specifying heat exchanger

8/17/2019 Specifying Heat Exchanger

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As an engineer, specifying heat exchangers for procurement is an important step in thesuccessful execution of any heat transfer or energy conservation project. Early recognition thatthere are many different

heat transfer technologies available can help in receivingoptimized bids for each type of equipment available to you.

Through process investigation, the specifying engineer can collectthe necessary data to allow the heat exchanger designer tooptimize both the mechanical and thermodynamic design of theheat exchanger. Through the specification process, you canuncover critical variables such solids loading, heat transfer duty requirements, available footprintspace, maintenance considerations, and others.

Heat Transfer Resources

Although most engineers who are as ed to specify a heat exchanger may have the appropriatebac ground in heat transfer nowledge, there are cases when the engineer could benefit from arefresher on the basics of heat transfer and the equipment types involved. !ere are someresources that will help you review the basics of industrial heat transfer"

#ndustrial !eat Transfer $asics"http"%%www.cheresources.com%heat&transfer&basics.shtml

'esign (onsiderations for )hell and Tube Exchangershttp"%%www.cheresources.com%designexzz.shtml

*verall !eat Transfer (oefficients in !eat Exchangershttp"%%www.cheresources.com%uexchangers.shtml

(orrelations for (onvective !eat Transfer http"%%www.cheresources.com%convection.shtml

)hell and Tube !eat Exchanger 'esign +anualhttp"%%www.wlv.com%products%databoo %databoo .pdf

Recognizing and Evaluating the Duty Requirements

The first step in specifying any heat exchanger is to properly evaluate and identify the necessaryheat transfer duty requirements. #n other words, what do you need the exchanger to do once it-sinstalled /

A useful tool in evaluating heat transfer duty requirements is the T01 diagram. This visual toolcan help the specifying engineer easily determine what is possible in a given heat exchanger.2et-s begin with a simple example.

Due to a process change, one of the plant’s main products is exiting the process unit 30 °F higher than before. Sending the product to the storage tank at this elevated temperature ma causesafet concerns. !s the plant engineer, ou’ve been tasked "ith specif ing a product cooler forthis ne" re#uirement. $he total product stream flo" rate is %00,000 lb&h

3reviously, the product stream was sent to storage at approximately 456 78. 9ow, it-s exiting theprocessing unit at 4:6 78. The new product cooler must be able to cool the product stream bacdown to 456 78 for safe operation. The product stream has physical properties that are very

http://www.cheresources.com/heat_transfer_basics.shtmlhttp://www.cheresources.com/designexzz.shtmlhttp://www.cheresources.com/uexchangers.shtmlhttp://www.cheresources.com/convection.shtmlhttp://www.wlv.com/products/databook/databook.pdfhttp://ad.doubleclick.net/jump/Cheresources.GSIAN;sz=300x250;ord=123456789?http://www.cheresources.com/heat_transfer_basics.shtmlhttp://www.cheresources.com/designexzz.shtmlhttp://www.cheresources.com/uexchangers.shtmlhttp://www.cheresources.com/convection.shtmlhttp://www.wlv.com/products/databook/databook.pdf


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close to those of phenol. 8or the initial heat balance examination, we-ll chec the heat capacity of phenol at the midpoint of the cooling duty which is 4;< 78 to get an average heat capacity throughthe exchanger. At 4;< 78, the heat capacity of phenol is reported as 6. $tu%lb 78. ?sing thefollowing equations"

@4

@=

Bhere"

1 C heat transferred in thermal unit per time @$tu%h or B+ C mass flow rateT C temperature(p C heat capacity or specific heat of fluid)ubscript !/ C hot fluid)ubscript (/ C cold fluid

)olving Equation 4, we find that the heat transfer duty is"

1 ! C @5:, ;6 lb%h % @F.= lb%gal % @:6 min%h C F66 G3+ @nearly a factor of :

9ow, we can construct our T01 diagram for our system"


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9ow, we have the basis for what our heat exchanger needs to perform and we-ve begun toidentify the utility requirements for the duty. At this time, we need to note of couple of items.8irstly, as defined, our heat exchanger may require as much as F66 G3+ of cooling tower waterto perform the cooling tas . An investigation should be made to determine if F66 G3+ of coolingtower water is actually available. #f not, the duty must be re0examined. #n this situation, theengineer finds that he has up to 4666 G3+ of water available, so this will not be a concern.

