182 C O M M I T T E E P E R S O N N E L ' FL-I

Report of Committee on

• Flammable Liquids

C o r r e l a t i n g C o m m i t t e e

P a u l C. L a m b , Chairman 140 Dwight Place, Englewood, N J 07631

Miles E. W o o d w o r t h , ~ ,~ecretary National Fire Protection Assn., 470 Atlantic Ave., Boston, MA 02210

G. E. Ca in , Manufactur ing Chemists' Assn. C l i f ton P. Ge ise r t , Insurance Services

Office of Illinois D o n a l d J o h n s o n , Western Oil & Gas Assn. F. O. K u b l a s , Glidden-Durkee, Div. of SCM

Corp.

J . C. S a n d e r s , Fire Marshals Asso, of N. America

W. J . S m i t h , Underwriters' Laboratories, Inc.

E. C . S o m m e r , American Petroleum In- stitute

Dr. ln~ . G e r t M a g n u s , ~ Mannheim, Germany

tNonvot ing Members

Sec t i ona l C o m m i t t e e o n M a i n t e n a n c e a n d R e p a i r

D o n a l d M. J o h n s o n , Chairman Standard Oil Co. of C&fifornls, 555 Market St., San Francisco, CA 94105

(rep. Westarn Oil & G ~ Assn.)

Miles E. W o o d w o r t h , t Secretary National Fire Protection Assn., 470 Atlantic Ave., Boston, MA 02210

J~ A. Cederva l l , Underwriters' Laboratories, Inc.

,Joe Egger , Fire Marshals Assn. of N. Amertes

H. J . Ko lodne r , Manufactur ing Chemiste' Assn.

R o b e r t J . Nespeco, National Oil Fuel Institute, Inc.

Felix P. R a c z a k , Fire Marshals Assn. of N. America

O. M. Slye, American Petroleum Inst i tute P a t R. Wrig ley , National Petroleum Re-

finers Aeen.

A l t e r n a t e s

R o b e r t D. L y n c h , National Oil Fuel In- J . F . M c K e n n a , American Petroleum In- stitute (Alternate to R. Nespeco) stitute (Alternate to O. M. Slye)

~Nonvo~ng

183 FL-2 REPORT OF COMMITTEE ON FLAMMABLE LIQUIDS

The report of the Committee on Flammable Liquids is in two parts.

Par t I, prepared by the Sectional Committee on Maintenance and Repair, proposes a revision to the Stafidard Procedures for Cleaning or Safeguarding Small Tanks and Containers, NFPA No. 327-1970 edition.

Par t I has been submitted to letter ballot of the Sectional Committee on Maintenance and Repair which consists oJ 8 voting members oJ whom 8 have voted affirmatively.

Par t I also has been submitted to ballot of the Flammable L,quids - Correlating Committee which consists of 8 members of whom 8 have voted

affirmatively.

Par t II) also prepared by the Sectional Committee on Mainte- nance and Repair, proposes editorial updates on the Control of Flammable and Combustible Liquids and Gases in Manholes, Sewers and Similar Underground Structures, NFPA No. 328-1970 edition.

Par t I I has been submitted to letter ballot of the Sectional Committee on Maintenance and Repair which consists oJ 8 voting members oJ whom 6 have voted affrmatively and Messrs. Nespeco and Raczak have not returned thez) ballots.

Par t I I also has been submitted to ballot of the Flammable Liquids Correlating Committee which consists of 8 members of whom 8 have voted affirmativety.

184 GENERAL PROVISIONS 327-5

Report of Committee on Flammable Liquids. ,

Part I

Standard Procedures for

Cleaning or Safeguarding

Small Tanks and Containers

N F P A N o . 3 2 7 - - 1 9 7 5

Chapter i General Provisions

1-1 Purpose. The procedures described herein are recommended for the safe removal of flammable vapors, liquids, gases, or solids from small tanks, drums or other containers, or safeguarding these vessels by other means. Such procedures are to permit hot work (welding or cutting) or other work which may create a potential fire or explosion hazard; and where necessary, for change of service or where desired for any other purpose.

