Brazed Plate Heat Exchanger Operations Manual

Brazed Plate Heat ExchangerOperations Manual

Brazed ExchangerOperations ManualTABLE OF CONTENTSBrazed Heat Exchangers from PolarisA. How the Polaris BrazedHeat Exchanger operatesdeliver exceptional strength andBApplicationsperformance in a compact package.CExchanger SpecificationsThese versatile units are widely used inrefrigeration, industrial and hydronicsapplications. The highly skilled Polarisengineering staff employs exclusivedesign software to be sure of providingyou with exactly the brazed exchangerto fit your application. Equally helpfulare Polaris’ experienced fieldrepresentatives, many of whom canprovide the brazed exchanger you needfrom stock.D Advantages of PolarisBrazed Heat ExchangersEInstallation GuideFAdditional Information onRefrigeration ApplicationsG Start-up ProceduresH Shut-down ProceduresICleaning

Typical Application for Brazed Heat ExchangersAStorage tankOilseparatorCompressorBrefrigerante.g. wateroil1. Condensor2. Subcooler3. Economizer4. Evaporator5. Oil cooler6. DesuperheaterFig. 2Fig. 1AHow the Polaris BrazedHeat Exchanger operatesEach Polaris Brazed Heat Exchangeris assembled from embossed platesof high-quality stainless steel – up to200 herringbone-patterned plates ina single exchanger. Adjoining platesare reversed so as to form a lattice ofcontact points from the ridges of theplates.With the plates vacuum-brazedtogether, a compact, pressure-resistantand very efficient heat exchanger iscreated. (See Fig. 1)In the finished unit, the ridges andindentations in the plates form twocompletely distinct channel systems,allowing maximum heat transferwhile keeping the transfer mediarigorously separated. With the mediaflowing in true countercurrent anda complex plate pattern that createsvigorous turbulence, heat transfer ishighly efficient. Our standardexchanger meets 390 F, 435 psistandards; maximum flow capacityin our largest unit is 250 gpm.BApplicationsPolaris Brazed Heat Exchangers arecost-effective, easy to install orreplace, providing a highly efficientmeans of heat transfer. Specify themfor any of the following applications:(See Fig. 2)Hydronics Snow melting –sidewalk or driveway Radiant heating Domestic hot waterIndustrial Boiler blowdown Hydraulic oil cooling Heat recovery from hotwaste streams Packaged systemsRefrigeration Condensers Evaporators Economizers De-superheaters Subcoolers Heat pumps

CExchanger SpecificationsBASTANDARD DATA Min. working temperature -300 F Max. working temperature 390 F Max. working pressure 435 psi Test pressure 652 psiMATERIALSDEFCTYPEABCDEF(inch)CONN. LONSL34TL11 1/2"9 1/2"4 5/8"2 1/2"(N x .08) 0.33/4"1"(N x .26) 1.30.3660.014SL70TL19 5/8"17 1/2"4 5/8"2 1/2"(N x .09) 0.33/4"1 1/2"(N x .48) 3.00.7530.023SL70TK19 5/8"17 1/2"4 5/8"2 1/2"(N x .09) 0.43/4"1 1/2"(N x .48) 3.00.7530.023SL140TL23 7/8"20 1/2"9 3/8"5 7/8"(N x .10) 0.43/4"2 1/2"(N x .95) 10.01.5060.084(N number of plates) (Solder connection available.)Higher working temperatures/pressures available.DAdvantages of Polaris Brazed Heat Exchangers Close Temperature Approach –A small difference in thetemperatures of the exchangemedia (for instance, betweencondensing and cooling water)can result in substantially higherefficiency to the overall system.It’s often possible with brazedexchangers to use smaller systemcomponents, such as compressors. High Working Pressures – PolarisBrazed Heat Exchangers are ratedto pressures of 40 bar, making themwell suited to high-pressureapplications including thecondensing side of refrigerationsystems. Freeze Resistance – Because of thehigh turbulence in the channels,any tendency toward freezing ofcooling water is minimized. Assuch, temperatures at the waterside can be lower than in any otherkind of heat exchanger. Should asystem failure cause freezing in theunit, Polaris Brazed HeatExchangers will recover betterthan other types of heatexchangers. Compactness – Polaris Brazed HeatExchangers occupy as little as onesixth the area of other types ofexchangers – a tremendousadvantage in many applications,especially prefabricated systems. Modularity – When systems arebuilt in modules, Polaris BrazedHeat Exchangers can easily bearranged in parallel. Economy – Considering theadvantages of brazed heatexchangers – low purchase price,fast and easy installation, lowshipping cost, simple tubinginstallation, smaller cabinets andso on – Polaris Brazed HeatExchangers are often considerablymore economical than alternatives.