)econdly, we note that our duty does not contain any thermodynamic violations and it does notcontain a temperature cross. There are two cases are illustrated below"

9otice the T01 diagram that shows a thermodynamic violation. The cold side is being heated to atemperature that is above the inlet temperature of the hot side. )uppose that in our example, theengineer found that there were only 466 G3+ of water available. !is analysis would have shownthe water would have exited the exchanger far above the 4:6 78 hot side inlet temperature. #n


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short, this is not enough water to accomplish the duty. At that point, he would have to investigateother utility options.

#n the second image above, the T01 diagram shows what is now as a temperature cross. Thecold side outlet temperature is higher than the hot side outlet temperature. #t-s important to notewhether or not your duty contains a temperature cross as it will have a significant impact on the

type and number of heat exchangers that may be required to perform the duty.

As the engineer is examining a new heat transfer duty, the concept of 9T? or 9umber of Transfer ?nits should be used to help guide the specification. A good rule of thumb is that a single shelland tube heat exchanger should be designed with a minimum temperature approach of 46 78.The temperature approach/ is defined as the temperature difference between the hot side outlettemperature and the cold side outlet temperature. #n our example above, the approachtemperature is 456 78046F78 C == 78. This duty can easily be accomplished in a single shell andtube heat exchanger.

9ow, consider the following duty shown in 'uty =/ above. This unit has a deep temperaturecross/. This is where the concept of 9T? can be helpful. 8or 'uty = above, we calculate the9T? for the hot side and the cold side as follows"

@5

@;

@<

2+T' C 5>.4< 789T? !*T C 4.4< C 5.F59T? (*2' C 4 6 % 5>.4< C ;.5;

The 9T? can be translated into the approximate number of shell and tube heat exchangers inseries that will be required to perform a given duty. The engineer must realize that if it isnecessary to perform 'uty = just as it is shown, it will be an expensive proposition in terms ofpurchased equipment costs, installation costs, and maintenance costs over the life of the shelland tube heat exchangers.

)hell and tube heat exchanger do a relatively poor job of temperature crossing/ due to their lacof purely countercurrent flow as shown here"


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The shell side of the exchanger is almost always baffled so that a reasonable heat transfercoefficient can be obtained. The tube side flow in this image shows a single tube pass. Bhilethis is possible, it-s not very common. The tube side velocity is the ey to the tube side heattransfer coefficient and the ability to mitigate fouling. 8or these reasons, multiple tube passes aretypically used in shell and tube exchangers. The result of these flow patterns is a lac ofcountercurrent flow. #n fact, the 2+T' or 2og +ean Temperature 'ifference in shell and tubeheat exchangers has be corrected for these flow patterns. Typically, the calculated 2+T' has tobe multiplied by a factor of 6. 6 to 6.>6 to account for the flow patterns.

#f 'uty = is required, the engineer may want to consider a heat exchanger type with trulycountercurrent flow such as a pipe0in0pipe @commonly called a hairpin exchanger or a plate heatexchanger. These devices, with their truly countercurrent flow patterns, can perform duties withtemperature crosses in a single unit rather than requiring multiple units in series.

Hegardless of the heat exchanger type chosen, the engineer must be aware of this scenarioduring the initial specification stage for the heat exchanger.

At this point, the engineer has established the basic parameters for the heat exchanger and nowother factors need to be investigated prior to the specification process.

