. A separate passivation step is required after the cleaning process to protect the bare metal from flash rust and to protect against the high initial corrosion rate that occurs when the equipment is initially placed into service. To achieve a one-step cleaning and passivation, there exists a need for a strong corrosion inhibitor chemistry that protects the steel surfaces from the aggressive cleaning chemistry and provides a strong passive film to protect the surfaces as they are placed into service. The starting point for corrosion inhibitor development was an inhibitor chemistry originally developed to comply with emerging restrictions on phosphorus discharge. The development and application of this corrosion inhibitor for use in cooling towers under normal operation has been described in earlier publications [4] [5]. This corrosion inhibitor chemistry was selected because it interacts directly with metal surfaces to form a reactive polyhy-droxy complex (RPC) that is independent of calcium, pH, or other water chemistry consitutents. It also possesses many of the other desired attributes including an excellent aquatic effects profile. The ability of the RPC chemistry to protect and passivate the base metal during preoperational cleaning is the focus of this study. Efficacy of the RPC chemistry was compared to traditional polyphosphate and organic phosphate cleaning and passivation chemistries.

Laboratory StudiesMost metallic corrosion occurs via electrochemical reactions at the interface between the metal and an electrolyte solution. Since cor-rosion phenomena are electrochemical in nature, they are governed by the measurement of equilibrium corrosion potential (Ecorr) of


the metal surface. During the late ‘70s and early ‘80s, corrosion specialists began to discover that electrochemical instruments and techniques could be valuable tools for mechanistic understand-ing and problem solving. Electrochemical methods can be very helpful in rapidly evaluating the persistence of a passive layer formed on a metallic specimen in the presence of inhibitor when that specimen is transferred into a second solution not containing a corrosion inhibitor.

electrochemical experimental The passivation chemistries selected for laboratory evaluation were two well-established phosphate chemistries and the RPC chemistry, which were compared to untreated blank water samples for their ability to form a persistent protective film. The organic phosphate (HEDPA) was evaluated at a concentration of 1,250 mg/L as PO4

=, the polyphosphate (TKPP) was evaluated at a concentration of 320 mg/L as PO4

=, and the RPC was evaluated at a concentration of 12 mg/L. The blank water contained 150 mg/L Ca as CaCO3, 100 mg/L Mg as CaCO3, 100 mg/L M-Alkalinity as CaCO3, 50 mg/L chloride as Cl-, 10 mg/L silica as SiO2, at pH 8.0.Working electrodes were made from cylindrical shaped carbon steel electrochemical coupons. Corrosion resistance performance of different passivation chemistries was evaluated using electro-chemical techniques including open circuit potential (OCP), cyclic polarization (CP), and electrochemical impedance spectroscopy (EIS) measurements. Carbon steel coupons were passivated for 8 hours in baths containing the passivation chemistries. After pas-sivation, the electrochemical coupons were rinsed with RO water and placed in the blank water. The pH of the blank solution was maintained at 8.0-8.2 using caustic soda. Electrochemical mea-surements were performed in a three electrode cell consisting of a graphite counter electrode, an Ag/AgCl reference electrode, and the carbon steel coupon. Electrochemical impedance spectroscopy (EIS) measurements were performed using the excitation signal of 10 mV sinusoidal potential through a frequency domain from 100 kHz down to 10 mHz. The impedance diagrams were recorded at the equilibrium OCP, while polarization scans were traced at a rate of 0.5 mV s-1. Unless otherwise stated, each experiment was conducted in at least triplicate using freshly prepared solution in each case and with the average of the reliable data reported. Figure 1 shows the electrochemical testing apparatus used for the experimental work.

Figure 1. Potentiostat arrangement used for electrochemical studies

Open Circuit Potential (OCP) evaluation – Open circuit poten-tial measurements were made in blank water with bare mild steel (MS) coupons and also on the coupons passivated as described above using the organic phosphate, polyphosphate, and RPC chemistries. OCP measurements were taken at 5 minute intervals for an extended period of 36 hours. Comparing the OCP profiles obtained for these electrodes indicate that after the electrode surface was passivated using RPC, the OCP is >200 mV more positive than that the MS coupons passivated with polyphosphate and organic phosphate chemistries. These results indicate that the RPC pas-sive film is thermodynamically more stable than phosphate and is very effective in reducing corrosion. Moreover, the passive film retained its effectiveness in the untreated blank water, with the OCP decreasing <100 mV during the 36-hour exposure. In the cases of the polyphosphate and organic phosphate passivations, the OCP values quickly become more negative, indicating rapid dissolution of the passive film by diffusion of aggressive ions and subsequent increase in corrosion rates.

Figure 2. Open circuit potential after passivated coupon is placed in untreated water

Figure 3. Cyclic polarization after passivated coupon is placed in untreated blank water

From the cyclic polarization curves, some electrochemical cor-rosion kinetic parameters can be obtained, such as the corrosion potential (Ecorr), Tafel slopes, corrosion current density (Icorr), and corrosion rates in Table 1.

Table 1. Cyclic polarization data of various passivation treatments


An immediate observation from comparing the Ecorr (Figure 3 & Table 1) and OCP (Figure 2) is that both the electrochemical techniques are in good agreement. Small differences could be attributed to the effect of polarization. It is clearly seen from Fig. 3 that the coupon passivated with RPC chemistry has lower pas-sivation current and lower currents at all applied potential values. The corrosion resistance of different passivation treatments was calculated using Stern-Geary Equation: Icorr = babc/ ( ba+bc)2.303 Rp (1)From the graph and the table, it is clear that the corrosion current for different passivation treatments increases in the order:(Icorr)RPC < (Icorr)Organic phosphate < (Icorr)Polyphosphate (2)Inhibition efficiency (% Inh) of various passivation treatment programs has been calculated using the formula:% Inh = (Icorr)blank – (Icorr)treatment / (Icorr)blank * 100 (3)It is clear from Table 1 that higher inhibition efficiency was ob-tained by the RPC passivation treatment than the polyphosphate and organic phosphate chemistries, indicating the stability and persistent nature of the RPC non-phosphate passive film.electrochemical Impedance Spectroscopy Measurements – The long-term corrosion behavior of the three passivation treatments on the surface of carbon steel electrodes was probed by electro-chemical impedance spectroscopy (EIS). Electrical resistance is a well-known parameter for characterization of the ability of a circuit element to resist the flow of electrical current. Similar to resistance, impedance is also a measure of the ability of a circuit to resist the flow of electrical current. However, unlike resistance, impedance is not limited by the simplifying properties of a single resistor. Electrochemical impedance is usually measured by applying an AC potential to an electrochemical cell and then measuring the AC current response through the cell. EIS is one of the most useful techniques to discern the corrosion mechanism, evaluate protective films on metals in aggressive solutions, and analyze film formation at the metal-electrolyte interface. When a metal surface is covered (passivated) with a protective layer, the corrosion is controlled by the transport of the species in the protective film through diffusion channels resulting from passive film breakdown or micro cracks. The response can be represented as the relationship between the imaginary and real components of impedance, referred to as a Nyquist plot. Figure 4 presents the Nyquist impedance diagram recorded at OCP for various passivation treatments.

Figure 4. Nyquist plots for different passivated coupons in untreated water

It is clear that the semicircle diameter increases in the order:Polyphosphate ≤ Unpassivated < Organic phosphate << RPCSince the diameter of the capacitive semicircle represents the resis-tance of the coating, an increase in diameter represents increased resistance. Figure 4 illustrates that the corrosion resistance of RPC passive film is much greater than other traditional organic phos-phate and polyphosphate passivation treatments, consistent with OCP and CP measurements in Figures 2 and 3. The EIS results also confirmed that RPC passivation forms a highly protective film on mild steel in the test water, significantly outperforming the polyphosphate and organic phosphate passivation chemistries.

Comparison with Nitrite and Molybdate Passiv-ationCarbon steel coupons were passivated for 6 hours in baths contain-ing the treatment solutions of interest in blank water (described above). Baths 1 and 2 contained the RPC corrosion inhibitor at 12 mg/L and 6 mg/L respectively, bath 3 contained 100 mg/L of molybdate (as MoO4

=), and bath 4 contained 1,200 mg/L of nitrite (as NO2

-). Following the 6-hour passivation period, the coupons were rinsed in DI water and placed into untreated blank water for a period of 3 days to evaluate the persistence of the passive film. After exposure, the coupons were removed and photographed. Average corrosion rate was determined by weight loss. The coupon appearance and corrosion rate are shown in Table 2.

Preoperational Cleaning Passivation OCP evaluation One of the major needs for passivation chemistry is during pre-operational cleaning when the freshly cleaned surfaces are most vulnerable to flash rust just prior to the equipment entering service. To simulate the condition of new steel heat exchangers subject to environmental rusting during the construction period, a new steel heat exchanger tube was first allowed to rust outdoors for several days, then cut into sections approximately 3 in (7.5 cm) long. One rusted tube section was placed into a beaker containing a neutral pH, precleaning and passivation solution containing organic phosphate, reducing agent, and surfactant. A second section from the same tube was placed into another beaker containing the same chemistry with the addition of the RPC passivating chemistry. The solutions were stirred for 6 hours until the both specimens were substantially free of rust. The pH of the cleaning solutions remained in the 6.5-6.7 range during the 6-hour exposure. Figure 5 and 6 show the specimens in the beakers before and after cleaning.

Table 2. Corrosion rate and coupon appearance after 6-hour passivation and 3-day exposure to untreated blank water.


Figure 5. Precleaning and passivation study at start of 6-hour exposure. Specimen on right contains the RPC passivation chemistry.

Figure 6. Precleaning and passivation study at completion of 6-hour exposure. Specimen on right contains the RPC passivation chemistry.

Figure 7. OCP measurement of cleaned tube specimens

As shown in Figure 6, after 6 hours, the cleaning solution without the RPC passivation chemistry is noticeably darker than the solu-tion with RPC chemistry due to additional corrosion of the base

metal. Following the cleaning, both specimens were placed in baths of untreated blank water for 24 hours to evaluate their ability to re-sist corrosion using open circuit potential as illustrated in Figure 7.In this test, the precleaning solution containing the RPC chemistry exhibited an open circuit potential more than 200 mV higher than the solution without RPC (Figure 8).

