basic operation questions

7/27/2019 Basic Operation Questions

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What could be a possible cause for sudden foaming in a cooling tower?

Assuming that no other changes have been made, especially to the water treatment chemicals, the most commystery is a leaking heat exchanger.Begin a systematic check of all of the heat exchangers that use the cooling tower water and inspect them thorsmall amounts of some chemicals can cause big foaming problems in the tower. Also, not all of these componconductivity alarm.

IS there a rule of thumb to estimate the footprint of a cooling tower during designphase?

Over the years, this one has seemed to stand the test of time:Every million Btu/h of tower capacity will require approximately 1000 ft2 of coolingtower basin area.

When specifying a cooling tower, should I look up historic wet bulbtemperatures for my area or should I take measurements?

If this is a new installation, look up historical wet bulb temperatures for area andbe sure to report them to the cooling tower manufacturer as "ambient wet bulbtemperatures". The manufacturer will adjust this temperature accordingly toestimate an "entering wet bulb temperature".If you have an existing tower that is to be replaced, take several wet bulbtemperature measurements near the air inlet during the hottest months. Reportthis as the "entering wet bulb temperature" to the tower manufacturer.

The difference between the ambient and the entering wet bulb temperatures is toaccount for wet recirculation from the tower exit back to the tower entrance. Theentering wet bulb temperature always higher than the ambient wet bulbtemperature.

Question:

How can I estimate the blowdown flow rate that should be used on a cooling tower?

Answer: Start by examining the feed water to the tower and determine the concentration of thefollowing: chloride, sulfate, sodium bicarbonate, and calcium based salts.As rule-of-thumb limits, try to keep the tower water below the following limits: 750 ppmchlorides, 1200 ppm sulfates, 1200 ppm calcium salts, 200 ppm sodium bicarbonate.With these limits in mind, it should be fairly clear via the feedwater examination which of thespecies will determine the blowdown rate (more often than not, it's the chloride levels...butwell waters can contain significant levels of calcium based salts).Now, use the following procedure:First, we’ll define the blowdown flow rate as:

Where:



BLOWDOWN = Blowdown flow rate in GPMEVAP = Rate of evaporation in GPMDRIFT = Rate of drift losses in GPMCONC = Number of allowable concentrationsSince evaporation and drift losses are very difficult to measure, the following estimates canbe used:EVAP (GPM) = Total Water Flow (GPM) x Cooling Range (°F) x 0.0008DRIFT (GPM) = Total Water Flow (GPM) x 0.0002

Considering an example, suppose that a tower is cooling 20,000 GPM of water from 115 °Fto 88 °F (27 °F cooling range). The make up water contains 150 ppm chlorides and the towerwater should not exceed 750 ppm chlorides. Calculate the following values:CONC = 750 / 150 = 5 conc cyclesEVAP = 20,000 GPM x 27 °F x 0.0008 = 432 GPMDRIFT = 20,000 GPM x 0.0002 = 4 GPMand the blowdown flow rate is calculated as:



Question:

What types of heat transfer fill are generally used in industrial, induced-flow cooling towers?

Answer:

Splash type fill is designed to interupt the progress of water as it falls through the coolingtower and to "splash" it into small droplets to maximize the efficiency of the cooling process.Splash fill yields a low resistance to air flow and minimizes the potential for clogging in thetower.Film type fill is designed to force the water to flow in to a thin film over large, vertically-oriented surfaces in the cooling tower. Film type fill will require a larger air side pressure lossand is much more suseptible to clogging due to the small areas between the fill.Below, you can see of samples of each type of fill discussed here:

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What are some typical applications for glass-lined reactors?

Glass-lined equipment give superior protection to all mineral acids at all concentration andtemperatures. One exception is hydrofluoric acid. They are also used is high-purity processeswhere cleanliness is very important. Using glass-lined equipment help eliminate the possibility of

metal contamination. A third application is in polymerization. Metallic vessels sometimes tend toallow the polymer to stick to the walls of the vessels while glass-lined vessels have good anti-stickproperties.

ow does circular rake clarifier capacity correspond to inline pump capacity for precipitation systems?

ee the chart below:

hat is the method of determining maximum differential pressure duringdrotesting of shell and tube heat exchangers?

r. Richard Lee of Plumlee International Consulting: Usually heat-exchangersave two sets of test pressures per side, one for strength tests and theher for "operating" or "leak" tests. The strength tests are set by the

esign code and if you have the original design data sheets for your



quipment then the information should be shown on these. If you don'ten you will have to do the calculations yourself, the exact method will

epend upon which design code you use, the most common one beingEMA (which uses the ANSI/ASME pressure vessel code for reference inis area). Most shell and tube exchangers are designed such that eachde of the unit will withstand the full design pressure, with onlymospheric pressure on the other side. In order to save money, somerger units will have the tube-sheets especially designed to withstandnly a much lower differential pressure (requiring both sides to bested simultaneously). This important information should be should

uite clearly on the design sheets and on the vessel name platessuming that either are available). If the only need is to check that a

asket has been properly installed then it can be permissible to performower pressure test based on the operating pressure. The acceptabilitythis lower pressure test will often depend upon the consequences of a

ak.

How can one determine if a particular solid can be fluidized as in a fluidized bed?

Mr. Alex C. Hoffmann of the Stratingh Institute for Chemistry and Chemical Engineering states:"Whether a material can be fluidized at all is the question: if it is fine or sticky, the bed will becohesive. It will then tend to form channels through which the aeration gas will escape rather thanbeing dispersed through the interstices supporting the particles. In the other extreme: if theparticles are too large and heavy the bed will not fluidize well either, but tend to be very turbulentand form a spout." He goes on to present classification of fluidization by Geldart by use of the chartshown below. On this chart, the x-axis is the average particle diameter and the y-axis is the bulkdensity of the bed.

Manipulating Fluidized Beds with Internals

http://www.fi.uib.no/~hoffmann/papershtml/npt00/npt99.html

http://www.fi.uib.no/~hoffmann/papershtml/npt00/npt99.html



How does a pressure regulator work?

A typical pressure regulator that is normally installed incompressed air/gas systems uses the downstream gas pressureto balance the force exerted by a spring that causes the valveportion of the device to open and close. The downstreampressure acts on a diaphragm which is attached to the valvestem & spring. Rising downstream pressure exerts force on thediaphragm (Force = press X area) which overcomes the springforce and closes the valve. Pre-tensioning the spring determinesthe force opening the valve and when the downstream pressexerts equal force on the spring the valve is in equilibrium(balanced). Any change in downstream pressure causes thevalve to open or close accordingly, until equilibrium is again

reached. Downstream pressure is adjusted by adjusting springtension. Source: Cheresources Message Board

Link1Pressure Regulators

http://www.fisherregulators.com/technical/tableofcontents/

http://www.fisherregulators.com/technical/tableofcontents/



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Question:

How can I find the wet bulb temperature if I know the dry bulb temperature andthe relative humidity?