Next > Exploring Other onsiderations in Heat Exchanger the !pecification

Exploring Other onsiderations in Heat Exchanger !pecification3rior to completing the heat exchanger specification data sheet, the engineer should answerquestions such as"

• Are there any phase changes expected to occur in the heat exchanger• Are there any dissolved gases in either stream• Are there any dissolved or suspended solids in either stream• Bhat are the operating pressures of the streams

http://www.cheresources.com/shell_tube_heat_exchanger_1a.shtmlhttp://www.cheresources.com/shell_tube_heat_exchanger_1a.shtml


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• !ow much pressure loss is available in the exchanger @for existing pumps• Bhat are the fouling tendencies of the fluids involved• Are either of the fluids non0newtonian• Are either of the fluids corrosive Bhat material of constructions are required• Bhat types of elastomers and%or compression gas ets are compatible with the fluids• Are either of the fluids considered lethal to plant personnel• #s mechanical cleaning expected to be necessary for one or both fluids• #s there a cleaning solution that may be effective for the exchanger• !ow much room is required for maintenance of the new exchanger

!aving answers to these questions can help ensure that your heat exchanger specification, andultimately the heat exchanger that you purchase, is right for your heat transfer duty.

3hase (hanges

Even in liquid0liquid heat transfer duties, it-s important to recognize the potential for phasechanges inside the heat exchanger. 8or example, if a process stream is available to 5


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powdered solid. ?sually, a plant will have a well documented history of what type of exchangerswor well with a solid0laden stream and often times, plants will establish velocity limitations forpipelines and other processing equipment.

*perating 3ressure

Examine the operating pressures of each stream that are to enter the heat exchanger. +anycompanies have policies dictating that the design pressure of a process vessel must be a certainfactor above the highest operating pressure. 8or example, if the highest operating pressure for aheat exchanger is to 466 psi, then a reasonable design pressure may be 4


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9otice how the stream can be allowed to actually cross pressures in the heat exchanger if the twostreams are close in operating pressures. This scenario, if extreme enough, can cause flexing ofthinner material surfaces inside of heat exchangers and lead to premature failures.

Available 3ressure 2oss

#f preparing to install a heat exchanger in an existing process system, the engineer shouldexamine any pumps in the system to determine how much pressure loss is available. Generallyspea ing, most heat exchangers should need between < and 4< psi of pressure loss to operateeffectively. 8or nown fouling fluids, a higher pressure loss @corresponding to a higher velocitywill help eep the exchanger clean for a longer period of time. Also remember that pressure lossis proportional to the fluid viscosity. )pecifying a pressure loss of < psi for a process fluid with aviscosity of 566 c3 may result in a very large heat exchanger.

#f your pumping system cannot handle the necessary additional pressure loss to obtain a goodheat exchanger design, then an impeller change out, a new pump, or an additional pump in seriesmay be justified. Bhen utilizing a shell and tube exchanger, you can expect the pressure loss onthe tube side to be higher than the shell side in most cases.

8ouling Tendencies of the 8luids

The engineer should also be aware of the fouling tendencies of the fluids involved. Throughpersonal experience, interviews with other plant personnel, or investigation into other heatexchangers, the engineer can usually determine how quic ly a particular fluid may foul anexchanger. +any plants will have a library of shell and tube fouling factors for various processduties.

3robably one of the most common errors made in specifying a new heat exchanger isoverdesign. Anticipating fouling is smart, overdesigning too far however will ensure that foulingwill occur. (hoose your fouling coefficient carefully. Hemember, that specifying too large afouling factor will often result in more tube or parallel channels. This will lower the velocity in theexchanger and actually promote the fouling. This is a balancing act that is well worth a little timeand effort.

Bhen considering a fouling factor, it-s very important to note the type of equipment that may beused in the service. Another common mista e during heat exchanger specification is to applyfouling factor information from one type of equipment to a completely different type of equipment.