Figure 8. OCP of cleaned specimens over 24 hours in untreated water, with and without RPC passivation chemistry

Figures 9 and 10 show the two specimens after the 24-hour expo-sure to the untreated blank water. The steel tube section that was exposed to the cleaning solution containing the RPC passivation chemistry clearly resisted rusting, while the specimen not exposed to RPC readily rusted after cleaning.

Figure 9. Tube section cleaned and passivated with RPC, organic phosphate, and reducing agent after 24-hour exposure to untreated blank water.

Figure 10. Tube section cleaned with organic phosphate and reducing agent after 24-hour exposure to untreated blank water.

Copper Sulfate Verification TestA simple, visual test for passivation is to expose steel or stain-less steel specimens to a copper sulfate solution. Immersion in a copper sulfate solution is one of the verification tests described in the ASTM A967 standard specification for chemical passivation treatments [6]. Copper ions in solution act as electron acceptors at the cathode of the corrosion cell and readily electroplate onto unpassivated or weakly passivated surfaces, producing a very pronounced copper discoloration to the steel surface (Figure 11). The test can be performed in the field as an acceptance test


criteria for equipment passivation procedures. A well passivated steel coupon will exhibit considerable resistance to copper plating even when exposed to a solution containing a high concentration of copper ions.

Figure 11. Mechanism of copper electroplating onto steel surfaces

Exposure to a copper sulfate solution was used to evaluate the ef-fectiveness of RPC passivation chemistry compared to established organic phosphate and polyphosphate passivation chemistries. Mild steel coupons were treated for 6 hours in passivation solutions and then exposed to a 15% copper sulfate solution for 20 seconds. Following exposure, the coupons were rinsed with deionized water, dried, and visually inspected for copper plating as an indication of passivation effectiveness. A relatively high concentration of cop-per sulfate was used in order to produce severe test conditions that would discriminate among the passivation chemistries. As shown in Figure 12, the RPC passivation chemistry clearly demonstrated effectiveness superior to organic phosphate and polyphosphate in the copper sulfate exposure test, and at significantly lower treatment concentrations.Organic phosphate passivation 640 mg/L as PO4

=, for 6 hours

Surface is copper plated. Passive film failed.

Polyphosphate passivation 320 mg/L as PO4

=, 6 hours Surface is copper plated. Passive film failed.

rPC passivation 3.8 mg/L as RPC, 6 hours Steel resisted copper plating, indicating a strong passive film.

Preoperational Cleaning applicationA Midwest manufacturing plant resumed operation after being idle for 18 months. Prior to resuming operation, the cooling system was cleaned using an acidic cleaning solution with surfactant and dispersants recirculated at a target pH of 3.0. The cleaning solution was inhibited using a triazole together with the RPC passivation chemistry. Mild steel coupons were installed to evaluate base metal loss and passivation effectiveness. The steel coupons were removed for after 2 days showed a dull grey passivated surface (Figures 13 and 14). The presence of RPC on the coupon was confirmed by surface analytical methods.

Figure 13. Passivated steel coupon after 2 day exposure to pH 3 cleaning solution containing RPC

Figure 14. Coupon surface magnified 40x

Carbon steel coupons exposed during the cleaning process were further evaluated to determine the corrosion resistance of the passive RPC film. The copper sulfate verification test described earlier was performed on the exposed coupon shown in Figure 13 and compared to a new, carbon steel coupon. The lower half of each coupon was exposed to a 15% copper sulfate solution for 20 seconds. As shown in Figure 15, the new coupon is copper plated on its lower half, while the coupon passivated during the acidic chemical cleaning effectively resisted copper plating.

Figure 15. New coupon (top) and coupon passivated with RPC during the acidic chemical cleaning (bottom) after half-exposure to a 15% copper sulfate solution for 20 seconds. Note the copper plating on the new coupon as compared to the

absence of copper plating on the RPC-passivated coupon.

A second carbon steel coupon that was exposed during the chemi-cal cleaning process was evaluated for passivation by placing it in untreated blank water and comparing its OCP to a new coupon over time as described in the Experimental section. The RPC pas-sivated coupon maintains its potential for several days in untreated water (Figure 16).

Figure 12. Passivated coupons after 20 sec. exposure to 15% CuSO4 solution


Figure 16. OCP measurement over time on carbon steel coupon passivated with RPC during chemical cleaning compared to a new carbon steel coupon.

As further visual evidence of passivation, the untreated OCP test baths were photographed after 3 days. Figure 17 shows the rust-colored solution containing the new coupon on the left and the clear solution containing the RPC-passivated coupon on the right.

Figure 17. OCP test baths after 3 days showing the rust-colored solution containing the new coupon on the left and the clear solution containing the RPC-passivated solution on the right.

Neutral pH Cleaning Formulations With rPCNeutral pH formulations containing various levels of RPC were studied for their effectiveness in cleaning rusted coupons and were also evaluated for corrosion rate on fresh coupons. Cleaning solutions were prepared according to Table 3 and applied at a dosage of 10%.

Figure 18 shows the coupon appearance before and after cleaning in the neutral pH formulations with and without RPC.

Figure 18. Before and after cleaning photos of the corroded coupons in standard neutral pH cleaners with and without RPC. Cleaning duration was 6 hours for all.

Formulations #1, #2, and #3 with RPC cleaned more effectively and left the coupons with a dull grey finish consistent with pas-sivation. A fresh corrosion coupon was inserted into each of the cleaning bath to study the effect of the cleaner product on the base metal. Corrosion rates were measured by weight loss. The clean-ing solutions containing RPC also exhibited a ~60-70% reduction in corrosion rate as compared to the standard neutral pH cleaner.

ConclusionsEffective cleaning and passivation of heat exchangers and pip-ing is required during initial start-up and periodically during the operational life of the system. Using advanced electrochemical techniques, a powerful new passivation chemistry has been devel-oped that protects the base metal during the cleaning process and provides a persistent passive film that resists corrosion for several days as the system is placed back in service. The new Reactive Polyhydroxy Complex (RPC) based chemistry was found to be superior to traditional polyphosphate and organic phosphate based treatments in terms of forming a stable and persistent passive film. The RPC chemistry can be used in conjunction with either acidic or neutral pH cleaners to achieve simultaneous cleaning and pas-sivation, eliminating the need for a separate passivation step.

acknowledgementsThe authors gratefully acknowledge DeAnn Wills-Guy of Chem-Treat for conducting the electrochemical studies.

Nomenclatureba Anodic Tafel slope, Eq. (1)bc Cathodic Tafel slope, Eq. (1)Beta Anodic Tafel slope, mV/decade, Table 2cfu Colony forming unitsCP Cyclic polarizationEcorr Corrosion potential at equilibrium, mV or VEIS Electrochemical impedance spectroscopyHEDPA 1-Hydroxyethylidene-1,1-diphosphonic acidIcorr Corrosion current at equilibrium, mA or ATable 3. Table showing neutral pH cleaning solution

chemistries used to clean coupons in Figure 18.


mHz Megahertzmpy Mils per year, 0.001 inch/yr., equivalent to 0.0254 mm/yr.OCP Open circuit potential mV or VRp Polarization resistance, Eq. (1)RPC Reactive polyhydroxy complexTKPP Tetrapotassium pyrophosphateZ Impedance (of surface), Ohm-cm2

Zimag Imaginary component of surface impedance, Ohm-cm2

Zreal Real component of surface Impedance, Ohm-cm2

references1. Initial Conditioning of Cooling Water Equipment, NACE

RP0182-95.

2. Rust Removal and Composition Thereof, Waller, J.E., Gray, J.A., and Aston, D.A., US Patent 4,810,405, 1989.

3. Proper Initial Passivation of Cooling Water Heat Exchangers - Is This a Lost Art? P.R. Puckorius, 63rd International Wa-ter Conference, IWC-02-62. Engineers' Society of Western Pennsylvania, Pittsburgh, 2002.

4. Development of Next Generation Phosphorus-Free Cooling Water Technology. R.M. Post, R.H. Tribble, & J.R. Richard-son, International Water Conference, IWC-10-23. Engineers Society of Western Pennsylvania, San Antonio, 2010.

5. Development and Application of Phosphorus Free Cool-ing Water Treatment. R.M. Post, R.P. Kalakodimi, & R.H. Tribble, CTI Journal Vol. 35, No. 2, pp. 52-67, 2014.

6. Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts, ASTM A967/A967M-13, 2013.


Mechanical Behavior of Polymer FillsNina Woicke, PH.D, Daniel Dierenfeld, eNeXIO Water technologies gmbH, 2H Components and Solutions

abstractThe paper outlines the mechanical properties of polymer fills and discusses the influence of dif-ferent parameters (e.g. PP vs. PVC, foil thickness, design) with particular regard to cooling tower aspects.

IntroductionThis paper will give an overview on the mechani-cal behavior of cooling tower fills. The main focus is thereby the short term behavior. Temperature dependent and time dependent properties play their role in the cooling tower fill life as well, but here these subjects will only touched briefly. The paper is structured in three sections:

1. Material properties2. Mechanical theory on cooling tower fills3. Results of specific tests in comparison

Material propertiesThe two main materials used for cooling tower fills are polyvinyl-chloride (PVC) and polypropylene (PP). In the following Table 1 the mechanical material properties (minimum values) defined by CTI STD 136 are summarized. These properties are for the non-engineered material only and are mainly used for general quality control.

StrengthThe strength is the maximum load a tensile bar can take under tensile load (ASTM D638 or EN ISO 527-1/-2) or a bending bar (ASTM D790 or EN ISO 178) under flexural load. In both cases the usual standard test bars are much thicker (about 10 times) than the final foils. That means if you want to test 100% according to the standard it is not possible to measure this property directly from the foils.

ModulusThe modulus defines the stiffness of the material. That means the stiffer the material the less deformation at certain loads. Therefore it is not recommended to use the strain as an absolute failure criteria over both materials discussed.Both PP and PVC modulus can be measured under tensile or flexural conditions since they are not directional reinforced (like e.g. FRP).