Answer:

Here are two choices: 1. Use psychrometric charts 2. Use the link to an onlinecalculator below

What are some good estimates for overall heat transfer coefficients in shell andtube heat exchangers?



Question:

How can one calculate how much steam will be required to heat water from onetemperature to another?

Answer:

Here is the equation that you want: X = (W)(Cp)(Delta T) / H where: X = lb/hr of steam W = lb/hr of water flow = (500)(gpm of water flow) Cp = specific heat of water = 1 BTU / lb / °F Delta T = how many degrees F that you want to heat thewater H = latent heat of vaporization of your steam, Btu / lb You can look up thelatent heat (i.e., H) of your steam in a set of Steam Tables. Alternatively, you canassume that H = 1000 Btu / lb and that will probably be close enough. Forexample, if you want to heat 100 gpm of water from 80 °F to 125 °F: X = (500)(100)(1)(125 - 80) / 1000 = 2250 lb/hr of steam Source: Cheresources Message



Board, Mr. Milton Beychok

Question:

Where can I find a heat of dilution chart for sodium hydroxide?

Answer

: See the chart below or request a printable copy from support:

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Question:

What is a barometric condenser?

Answer:

Single-stage or multi-stage steam jet ejectors are often used to create a vacuum ina process vessel. The exhaust from such ejector systems will contain steam (andperhaps other condensible vapors) as well as non-condensible vapors. Suchexhaust streams can be routed into a "barometric condenser" which is a verticalvessel where the exhaust streams are cooled and condensed by direct contactwith downward flowing cold water injected into the top of the vessel. The vessel isinstalled so that its bottom is at least 34 feet (10.4 meters) above the ground, andthe effluent cooling water and condensed vapors flow through a 34 foot length of vertical pipe called a "barometric leg" into small tank called a "hotwell". The

mailto:[email protected]

mailto:[email protected]



"barometric leg" allows the effluent coolant and condensed vapors to exit nomatter what the vacuum is in the process vessel. Such a system is called a"barometric condenser". The non-condesible vapors are withdrawn from the top of the condenser by using a vacuum pump or perhaps a small steam ejector. Theeffluent coolant and condensed vapors are removed from the hotwell with a pump.Source: CERP Message Board, Mr. Milton Beychok

Question:

Why is a vacuum breaker used on shell and tube heat exchangers that are utilizingsteam as the heating utility?

Answer:

Vacuum breakers are often installed on the shell side (steam side) of shell andtube exchangers to allow air to enter the shell in case of vacuum conditionsdeveloping inside the shell. For an exchanger such as this, the shell side shouldalready be rated for full vacuum so the vacuum breaker is not a pressure (vacuum)relief device. Development of vacuum in the shell could allow condensate to buildin the unit and water hammer may result.

Questi

on:

Where can one get a quick estimate on the size of a barometric

condenser?

Answer:

Goto the site below. These types of condenser are very popular in thesugar industry. This online calculation will even give you a nicelyformatted output.www.sugartech.co.za/rapiddesign/condenser/index.php3

Link1: Online Barometric Condenser Design

Questio

n: What is a quick way to calculate frictional pressure drops in carbon steel pipe?

Answer:

The relationship shown below is valid for Reynolds numbers in the range of 2100to 106. For smooth tubes, a constant of 23,000 should be used rather than 20,000.

Image

1:

http://www.sugartech.co.za/rapiddesign/condenser/index.php3

http://www.sugartech.co.za/rapiddesign/condenser/index.php3



Category:

Fluid Dynamics

Question:

How can I estimate a gas flow based on two pressure measurements?

Answer: You can use the Weymouth equation to estimate the gas flow. Below is theequation. The compressibility should be evaluated at Pavg shown below.Nomenclature is as follows: Q = flow rate, Million Cubic Feet per Day (MCFD) Tb =base Temperature, degrees Rankin Pb = base pressure, psia G = gas specificgravity (reference air=1) L = line length, miles T = gas temperature, degreesRankin Z = gas compressibility factor D = pipe inside diameter, in. E = Efficiencyfactor E=1 for new pipes with no bends E=0.95 for pipe less than a year oldE=0.92 for average operating conditions E=0.85 for unfavorable operatingconditions

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Question:

How can I calculate the sonic velocity of a gas stream?

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Question

: What are the affinity laws associated with dynamics pumps?

Answer: 1. Capacity varies directly with impeller diameter and speed. 2. Head variesdirectly with the square of impeller diameter and speed. 3. Horsepower variesdirectly with the cube of impeller diameter and speed.

Question:

How can I quickly estimate the horsepower of a pump?



Answer: Try this handy little equation: Horsepower = (GPM)(Delivered Pressure) / 1715(Efficiency) GPM = Gallon per minute of flow Delivered pressure = Dischargeminus suction pressure, psi Efficiency = Fractional pump efficiency

Question: How can I estimate the efficiency of a pump?

Answer: The following method, developed by M.W. Kellogg, gives results within 3.5% of

most manufacturers curves. Eff % = 80-0.2855H+3.78x10-4HF-2.23x10-

7HF2+5.39x10-4H2-6.39x10-7H2F+4.0x10-10H2F2 H = Developed head, ft F = Flowin GPM (gallons per minute) Applicable for heads from 50 to 300 ft and flowsfrom 100 to 1000 GPM

Question: What is the significance of the minimum flow required by a pump?

Answer: The minimum flow that a pump requires descibes the flow below which thepump will experience what is called "shutoff". At shutoff, most of the pump'shorsepower or work is converted to heat that can vaporize the fluid and causecavitation that will severely damage the pump. The minimum flow of a pump isparticularily important in the design of boiler feed pumps where the fluid is nearit's boiling point.

Question: How can I determine the largest impeller that a pump can handle?

Answer: The motor amperage should be measured in the field with the pump dischargevalve wide open. Subtract about 10% from the pumps maximum ratedamperage. Then the maximum impeller size can be determined from: A2 =A1(d2/d1)

3 A2 = Maximum amperage minus 10% A1 = Current operatingamperage d2 = Maximum impeller diameter d1 = Current impeller diameter

Question: What is a good estimate for the absolute roughness for epoxy lined carbon steelpipe?

Answer: The specific roughness for welded, seamless steel is .0002 ft. PVC has a specificroughness of 0.000005 ft. You may also want to consider using the Hazen-Williams formula, which lists a coefficient of 130-140 for cement-lined cast ironpiping. You need to decide which is more conservative for your application.

Question:

How can one determine if a pipe is running full or is at its sealing flowrate?

Answer: The following equation gives a quick check to determine the sealing velocity for a

pipe: Q = 10.2 D 2.5 where Q is the liquid flowrate in gallons per minute D is thepipe diameter in inches If the current flowrate in the pipe is less than the valuecalculated for Q above, then the pipe is below its sealing flowrate or is said to bepartially flooded. In order to calculate the velocity in this pipe you must use a setof flow area equation presented in Chemical Engineering magazine (March 1998,p. 129). The above equation is valid for liquid flow through a horizontal pipe.