Hemember that shell and tube fouling factors have been compiled over decades throughexperience and temperature measurement. Also, realize that typical overall heat transfercoefficients for shell and tube may range from 4


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)o, the ?0value for the shell and tube went from 45: to 4=6 $tu%h ft = 78 through the foulingcoefficient. The ?0value for the compact exchanger went from ;;< to 56F $tu%h ft = 78 through thefouling coefficient. Therefore, the shell and tube overdesign is about 4=I while the compactexchanger overdesign is over ;6I.

The specifying engineer must realize where the fouling factor information is derived from andapply it properly in the future. Bhile shell and tube exchangers have long used fouling factors,compact heat exchangers generally utilize a heat transfer margin/ that is typically 460=


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Elastomers and (ompression Gas et (ompatibility

'epending on the type of heat transfer technology that is being considered for the application, achec of gas et compatibility may be required. Elastomer gas ets are most commonly offered inmaterials such as E3'+, 9itrile, 3T8E, and 8J+G @a generic form of Kiton0G from 'upont .Elastomer gas ets can seldom be rated for temperatures in excess of 5=6 78. Generally

spea ing, the engineer should see a recommendation from the heat exchanger manufacturer asthey usually have extensive databases that show the best gas et choice for a given application.

8or compression gas ets, such as those used on the heads of shell and tube exchangers, thereare a couple of rules of thumb to eep in mind. #n addition to the need for the gas et to becompatible with the process or service fluid, the engineer may need to decide between a metallicor non0metallic compression gas et. (onsider this guideline"

Find the value of ' (perating )ressure *psig+ x (perating $emperature *°F+f this value exceeds -%0,000, the use of a metallic gasket should be strongl considered.

!dditionall , non metallic gaskets are seldom used at pressures in excess of /-00 psig andtemperatures in excess of %0 °F.

2ethal )ervice Hequirements

The A)+E pressure vessel code stipulates very specific pressure vessel requirements for heattransfer service that are qualified as lethal/. #f the service requires an A)+E 2/ stamp, be sureto specify this to the heat exchanger manufacturer.

(leaning (onsiderations

)ome process fluids can leave fouling deposits that can be especially difficult to remove.)ometimes, these deposits can be removed by chemical cleaning. (hemical cleaning of heatexchangers, in general, is popular in industries that utilize sanitary protocols @food,pharmaceutical, etc. and chemical cleaning is widely accepted in the chemical process industryin Europe. (hemical cleaning requires additional equipment, cleaning chemical, and a method of disposing of the chemical cleaning agent. (hemical cleaning can be a good choice in thefollowing instances"

4. The fouling deposit can be easily dissolved and removed by a readily available cleaningagent.

=. The heat exchanger fouls quic ly and must be cleaned fairly often @; or more times ayear

5. The heat exchanger to be cleaned has a relatively small hold up volume so that chemicalcleaning equipment and the volume of cleaning agents can be minimized.

8or heat transfer duties where chemical cleaning does not seem li e the best choice, theengineer must be sure that the fouling fluid is placed on a side of the heat exchanger that isreadily accessible for mechanical cleaning. +echanical cleaning usually consists of a highpressure water spray of the affect area, although additional scraping can sometimes benecessary. 8loating head shell and tube heat exchangers, gas eted plate exchangers, spiralheat exchangers, and some welded plate heat exchangers allow good access for mechanicalcleaning.

A final consideration for mechanical cleaning is the space required around the heat exchanger.Bhen choosing an installation location, be sure that the necessary maintenance space isavailable for proper and safe maintenance of the new equipment.