Impact resistanceThere are several different standards available to measure the impact resistance. One standard is the Gardner impact strength, which is also called “falling dart” test, which already describes the method of impact (test set-up in Figure 1).

PP normally performs well under Gardner condi-tions, because it is more ductile then PVC. To visualize this effect, in Figure 2 the results of instrumented indention test are shown. The di-ameter of the test “dart” in this case was 1.65 mm (0.065’’). Two foils with the same weight, one PP and one PVC, have been tested. The results can be seen in Figure 2. The PVC breaks, when the maximum force is reached. PP on the other hand will stretch locally more than 100% extra distortion before the final failure.Therefore normally impact tests with notched test bars like the notched Izod test are used for

the characterization of PP (blue specimen in Figure 3). The notch increases the local stress, so that as well PP will break at the hit of the hammer and a distinctive value can be given. Unfortunately the values of Gardner tests and notched Izod tests are not directly comparable, since the overall test set-up is quite different.

Heat deflection temperatureThe heat deflection temperature (ASTM D648) is a technological test. A small specimen is put in an oil bath and preloaded with a certain load (either 66 or 264 PSI) under bending. The bath then is slowly heated. The heat deflection temperature is reached, when the specimen has a certain deflection (0.2%). Even though this test is used in the STD 136 as a reference, neither the load case nor the deflection limit is in linked to the ones of drift eliminators or fills. Therefore this temperature cannot directly be related to temperatures in use in a cooling tower.The mechanical behavior of PP and PVC is different as the tempera-ture increases. PVC is very rigid and stiff at temperatures between room temperature and about 55 °C (131 °F). The change in modulus is very low for this regime. Above 55 °C the material reaches its glass transition and changes its behavior drastically, so there is not a lot structural integrity left above 65 °C (149 °F). To reduce this effect, PVC can be partly mixed with other polymers like ABS or SAN. This composition is is normally referred as “HPVC”. Another possibility is to use chlorinated polyvinyl chloride (CPVC), which as well has higher glass transition temperature.PP on the other hand has its main melting onset at about 140 °C (284 °F). Therefore upto 110 °C (212 °F) the mechanics if sized properly can be still strong enough and applicable to be used [5]. Nevertheless the softening slope of the material is there as well and at the same time the thermal degradation through oxidation has to be carefully addressed through engineering and product design characteristics. Therefore at higher temperatures the use of specially heat stabilized and probably thicker material is advisable.

DensityAdditionally to the properties mentioned in the CTI STD 136 material density has to be recognized for the full understanding of the mechanical behavior of cooling tower fill.

Nina Woicke


The densities of the two materials differ quite a lot due to the fact that the chloride in the PVC is a rather “heavy” atom. Additionally both materials can be added with inorganic fillers. The density ranges about 0.92-1 kg/l (0.033-0.036 lb/in³) for PP and 1.35-1.55 kg/l (0.049-0.056 lb/in³) for PVC. Therefore, if you compare two products (PP and PVC) with the same material gauge, the PP product will be lighter than the PVC.

Mechanical behavior of cooling tower fillThe overall mechanical fill properties are a combination of the material properties, the fill design, the thickness respectively the overall weight of the product and the quality of the bonding. The second aspect is not the main focus of this paper, but of course has to be taken into account as well. A fill that has been badly bonded can have totally different strength than one that is bonded properly. In this case the number of bonding points and the bonding quality of a single point is important.

Foil thicknessIn former times nearly all film fills were produced by thermoform-ing. At that time it was established, that a fill was defined by its foil (sheet/film) thickness (normally measured in mil), especially before forming. In that case you have a flat foil, where it is pretty easy to measure the thickness at any point. After the corrugation process, the measurements already become a lot more complicated depending on the complexity of the corrugation or forming. After bonding only the outer edges are available for any check on site. Even with a single foil you will have a differential of the thickness throughout the sheet and it is then difficult to measure to a fair level of accuracy, the actual foil thickness for the entire sheet.Nowadays there are several more methods to produce a fill; e.g. injection molding for the so called “hybrid” fills or the direct extrusion processes without any defined semi-finished product in between. These methods even allow having an optimized, uneven foil thickness to enhance higher loaded parts. Especially the edges of the fill are more likely to be battered by the water impact or inspection traffic. Erosion is therefore a typical cooling tower fill problem. In this respect an uneven thickness distribution to strengthen the edges (Figure 4) of the fill can help to minimize this problem with PP as well as with PVC fills.Therefore it is recommendable to use the fill weight as an extra measure. It is, of course an overall property and doesn’t give you any indication on the specific distribution, but a fill from the same material and same design, bonded the same way, but has e.g. 30% higher weight will behave stronger under mechanical load.To get an idea how the weight and the mean foil thickness are related, use the following equation:

1

TF: Thickness of the foil (mil)M: Mass of the fill (lb)L: Length of the fill (ft)W: Width of the fill (ft)H: Height of the fill (ft)ρ: Density of the fill material (lb/in³)

Asp: Specific surface of the fill (ft²/ft³). This is a fill type specific number and is normally provided by the fill supplier. Nevertheless in Table 2 there are indication numbers for some usual fill types. The area has to be divided by two because of the two sided of a foil. Weighing a fill is a simple method to cross check, if the foil thick-ness is about what the supplier stated.

Buckling under compressionIf the foil bonding is done properly cooling tower fills under pres-sure normally fail by buckling of the foil. In Figure 5 you can see a completely vertical fluted fill, which is buckling between the connection points.The theory of buckling is rather complicated; nevertheless it is necessary to understand the main idea to understand the fill be-havior. To keep it as simple as possible we model it as a column between two supports, which are represented by the bonding points (see Figure 6).Euler established a formula for the maximum force a slender column can carry (Euler case 2 [3]). Of course, cooling tower fills are far from a perfect slender column, but still the equation can be used for the general understanding:

2

F: The maximum ForceE: The modulus, influenced by the material as discussed in 3.2LS: The unsupported length. This is influenced by the design as well as the quality of bonding. For example, a 1 ft high fill, which is only bonded at the edges, is four times more likely to Eulerian buckling than a fill, which has an additional bonding in the middle of the fill.IF: is the so called momentum of inertia of the foil, which is in-fluenced by the design (overall design as well as the corrugation design). This is hard to calculate for a so complex geometry like a corrugated cooling tower foil. Nowadays the only meaningful method to calculate the buckling is finite elements analysis (FEA) (see Figure 7 as an example). Only with this method you can get the height and distribution of the load.If you have a look at one single, rectangular element, the momen-tum of inertia is then easy to calculate:

3

IE: Momentum of inertia of elementWE: Width of the elementTE: Thickness of the element, which normally is directly related to the thickness of the foil. That means the thickness of the foils is influencing the local momentum of inertia by the power of three and is therefore an important figure.

BendingThe fill in the cooling tower is not only loaded under direct pres-sure, but the bottom layer is normally on a support structure, which implies local compression point loading as well as bending into the fill. In most of the cases that makes the bottom layer to the


most critical layer. This is not only influenced by the fill, but also by the distance between the supports, the width of the support and the arrangement of the fills. As an example, according to elastic bending theory [4] two 3 ft long blocks will bend more than double to one 6 ft long block on the same support structure. Similar it is true that the same fill one or two feet high will bend differently. Even though there may be a small drawback in per-formance, normally it is recommendable to use a 2 ft high block as a bottom layer to improve the overall stability.Bending as well depends on the stiffness and the momentum of inertia, but this time not only of the local foil, but of the whole fill structure. This is again not really computable by easy equations, so the best possibility to get an impression of the flexural behavior is a direct test of the fill.

Results of specific cooling tower fillsTo illustrate the theoretical background of the previous chapters, in this chapter specific data is given, mainly in a qualitative manor to emphasis the main differences. They all refer to data measured with 2H® fill. The measured fill were the KFP 619/KVC 619 for the 19 mm crossfluted fill, the KPP 612 for the 12mm crossfluted fill, the KVP 623 for the vertical fluted fill and KGP 620/KBP 620 for the offset fill types. All results are plotted qualitatively to show the general influence of the parameters.

Compression test set-up The pure compression tests have been conducted with a 305 mm (1 ft) x 305 mm (1 ft) x 610 mm (2 ft) set-up at room temperature and a test speed of about 2 ft/min (see Figure 9). The respective strain rate in this test is in the magnitude than the strain rate to determine the tensile strength (ASTM D638). So these results can be used for direct correlations between the material strength and the fill strength. Of course this only tests the short time behavior of the fill. Normally the same test is done with 3 different specimens. In Figure 8 one can see the normal output of the force deflection curve. For the evaluation of the tests the mean value of the maxi-mum force is taken.

Bending test set-up for the bottom layerThe tests to simulate the bending situation of the bottom layer were done with 610 mm (2 ft) high and 2440 mm (8 ft) long test specimens. The support structure was spaced 900 mm (2.95 ft) and a cantilever of 320 mm (1.05 ft) on each side (see Figure 10). The width of the support was 60 mm (2.4 ’’). There were seven measur-ing points along the side of the fill. The different points were chosen to separate the local deformation at the supports from the bending between the supports, which adds up to the overall deflection. Static loads were applied on top of the fill (see Figure 10). The distance of fill points to the flooring was detected before loading and after 24 h after applying the load.

MaterialSince all of the mechanical data is very different, it is not so easy to directly compare PP with PVC fill. And as well it very much de-pends on the specific design, how high a certain effect is. Therefore in the following only relative measures are given to illustrate the general tendencies. As a reference 27 kg/m³ (1.68 lb/ft³) 19 mm cross fluted fill, thermally bonded, has been taken as a reference of being 100%.

One approach of comparison is to use the same specific fill weight. Due to the differences in densities this results in differences in the foil thickness. Under these circumstances, the pure compression strength of PVC fills is lower.For the same border conditions the deflection under load looks dif-ferent: Both, the bending and the local deformation for the PP fill, are slightly higher due to the lower modulus of the material. For a direct visual comparison it is useful not to take the direct strain but its inverse (which is called bending resistance and compression resistance in this paper).This is done, so higher values represent “better” and not the opposite.The overall comparison summarized in Figure 11.