Question:

What types of valves are recommended for slurry services?

Answer: Typically straight-through diaphragm, clamp or pinch, and full-port ball valveswith cavity fillers are the preferred type of slurry valves. In general, gate, needle,

and globe valves are NOT recommended for slurry services.

Link1: Red Valve Company Website

Question: Should slurry pipes be sloped during horizontal runs?

Answer: If possible, slurry lines should indeed be sloped. As a general rule, sloping thepipes 1/2 inches for every 10 feet of pipe is recommended.

Question: What type of flow measurement devices are best for slurries?

Answer: Any device that restricts the flow to perform measurements are not

recommended for slurries. These devices include orifices and dampeners. Thesedevices can lead to liquid/solid separation and they can lead to excessiveerosion. Instead, measuring devices that do not restrict the flow should be used.One example of such a device is the magnetic flowmeter.

Link1: Focus on Liquid Flow Measurements

Link2: Magnum Magnetic Flowmeter

Question:

For mixing with a circulation pump, what's a good rule of thumb to determinewhen the tank will be "well mixed"?

Answer: A common used rule is: time = (3* volume)/circulation rate for mixing with acirculation tank.

Question:

How is the NPSH (Net Positive Suction Head) calculated for a process vesselfollowed by a pump?

Answer: See the graphic below:

http://www.redvalve.com/

http://www.cheresources.com/flowmeas.shtml


http://www.magmeter.com/

http://www.redvalve.com/


http://www.magmeter.com/



Image1:

Question:

Can I develop a new pump curve if changing a centrifugal pump from a water to agasoline duty?

Answer: A new pump curve can be developed with the help of a viscosity correctiondiagram. See the link below for more information:

Link1: Rand McNally

http://www.mcnallyinstitute.com/CDweb/u-to-z-html/v020.htm

http://www.mcnallyinstitute.com/CDweb/u-to-z-html/v020.htm



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Question:

What type of pump may be appropriate for a liquid near saturation, a low flowrate, and very limited NPSHa (net positive suction head available)?

Answer: This application is nearly perfect for a turbine regenerative type of pump. Factorsthat immediately identify your application and pump type are: the small flowrate,low NPSHa, and high temperature. The regenerative turbine was specificallydeveloped for these conditions and one more: high discharge pressures. The highdischarge pressure may not be necessary, but the regenerative turbine can giveyou a NPSHr of 0.5 feet with ease. They are particularly suited to saturated boiler



feed water and your application is similar, albeit not in pressue. You can visit thesite below to learn more about these types of pumps. Source: CERP MessageBoard

Link1: Roth Pump

Link2: Aurora Pump

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1:

Question: How can one estimate how the friction factor changes in heat exchanger tubeswith a change in temperature?

Answer: Seider and Tate recommended the following for determine friction factors insideheat exchanger tubes with varying temperatures: First, determine the average,bulk mean temperature in the processing line. For example if the fluid enters theline at 300 °C and leaves at 280 °C, use 290 °C to determine the physicalproperties and friction factors. As for corrections: Laminar Flow If the liquid iscooling, the friction factor obtained from the mean temperature and bulkproperties is divided by (bulk viscosity/wall viscosity)0.23 and for heating, it'sdivided by (bulk viscosity/wall viscosity)0.38. Here, the bulk and wall viscosity aredetermined at the mean temperature over the length of the line. Turbulent FlowIf the liquid is cooling, the friction factor obtained from the mean temperatureand bulk properties is divided by (bulk viscosity/wall viscosity)0.11 and for heating,it's divided by (bulk viscosity/wall viscosity)0.17. Here, the bulk and wall viscosityare determined at the mean temperature over the length of the line. Source:Perry's Chemical Engineers' Handbook

Question: Under what circumstances are vortex flowmeters the most accurate?

Answer: The accuracy of vortex flowmeters can be within 1% so long as they're beingoperating within their recommended flow range, have a steady stream, and youhave 10 pipe diameters of straight pipe behind the in front of the flowmeters.Outside of these parameters, these flowmeters are not accurate.

Question: What are the advantages and disadvantages of using gear pumps?

http://www.rothpump.com/

http://www.aurorapump.com/

http://www.rothpump.com/

http://www.aurorapump.com/



Answer: Gear pumps are a type of positive displacement pump that are appropriate forpumping relatively high pressures and low capacities. Advantages include theability to handle a wide range of viscosities, less sensitivity to cavitation (thancentrigual style pumps), relatively simple to maintain and rebuild. Disadvantgescan include a limited array of materials of construction due to tight tolerancesrequired, high shear placed on the liquid, and the fluid must be free of abrasives.Also note that gear pumps must be controlled via the motor speed. Throttling the

discharge is not an acceptable means of control. Reference: The Pilot Plant RealBook, FXM Engineering, ISBN 0972176918

Question: Is there a handy way to determine if a horizontal pipe is running full if the flowrate is known?

Answer: Generally speaking if Q/d2.5 is greater than or equal to about 10.2, then the pipe issaid to full. In this case, Q is in GPM (U.S. Imperial gallons per minute) and d is ininches. Reference: Pocket Guide to Chemical Engineering, ISBN: 0884153118

Question: What is the best way to control a positive displacement pump?

Answer: When controlling a positive displacement pump, the very first thing to remember is

this: YOU CANNOT CONTROL IT BY THROTTLING THE DISCHARGE! Trying to do so if fruitless and in most cases, you'll actually cause damage to the pump. The secondthing to remember is this: YOU CANNOT CONTROL A PD PUMP BY THROTTLING THESUCTION SIDE. It's important to get these two points out of the way. PD pumps areNOT centrifugal pumps, and they cannot be controlled in the same way ascentrifugal pumps. O.K., now that we've addresses to you cannot control thesetypes of pump, we'll move on to how you CAN control them. The recommendedway to control a PD pump is via a recycle from the discharge line to the liquidsource. The recycle line is fitted with a control valve. Essentially, the flow (andsubsequent pressure) to the process is reduced by the flow that is allowed torecycle. This keeps the PD pump operating at a consistent flow and pressure, butallows for control of what continues to the process.

Link1: More of PD Pump Control

Question:

What is a good estimate for a roughness factor for a pipeline that is severly rusted?

Answer: As pipes age, their roughness can increase substantially which makes fluid dynamiccalculations quite a challenge. Before are some good estimates to use for aged

piping:

http://www.driedger.ca/ce2_pdp/CE2_PDP.html

http://www.driedger.ca/ce2_pdp/CE2_PDP.html



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Question: How can you separate hydrogen peroxide into hydrogen and oxygen?

Answer: This is easily done. Just expose hydrogen peroxide to air. The oxygen in the airwill oxidize the hydrogen peroxide into it's component gases. It happens far tooslowly for industrial or most other purposes (an enzyme catalyst can be used tospeed up the process). However, neither hydrogen nor oxygen are produced inthis manner in industry. The enzyme catalyst is called "catalase" and if Iremember correctly, it can be found in potatoes.