1-2 Scope. These procedures are intended to apply only to the cleaning or safeguarding of small tanks or containers that cannot be entered, and that have contained flammable or combustible liquids, gases, or solids.

They are not intended to apply to the cleaning or safeguarding of tanks that may be entered; tank vehicles or tank cars; tanks, bunkers or compartments on ships or barges; gas plant equipment or gas distributing systems for natural or manufactured gas; nor to compressed and liquefied gas cylinders. Procedures for cleaning or safeguarding some of these vessels are covered separately in the following publications:

(a) Cleaning Petroleum Storage Tanks, RP 2015, published by the American Petroleum Institute, 1801 K Street, N.W., Washing- ton, D.C. 20006.

327-0 C L E A N I N G S M A L L T A N K S AND C O N T A I N E R S

185

(b) Cleaning Tank Vehicles Used for Transportation of Flam- mable Liquids, Fourth Edition, 1967 RP 2013, published by the American Petroleum Institute, 1801 K Street, N.W., Washington, D.C. 20006. This procedure is also recommended for cleaning tank vehicles and tank cars used for transporting liquefied petroleum gas.

(c) Tanks, Bunkers or Compartments on Ships and Barges. The NFPA Standard No. 306, Control of Gas Hazards on Vessels to be Repaired, available from the National Fire Protection Associ- ation, 470 Atlantic Ave., Boston, MA 02210, should be followed for cleaning ships' tanks.

(d) Gas Plant Equipment or Gas Distribution Systems for Natural or Manufactured Gas. The standards of the American Gas Association, "Purging Principles and Practices, 1954," published by the American Gas Association, 1515 Wilson Blvd., Arlington, VA 22209, should be followed for removing from and returning to service gas equipment.

(e) Compressed and Liquefied Gas Cylinders. Hot work on gas cylinders should be performed only by a regular cylinder manu- facturer in accordance with the U.S. Department of Transportation Regulations.

1-3 Definitions. For the purpose of these recommended pro- cedures, the following definitions shall apply:

Bonding shall mean the electrical interconnection (bare metallic bond wire or metal to metal contact) between two conductors other- wise electrically insulated from or remotely electrically connected to each other.

Flammable gas shall mean any substance that exists in the gaseous stage at normal atmospheric temperature and pressure and which is capable of being ignited and rapidly oxidized when mixed with proper proportions of air or oxygen.

Hazardous work shall mean, when not otherwise identified, both hot work and cold work.

(a) Hot Work. Hazardous work involving open flames, cutting and welding using open flames or electric arcs, grinding, buffing or open unguarded sources of ignition.

(b) Cold Work. Hazardous work involving metal cutting tools such as chisels, saws or other similar operations which may create hot metal sparks or surfaces from friction or impact of metal on metal.

186 GENERAL PROVISIONS 327-7

Inert gas shall mean any gas which is nonflammable, chemically inactive, and noncontaminating for the use intended.

Iner t lng shall mean the use of an inert gas to render the atmos- phere of an enclosure substantially oxygen-free or to reduce the oxygen content to a point at which combustion cannot take place.

Liquid shall mean, when not otherwise identified, both flammable and combustible liquids.

(a) Combustible Liquid. Combustible liquid shall mean any liquid having a flash point at or above 100°F (37.8°C).

(b) Flammable Liquid. Flammable liquid shall mean any liquid having a flash point below 100°F (37.8°C) and a vapor pressure not exceeding 40 lb. per sq. in. absolute at 100°F (37.8°C).

Purg ing shall mean the process of displacing the flammable vapors from an enclosure.

1-4 Purpose and Extent of Cleaning. Small tanks and con- tainers may be cleaned in preparation for hazardous work, change in tank or container service, or for other purposes.

1-4.1 Cleaning in Preparation for Hazardous Work. Clean- ing of a tank or container prior to hazardous work which may involve a potential source of ignition shall remove flammable vapors and liquid or solid residues which might release further flammable vapors.