Fill weight/foil thicknessThe foil thickness (fill weight) has obviously a major influence on the fill mechanics (for one material the thicker the better). If you look at the same fill weight (see also 5.3) the compression strength of the PP is higher. In contrast to that, if you look on the same mean foil thickness of the formed foil, the PVC fill has the higher compression strength. This variation is visualized in Figure 12.Concerning the bending the influence of the specific thickness is even harder to determine. The general behavior is of course that the deflection is lower the higher the fill weight respectively the foil thickness is. As an example 22 kg/m³ (1.37 lb/ft³) and 27 kg/m³ (1.68 lb/ft³) PP 19 mm crossfluted fill is compared in the local compression as well as in bending in Figure 13. You can see that the lower weight has significantly higher deformations.If you choose a too low weight (too thin foil) for a certain distrib-uted load, the fill will fail at the support by a local buckling (see Figure 14). Therefore one must carefully choose the right fill for the design load.

Influence of fill designBeside all aspects discussed before, the fill design has a tremendous influence on the overall stability and performance. And again, the aspect of buckling (due to compression) has to be looked at as well as the bending.Fills with cross flutes have normally a good combination between the necessary properties. They even have an extra value in their design: They distribute local load along the flute inclination into the fill. Due to the bonding of the foils, the cross-fluted fills behave similar to carpenters work in house. Fills with offset are normally a lot more sensible to pure compression than the fills mentioned before, while for the bending issue the offset again helps to sta-bilize the fill. In Figure 15 you can see the comparison of different compression stability of different fill types in PP. The blue columns are for a comparison at the same foil thickness of the final product and the red columns at the same specific weight, which equals a calcu-lated mean thickness of the 15 mil of 19 mm crossfluted fill. The compression strength has been normalized to the value of the 19 mm fill, so this diagram can be used in principle for other weights/thicknesses and PVC similarly.What you can see is that you have to be careful when you compare different fills, because due to the differences in corrugation height, the general tendencies can vary (see also 5.3).


At the same time there is the bending behavior of the different fills. From the pure compression point of view the fully vertical flute is the best, because the column-like structure supports strongly in the vertical direction. These columns on the other side have only a low stability into the other two directions. Therefore bending stability of this design is not as good. Therefore the bottom layer of such fill should be stiffened with flat sheets as shown in Figure 16. This problem is due to the design and has to be addressed for PP and PVC alike.The results of the deformations of these variations are summarized in Figure 17. Again here fill with 27 kg/m³ (1.68 lb/ft³), thermally bonded, is compared. That reflects about 15mil for the 19mm crossfluted and

SummaryThis paper illustrates different aspects of the cooling tower fill mechanics:PP and PVC differ in all properties and therefore can’t be directly compared by comparing pure material values

• The material thickness is an important measure, but hard to check. Therefore the specific weight of the fill is the better measure for a comparison for all product types

• The design has equal if not more influence as the material on the overall mechanical strength of a fill

• To judge the overall mechanical behavior of a fill, it is necessary to evaluate the bending properties as well as the compression strength of the final product

Even though it has not been verified by this study, the mechanical strength of the fill also depend on the type and frequency of the bonding points.For the final decision for a certain cooling tower fill it is therefore necessary to evaluate carefully all aspects of engineering and product design.

tables

Table 1: Overview of material properties of PP and PVC [1]

Table 2: Overview of specific surface area of different fill types

Figures

Figure 1: Gardner “falling dart” test set-up

Figure 2: Instrumented indention test of PP and PVC foils of the same weight

Figure 3: Notched Izod test set-up

Figure 4: Sketch of a 2 ft wide foil/sheet with optimized thickness distribution


Figure 5: Foil buckling (thermally bonded)

Figure 6: Principle of buckling [2]

Figure 7: FEA visualizing the stress distribution of two bonded fill sheets

Figure 8: Force-deflection curve of a compression test

Figure 9: Picture of the test set-up


Figure 10: bending test set-up

Figure 11: Comparison of PP and PVC for the same fill weight (27 kg/m³, 19 mm cross fluted fill, thermally bonded)

Figure 12: Relative compression strength of 19 mm cross fluted fill, thermally bonded in dependence of different parameters (A: Spec. weight, B: Foil

thickness) (test method as described in 5.1)

Figure 13: Relative deformation for two different fill weights (thermally bonded)

Figure 14: Fill under local buckling (set-up like in Figure 10)


Figure 15: Compression strength comparison for different fill types (thermally bonded)

Figure 16: Flat foil will improve the bending properties of fully vertical flutes

Figure 17: Comparison of deformation behavior of different fill types in PP (27 kg/m³, thermally bonded)

Literature[1] CTI STD 136-2010[2] Wikimedia Commons[3] DUBBEL - Handbook of Mechanical Engineering, Wolfgang

Beitz, Karl-Heinz Küttner, Springer, 1994, page B45[4] DUBBEL - Handbook of Mechanical Engineering, Wolfgang

Beitz, Karl-Heinz Küttner, Springer, 1994, page B19-B22[5] DUBBEL - Handbook of Mechanical Engineering, Wolfgang

Beitz, Karl-Heinz Küttner, Springer, 1994, page D57


ASHRAE Legionella Standard 188: Evidence-Based Interpretation And ApplicationJanet e. Stout, Ph.D.Special Pathogens Laboratory &university Of Pittsburgh

abstractThe first U.S. standard for the prevention of Legionnaires' disease was published by the American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE) on June 26, 2015. The normative sections of the standard include development of a Water Management Plan for building water systems and devices including open and closed circuit cooling towers and evapo-rative condensers. ASHRAE Standard 188 is a process standard and critical decisions are left to the discretion of the Water Management Team. Information will be shared to help inform these decisions so that they are evidence-based and defensible.

IntroductionANSI/ASHRAE Standard 188-2015 Legionellosis: Risk Manage-ment for Building Water Systems is a good step in preventing Legionnaires’ disease in building water systems. However, the standard provides only minimum requirements and compliance would not insure Legionella control. Building owners are presented with a framework for a risk management approach to the preven-tion of Legionellosis, but are left to rely on their own judgment and knowledge in deciding the most appropriate course of action. This gap between the understanding of the how, what and why of compliance, and the creation of an effective Water Management Program could leave building owners vulnerable to liability claims if cases occur. At the end of the day, building owners could develop a plan without Legionella control.

Implementing the StandardCompliance is based on defining water systems in buildings, de-termining if they are covered by the standard, and going through risk management steps in the standard, but not necessarily dem-onstrating the effectiveness of the plan in controlling Legionella. This represents a critical "gap" that could be closed with in-depth knowledge and decision-making. ASHRAE has placed the standard on "continuous maintenance” providing a mechanism for changes throughout this process that could address these “gaps” in future iterations of the standard.The plan must include confirmation that the Program effectively controls the hazardous conditions throughout the building water systems. Practically speaking, the “hazard” is growth and exposure to Legionella bacteria in the building water systems and subsequent risk of illness. A Water Management Team is formed to develop and implement the Water Management Program for Legionella control

in the building water systems. The standard tells the team what to do, but provides little specific information on how to successfully control Le-gionella in building water systems. Reliance on evidence-based decisions validated from peer-reviewed scientific investigations will strengthen the effectiveness of the Team and defensibility of the Program and close the “gaps.”

the “gaps”Following are a few instances of potential gaps

within the standard: 1. Critical knowledge for effective disease prevention

• The “Water Management Program Team" must have "knowledge of the building water system design and water management as it relates to Legionellosis."

• This critical knowledge of Legionella will not typi-cally be available in-house as most building owners don’t possess the necessary specialized knowledge of Legionella in the built environment.

• For example, the presence and growth of Legionella can be impacted by how water systems are operated and maintained. The Water Management Team should understand the differential effectiveness of control strategies, including defining control limits and monitoring of the water treatment/biocide program for cooling towers and secondary water treatment of the building water system if applicable.

• For the first time, many building owners may be confronted with decisions such as whether or not to install a disinfection system. Selecting the most appropriate and cost-effective technology requires knowledge of Legionella and engineering, as well as water treatment expertise.

2. The microbiology of prevention• In the case of outbreaks involving cooling towers,

the causative agent has almost exclusively been Legionella pneumophila, serogroup 1. The majority of drinking water-associated outbreaks are caused by Legionella pneumophila. Overall, most reported cases of Legionnaires’ disease are caused by L. pneumophila, serogroup 1, with other serogroups (mostly 3, 4 and 6) and Legionella micdadei, and Legionella longbeachae accounting for a small percentage of cases.

• Interpreting the relative risk of these disease-causing strains is important for determining and deploy-ing resources for risk management. The Water

Janet E. Stout


Management Team is tasked with decisions for testing (if, where, how many locations) and results interpretation.

3. Sources of exposure to Legionella • For sporadic community-acquired cases, the public

health threat from improperly managed cooling towers is relatively unknown—with the exception of well-defined outbreaks like the 2015 outbreak in the Bronx in New York City that reportedly caused 138 cases and 16 deaths. In contrast, warm water distribution systems inside buildings are a well-defined source of exposure.

• The risk of illness from building water systems was established with our 1982 publication in The New England Journal of Medicine. We showed that hospitalized patients acquired Legionnaires’ disease from the water in their hospital rooms, not from cooling towers. Since then, the link between illness and exposure to Legionella from building warm water distribution systems in hospitals, hotels, senior high rise apartments, prisons, nursing homes, and private homes has been well established.

• In 2006, a National Research Council report cited Legionella as “the single most common etiologic [disease-causing] agent associated with outbreaks involving drinking water.”

• Recently, the Centers for Disease Control and Pre-vention (CDC) reported that for the period between 2011 and 2012, Legionella accounted for 66% of the

drinking water–associated outbreaks that resulted in 431 cases of illness, 102 hospitalizations, and 14 deaths. All 14 outbreak-associated deaths reported were caused by Legionella, including 12 (86%) cases associated with health care facilities. Legio-nella in building plumbing systems was among the two most commonly identified deficiencies [factors] leading to drinking water–associated outbreaks.