Question:

What is the Wet Bulb Globe Temperature (WBGT)?

Answer: The sultriness of the ambient environment is more than a comfort factor. Forworkers, soldiers and athletes, high levels of sultriness may result in heat stressthat could very well be life threatening. To determine the actual degree of sultriness in a quantifiable manner, the Wet Bulb Globe Temperature (WBGT)index is used. It includes the effects of humidity, air speed, air temperature andthe radiant heating factor (from the sun). This index was developed by the U.S.Military in the 1950's and has become widely accepted for industrial temperaturemeasurements to protect employees. It combines three temperature readings:the wet bulb temperature; the ordinary dry bulb temperature; and a black bulbglobe temperature. There are also instruments available which measure WBGTindex directly, combining the three factors and their appropriate weightingvalues.

Category:

Chemistry Basics

Question:

What are some common precipitating agents used to remove metals fromaqueous waste streams?

Answer: Perhaps the most common agents used are:



• Metal hydroxides

• Lime or caustic soda

• Metal sulfides

• Alum or ferric salts

• Phosphate or carbonate ions

Question: What types of metals are typically removed via chemical precipitation?

Answer: Some of the more common metals or other substances removed viaprecipitation include:

• Aluminum

• Arsenic

• Barium

• Cadmium

• Calcium

• Trivalent chromium

• Hexavelent chromium

• Copper

• Iron• Lead

• Magnesium

• Manganese

• Mercury

• Nickel

• Selenium

• Zinc

Question: Where can I find a listing of the properties of Titanium?

Answer: Try the link below:

Link1: www.titanium.net

Question: How can wet carbon dioxide be responsible for a corrosion problem in iron-containing metals?

Answer: Carbon dioxide reacts with water according to the following equation: CO2 + H2O

--> HCO3-

+ H+

As the concentration of CO2 increases, so does the concentrationof the H+ ion. This ion can then react with Fe in metals as follows: Fe + 2H+ -->2H (atom) + Fe2+ As corrosion proceeds, the ferrous ions produced can reactwith the bicarbonate ions to form ferrous carbonate which precipates as a scale.

Question:

Is it possible to compare the resistance to chloride attack of several materials of construction?

http://www.titanium.net/

http://www.titanium.net/



Answer: The Pitting Resistance Equivalent Index (PRE) can be used for such a comparisonif the chemical make-up of each material is known. The formula for the PRE is:PRE = % Cr + (3.3 x % Mo) + (30 x % N) As an example, let's say that onewanted to compare the resistance to pitting of 316 SS, Incoloy 825, and 254SMO. The major components of each material is: 316 SS : 17% Chromium, 2.5%Molybdenum, and 0.10% Nitrogen Incoloy 825:21.5% Chromium, 3.0%Molybdenum, and no N2 254 SMO:19.5% Chromium, 6.0% Molybdenum, and

0.18% Nitrogen PRE (316SS) = 28 PRE (Incoloy 825) = 31 PRE (254 SMO) = 45So, we can confirm from this index that under most circumstances, 254 SMO willbe more resistant to cloride pitting attack that both 316 SS and Incoloy 825.

Link1: Online PRE Calculator

Question:

Are carbon steel storage tanks appropriate for NaOH solutions?

Answer: Carbon steel storage tanks can be used for NaOH storage tanks under certainconditions. Carbon steel tanks with no stress relieving can be used in the

following situation: A. NaOH concentration below 20% by weight, up to about 160°F (70 °C) B. NaOH concentration from 20-30% by weight, up to about 140 °F (60°C) C. NaOH concentration from 30-50% by weight, up to about 120 °F (50 °C)

The use of carbon steel tanks in this service can be extended by stress relievingwelds and bends. A tank that has been stress relieved can be used in thefollowing situations: A. NaOH concentration below 20% by weight, up to about 220°F (105 °C) B. NaOH concentration from 20-30% by weight, up to about 210 °F (99°C) C. NaOH concentration from 30-50% by weight, up to about 170 °F (77 °C)Beyond these constraints, a nickel alloy material will generally need to beconsidered. There are also some types of plastics that can be used for NaOHstorage. Reference: Chemical Engineering Magazine, September 2000

http://www.ionikconsulting.com/toolbox/pren.htm

http://www.ionikconsulting.com/toolbox/pren.htm



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Why is post-weld heat treatment (stress relieving) sometimes necessary forwelded vessels?

During the welding process, the two metal pieces being joined are subject toextreme temperatures and can cause the crystalline structure of the metal to

pass through various metallurgical phases. As a result, hardening (andembrittlement) of the metal can occur to varying degrees (usually dependenton carbon content). Heat treatment is designed to reduce the hardness in theheat affected zone of the metals and also increase ductility in these sections.Various pressure vessel codes contain the specifics regarding the proceduresfor post-weld heat treatment. Heat is usually held for one hour per inch of thickness of the metal. The temperature used is based on the "P-number" of the metals. P-numbers are assigned based on the chemical composition of themetals. Holding temperatures can range from 1100-1350 °F (593-732 °C).

What are some good tank mixing rules of thumb?

Rules of thumb?....well, here are some basics of mixing: For fluid with

viscosities under 10,000 Cp, baffles are highly recommended. Thereshould be four baffles, 90 degrees apart. The baffles should be 1/12ththe tank diameter in width and should be spaced off the wall by 1/5ththe baffle width. The off wall spacing helps to eliminate dead zones. If baffles are used, the mixer should be mounted in the vertical positionin the center of the tank. If baffles are not used, the mixer should bemounted on an angle, ~15 degrees to the right and positioned off center. This breaks up the symetry of the tank and simulates bafflesalthough not nearly as good as baffles. The pupose of baffles is to



prevent solid body rotation, all points in the tank are moving at thesame angular velocity and no top to bottom turnover. The formationof a large central vortex is a characteristic of solid body rotation.However small vortices which travel around the fluid surface, collapseand reform are more a function of the level of agitation. Violent andvigorous agitation will have these vortices present. In fact, they aredesired for processes which require solids addition from the liquidsurface. The impellers are located at different positions depending onthe design. Axial flow impellers, those pumping parallel to the shaftshould be positioned between 0.5 and 1.5 impeller diameters off thebottom of the tank. Radial flow impellers, those pumpingperpendicular to the shaft can be positioned just inches off thebottom. If multiple impellers are used, the spacing will depend on theliquid height to tank diameter ratio. Care must be taken to preventimpeller spacings on 1 impeller diameter. This can lead to acancellation of flow. Torque is one of the most important factors. Alarge diameter slow spinning impeller is much better for blendingthan a small diameter fast spinning impeller at equal power levels.

Torque = Work. Impeller diameters for relatively low viscositiesshould be between 0.25 and 0.45 times the tank diameter with someexceptions.

Question:

How can a vortex be prevented at the bottom of a separation column?