1-4.2 Cleaning for Change in Service. Cleaning of a tank or container to remove residues which could contaminate new ma- terials in the tank or container. Particularly important is cleaning to remove residues which may be incompatible With new materials to be placed in the tank or container. Selection of a cleaning pro- cedure shall take into consideration the chemical nature and characteristics of the known or suspected contaminating material.

1-4.3 Cleaning for Other Purposes. In some cases, such as for transportation or storage of empty containers, it may be neces- sary to clean a tank or container. Selection of a cleaning procedure shall take into consideration the desired use of the container, chemical nature and characteristics of the new material, and the known or suspected contaminating material.

327-8 CLEANING SMALL T A N K S AND CONTAINERS

187

Chapter 2 General Precautions

2-1 Work on tanks or containers that have held liquids or gases shall be done under the supervision of persons who understand the fire and explosion potential and the workmen shall be sufficiently skilled to safely carry out the operations necessary. The character- istics of the previous contents of the tank or container shall be determined.

2-1.1 Before cleaning work is started on tanks or containers that may be under pressure, the pressure shall be reduced to atmos- pheric. The tank or container contents shall be vented to a safe location.

2-1.2 Information on cleaning tanks or containers that have held nitrocellulose, pyroxylin solutions, nitrates, chlorates, perchlo- rates, peroxides, and other materials which may contain enough oxygen to support combustion in an otherwise inerted atmosphere shall be obtained before cleaning operations are started.

2-1.3 Tanks or containers which have contained reactive or un- stable materials shall not be cleaned until information is obtained on safe cleaning procedures. Special precautions are required on the selection of nonreactive cleaning materials.

2-1.4 The cleaning procedure selected from Chapter 3 shall establish and maintain a safe atmosphere within the tank or con- tainer. The atmosphere shall be compatible with the intended pur- pose of the tank or container cleaning operation.

2-1.5 Special precautions are required after cleaning the tank or container which shall be inspected internally to determine the effectiveness of cleaning. Such inspection may be made with the aid of a flashlight or with one of several forms of internal inspection lamps approved for Class I, Division 1 hazardous locations, or a mirror may be used to reflect light into the container.

2-2 Any equipment which may provide a source of ignition shall not be permitted within the vicinity of a tank or container being cleaned until the area has been tested and found vfipor free.

188 GEXER4L PROVISIONS 327-9

2-3 To insure a safe condition within the tank or container, tests for flammable vapors, generally with a combustible gas indi- cator, shall be made: (1) before commencing alterations or repairs; (2) immediately before and after starting any welding, cutting, or heating operations; and (3) frequently during the course of the work. All work shall be stopped immediately when the presence of flammable vapors is indicated by tests with a combustible gas indicator. The source of the vapor release shall then be located and removed.

2-3.1 Tanks or container's which have held high flash point liquids may become hazardous during cutting or welding operations or when heated.

327-10 C L E A N I N G S M A L L T A N K S A N D C O N T A I N E R S

189

Chapter 3 Cleaning Procedures

3-1 General . Cleaning operations shall be conducted in the open if practicable. Where •indoor cleaning is necessary, ventilation shall be sufficient to prevent the accumulation of flammable vapors.

3-1.1 Disconnect or remove sources of ignition from the vicinity of the tank or container before venting or cleaning operations are started.

3-1.2 Take apl6ropriate steps to protect personnel from harm- ful exposure to toxic or corrosive vapors or gases.

3-1.3 Empty and drain the tank or container of all contents. This should include removal of liquids or gases from any internal piping, traps, and standpipes. Flushing with a proper cleaning liquid may be necessary.

• 3-1.4 Disconnect, plug, or blank off all piping and other con- nections to the tank or container being cleaned. Reliance shall not be placed o n valves to prevent a flow of material unless a double block valve and bleeder arrangement is available.

3-1.5 Safely dispose of all liquid or solid residue material.