4. ASHRAE 188 does not require Legionella testing to validate that your risk management program is working.

• Studies show that the only reliable way to validate efficacy of your risk management program and residual disinfectant (if you are using one) and the threat from Legionella is to test for Legionella.

• Culture of viable Legionella is the standard method for detection. The International Organization for Standardization: ISO 11731 -1998, “Water Qual-ity - Detection and Enumeration of Legionella” is a method that is ‎accepted internationally as best practice for Legionella culture.

5. ASHRAE 188 requires hazardous conditions be redressed to “acceptable” levels but doesn’t define “acceptable.” That’s left up to the Water Management Team.

The approval of ASHRAE standard 188 has the potential to in-troduce a new era Legionnaires’ disease prevention. The success of this effort will depend upon well-informed Water Management Team and evidence-based Water Management Programs. Such efforts could prevent illness and death from a preventable water-borne disease.


New York Legionella Regulations: Are They Missing The Boat?by Sarah Ferrari

abstractA large outbreak of Legionnaires’ disease in the Bronx in 2015 prompted NYC to enact law and NYS to propose emergency regulations on the registration and maintenance of cooling towers. This paper describes the fundamental character-istics of point sourced vs. potable water sourced outbreaks and discusses the Bronx outbreak from those perspectives. Ultimately a case is made that these new regulations will not have a measurable impact on reducing the incidence of Legionellosis. Rather, more detailed and open-minded investigations of future outbreaks, including investigation of potential potable wa-ter sources, are called for to inform appropriate regulations and disease prevention activities.

IntroductionLegionnaires’ disease (LD) is a severe form of pneumonia which is contracted by inhaling or aspirating water droplets containing Legionella deeply into the lungs. For many years it was believed the disease could be transmitted only by large equipment which emits aerosols or by equipment designed to aerosolize. Thus spas, decorative fountains, grocery misters, spray humidifiers, cooling towers and other aerosol sources were the only water systems investigated when an outbreak occurred. In the early 1980s inves-tigations of potable water systems in hospital outbreaks indicated that the potable water is also a vector in disease transmission, either via aspiration of Legionella from the mouth into the lungs 1 or via inhalation of droplets emitted by sinks and showers. It now appears that many LD outbreaks were initially blamed on cooling towers due to a “detection bias” that has not been widely recognized, and that these outbreaks were actually caused by potable water issues. In more recent years it has been found that the primary source of hospital-acquired Legionnaires’ disease is potable water 2.In the United States there have been requirements to address Le-gionella in hospital potable water systems from the Joint Commis-sion on the Accreditation of Healthcare Organizations (JCAHO), Allegheny County (Pittsburgh), Maryland, New York, and others; however, until recently there have been no similar mandates in the United States for cooling towers. Although not mandated, many industrial groups such as CTI, ASHRAE, and AWT have published best practice guides that describe methods for maintaining equip-ment to minimize the risk of Legionellosis. More than fifty Legionella species have been identified, but not all have been linked to disease. Legionella pneumophila serogroup 1 is the most virulent strain causing the majority of infections3. Virulence varies not only between strains and their subtypes but can also vary within a particular cell. There are two major phases to the life cycle; a non-pathogenic vegetative phase and a virulent transmissive phase. The concepts of ‘infectious dose’ or of ‘relative

Legionella concentrations’ discussed within this paper pertain only to the virulent, or infectious, form of the bacteria.The vast majority of LD occurs as apparently isolated cases. Of cases reported to the CDC, 96% are classified as sporadic and are not typically investigated4. A cluster of cases is classified as an outbreak when two or more people are exposed to Legionella and get sick in the same place at about the same time. Recognized outbreaks of LD are rare; but when they occur, they provide opportuni-ties to understand the epidemiology of the illness and improve prevention strategies. This opportu-nity is wasted if the extensive data that is generated during an outbreak is not evaluated impartially.The recent outbreak in the South Bronx has re-

sulted in New York City enacting a local law5 on the registration and maintenance of cooling towers in the city. Also, the State of New York has proposed emergency regulations for the registration and maintenance of cooling towers state-wide6. As more facts have emerged, it appears that the hastily prepared emergency regulations have fallen victim to the “detection bias” referred to in the first paragraph above and that authorities have not only squandered an opportunity to expand our understanding of the disease but imposed regulations and cost on cooling tower owners that have little chance of reducing the incidence of disease.This paper will describe the outbreak in the Bronx that instigated these regulations. While a specific cooling tower was identified as the source of the original outbreak, two subsequent outbreaks occurred. Potable water in the building where people lived was positively identified as the source for second outbreak. Two months after the third outbreak ended a cooling tower was identified as the source, even though all of the cooling towers in the area had been recently cleaned in accordance with the newly enacted NYC laws.The Bronx outbreak and regulatory response has many similarities to a French outbreak in the winter of 2003-2004. In Pas-de-Calais a large outbreak was attributed to a cooling tower and resulted in the promulgation of regulations for the registration and maintenance of cooling towers. The inconsequential result of those regulations on the reduction of the incidence of disease will also be described in this paper.

Outbreak Characteristicsaerosol Point-Source There have been many Legionnaires’ disease outbreaks traced to an aerosolized point source of the bacteria. Point sources of aerosols include decorative fountains, spas, grocery misters, and cooling towers. Investigation of these outbreaks typically reveals a close relationship between time spent near the source and incidence of infection. A dose-response relationship between exposure and illness has been demonstrated in numerous carefully investigated

Sarah Ferrari


studies. This is particularly true for indoor sources where proxim-ity to the aerosol source has been identified as an essential factor for infection. For cooling tower sources the same relationship exists, i.e., a close correlation between proximity to the source and incidence of disease. However, for some outbreaks where the purported source is a cooling tower there is little spatial correla-tion between the incidence of disease and the alleged source. The unstated assumption is that there is a hidden variable that causes disease seemingly randomly a great distance from the source. This lack of spatial correlation was evident in the South Bronx outbreak where there was no clustering of cases near the purported tower at the Opera House Hotel. What that hidden variable could be is not clear. The following paragraphs describe several well studied outbreaks where, as one would expect, proximity to the source strongly affected the incidence of disease. In 1999 a spa at a floral trade show in the Netherlands was identi-fied as the source of a large outbreak of Legionnaires’ disease. Among exhibitors a close correlation was found between elevated antibodies to Legionella and proximity of their booth to the source. The most important visitor-related risk factor was pausing at the whirlpool spa display7. Clive Brown et al. investigated a 29-case community outbreak of Legionnaires’ disease in 1994 linked to a hospital cooling tower8. This investigation showed that the risk of infection decreased by 20% for each 0.1 miles from the hospital and increased by 80% for each visit to the hospital. The paper described an Aerosol Exposure Unit defined as the ratio of time spent near the source and the distance from the source and found a strong correlation between exposure and incidence of disease. The image in Figure 1 taken from this study illustrates the expected distribution of cases of disease from a single aerosol source. The cases are clustered near the source and taper off rapidly at increasing distance.Proximity was well demonstrated in a 1993 outbreak at a Michi-gan prison which was traced to a hospital cooling tower. Fourteen (0.6%) of 2253 prisoners who used exercise yards each day within 100 yards of the prison hospital were infected, compared with only two (0.1%) of the 2270 inmates who used yards at least 400 yards from the prison hospital.9 This equates to roughly a 50% reduction in infection risk in 0.1 miles.The influence of prevailing wind on aerosol dispersion was ad-dressed by P. Wilmot et al. using geographic information system (GIS) data10. They developed plume dispersion models to help locate a potential cooling tower source during outbreak investiga-tions. A plume refers to the moist exhaust air from a cooling tower. The plume will mix with ambient air as it travels away from the tower becoming more and more dilute. If a case occurs outside of the plume dispersion model “the chance that it originated from that cooling tower remains highly unlikely”. Figure 2 displays a case where the cooling tower would not be considered a likely source.The plume is diluted with increasing distance from the tower re-ducing the concentration of Legionella in the air. Legionella can live only a relatively short time in the air and contamination at a large distance from the tower is unlikely. A person would need to spend sufficient time near to the tower in order to inhale an infec-tious dose of bacteria.Dr. Richard Miller at the University of Louisville has stated: “Legionnaires' Disease, like all infectious diseases, requires a minimum infectious dose in order to cause disease. While the exact number required for humans varies depending on the susceptibility (i.e. immune status) of the individual, it is likely that the number for most individuals is relatively large. It should be apparent from

the ubiquitous nature of this bacterium in the environment, that in order to cause disease, the number of Legionella in the water would need to be much higher than that found in most normal aquatic habitats11.”The virulence of a particular genetic type of Legionella is not a constant and may change during its lifecycle and also may change by exposure to chemicals, heat, or interaction with amoebae. Nev-ertheless, the ubiquity of Legionella in nature implies that everyone has been exposed to at least a low concentration of the bacteria.In addition to dilution of the aerosol over distance, cooling towers have made dramatic improvements in drift eliminator technology. Drift eliminators are the component of cooling towers that separates recirculating water from exiting air. Over a period of about five years ending around 2000 all major manufacturers of factory-built cooling towers developed low-drift eliminators. These modern drift eliminators reduce aerosol emissions by an order of magnitude from the previous generation of towers. If the water in a cool-ing tower was contaminated with 1,000 CFU/ml of Legionella, a person standing on top of the tower and breathing in only tower exhaust for 1 hour would breathe in droplets containing a total of 10 bacteria12. As a comparison of transmission pathways between inhalation and aspiration, a person drinking 4 ounces of water from a potable water source contaminated with only 10 CFU/ml would consume over 1,000 bacteria in the few seconds it took to drink the water. These bacteria would be in the mouth and not in the lungs, but the numbers of bacteria that can enter the body are significantly higher with an aspiration route from potable water than inhalation from a modern cooling tower.As the C. Brown hospital study, the Netherlands flower show study, and the Michigan prison study imply, there should be a dose-response with exposure and incidence of disease. The higher the dose that a particularly susceptible individual receives, the higher will be the likelihood of infection. Also, because of Legionella’s ubiquitous presence in nature, there should be a threshold dosage below which there is no disease.The key characteristics of an aerosolized point source exposure to Legionella are:

1. The original source of the bacteria is colonization of the potable water supply.

2. While many water-based devices could be contaminated due to an upset in the potable water system, only in one will the bacteria find hospitable growing conditions for amplification and susceptible individuals to infect.