Answer:

Try raising the level in the bottom of the column. If you don't have avortex breaker in the bottom of the column, add one. If you can't weldon the column, you might be able to make an insert into the bottomnozzle such as a cross.

Question:

What is a Zeta potential?

Answer:

A Zeta potential in the difference is charges that exists between a liquid/liquid orsolid/liquid interface. The Zeta potential is the result of the natural electrokineticgradient between the two surfaces. In emulsion, ionized emulsifiers can be addedto an immiscible mixture to build up electrically repulsive forces. These forces canthem help to slow down the coalescence rate of one of the phases.

Link1: Learn Even More About Zeta Potentials

Question:

Can one cool air using the Joule-Thomson effect?

Answer:

I have 250 cfm of 6 bar air at 35 0C. Can I release this pressure in athrottle and cool this air by using the Joule-Thomson effect? To say thatyou're going to "cool air using the Joule-Thomson effect" sounds a bitfunny. The Joule-Thomson effect is more of an observation of cooling byadiabatic expansion. You sure can cool air at 35 0C and 6 bar byreleasing the pressure, that much is certain. I'm sure that you'reinterested in finding out what the new temperature will be for a given

http://www.bic.com/ztheory1.htm

http://www.bic.com/ztheory1.htm



pressure. You could start by estimating the solution by using Boyle's Law(I think?) which states that P1/T1 = P2/T2. This relation will give you anestimate only because it assumes that the gas is "ideal" which meansthat the molecular collisions are perfectly elastic. This of course is seldomthe case, especially at higher pressures like you have here. You shouldreally use what is called an "Equation of State" or an EOS. There aremany of them. Try looking up the Peng-Robinson equation or the Redlich-Wong equation. Another option that can be used is a compressibility

factor with the ideal gas law. The compressibility factor helps bring asense of reality to the equation PV=znRT which I'm sure you're familiarwith. So, you can use an EOS or the Ideal Gas Law with thecompressibility factor to find out what the temperature of air will be at agiven pressure.

Question:

What is a steam jet ejector?

Answer:

R.M. Price describes steam ejectors as follows: Steam jet ejectors areoften used to pull vacuum on surface condensers, evaporators, etc. Ahigh pressure, motive, fluid (usually steam) enters the ejector chest

through a nozzle and then expands. This converts its pressure energy to velocity. The increased velocity causes reduced pressure, whichsucks in and entrains gas from the suction. The diffuser section thenrecompresses the mixed steam/gas stream to some intermediate

pressure. The exhaust is then sent to a condenser which quickly condenses the steam at a low pressure and temperature so that thevolume quickly decreases.

Link1: More of Steam Jet Ejectors

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1:

Question:

What vacuum pressures are possible with steam jet ejectors?

Answer:

By arranging steam jet ejectors into stages, a wide range of vacuum pressures canbe obtained:

One-

stage75 torr

Two- 12 torr

http://www.croll.com/




stage

Three-

stage1 torr

Four-

stage0.2 torr

Five-

stage0.02 torr

Six-

stage0.003 torr

Link1: More of Steam Jet Ejectors

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Question:

What industries require filtered compressed air?

Answer: Almost every chemical process, power plant food processing etc. plant has sometype of air-operated device.. from control valves to air operated pumps... and allhave an air compressor delivering filtered air.

Question: How can I control the pH level in our cooling water with respect toammonia contamination?

Answer: BACKGROUND A cooling tower in a urea manufacturing facility isexperiencing very high ammonia levels (200 to 300 ppm) in thecooling water. The ammonia level fluctuates with wind direction.RESPONSE If your cooling water has 200-300 ppm of ammonia,you have a problem which must be solved. You may have a water-cooled process heat exchanger which has a tube leak that isleaking ammonia into your cooling water. Or the ambient air inyour urea plant has a significant ammonia content (from variousfugitive leak sources such as piping flanges, control valve packingglands, pump and compressor seals, etc.) and when the windblows that ambient air into the cooling tower, the ammonia isabsorbed in the cooling water. In either event, you have anunhealthy situation which must be corrected. Contacting acompany that specializes this these types of water treatmentproblems may be a wise decision (Ex/ Nalco).

Link1: Nalco's Homepage

Question:

How can I stop chlorine from condensing during transport from an outsidecylinder?

Answer: BACKGROUND The gas is piped normally from an outside cylinder storage facillityto a process control panel at approximately 60 psig. The panel output chlorinepressure is 15 psig and a flow rate of approximately 0.03 scfm. Occasionally theflow control devices in the process panel are contaminated by what appears to beliquid chlorine. It seems that temperature variations in the iron transport pipemay have some influence on the liquid formation. RESPONSE The condensationtemperature of gaseous chlorine at 65 psig is 54 deg F. Thus, if your transportline is fairly long, it is quite likely that ambient temperatures lower than 54 deg Fcould result in cooling the line enough to cause condensation of the chlorine gas.

Question:

What are the two classes of multi-stage steam jet ejectors?

Answer: Multi-stage steam jet ejectors can be classified as either beingnoncondensing or condensing. Noncondensing systems canproduce vacuums up to 4 in Hg absolute. Condensing systemscontain either direct contact or surface condensers between stagesand can achieve vacuums up to 5 micrometers Hg absolute.

Link1: More on Steam Jet Ejectors

http://www.nalco.com/



http://www.nalco.com/



If you lower the transport pressure to 25 psig, the condensation temperaturewould be 24 deg F ... which should significantly lower the likelihood of coldambient temperature causing the gas to condense. Before you lower thetransport pressure, you might consider insulating the transport line ... or steamtracing plus insulation ... to keep the line warm.

Question:

What are some guidelines for designing for liquid and gas velocities in processplant piping?

Answer: For normal process plant design liquid pump discharges, look for velocities in therange 5-7 ft/sec. Probably not a bad idea to keep design vapor velocities below125 ft/sec. These are guidelines that might be applied by an engineeringcompany for design. If you are looking at plant operation, its not uncommon tofind velocities in the 9-12 ft/sec range. Erosion problems can also complicate theanswer to this question. Erosion is highly dependent on the nature of the fluid.For example, 98% H2SO4 is not corrosive to carbon steel pipe, however it veryerosive at "normal design" velocities. A design criteria for 98% H2SO4 might be:0.70 ft/sec MAXIMUM. However, it is also well known that if the same 98% H2SO4has a little emulsified hydrocarbon, it is substantially less erosive.

Question:

How is instrument air continually supplied in process plant?

Answer: The instrument air supply is guaranteed by dedicated air supply with -40 oC dewpoint. Apart from this there is about 20 to 30 minutes of back-up provided foremergencies like power failure, instrument air generation failure, etc.

Question: What is the maximum recommend pipe velocity for dry and wet gases?

Answer: For dry gases, you should design for a velocity of about 100 ft/s while wet gasesshould be limited to about 60 ft/s.

Question: What is the maximum recommended velocity for steam in a plant pipe network?

Answer: High pressure steam should be limited to about 150 ft/s and low pressure steamshould be limited to about 100 ft/s.