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!hell and Tu"es # $here !hould % &ut the 'luids(

#n shell and tube heat exchangers, the specifying engineer has to decide whether each fluidshould be placed on the shell side or the tube side. #n general, fluids that exhibit thesecharacteristic are preferred for the tube side"

4. !igh pressure fluids=. (orrosive fluids5. 8ouling fluids;. Kiscous fluids


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Each shell and tube exchanger is designated by a three @5 letter code. The letters refer to thespecific type of stationary head at the front, the shell type, and rear head type. 8ixed tube sheetstyle exchangers with TE+A designations of $E+, AE+, or 9E9 are fairly common for liquid0liquid heat transfer duties. Bhile fixed head arrangements have the advantage of beinginexpensive and avoiding gas ets or pac ing to contain the shell side fluid, they do not allow formechanical cleaning of the shell side.

8or liquid0liquid heat transfer duties where the ability to mechanically clean the shell side as wellas the tube side is a requirement, a floating head design should be chosen. Bith a floating headdesign, the tube bundle can be pulled out of the shell to allow access to the shell side. )ome ofthe most commonly used floating head designs for liquid0liquid duties include AE) and $E).

Another advantage of the floating head design is the ability to accommodate larger temperaturedifferentials between the hot side and cold side fluids.

All of the designations discussed so far @$E+, AE+, 9E9, AE), and $E) allow for multiple tubepasses which are usually required for liquid0liquid duties so that the tube side velocities can bemanipulated during the design stage of the exchanger.

The final type of shell and tube exchanger commonly used for liquid0liquid duties is commonly

referred to as the ?0tube/ type. (ommon TE+A designations are $E? and AE?. #n thisarrangement the tubes are bent into a series of concentrically tighter ?0shapes with the end of thetubes being attached to the tube sheet.

The ?0tube bundle can be removed to access the shell side for mechanical cleaning. The ?0tubedesign is preferred for services with temperature or pressure cycling, intermittent service, andwhen there is a large temperature differential between the shell side and tube side fluids.

)ince the ?/ bend of the tubes cannot be accessed for mechanical cleaning, the tube side fluidshould be clean or a suitable chemical cleaning agent should be identified.


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)ethods of Estimating &hysical &roperties

Bhen specifying a liquid0liquid heat exchanger, the specifying engineer must be able to providephysical properties that are as accurate as possible. 8or liquid0liquid duties, the following datashould be provided for each fluid" density, thermal conductivity, specific heat @sometimes calledheat capacity , and viscosity. #deally, these properties should be provided for each fluid at boththe inlet and outlet temperature of the exchanger.

#f data is limited, there are some estimating rules that be of assistance. The physical propertiesthat will impact the design of the exchangers the most are the viscosity and the specific heat. Hecall that the specific heat of a fluid is required in order to accurately specify the exchanger.9ow, we-ll examine estimation methods for each of the physical properties. Bhile actual plantdata or experimentally determined data is preferred, these methods can be used when no otherdata is available. 8or our estimation methods, we-ll assume that typical process fluids are madeup of mixtures of components and that the data for each component is available. This is almostalways the case.

)pecific !eat

8or fluid mixtures where there is no nown heat of mixing, a weighted average can be used"

@F

Bhere"

( pmix C !eat capacity of the mixture in consistent unitsB 4 C Beight fraction of component one( p24 C !eat capacity of component one in consistent unitsB = C Beight fraction of component two( p2= C !eat capacity of component two in consistent units

#f using the above method, loo up the heat capacity of the components at the averagetemperature through the heat exchanger. #t-s not uncommon to provide heat exchangerdesigners with a single heat capacity point for each fluid. $e aware that the heat capacity of mostliquids will increase with temperature.

Kiscosity

Bhile it-s not critical to supply a physical property point at the inlet and outlet temperature for

other properties, it-s very beneficial to do for the viscosity of the fluids. ?sing only a singleviscosity point will affect both the heat transfer and pressure drop calculation of any heatexchanger.