3. The bacteria reproduce in an individual aerosol producing device. This usually requires the water in the equipment to reach temperatures that permit amplification.

4. The bacteria are emitted from a single point.There is a strong correlation between incidence of infection and proximity of the individual to the aerosol source in both time and space.While a correlation between proximity to the aerosol source and disease incidence seems fundamental, there are many outbreaks where investigations concluded that this was not the case. This is particularly true of outbreaks attributed to cooling towers. There have been numerous cases, including the July 2015 outbreak in the Bronx, where a cooling tower in the general area was blamed for causing disease without any apparent association of patients with the aerosol source. This lack of spatial correlation between disease incidence and the purported source is an extremely strong indication that the specific cooling tower is not the source of the outbreak.


Potable Water Supply SourceMunicipal potable water systems in the United States and Eu-ropean countries have been very effective at reducing, but not eliminating, waterborne diseases. Potable water is sanitary but not sterile. Disinfection is designed to eliminate many pathogens transmitted by the oral-fecal route, such as cholera and typhoid, however many other bacteria that are natural inhabitants of aquatic environments may survive. Most water pipes contain a layer of biofilm. This biofilm may harbor many non-pathogenic bacteria but can also harbor bacteria such as Legionella. When a known upset occurs, such as a power outage or water main break which causes loss of system pressure, warnings to boil water before using are sent to the system users. There are an estimated 240,000 water main breaks per year in the United States13. Minor upsets such as pressure surges that could disturb biofilms in the pipes may seem unremarkable or go unnoticed yet could release bacteria into the water stream. A study conducted in Wales and northwest England from 2001 to 2002 found a very strong association between self-reported diarrhea and reported low water pressure at the home tap14. The investigators hypothesized that most of the reported episodes of pressure loss were due to main breaks in which contamination entered the distribution system. As the infrastructure ages, the frequency of upsets that can potentially cause contamination in the system has increased. The first incidence in which a municipal water system was found to be the vector for disease transmission occurred during the cholera epidemics in mid-19th century London. Sir John Snow, an English physician, prepared a map of where cholera deaths had occurred. This map15 clearly showed that most of the deaths were in build-ings that received their water from a particular contaminated well that was the source of the disease. However, it took 20 years after Snow generated his map and 8 years after Snow passed away before the correlation between contaminated water and cholera was accepted16. The “detection bias” that cholera was caused by airborne “miasma” was too firmly entrenched in the nineteenth century zeitgeist to be easily dislodged. Figure 3 reproduces Sir John Snow’s map. Cholera fatalities are indicated by small red circles; public drinking water wells are indicated by larger blue circles. The cases are spread uniformly over the area where the contaminated water was used.A more recent potable waterborne infection occurred in Denmark in 200717. There an outbreak of gastroenteritis affected a high percentage of residents in one section of the city. Investigation showed massive contamination of a part of the water distribution system, while other parts of the distribution system appeared to be unaffected. The source was eventually identified as backflow of sewage into that portion of the drinking water system. Figure 4 shows the case map for this outbreak with contamination in one subsection of the water supply.Legionellosis is a waterborne disease. Since the early 1980’s, potable water has been known to be a vector for Legionnaires’ disease. The best studied cases with a potable water source are hospital acquired infections. A hospital’s internal piping system can become contaminated with Legionella from the municipal potable water supply. In warm areas of piping, particularly if there is a biofilm on surfaces or sediment in the system, the Legionella can multiply and occasionally release large numbers of bacteria into the water18. The bacteria may be transmitted to many hospital patients via aspiration of contaminated drinking water or ice chips or, more commonly, via aerosols generated by sinks and showers. Since Legionella are not as virulent as cholera this contamination

may infect only a few patients per year and appear somewhat sporadically. The key factors of a potable water outbreak of Legionnaires’ disease are:

1. The original source of the bacteria is colonization of the potable water supply.

2. While many buildings could be contaminated due to an upset in the potable water system, only in some buildings will the bacteria find hospitable growing conditions for amplification and susceptible individuals to infect.

3. The bacteria reproduce within several building potable wa-ter piping systems to reach infectious levels. This usually requires the water in the system to reach temperatures that permit amplification.

4. The bacteria are emitted at multiple points in multiple build-ings throughout the affected portion of the municipal water distribution system.

5. Since the bacteria are emitted from widespread sources there is a seemingly random distribution of cases of disease all within the same municipal water distribution system.

Potable water has also been identified as the source for Legion-naires’ disease in non-hospital settings, but again usually with very low infection rates. High risk buildings tend to be tall with complex piping and many residents. If Legionella from the municipal water supply colonize sediment and biofilm in a building water system there may be occasional incidents of disease. When multiple cases occur in a single building, the health department will evaluate that building for contamination but rarely investigate other buildings receiving water from the same municipal system. An incident in the municipal potable water supply system that contaminated many buildings over a short period of time could result in an outbreak of disease occurring in the area downstream from the incident over a relatively short period of time.

epidemiology – Not an exact ScienceDetermining the source of a particular outbreak requires gather-ing and sifting through large amounts of information. Patients are interviewed, commonality between sites visited by patients is evaluated, possible sources are examined, and an attempt is made to match the DNA of infectious bacteria grown from patient isolates to that found in the environment. It is only when all of these fall in line that a source of the disease can be definitively imputed. As of this writing, there are approximately 2,000 different Legio-nella pneumophila genotypes known worldwide, but only 10% of those are known to be associated with disease in the US19 20. A DNA match between environmental and patient isolates is not as determinative of the infection source as one might expect. In a specific geographical region there are usually fewer than several dozen genotypes endemic to the water systems21. Since potable water is the ultimate source of the bacteria, many water features in an area can be contaminated with the same genotype of bacteria. In fact particular genetic types of Legionella can become endemic to a given water system with the same genetic match appearing in seemingly unrelated environmental sources. Thus the lack of a DNA match can disprove that a particular feature is the source, but a DNA match on its own cannot prove that it is the source.The difficulty of determining a source was clearly seen in an out-break in South Dakota in 200722. There had been a dramatic in-crease in the incidence of Legionnaires’ disease over a short period of time. There was little in common with the patients except that they spent time in Rapid City. To the investigators this at first ap-


peared to be a likely cooling tower issue, though there was no clear relationship with time spent near a tower and incidence of disease. Cooling towers throughout the city were located and sampled. Many had detectable levels of Legionella and were required to be disinfected. However, none of the towers Legionella were a genetic match to the patients’ isolates. The investigators continued to look for other aerosol sources without success as infections were still occurring. Then the investigators noticed that many of the patients had eaten at the same restaurant during their likely infection period. When investigators revisited the restaurant they sampled a small fountain and found both a high level of Legionella in the fountain and an exact genetic match to the Legionella found in the patients. The fountain was removed and no additional infections occurred.It was fortunate that none of the cooling towers testing positive for Legionella were a genetic match to the particular bacteria that infected patients. Had there been a match, even with little data showing that infected persons spent more time near the towers than the general population, that tower may likely have been de-clared the source and the fountain would have continued to infect restaurant patrons.

2015 Bronx OutbreaksInitial Outbreak in South BronxDuring the summer of 2015 a large outbreak of Legionnaires’ disease occurred in the South Bronx. The onset dates, 2 to 10 days after the infection dates, were between July 8th and August 3rd. The outbreak was officially declared over on August 20th. During this outbreak 133 individuals were diagnosed with the disease with 16 deaths. The graph in Figure 5 is from the NYC Department of Health23. This epidemic curve is characteristic of a common source outbreak where the individuals were exposed to a source of the bacteria over a short period of time. Based on the shape of the curve, this common origin could be an aerosolized source with an upset condition or a municipal water system with an upset condition. The source of this outbreak was identified by the NYC DOH as a cooling tower on the Opera House Hotel. Note that the particular cooling tower at the Opera House Hotel that was identified as the source of the outbreak had a small 7.5 HP fan and was equipped with modern low-drift eliminators that reduce by an order of magnitude the quantity of drift that the tower emits. The cooling tower was disinfected on August 1st with the last reported case onset on August 3rd. The infection date for all of these cases could have been prior to the cleaning of the cooling tower, though the declining case rate in late July indicates that the outbreak had likely stopped before the tower was disinfected. It is likely that none of the testing and cleaning of cooling towers demanded by the NYC DOH had any effect on ending the initial outbreak. The cases were distributed fairly uniformly over a large area of the South Bronx. The NYC DOH has provided the map in Figure 6 showing approximately 85 of 133 case locations and the locations of cooling towers.23 Circles represent cases and triangles cooling towers with the large red triangle at the location of the cooling tower at the Opera House Hotel. Red circles are cases where ge-netic testing of the Legionella was performed. The patient samples and the bacteria found at the Opera House Hotel were of the same genetic type, but as discussed above, genetic typing alone can rule out a potential source but cannot, on its own, definitively establish a source. In fact the particular strain found in the patients and in the Opera House Hotel cooling tower was also found in other features in the area and had caused previous outbreaks in NYC24.