Question:

What is the difference between CFM (cubic feet per minute) and SCFM (standardcubic feet per minute)?

Answer: CFM and SCFM are both measures of flow rate. CFM might refer to either the flowrate of a gas or a liquid, whereas SCFM refers only to the flow rate of a gas. Thesame mass flow rate of a gas (i.e., lbs/minute) is equivalent to various volumetricflow rates (i.e., CFM) depending upon the gas pressure and temperature. Thus,when gas flow rates are specified, it is very important to also specify at whatpressure and temperature the gas was measured. When the gas flow rate isspecified as SCFM, it means that the flow rate was measured at a set of standard



pressure and temperature conditions. In the USA, the most common set of standard conditions used in industry is 60 degrees Fahrenheit and 1 atmosphereof pressure. Note that we have stressed most common, because there are otherstandard conditions that may be used. It is always best to spell out what standardconditions are being used (i.e., 1200 SCFM at 60 degrees F and 1 atmospherepressure). When gas flows are expressed simply as CFM, the reader is can onlyspeculate as to what gas temperature and pressure apply to that flow rate ... and,because of that, the CFM flow rate cannot be converted to a mass flow rate.

Question:

How much water is lost through a commercial cooling tower system with athroughput of about 600 GPM?

Answer: This question depends on many factors. Sounds like the tower is fairly small. Arule of thumb suggests that the tower will see an evaporation loss of about 0.1%of the circulation flowrate for each Fahrenheit degree of cooling. Other lossesinclude drift losses (probably very small for your tower) and blowdown. Blowdownis simply a purge of tower water to prohibit the buildup of solids.

Question:

What are some common causes of control valve noise?

Answer: If you have excessive pressure drop accross the control valve and thedownstream pressure is low enough to cause the liquid to flash, a great deal of noise in the control valve can result. Excessive damage can be done as well. Thisis a common problem at low flows. Review the design information on the valveand the process to see if low flow may be the problem. If the valve is incorrectlysized the noise will be apparent from the day of installation. If flows have recentlybeen changed, the valve may have been designed correctly at the time, but is toolarge for current operation.

Question:

What are flameless oxidizers?

Answer: Flameless oxidizers are used to treat volatile organic compounds (VOC) andliquid organic streams. Traditionally, these types of streams were combusted tobreak down the molecules. The disadvantage of this treatment method was theformation of NOx. Flameless oxidizers use electrically heated ceramic packingand a high velocity introduction system to intiate the destruction of the organiccompounds into carbon dioxide and water. Once this oxidation reaction begins, itcontinues via self-perpetuation. Capital cost for such systems are usually about25% less than traditional combustion systems and capacities can range from250 to 40,000 SCFM (standard cubic feet per minute). Thermatrix Inc. is thepioneer for this technology. Visit their website below.

Link1: Visit Thermatrix on the Web

http://www.thermatrix.com/

http://www.thermatrix.com/



Image1:

Question:

What particle sizes are electrostatic precipitators used to remove?

Answer: A. Duprey conducted testing on an electrostatic precipitator in a pulp mill. Theresults were published in a National Air Pollution Control Administration reportcalled "Compilation of air Pollutant Emission Factors." Below is sample datacollected on the inlet and the outlet of an electrostatic precipitator:

Image1:



Question:

Are there any general rules for flushing slurry lines?

Answer: Slurry lines should be flushed with a minimum fluid velocity of 10 ft/s and the totalflushing liquid volume should equal 3-6 times the total piping volume.

Question:

What are some good uses of low grade steam at 12 atm and 1920C?

Answer: There are various traditional methods to employ waste steam in an operatingplant: 1. You can generate electricity through a steam turbine-generator set. Theelectricity is usually put back in the line; this is the idea behind the "Co-Gen"concept used today in many USA plants. Steam turbines can effectively usesaturated steam supply down to 75 - 100 psig. Some people have reported to methat, in special conditions, they have used down to 50 psig as a turbine steamsupply. I have used steam as low as 100 psig. 2. You can pre-heat processstreams that require pre-heating; this is done by applying heat exchangers. 3. Youcan employ the waste steam as a refrigeration source by employing it in vacuum

jet ejectors and producing 50 oF cooling water; I have used all 3 methods aseconomy and optimization improvements in the past. You have to consider theseas viable options if you can identify the heating, cooling and energy conservationrequirements. An economic analysis is required to identify the most attractiveoption. You usually utilize a Discounted Cash Flow analysis to base your decisionand that means you must study each case as to savings generated. A fourthmethod might be that you can use the steam for environmental heating (if youlive in a cold climate). This is a rare application, although I've seen this used insmall towns.

Question:

Is there any way to repair a valve that is passing (leaking internally) withouttaking our process offline?

Answer: BACKGROUND A 600 psig, 3" steam line is experiencing "passing" or internalleakage. If order to replace the valve, the process would have to be taken offline.A temporary solution to the problem is sought to get the plant to their nextscheduled shut down ANSWER Research on-stream leak sealing services. Thisproblem is quite common. What they would do in this case is drill a hole into thebypass valve on the upstream side but not completely into the line. They wouldthen tap the hole and install one of your injection fittings which is like a small plugvalve. They would then take a long 1/8" drill bit and drill through the openinjection fitting and into the pressurised line. The drill bit is then removed and ourinjection equipment is then attached. Sealant (heavy fibres and grease) ispumped into the line and caught in the flow which will bind up against the leaking

seat on the bypass valve. If done properly, this technique can be both effectiveand safe.

Link1: Eveready Industrial

Question:

Can air be used to properly conduct a leak test on a plant during commissioning?

http://www.evereadyindustrial.com/

http://www.evereadyindustrial.com/



Answer: If you're commissioning a plant, you can use clean, regulated compressed air forleak testing. Of course, as you know, this will only show that the joints and otherleak-prone areas do not leak at the testing temperature -not at the processtemperatures which can be higher. What I have done in the past is appliedmasking tape around the flanges' gasketed joint with a small pin hole madeafterwards. Then I use "soap and bubble" technology with a fine brush, searchingfor the tell-tale bubbles that reveal an air leak. If the flange joint leaks, the pin

hole will form a soap bubble. Be aware that before you undertake to subject yourprocess or unit to a pneumatic pressure, you should have a thorough and detailedknowledge of the lowest pressure rating in your pressurized system. You must becareful not to surpass the lowest pressure rating. For example, you may be usingcast iron casings on your centrifugal pumps and these are normally rated wellbelow the pressure rating of the connected piping. If some of the equipment israted below the pipe, you can isolate the equipment and test the pipe on its ownrating, followed by testing the equipment one-by-one. I have seen what amisguided pneumatic test can cause with a ruptured piece of equipment. That iswhy I am very, very cautious of pneumatic testing and would use it only if I werein control of all the procedures. I am particularly of any cast iron equipment. Castiron pieces or components can have foundry defects or flaws and this can bedevasting if they fail under a pneumatic test because the net effect is the same as

a grenade exploding. That is why I prefer to test plant equipment hydrostatically -with water. The result of a hydrostatic test failure is benign compared with apneumatic one. A vacuum test is safer but is difficult to detect leaks. The onlypractical measure you have is loss of the vacuum as witnessed on a sensitivepressure gauge. This takes time and patience. Again, while you can pneumaticallytest an entire unit at one time, take time and trouble to make sure you are incomplete control as to the safe, rated pressure on each component in your systembefore applying air pressure. I would recommend that you use a 2-stage airregulator to set the test pressure. This is much more accurate and is consideredsafer that a single stage regulator. Source: Cheresources Message Board, Mr. Art Montemayor

Question:

What is the minimum required vent steam for a boiler feed water dearator?