3-2 Removal of Flammable Vapors

3-2.1 Displacement with Water . Where the liquid or gas previously contained is known to be readily displaced by or easily soluble in water, it can be removed by completely filling the con- tainer .with water .and draining, repeating the operation several times. An example of a readily displaced gas is liquefied petroleum gas; examples Of water soluble liquids are acetone and ethyl alcohol. Under some.circumstances hot work may be performed on tanks or containers completely filled with water. When this method is used, extreme care should be taken to eliminate any vapor spaces by pro- viding proper venting or b y positioning of container during the filling operation.

190 CLEANING PROCEDURES 527-11

3-2.2 Displacement with Air. Gas freeing ma); be accom- plished by purging with air and a safe atmosphere may be sustained by continuing the ventilation. When openings of sufficient size are available, air movers that do not provide an ignition source may be attached so that air is drawn through one opening and discharged through another opening. When openings cannot accommodate an air mover the container may be purged by introducing air so that it will circulate through the tank or container and be discharged to the outside. In air purging the concentration of vapor in air in the tank or container may go through the flammable range before a safe atmosphere is obtained; therefore, all precautions shall be taken to insure that all ignition sources have been removed from the vicinity. An effective bond shall be maintained between the air mover and the tank or container being cleaned.

3-2.3 Displacement with Ine r t Gas. To minimize the hazards of passing through the flammable range, the tank or container can be first purged with an inert gas, and then ventilated with air..

3-2.4 Flammable vapors may be displaced by an adequate supply of steam in accordance with 3-4.1.

3-3 Ine r t lng of Vapor "Space. I f properly used, inert ing is a means of safeguarding a container so it may be worked on by reduc- hag the oxygen content,to the point where combustion cannot take place. However, individuals in direct eharge of ' the work must be thoroughly famifiar with the limitations and characteristics of the inert gas being used. The oxygen content shall be maintained at substantially zero during the entire period when work is i n p r o - gress. Attempting such work without proper knowledge or equip- ment can be hazardous since it may create a false sense o f security. Permissible inert gases commonly used are carbon dioxide and nitrogen. Both may be obtained in cylinders and in truck tanks, and carbon dioxide may be obtained in solid forms. Briefly, the procedure for inerting is as follows:

• 3-3.1 Close all openings in the tanks or containers with the exception of the filling connection and vent.

3-3.2 Cracks or other damaged sections should be plugged.

3-3.3 Introduce the inert gas into the tank or container through a pipe~or hose extending to a point near the bot tom of the tank or container so that the inert gas produces a substantially,

327-12 C L E A N I N G SMALL T A N K S AND CONTAINERS

191

oxygen free atmosphere in the container. Any metal components of the filling pipe or hose shall be bonded to the tank or container.

3-3.4 When using carbon dioxide, low pressure shall be used to avoid generation of static electricity~ Portable carbon dioxide extinguishers shall not be used for this purpose.

3-3.5 If solid carbon dioxide is to be used, it sl~ould~'~e crushed and distributed evenly over the greatest possibie-are~t to secure rapid evaporation. Avoid contact with solid carbon dioxide since it may produce burns.

3-3.6 In the case of a tank or container inerted with nitrogen, the oxygen content may be measured directly, by an oxygen in- dicator or with an Orsat. When carbon dioxide is used, the oxygen percentage can be calculated from the percentage of carbon dioxide in the container measured by means of a carbon dioxide indicator. I f it is possible to put one's head into an opening, for examination, signs shall be posted in a conspicuous location which warn of inert atmosphere.

3-4 Removal of Residual Liquids or Solids. In certain eases it may be impossible to remove all potentially hazardous liquid or solid residues that will produce flammable vapors when heated. Such residues may be trapped behind heavy scale or rust and may not easily be detected. Whenever examination._ after cleaning indicates that this hazardous condition exists, hot work shall not proceed without additional precautions being taken. As a minimum, an inert atmosphere shall be maintained in the tank or container while hot work is in progress.