A particular strain is likely to be present throughout the potable water system, so commonality in activity among patients relative to a particular potential source must be established in order to deduce the specific source(s) of infections.The particular cooling tower located at the Opera House Hotel circulated water at 800 gpm; at full fan power it moves 49,700 CFM; and it is equipped with drift eliminators that reduce the drift to less than 0.001%. The drift rate then is: 0.00001 x 800 gpm x 3785 ml/gal = 30 ml/min. At full fan power this drift results in a concentration of: 30/49700CFM x 1CF/7.48 gal x 1 gal/3.785 liters = 0.00002 ml of drift /liter of exhaust air. If each ml contained 1000 CFU of Legionella, then on average there would be 0.02 Legionella per liter of undiluted tower exhaust air or in every 50 liters of air there would be a single bacteria. If a typical person has a 500 ml tidal volume and takes 15 breaths per minute, and if they were breathing only undiluted tower exhaust for an hour, they would inhale 0.5 x 15 x 60 = 450 liters of air or only about 10 bacteria. As one moves away from the tower the exhaust air containing the drift becomes more dilute and a person would re-quire much longer time in the diluted exhaust air to inhale a similar number of bacteria.12 Recall that proximity has been well established in aerosol point-sourced outbreaks, with reduced infection rates at increasing distance from a source. The circle around the Opera House Hotel in Figure 6 indicates a 0.1 mile radius. This is the area where one would expect the highest cluster of cases, but there is no cluster of cases at or immediately adjacent to the hotel. There is no gradient with radial or, presuming wind, with directional distance. Rather, the cases appear randomly across a broad area, producing a case map with more similarity to the waterborne cholera outbreak. Cool-ing towers and fountains were sampled as part of the investigation, but potable water was not. City officials repeatedly claimed that “the drinking water is unaffected”. This claim was not substanti-ated with data by NYC because no testing of potable water was performed. In fact it was dramatically disproven in only a few weeks when the cases associated with the Melrose Houses were more fully evaluated.

Outbreak at Melrose HousesThere was a second outbreak of four cases of Legionnaires disease at the Melrose Houses in the South Bronx identified after the initial outbreak. An arrow in Figure 6 indicates the location of the Melrose Houses, less than 0.4 miles from the Opera House Hotel. The first case in the Melrose Houses outbreak occurred in March 2015 and was not investigated at that time. Two more cases occurred during the July outbreak and were originally included in that outbreak, and the latest occurred in late August after the July outbreak was declared over. No potable water sources were investigated by the NYC DOH until four cases were identified at a single location at Melrose Houses. When the potable water at Melrose Houses with over two thousand residents was investigated, Legionella were found in the potable water and the potable water was positively identified as the source of infection. Point-of-use water filters were installed on all faucets and showerheads and a copper-silver ioniza-tion system was installed in the buildings’ potable water piping. In spite of 3 cases occurring in the same facility over a period of only a few months, potable water was not sampled. It was only after the original outbreak was declared over yet an additional case occurred that the potable water was sampled and identified as the source of the infections.


Outbreak at Morris ParkA third outbreak of Legionnaires’ disease occurred in the Morris Park neighborhood of the Bronx. Morris Park is about 4 miles from the Opera House Hotel in the East Bronx. There were 13 cases in this outbreak and 1 death. Figure 7 shows the epidemic curve for this outbreak. The onset dates for all but one of the cases included in the outbreak were between September 14th and September 21st with infection occurring 2 to 10 days prior. On August 6 a city wide order had been issued which mandated that:“Regardless of the outcome of the evaluation required by item (2) above, direct the environmental consultant to carry out a disinfection/treatment sufficient to remove organic material, biofilm, algae and other contami-nants and disinfect in a manner sufficient to control for the presence of Legionella organisms within 14 days of receipt of this letter”25

Due to this city-wide order, all cooling towers in the area had been dis-infected by August 20th a few weeks prior to the earliest possible date of infection. If indeed a cooling tower was responsible for the outbreak, then the remediation requirements in the NYC newly enacted laws were ineffective at preventing an outbreak. If potable water or another feature was the source or sources then the newly enacted laws which focus only on cooling towers actually hindered a proper investigation of the outbreak.In late September, thirty-five cooling towers in the area were tested for Legionella and 15 had detectable levels of the bacteria. These 15 towers were disinfected for a second time beginning September 29th, significantly after the outbreak had ended. A press release issued by the NYC DOH on November 20, fully two months after the outbreak had ended, identified a cooling tower as the source26. With this outbreak it is unequivocally clear that none of the testing and cleaning of cooling towers demanded by the NYC DOH had any effect on ending the outbreak. In the large South Bronx outbreak and also in the Morris Park outbreak, infection occurred over a relatively large area in a short time-span. Al-though the pattern could be due to an upset in the municipal water system simultaneously infecting a large number of buildings, the only sources that were investigated were aerosol point sources such as cooling towers, spas and fountains.

Impact of regulations on public healthIncidence of Disease in the united States and europeLegionnaires’ disease is a reportable illness in the United States and many European Countries. Records are made available by the CDC27 in the US and the ECDC28 in Europe. For 5 European countries these records go back at least to 2003. Figure 8 shows the reported incidence of LD for these countries and the US in illness per 100,000 of population.There are many factors which can affect the shape of the curves besides actual incidence of disease. Legionnaires’ disease is believed to be un-derreported. The US reported incidence rate has steadily increased over the period shown. The CDC believes that this may be partially due to:“An increasing population of older persons contributed to the increase in reported legionellosis cases. Other factors that might have contributed include an increasing population of persons at high risk for infection; improved diagnosis and reporting, possibly stimulated by the 2005 CSTE endorsement of more timely and sensitive legionellosis surveillance; and increased use of urine Legionella antigen testing29”. The graph in Figure 8 shows that there is little difference in the incidence rate of Legionnaires’ disease between Western Europe and the United States. This lack of difference exists in spite of burdensome regulation of cooling towers which has been in place in Europe for many years.

Legionella regulations in FranceFrance provides an interesting study of the effects of cooling tower regula-tions on the incidence of disease. Guidelines to improve underreporting of the disease were written in 1997 along with introduction of the urinary antigen detection test30. In the winter of 2003 to 2004 a large outbreak with 86 confirmed cases and 18 fatalities occurred in Pas-de-Calais, France31. An industrial cooling tower was implicated as the source for the

contamination. As a result of this outbreak regulations were promulgated for the control of cooling towers. Cooling tower regulations for hospitals had been enacted in 2003 but with the Pas-de-Calais outbreak they were extended to all cooling towers32. The 2004 regulations require frequent testing of cooling towers for Legio-nella. The regulations mandate monthly testing for Legionella unless 12 consecutive monthly tests are less than 1 CFU/ml then the testing can be reduced to quarterly. If the reading exceeds 100 CFU/ml the tower must be immediately shut down and cleaned. More frequent testing is then required until the system again meets the strict low limits.The graph in Figure 9 indicates that the incidence rate for LD infection has been hovering around 2 per 100,000 of population for over a decade. After the regulations were issued at the end of 2004, there was an increase in the reported incidence of LD. This could well be due to a heightened awareness of the disease from both the issuing of the regulations and the widely publicized outbreak at Pas-de-Calais. There has been a gradual decline in the reported incidence since 2005, but a dramatic reduction has not been observed since the regulations were implemented. The author be-lieves that these results indicate that the cooling tower regulations had little to no effect on the incidence of sporadic cases of Legionnaires’ disease.

ConclusionThere are outbreaks of Legionnaires’ disease which have been clearly linked to a sole aerosolized source of bacteria. In these outbreaks, acute proximity and duration were shown to govern exposure and incidence of Legionnaires’ disease. However, there are many outbreaks attributed to a cooling tower source which do not adhere to these rules. These outbreaks have case profiles which are more random and cover larger areas. These outbreaks mimic the documented profile of certain potable water outbreaks where a single ‘upstream’ source contaminates multiple exposure sites. The source(s) of future Legionnaires’ disease outbreaks must be inves-tigated more thoroughly, exploring the possibility of multiple exposure sites including potable water, in order to advance our understanding of LD transmission. The traditional epidemiological models that assume cau-sality with a genetic match but with only a tenuous exposure mechanism have resulted in the promulgation of regulations that have not resulted in a significant reduction in the incidence of disease. Increased awareness and the issuing of explicit orders for the care of cooling towers did not prevent the outbreaks from occurring at Melrose Houses or in Morris Park. Strict cooling tower regulations imposed in France after the Pas de Calais outbreak have not resulted in any significant reduction of disease. Is it time we say, perhaps, that it is not always the cooling tower? And what of the other 96% of reported LD cases, those considered sporadic? A 2006 report issued by the National Academy of Sciences states “Communi-ties should squarely address the problem of Legionella, both via changes to the plumbing code and new technologies.”14 The report goes on to call for research projects which specifically address potential problems arising from premise plumbing. Regarding outbreaks the report states, “Environmental assessments of outbreaks should begin to incorporate new insights and al-low possible cause-and-effect relationships to be established.” This would include a much greater emphasis on dose reconciliation in outbreaks in order to develop basic practical data on dose-response relationships.Clearly the scientific community recognizes the health risks associated with premise plumbing, or building potable water systems. These potential risks were also well-recognized by the team of experts who contributed to ASHRAE Standard 188 Legionellosis: Risk Management for Build-ing Water Systems. The Standard provides minimum Legionellosis risk management requirements for buildings and their associated potable and non-potable water systems. Subsequent to the recent outbreaks, NYC adopted a small subset of the Standard, the portion addressing cooling towers. Adoption of the full Standard, as intended by the expert authors, is necessary in order to have a significant positive effect on public health.


Figure 1 – Case Map from Aerosolized Point-Source

Figure 2 – Case Outside Dispersion Model

Figure 3 – Cholera Epidemiology London 1854

Figure 4 – Gastroenteritis Epidemiology Denmark 2007

Figure 5 – Epidemic Curve of Initial Outbreak in South Bronx 2015

Figure 6 – Map of Cases and Cooling Towers in South Bronx July 2015 Outbreak


Figure 7 – Epidemic Curve for the Third Outbreak in East Bronx 2015

Figure 8 – Incidence of Legionnaires’ Disease in the US and Western European Countries

Figure 9 – Incidence of Legionnaires’ Disease in France

references:1. Stout, J. et al. (1982) Ubiquitousness of Legionella Pneumophila in

the Water Supply of a Hospital with Endemic Legionnaires’ Disease, New England Journal of Medicine (Feb. 25).