8or non0polar mixtures, the following has shown to provide viscosity estimates to within L%0 <046I"


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@>

Bhere"

Mmix C Kiscosity of mixture in centipoiseB 4 C Beight fraction of component oneM4 C Kiscosity of component one in centipoiseB = C Beight fraction of component twoM= C Kiscosity of component two in centipoises

8or polar fluids, electrolyte solutions, and non0newtonian fluids, it is highly advisable to either findreliable data or have an outside lab perform testing. There is an estimation method available forpolar mixtures called the +ethod of Grunberg and 9issan/. This method is detailed in )ropertiesof 1i#uids and 2ases , Edition ; by Heid et al. @#)$9 66 6>4, see page ; ; .

#f viscosity data is available at one temperature, the following correlation chart that has been usedfor years to estimate the viscosity at a second temperature. This chart is used by finding thesingle available viscosity point on the N0axis and move left to meet the curve. Then, on the O0axis, adjust the temperature difference up or down by the temperature change required. 9ext,move up to hit the curve again and read the resulting viscosity from the N0axis.


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Thermal (onductivity


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The thermal conductivities of mixtures can be estimated via the same weighted average methodshown in Equation > for specific heat calculations. The calculation is the same, just replace thecomponent specific heats with the component thermal conductivities. #n cases where there is acomplete absence of data, eep the following ranges in mind"

Bater based mixtures, thermal conductivity range is about 6.=F to 6.5< $tu% h ft 78

!ydrocarbon based mixtures, thermal conductivity range is about 6.6


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The information on the first page of the specification is essentially a description of the problem ashas been covered herein. *n the second page, the specifying engineer is as ed to indicate thedesign pressure and temperature. The test pressure is generally accepted as 4.5 times thedesign pressure as specified by the latest version of the A)+E 3ressure Kessel code. )ometimes, however, the specifying engineer may request a higher design pressure @perhaps 4.< times


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design pressure . The engineer is also expected to specify materials or choices of materials forthe heads, shell, tube sheets, tubes, and the compression gas ets @if applicable .

The specifying engineer can also indicate any required corrosion allowances required as well asany special mechanical or non0destructive testing that may be required for an exchanger to beinstalled in a particular duty.

#f the installation of the exchanger would be simplified by a particular nozzle arrangement ormaximum overall length, this type of information can be provided in the s etch box or in theremar s section. ?se the remar s section to convey any other pertinent information to thedesigner.

onclusions

)pecifying a liquid0liquid heat exchanger is not always as easy as it may appear. $ut an engineer who examines the problem carefully and prepares an accurate, yet flexible, specification will findthe entire process much easier. Thin ing about all aspects of the heat exchanger to be installedcan also help avoid problems in the future or surprises during the installation of the equipment.

CHOICE OF DESCALING CHEMICAL AND QUANTITY REQUIRED:For mild steel heat e !ha"#ers$ e%e" &ith !o''er$ (rass or (ro")e a"!illar*!om'o"e"ts$ +se SCALE,REA-ER HD.I/ the heat e !ha"#er +tilises a"* stai"less steel i" the !o"str+!tio"$ SCALE,REA-ERHD sho+ld "ot (e +sed. Either SCALE,REA-ER SR or SCALE,REA-ER F0 sho+ld (e+sed$ de'e"de"t o" the t*'e o/ /o+li"#.1. Che!2 the %ol+me 3 !a'a!it* o/ the se!tio" to (e des!aled 4+s+all* the &ater5side6$

a"d !al!+late the amo+"t o/ des!ali"# !hemi!al re7+ired.8. As a #+ide$ /or a 89 litre !a'a!it* heat e !ha"#er$ +se 1 89 litre o/ des!ali"#

!hemi!al 4ie. a 1 ; sol+tio" (* %ol+me6. A &ea2er sol+tio" ma* (e +sed$ (+t &ill

ta2e lo"#er to remo%e a #i%e" amo+"t o/ s!ale.


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9. Co""e!tio"s sho+ld (e made so that there is a !losed !ir!+it (et&ee" the '+m'o+t'+t hose$ thro+#h the heat e !ha"#er to the ret+r" hose.