Answer: There is no minimum amount of vent steam required. The vent should be adjustedso that the dissolved oxygen level in the feedwater is just on spec (typically ~7ppb), then opened a little more for contingency. One method of adjustment is toslowly pinch in the vent while monitoring BFW O2 levels. When the O2 levelreaches/exceeds spec, open the vent enough to reduce the reading to below spec.

Typically there is not enough steam lost to be concerned with the amount of supply steam required. If you are concerned, however, with loss of heat energy, itis not difficult or expensive to build a vent condensor, which will often performbetter than OEM, esp if the BFW supply is relatively cool. Corrosion is, of course, a

concern, but it is the same problem w/o a good vent condensor. Source:Cheresources Message Board

Question:

What type of fasteners should be used with stainless steel piping?



Answer: There's risk of galvanic corrosion if you were to use mild steel fasteners. It'srecommended to use bolts that of the same material as the piping material in thiscase. Another concern is that the threads on stainless steel bolts are oftendistorted or "galled" after being tightened and loosened a couple of times.Consider using a different stainless alloy designed with "anti-galling"characteristics for the nuts. There are also inserts available for SS nuts to preventthis as well.

Question:

What are some good methods of avoiding condensation in a compressor suctionline?

Answer: BACKGROUND A twin lobe compressor is suffering repeated failure due tomoisture in the suction line. The vapor is coming from a vertical two-phaseseparator ANSWER The liquid may be forming as the result of either: 1.Condensation in the line between the separator and the compressor. 2. Liquidcarry over from the separator. If the suction line is well insulated and/or heattraced (it probably should be), then begin with the separator. From generallyaccepted rules, be sure that the separator is properly sized. If the separator doesnot include a mesh pad, consider installing one to see if this helps. You also maywant to install a mist eliminator in the line leading to the compressor (and change

it at least twice a year). If your connection into the separator is a straightconnection (versus tangential), you may want to install a straight pipe that runsfrom the inlet to the vessel all of the way to the opposite vessel wall. This pipeshould have the bottom 40% cut out. The downward entry motion will help giveadditional separation of the vapor from the liquid. You can see such a pipe in thegraphic below.

Image1:



Question: What is an air knife?

Answer: An air knife is device that is used for drying surfaces of liquid (usually water). Itworks by pushing the bulk of the liquid along of the surface being dried via anair stream. Residual film moisture is then atomized by the force of the air andthe surface is left very dry. Air knives can also be used to remove solid particlesfrom surfaces as well. You can read more about them at the website below.

Link1: Air Knife

Question: What is a synchronous motor?

Answer: A synchronous motor is an electric motor driver that is in unison, or in step, withthe phase of the alternating current operating it. It is constructed of essentially 2elements: * A stator (armature); * A rotor (field). It may have either the armatureor the field revolving, although most synchronous motors are of the revolving-field type. The stationary armature is attached to the stator frame and fieldmagnets are attached to a frame which revolves with the shaft. The field rotor

coils are "excited" by direct currents - either from a small d.c. generator (usuallymounted on the same motor shaft & called an exciter), or from some other d.c.source. It is not inherently a self-starting motor, but must necessarily beequipped with some form of auxiliary starting device, such as a squirrel cagewinding. For a synchronous motor pulling a constant load, there is a single valueof field current that will give unity Power Factor at the motor terminals.Increasing or decreasing the field current from this value will give a power factorless than unity - increasing the field current will give "leading" power facor,decreasing the field current will give "lagging" power factor. Thus, you can vary(or control) the imposed power factor - depending on the load. In a squirrel cage(induction) motor the secondary or squirrel cage winding takes the place of thefield winding found in a synchronous motor. As in a synchronous motor, arotating magnetic field is set up by the currents in the stator. There is one

important difference between the synchronous and induction motor: the rotor of the latter does not rotate as fast as the rotating field in the armature. For asquirrel cage motor, the motor slows down when loaded an amount justsufficient to produce the increased current to meet the required torque. Thedifference in speed for any given load between synchronous and load speed iscalled the "slip" - usually expressed as % of the synchronous speed. Thesynchronous motor is a constant speed machine - there is no slip. That is onereason why synchronous machines are favored in large sizes for steady,constant (low) speed operations - such as reciprocating compressors.Mechanically, the synchronous motor requires carbon brushes for the exciterand these are subject to wear. The squirrel cage motor has an air gap and nowearing parts on the electric side. Of course, both types have bearings on theirrotating shafts. Reference: CERP Message Board, Mr. Art Montemayor

Question: What types of gaskets are good for services that include pyrophoric materials?

Answer: Typical elastomer gaskets melt and can "flow" under fire conditions, so they'reout! Consider using a BINDER FREE graphite gasket for such services. They canbe either flat or spiral wound. Additionally, there are many different types of

http://www.airknife.com/

http://www.airknife.com/



metal gaskets available. Check with suppliers to see if they're gaskets areappropriate for pyrophoric materials.

Question:

For insulated pipes and vessels, what can be considered a "safe touchtemperature"?

Answer: This is usually a matter left for individual company policy, however in somecountry, safety organization may have a specific rule. Our research shows thatthe maximum "safe touch temperature" can be as low as 120 °F (49 °C) or ashigh as 150 °F (65 °C). The most common maximum temperature cited is 140 °F(60 °C). Usually, the difference in interpretation depends on how long (beforediscomfort or injury) a person should be in contact with the hot surface.Naturally, one could wrap their hand around a 120 °F pipe and keep it therelonger than a 150 °F pipe before being burned.

Link1: Making Decisions with Insulation

Question:

What is an effective way to dry out a piping system after hydrotest?

Answer: We found the following advice on the internet from Sean Shepard of SASOL NorthAmerica in Lake Charles, LA. Sean explains: "About 15 years ago an operatortaught me a good trick for drying out piping. We were drying a new line forethylene service by blowing it with hot nitrogen and testing the dewpoint at theother end. The drying process was taking a long time and costing more than wehad anticipated. The operator recommended 'pressure and depressure' and thenproceeded to close the outlet valve. When the gage read a positive pressure, hequickly opened the 8" gate valve. Each time he did this a quart or more of residualhydrotest water came pouring out, and the pipe was quickly dried. Since then the'pressure and depressure' method of drying has been my method of choice. I'mnot sure why it works so good (even without heat). It may be that this actionforces the gas to fill the entire cross section of the pipe and 'lift' water from placesthat the free flowing gas misses."