2. Sabria, M; Yu, V. (2002) Hospital-acquired Legionellosis: solutions for preventable infection, THE LANCET (Jun).

3. Yu et al. (2002) Distribution of Legionella species and serogroups isolated by culture in patients with sporadic community-acquired legionellosis: an international collaborative survey. J Infect Dis, 186:127–128

4. CDC Morbidity and Mortality Weekly Report (2015) August 14.5. Local Laws of the City of New York No. 77, Article 317 Cooling

Towers6. NYS Department of Health Emergency Rule Making, Protection

Against Legionella, HLT-35-15-00005-E, NYS Register/December 2, 2015.

7. Den Boer, J. (2002) A Large Outbreak of Legionnaires’ disease at a Flower Show, the Netherlands, 1999, Emerging Infectious Diseases (Jan).

8. Brown, C. et al. (1999) A Community outbreak of Legionnaires’ disease linked to hospital cooling towers: an epidemiological method to calculate dose of exposure, International Epidemiological Associa-tion Vol 26:353-359.

9. CDC Morbidity and Mortality Weekly Report (1994) July 15.10. Wilmot, P. et al., (2004) Modelling Cooling Towers Risk for Legion-

naires’ Disease using Bayesian Networks and Geographical Informa-tion System, University of Adelaide.

11. Miller, R., Reducing the risk of Legionnaires’ Disease, Environmental Safety Technologies

12. Bugler, T. et al. (2008) Cooling Towers, Drift, and Legionellosis, IWC-08-21, International Water Conference.

13. 2013 Report Card for America’s Infrastructure. American Society of Civil Engineers. Web. 2 Nov. 2015.

14. Committee on Public Water Supply Distribution Systems: Assessing and Reducing Risks, Water Science and Technology Board, Division on Earth and Life Studies, National Research Council, National Academies Press, Dec 22, 2006.

15. http://www.udel.edu/johnmack/frec480/cholera/cholera2.html16. Competing Theories of Cholera. UCLA Department of Epidemiology,

School of Public Health. Web. 2 Nov. 2015.17. Vestergaard, LS. et al. (2007) Outbreak of Severe Gastroenteritis

With Multiple Aetiologies Caused by Contaminated Drinking Water in Denmark, January 2007, Eurosurveillance, Vol 12 Issue 13.

18. Stout, J. et al. (1984) Ecology of Legionella pneumophila within Water Distribution Systems, Applied and Environmental Microbiol-ogy (Oct).

19. Kozak-Muiznieks N. et al. (2013) Prevalence of Sequence Types among Clinical and Environmental Isolates of Legionella pneu-mophila Serogroup 1 in the United States from 1982 to 2012, Journal of Clinical Microbiology.

20. EWGLI Sequence-Based Typing (SBT) Database for Legionella pneumophila. The European Working Group for Legionella Infec-tions. Web. 21 Dec 2015.

21. Drenning S. et al. (2001)Unexpected Similarity of Pulsed-Field Gel Electrophoresis Patterns of Unrelated Clinical Isolates of Legionella pneumophila, Serogroup 1, Journal of Infectious Disease.

22. O’Loughlin, R. E. (2007) Restaurant outbreak of Legionnaires’ disease associated with a decorative fountain: an environmental and case-control study, BMC Infectious Diseases (Aug).

23. http://www.nyc.gov/html/doh/html/diseases/cdlegi.shtml24. Private Communications with CDC.25. NYC DOH Order of the Commisioner, August 6, 2015.26. “Bronx Psychiatric Center Cooling Tower Blamed For Morris Park

Legionnaires’ Outbreak”, CBS New York, 20 November 2015, Web, 12 Dec. 2015.

27. Morbidity and Mortality Weekly Report (2015) October 23.28. ECDC Annual Surveillance Report Legionnaires’ disease in Europe.29. CDC Morbidity and Mortality Weekly Report (2011) August 19.30. Campese, C. et al. (2011) Progress in the surveillance and control of

Legionella infection in France 1998-2008, International Journal of Infectious Diseases.

31. Eurosurveillance (2004) Vol.9 Issue 1-3.32. Arrêté du 13 décembre 2004 relatif aux installations de refroidisse-

ment par dispersion d’eaudans un flux d’air soumises à autorisation au titre de la rubrique no 2921, Journal Officiel de la République Français.

acknowledgementsThe author gratefully acknowledges Dr. Claressa Lucas of the Centers for Disease Control and Prevention National Center for Infectious Respira-tory Diseases, Division of Bacterial Diseases for her careful review of the technical portions of this paper.


Cooling Technology InstituteLicensed Testing Agencies

For nearly thirty years, the Cooling Technology Institute has provided a truly independent, third party, thermal performance testing service to the cooling tower industry. In 1995, the CTI also began providing an independent, third party, drift performance testing service as well. Both these services are administered through the CTI Multi-Agency Tower Performance Test Program and provide comparisons of the actual operating performance of a specific tower installation to the design performance. By providing such information on a specific tower installation, the CTI Multi-Agency Testing Program stands in contrast to the CTI Cooling Tower Certification Program which certifies all models of a specific manufacturer's line of cooling towers perform in accordance with their published thermal ratings.

To be licensed as a CTI Cooling Tower Performance Test Agency, the agency must pass a rigorous screening process and demonstrate a high level of technical expertise. Additionally, it must have a suf-ficient number of test instruments, all meeting rigid requirements for accuracy and calibration.Once licensed, the Test Agencies for both thermal and drift testing must operate in full compliance with the provisions of the CTI License Agreements and Testing Manuals which were developed by a panel of testing experts specifically for this program. Included in these requirements are strict guidelines regarding conflict of interest to insure CTI Tests are conducted in a fair, unbiased manner.Cooling tower owners and manufacturers are strongly encouraged to utilize the services of the licensed CTI Cooling Tower Performance Test Agencies. The currently licensed agencies are listed below.

Licensed CTI Thermal Testing Agencies

License Type A, B*

Clean air engineering7936 Conner Rd, Powell, TN 37849

800.208.6162 or 865.938.7555Fax 865.938.7569

www.cleanair.com / [email protected]: Kenneth (Ken) Hennon

Cooling tower technologies Pty LtdPO Box N157, Bexley North, NSW 2207

AUSTRALIA+61.2.9789.5900 / (F) +61.2.9789.5922

[email protected]: Ronald Rayner

Cooling tower test associates, Inc.15325 Melrose Dr., Stanley, KS 66221

913.681.0027 / (F) 913.681.0039www.cttai.com / [email protected]: Thomas E. (Tom) Weast

McHale & associates, Inc.4700 Coster Rd, Knoxville, TN 37912

856.588.2654 / (F) 865.934.4779www.mchale.org / [email protected]

Contact: Jared Medlen * Type A license is for the use of mercury in glass thermometers

typically used for smaller towers. Type B license is for the use of remote data acquisition devices

which can accommodate multiple measurement locations required by larger towers.

Licensed CTI Drift Testing Agencies

Clean air engineering7936 Conner Rd, Powell, TN 37849

800.208.6162 or 865.938.7555Fax 865.938.7569

www.cleanair.com / [email protected]: Kenneth (Ken) Hennon

McHale & associates, Inc.4700 Coster Rd, Knoxville, TN 37912

856.588.2654 / (F) 865.934.4779www.mchale.org / [email protected]

Contact: Jared Medlen


As stated in its opening paragraph, CTI Standard 201... "sets forth a program whereby the Cool-ing Technology Institute will certify that all models of a line of water cooling towers offered for sale by a specific Manufacturer will perform thermally in accordance with the Manufacturer's published ratings..." By the purchase of a "certified" model, the User has assurance that the tower will perform as specified, provided that its circulating water is no more than acceptably contaminated-and that its air supply is ample and unobstructed. Either that model, or one of its close design family members, will have been thoroughly tested by the single CTI-licensed testing agency for Certification and found to perform as clained by the Manufacturer.CTI Certification under STD-201 is limited to thermal operating conditions with entering wet

bulb temperatures between 12.8oC and 32.2oC (55oF to 90oF), a maximum process fluid temperature of 51.7oC (125oF), a cooling range of 2.2oC (4oF) or greater, and a cooling approach of 2.8oC (5oF) or greater. The manufacturer may set more restrictive limits if desired or publish less restrictive limits if the CTI limits are clearly defined and noted int he publication.Those Manufacturers who have not yet chosen to certify their product lines are invited to do so at the earliest opportunity. You can contact Virginia A. Manser, Cooling Technology Institute at 281.583.4087, or vmanser.cti.org or PO Box 681807, Houston, TX 77268 for further information

Licensed CTI Thermal Certification Agencies agency Name Contact Person telephone/ address Website / email Fax

Clean air engineering Kenneth (Ken) Hennon 800.208.6162 or 7936 Conner Rd www.cleanair.com 865.938.7555 Powell, TN 37849 [email protected] (F) 865.938.7569

Cooling tower test associates, Inc. Thomas E. (Tom) Weast 913.681.0027 15325 Melrose Dr. www.cttai.com (F) 913.681.0039 Stanley, KS 66221 [email protected]

McHale Performance Jared Medlen 865.588.2654 4700 Coster Rd www.mchale.org (F) 865.934.4779 Knoxville, TN 37912 [email protected]

Cooling Technology Institute Certification ProgramStD-201 for thermal Performance

Cooling towers are used extensively wherever water is used as a cooling medium or pro-cess fluid, ranging from HVAC to a natural draft cooling tower on a power plant. Sound emanating from a cooling tower is a factor in the surrounding environment and limits on those sound levels, and quality, are frequently specified and dictated in project specifica-tions. The project specifications are expected to conform to local building codes or safety standards. Consequently, it may be in the interest of the cooling tower purchaser to contract for field sound testing per CTI ATC-128 in order to insure compliance with specification requirements associated with cooling tower sound.

Cooling technology InstituteSound testing

Licensed CtI Soundtesting agencies Clean air engineering McHale Performance 7936 Conner Rd 4700 Coster Rd Powell, TN 37849 Knoxville, TN 37912 800.208.6162 or 865.938.7555 865.588.2654 Fax 865.938.7569 Fax 865.934.4779 www.cleanair.com www.mchale.org [email protected] [email protected] Contact: Kenneth (Ken) Hennon Contact: Jared Medlen


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cti journal, vol. 37, no. 2 · 1934 - 2016 arthur frederick brunn, jr., 81, of beaumont, died...

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