3-4.1 Steam Cleaning. Steam may be introduced into the tank or container through a pipe inserted through an opening and bonded to the container, or by connecting a steam hose ~r~ctly to one of the vessel nozzles. The rate of supply of stearr(stlo~10, be sufficient to exceed the r a t e of condensation so that ~he-whole tank or container is heated close to the boiling point of water. The vessel must be steamed long enough to vaporize the residues from all portions of the walls (shell and heads). When testing the atmosphere in the vessel with a combustible gas indicator, the sample should be drawn through a drying tube filled with calcium chloride or other drying agent to insure that water vapor does not enter the instru- ment. If a drying agent is not available, the container must be allowed to cool off until excess water vapor has condensed.

192 CLEANING PROCEDURES 327-13

3-4.2 Chemical Cleaning." The tank or container may be cleaned with a chemical solution. The use of goggles, gloves, and

o the r necessary protective clothing should be considered when cleaning with chemicals in order to guard against possible injury to the skin or eyes. When using a proprietary cleaning solution, the manufacturer's instructions shall be followed. A typical cleaning procedure using trisodium phosphate is as follows:

3-4.2.1 Insert the hose through the filling connection or vent and fill the container with water until it overflows. Extend the hose to the bottom of the tank or container to get agitation from the bottom upward causing any remaining vapor, liquid, scum, or sludge to be carried upward and out of the tank or container where it may be removed to a safe location.

3-4.2.2 Drain the tank or container.

3.4.2.3 Dissolve sufficient trisodium phosphate in hot water ,that the final concentration of the solution will be 2 to 4 ounces

per gallon when the tank or container is liquid full. Pour the solution into the tank or container and fill with water.

3-4.2.4 Introduce steam to the bottom of the tank or Con-. tainer either through a bottom connection or through a pipe to the bottom which enters the vessel through the filling connection or through_the vent. Maintain the solution at a temperature of 170 ° to 190°F., and at intervals during the steaming add enough water to allow discharge by overflowing of any volatile liquid, scum, or sludge that may have collected at the top. Ventilation of the area shall be provided for the removal of any flammable vapors and means provided for preventing potentially hazardous material from entering a public sewer system. I t may be advisable in some cases to discharge the overflow water into another tank. or container. Continue steaming at maximum temperature for at least 15 to 20 minutes and longer if necessary until .the point is reached when no appreciable amount of volatile liquid, scum, or sludge appears at the top of the tank or container.

3-4.2.5 Drain the container.

3-4.2.6 Inspect the inside of the tank or container to see if it is clean. See 2-1.5. If examination shows that the tank or container is not clean, the cleaning procedure shall be repeated.

327-14 C L E A N I N G S M A L L T A N K S A N D C O N T A I N E R S

193

3-4.2.7 If the tank or container appears to be clean, the atmosphere within the tank or container should be tested with a combustible gas indicator. If the instrument indicates the presence of flammable vapor, this vapor shall be removed by one of the methods described in 3-2.

3-4.2.8 If steam is not available, a less effective method is the use of a cold water solution with the concentration of cleaning com- pounds such as trisodium phosphate increased to about 6 ounces per gallon of water. The solution should then be agitated. After the tank or container has been drained, it shall be inspected and tested for the presence of flammable vapors as above.

3-4.3 Nonflammable Solids. Occasionally hard solid de- posits will be found in tanks or containers which cannot be removed by the abov.e method and which do not produce flammable vapors. In such cases, and in the absence of flammable vapors, cleaning may be supplemented by tumbling the container with a length of chain inside to assist in the removal of such solids.

194 TESTING PROCEDURES 327-15

Chapter 4 Testing Procedures

4-1 Testing for Flammability. The test for flammability is the most important phase of the cleaning procedure and determines whether or not the cleaning has been effective. These tests may be made with a combustible gas indicator. Readings from most com- bustible gas indicators give the percentage of the lower flammable limit of the vapors present in an atmosphere. The readings may be misleading where the atmosphere contains less than about 5 per- cent by volume of oxygen as in an inerted container although in general the readings in oxygen-lean atmospheres will be on the high or safe side. I t is essential that the operator using the indicator be well-schooled in the use of the instrument and that he perform the checks recommended by the manufacturer to insure that the instru- ment is in good operating condition. The vapor content of the gas leaving the tank or container should be tested periodically while ventilation or air purging is in progress. If an air mover is used to exhaust air from a tank or container the discharge from the air mover will be diluted with air used in the jet, but the results of the test at this point will still be indicative of the change of vapor con- centration within the vessel and when the desired low concentration is reached, the condition of the tank or container itself may be checked by taking samples at appropriate points. When testing a tank or container for hot work, any indication of the presence of flammables by the combustible gas indicator shall require recleaning or further safeguarding of the vessel by one of the methods previously discussed prior to performing hot work.