Question:

What are the most common methods of gas purging a vessel?

Answer: The four (4) most common methods of batch gas purging are: syphon, vacuum,pressure, and sweep-through Syphon purging involves filling the vessel with liquid

(product or water) and then the gas purge is introduced into the vapor space andthe liquid is drained. The purge gas volume is equal to the volume of the vessel.Vacuum purging is perhaps the most common method for purging vessel rated forthe needed vacuum condition. Vacuum is drawn on the vessel and then purge gasis used to relieve the vessel to atmospheric pressure. This proceed is oftenrepeated until an acceptable level of a component (usually oxygen) is reached.

The acceptable level will determine the number of cycles that will be necessary.Pressure purging involves the introduction of the purge gas under pressure todilute the component gas. Then the vessel is relieved to atmosphere (or other

http://www.cheresources.com/insulationzz.shtml

http://www.cheresources.com/insulationzz.shtml



treatment device depending on the gas component to be diluted). Then additionalpressure cycles can be executed to reach the desired component level. Sweep-through purging is common used for vessels that are not rated for sufficientpressure or vacuum conditions. Purge gas enters one connections and issimultaneously withdrawn from another connection until the component level iswithin acceptable limits. Reference: CEP Magazine, February 2001

Question:

How can I determine the length of a pulley belt without stopping our machine?

Answer: Approximate length: L = 2C + 1.57 (D + d) Exact length: L = 2C + 1.57 (D + d) +((D -d)2/4C) Where: L = Pitch length of belt C = Center distance D = Pitchdiameter of large pulley d = Pitch diameter of small pulley Ref:www.rhvactools.com

Image1:

Question

:

1. What exactly do engineers do? 2. What are some mathematical equations that

engineers use?

Answer: 1. What exactly do engineers do? The word "engineer" means to design,make, orimprove something. There are many different types of engineers. I am a chemicalengineer...so I design or make chemicals. For example, at the first chemical plantthat I worked at we manufactured (made) a chemical called polyester. Polyesteris used in many different types of clothing. Polyester is also the plastic that isused to make plastic pepsi and coke bottles. My job was to watch over thechemical reactions and make sure that the plastic was coming out of the processas is should be. For example, the plastic that we produced was expected to meltat a very specific temperature (we'll say 400 degrees Farenheit). Sometimes, theplastic would melt at a lower temperature, say around 390 degrees. This wouldcause serious problems for the people who buy the plastic. My job was to find out

what was causing this and correct the problem. This type of work is called"Process Engineering" because I was monitoring the process of making thisplastic. Chemical engineers also design or make the equipment in which thesechemical reactions take place. Most of these pieces of equipment are very largeand it takes much education to learn how to size these pieces of equipment. Forexample, if I'm designing a plant that must be able to produce 100,000 tons/yearof polyester, how big do the reactors have to be? It is a very difficult problem thatchemical engineers must solve. You should also know that there are many othertypes of engineers. Civil engineers design roadway systems much like the road



you took to school today. They also design drainage systems for sewers andmany other things. Mechanical engineers design mostly machines. Cars areusually designed by mechanical engineers. Mechanical engineers also designother complex machines that are necessary in industry. For example, the plasticbottles that people make from polyester are filled with pop (or soda) by complexmachines (not people). Mechanical engineers design these complex machines.Another type of engineer is an Industrial engineer. Industrial engineers designspecifications for building. For example, how high should a shower head be fromthe floor? How far apart should one door be from another? Industrial engineersalso handle heating and cooling systems in large building. Computer engineersdesign computers. The computer you're using had to be thought of bysomeone....probably a computer engineer. They also design other complexelectronics. (Do not confuse a computer engineer with a computer scientist,computer scientist general write programs while computer engineers design thehardware). Finally, Electrical engineers design all kinds of electrical devices.Some work of electrical and computer engineers are similar. The electricalengineer may design the computer chip that the computer engineer uses inhis/her computer. Realize that there are more types of engineers, but these arethe most common. The jobs that each engineer does that I've described here arein the most general of terms. There are unlimited possibilites that each one of these types of engineers may be involved in. To give you an idea of how populareach one is....when I graduated from West Virginia University, the Engineeringcollege graduated 75 mechanical engineer compared to only 25 chemicalengineers. Generally, chemical engineering is considered the "most difficult". Ibelieve that this is due to the fact that many people find chemistry to be ratherdifficult and a chemical engineer must be very good with chemistry. 2. What aresome mathematical equations that engineers use? This one's really hard toanswer. Each type of engineer has thousands (maybe millions) of equations thatthey use all of time. The basis of chemical engineering is called the "Law of Conservation of Mass". Simply stated, it means that if you put 30 lbs of materialinto a piece of equipment, you must get 30 lbs of material out that piece of equipment. Each division of engineering has an equation that describes the verynature of that type of engineer: Chemical Engineering: Mass in = Mass outMechanical Engineering: Force = Mass x Acceleration Electrical Engineering:Power = Voltage x Current These are some examples of what I mean. You can

look around The Chemical Engineers' Resource Page and find thousands of equations related to chemical engineering. Perhaps more important thanequations themselves is the branch of mathmatics that is important to eachengineer. Most engineers use a branch of math called "Calculas". Calculas is usedto describe "rates of changes" through derivates and areas through integration. Itis considered one of the highest level of mathematics. "Rate of changes" areimportant to chemical engineers because they helps us understand how achemical reaction proceeds and it help us to determine the extent to which areaction will take place for a given amount of space. This is very important indesigning chemical reactors. Mechanical engineers may be a bit of an exceptionto this rule. Mechanical engineers utilized a branch of mathematics call"Trigonometry", much more that any other type of engineer. Although I'm surethat they also use Calculas quite often.

Question:

How can I predict the pressure drop per unit time if a rupture occurs in a full sizedgas line?

Answer: Set up an excel spread sheet that first caluculates the amount in the pipe section(assume a 20 mile block valve section, then calculates the amount of fluid losttrough a fixed orifice (or hole) in the line with a given pressure (use sonic flowequation used in relief valves). Then calculate how much gas was released in 1



second. Now recalculate how much gas is left in the line and the correspondingpressure it would take to represent the new volume. Replicate the lines with theseequations and watch the pressure drop over 1 second intervals. This is anapproximation because there will actually be a flow and pressure drop toward theleak point an pressure profile will occur. From experience, people often start witha 15 psi/minute rate of change alarm and then adjusted it based on typical flowingconditions. Line balancing is performed from SCADA data every 5 minutes. If thetrend kept going in a loss for several cycles we started a detailed pressure watch.

The link below will show you a report that details the accuracy of various methodsin modeling pipeline failures.

Link1: Pipeline Failure Study

http://www.hse.gov.uk/research/crr_pdf/2000/crr00294.pdf



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