CorrectMountingPositionMounting OptionsMaximum connection loads on brazed heat exchangersAllowable Torque, NmStandard Connectionsfor Brazed Heat ExchangersSL 34SL 70SL 140Bottom SupportFig. 3Crossbar & boltsStudboltsAssembly conditions*BendingTwisting3060160Operating conditions**BendingTwisting5015035020401003090200* Single assembly loading in cold condition** Load due to piping forces during normal operation,not considering high cycle fatigueFig. 4Fig. 5EInstallation guide1. GeneralWhere possible, Polaris Brazed HeatExchangers should be mounted inthe vertical position. (See Fig. 3)Install mufflers or vibration absorbersas necessary to make sure vibrationcannot be transmitted to the heatexchanger. For larger connectiondiameters, use an expansion devicein the pipeline. A rubber mountingstrip can serve as a buffer betweenthe unit and the mounting clamp.(See Fig. 4)2. Connecting to the system Use flexible connectors. It’s criticalthat vibrations from pipework andcontrol valves not be transferredto the heat exchanger. Don’t overtighten female unionsonto the threaded connections;excessive force will shear theconnection braze.The threads areparallel. Polaris advises use of aconnection with the female partsealing against the top of the heatexchanger connection. (Check thechart below for maximumallowable torque.) Seal unions withO-rings or round gaskets at the endof the connection.Tape may alsobe used to seal the threads. Be sure that adequateexpansion/safety valves areinstalled into the adjacentpipework. Polaris recommendsthe use of expansion tanks. If pipework is to be soldered intothe nozzles on the exchanger:– Fill the outer circuit with water;the circuit must be open to the air.– Wrap a wet towel around the baseof the connection to be soldered.– Use solder containing at least 45percent silver.– Never weld connections onto ornear the exchanger. (See Fig. 5)3. Avoiding water hammer.Sudden changes in the velocity of anoncompressible fluid (such aswater) can result in “water hammer,”a condition that damages pipes,valves, heat exchangers and otherequipment.The quick closing of asolenoid valve in liquid lines is atypical cause. Sudden interruptionsof the fluid flow increase pressurefar above normal levels. Highintensity pressure waves then moveback and forth in the pipe betweenclosure and relief points. At a reliefpoint such as a large-diameter header,these waves can strike at extremelyhigh speed.

Water hammerNormal workingconditions, open valveQuick closing of solenoidvalve, producing suddenpressure riseFlow Pattern for CondensorGas inWater outRefrigerant sideWater sideCondensate outWater inHigh-intensity pressurewaves travel back andforth in the pipesFig. 6The shock wave produced in thisway can cause substantial damageas it alternately expands andcontracts the pipe lines. In brazedheat exchangers, water hammer candeform the front or back plate intoa bulb shape, with resulting internalor external leakage.An air chamber or water hammerarrestor can avoid or eliminate theseproblems. Valves with controlledclosing times or characteristics canalso control the problem.(See Fig. 6)4. Refrigeration detailsCondensersRefrigerant gas flows in at the topleft. Condensate liquid flows out atbottom left. Water inlet is at thebottom right and water outlet at thetop right. Connect water andrefrigerant for countercurrent flow.Fig. 7Regulate and control the system viathe service medium circuit. Solderconnections to the refrigerant sidewhen using Polaris Brazed HeatExchangers as condensers.(See Fig. 7)EvaporatorsThe mixture of liquid and refrigerantgas flows in at bottom left. Gas flowsout at top left. Water inlet is at thetop right and water outlet at bottomright. Connect water and refrigerantfor countercurrent flow in mostcases.Place the expansion valve near theinlet connection.The valve shouldbe of slightly higher capacity thanthe unit, and should have an externalpressure equalizing connection toavoid unnecessary heating.The sensor bulb located on thesuction side should be insulated fromambient air. It must be sensitiveenough to respond quickly tochanges in gas temperature.Allow atleast 500 mm between bulb and therefrigerant outlet connection.Pipe diameter between theexpansion valve and the brazedexchanger should be the same asthat of the liquid line. Solderconnections to the refrigerant sidewhen using Polaris Brazed HeatExchangers as evaporators.(See Fig. 8)FAdditional Informationon RefrigerationApplicationsa. When operating temperatures arelow, insulate the unit to keepcondensation from freezing on theouter surface of the plate pack.b. Use quick-acting controls for mostrefrigeration applications.

Evaporator Flow ArrangementCleaning in placeGas outWater inRefrigerant sideWater sideHeat exchangerWeak AcidGas/liquid inWater outFig. 8GFig. 9HIStart-up ProceduresShut-down ProceduresCleaning1. Close all isolation valves.2. Fill and vent the coldest circuitfirst.3. Start circulation of the cold circuit,opening isolation valves gradually.4. Repeat the process with the hotcircuit.5. Start automatic control regulation.6. In steam systems, drain the steamcircuit before opening steamvalves.This precaution helpsreduce the chance of waterhammer and damage to theexchanger.1. Close down the hot circuit byslowly adjusting the control valve.Maintain full flow on the coldcircuit.2. When the control valve is fullyclosed, switch off the pump.3. Slowly close down the cold circuit,then switch off the pump.4. Close all isolation valves.5. When the unit is cool, drain itcompletely.When the likelihood of fouling ishigh (for instance, when hard wateris used), clean the exchanger bycirculating a cleaning liquid throughit. Use a tank with a weak acid forthis clean-in-place (CIP) process.A five-percent solution of phosphoricacid is a safe and effective choice formost units. If the exchanger iscleaned frequently, use a five-percentsolution of oxalic acid.For best results, the cleaning solutionflow rate should be at least 1.5 timesthe normal flow rate, preferably inbackflush mode. Before restarting,flush the unit with plenty of freshwater to purge any remaining acid.Clean at regular intervals.(See Fig. 9)

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Heat Exchangers can easily be arranged in parallel. ÊEconomy – Considering the advantages of brazed heat exchangers – low purchase price, fast and easy installation, low shipping cost, simple tubing installation, smaller cabinets and so on – Polaris Brazed Heat Exchangers