4-2 Testing for Oxygen Content. When purging a tank or con- tainer with an inert gas, a combustible gas indicator may not indicate correctly the actual flammability of the sample. The con- centration of oxygen may be determined by an oxygen indicator or by an Orsat analyzer. Oxygen indicators of the single solution type shall be tested to prove they are satisfactory for the inert gas used.

R]~VlSIONS TO NgPA No 328

195 F L - 3

Part II

Revisions to the Standard on the

Contro l of F l a m m a b l e a n d C o m b u s t i b l e Liquids a n d

Gases in M a n h o l e s a n d Sewers

NFPA No. 328 -- 1970

1. On page 328-71, change the third paragraph to read:

L i q u e f i e d p e t r o l e u m gases a n d u t i l i ty gases a r e o d o r i z e d to fac i l i t a te d e t e c t i o n unless the o d o r a n t w o u l d serve no useful pu rpose as a w a r n i n g agent . S u c h purposes a re r e l a t ive ly r a re a n d p r a c - t ica l ly al l such gases d i s t r i bu t ed by u n d e r g r o u n d p ipe l ines a r e odor i zed . E x p e r i e n c e has shown t h a t o d o r a n t s c a n be abso rbed in t r a v e l i n g t h r o u g h the soil.

2. On page 328-13, change the last 2 lines of the th#d paragraph to read:

w i t h the r e q u i r e m e n t s of F e d e r a l a n d S ta te P ipe l ine Regu l a t i ons .

3. On page 328-13, change the fourth paragraph to read:

I n a c t i v e gas services a n d ma ins shou ld be a b a n d o n e d in ac- c o r d a n c e wi th F e d e r a l a n d S ta t e Regu la t i ons .

d. Add to Appendix B

Gaso l ine in S e w e r - - Nashv i l l e , T e n n . - - J a n u a r y 18, 1970.

Gasoline that had leaked from a bulk storage plant entered the sewer system and, eventually, the sewerage treatment plant resulting in two explosions. The piping for the roof drain of a floating roof tank, which goes down inside the tank, had frozen and ruptured. Since the valve at the discharge end had been left open, gasoline flowed from that drain valve into the diked area surrounding the tank. The dike drain had also been left open, allowing the gasoline to flow out of the diked area into an open sewer connection nearby. The gasoline eventually made its way to the treatment plant, where the explosions occurred. It was estimated that 46,000 gallons of gasoline entered the sewer system.

1flammable L i q u i d s in S e w e r m P e a b o d y , Mass . - - M a y 23, 1972.

Flammable liquids from an unknown source leaked into the sewerage system and ignited from a welding torch at the sewerage treatment building. The ensuing fire completely damaged the building.

196 FL-4 REPORT OF. COMMITTEE ON FLAMMABLE LIQUIDS

LP Gas Leak in Cave - - Walthill, N e w Brunswick, Canada - - J a n u a r y 24, 1973.

A leak in an unde rg round LP-Gas installation seeped th rough the g round a n d into a cave. W h e n a l ight switch was thrown, an explosion occurred tha t seriously in jured two boys. T h e minor fire tha t followed was ext inguished by the boys ' father.

Gas in Manhole - - Savannah, Ga. - - J u n e 1973.

An u n k n o w n gas had accumula t ed in a manho le and was ignited by a welder 's torch. All the circuits in the manho l e were de-energized by the explosion a n d the ensuing fire was ext inguished b~' CO~ extinguishers .