B. e"ti"# o/ the !ar(o" dio ide #as e%ol%ed is a!hie%ed thro+#h the '+m' ta"2 =ller!a' a'ert+re. The !a' sho+ld (e s!re&ed o" (* "o more tha" o"e 7+arter o/ at+r". This is

DESCALING TU,ULARHEAT E0CHANGERS

G+ida"!e "otes HEATE0CHANGER Drai"%al%eTa''i"#3'ress+re #a+#e =tti"# DESCALING UM ?o& a"d ret+r"

t+(i"#?o& a"dret+r" t+(i"# ?o&re%erser


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-am!o Limited 8 > Des!ali"# T+(+lar Heat E !ha"#ers: G+ida"!e Notes -am!o Limited8 > Des!ali"# T+(+lar Heat E !ha"#ers: G+ida"!e Notess+ !ie"t to %e"t the #as$ (+t at the same time red+!es /+mes a"d 're%e"ts

s'lashes.. Co""e!t the '+m' to a s+ita(le earthed 'o&er s+''l* 488 or 11 %olt$ a!!ordi"#

to model6. As the '+m' &ill (e +sed i" a dam' lo!atio"$ &e re!omme"d that aresid+al !+rre"t !ir!+it (rea2er 'l+# to' (e +sed.

. The ?o& re%erser ha"dle 'oi"ts i" the dire!tio" o/ ?o& o/ the li7+id. T+r" theha"dle so that it i"itiall* 'oi"ts to&ards the hose #oi"# to the lo&er heate !ha"#er !o""e!tio". The hose /rom the to' o/ the heat e !ha"#er &ill the" (ethe ret+r" to the '+m' ta"2.

. rior to addi"# des!ali"# !hemi!al to '+m' ta"2$ =rst 'ro%e the !ir!+it &ith /resh&ater alo"e. Add &ater to '+m' ta"2 to a''ro . !m. a(o%e mi"im+m li7+id le%el$s&it!h o" '+m'$ a"d immediatel* o'e" the %al%e detailed i" 'oi"t > a(o%e$ toallo& !ir!+latio" to !omme"!e. I/ &ater le%el dro's i"itiall*$ add more &ater to'+m' ta"2$ a"d !he!2 that all !o""e!tio"s are ti#ht.

1 . To !omme"!e des!ali"#$ slo&l* add des!ali"# !hemi!al i"to '+m' ta"2$ &aiti"#+"til li7+id is ret+r"i"# i"to the des!ali"# '+m' ta"2 /rom the heat e !ha"#er$ a"d!he!2 to see i/ there is a ra'id (+ild +' o/ /oam o" to' o/ the li7+id i" the '+m'.

This ma* ha''e" &he" there is a lar#e (+ild +' o/ rea!ti%e limes!ale i" the heate !ha"#er. I/ this is e !essi%e$ add a little FOAM,REA-ER !are/+ll* to the ta"2.

11. As '+m'i"# !omme"!es$ (+((les a"d /oami"# &ill (e see" i" the ret+r" hose tothe '+m'$ i"di!ati"# that limes!ale is (ei"# dissol%ed. I/ /oam /ormatio" ise !essi%e$ !are/+ll* remo%e des!ali"# '+m' ta"2 !a'$ a"d add FOAM,REA-ER tothe '+m' ta"2 to sto' the /oami"#.

18. Re%erse the dire!tio" o/ ?o& 'eriodi!all*$ !he!2i"# all !o""e!tio"s /or ti#ht"essa"d a(se"!e o/ lea2s.

1


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e !ha"#ers i" #e"eral. It is #i%e" i" #ood /aith$ (+t d+e to the di%erse a"d %aried"at+re o/ s+!h e7+i'me"t$ the +ser m+st satis/* himsel/ that the a(o%e 'ro!ed+re is%ia(le i" the 're%aili"# sit+atio".

specifying heat exchanger

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