Brazed Plate Heat Exchanger Operating & Instructin Manual U K Exchangers Ltd Unit 55, Stilebrk Rad Olney Buckinghamshire MK46 5EA Tel: (01234) 244320 Fax: (01234) 714978 Email: sales@ukeltd.cm Web: www.uk-exchangers.cm
1. Cnnectin Designatin and Use:- 2
3 Cnnectin Designatin and Use cntinued: Cnnecting up t the PHE use the sketch n the previus page as a guide. In general, the primary circuit is labelled red in/ut, and the secndary circuit is labelled blue in/ut. Primary flw = F1 (red in) Primary return = F4 (red ut) Secndary return = F3 (blue in) Secndary flw = F2 (blue ut) Refrigerant cndensing: Refrigerant inlet/utlet = F1 / F4 Water inlet / utlet = F3 / F2 Refrigerant evapratin Refrigerant inlet / utlet = F4 / F1 Water/glycl inlet / utlet = F2 / F3 fr max. amunt f superheating.if the temperatures are clse t the fridge Evap. temperature. F3 / F2 fr quickest biling
4 2. Installatin - General Pints:- Supprting: A) Place n a suitable shelf. B) By brackets. C) By using the pipe wrk (prviding weight f unit taken by anther supprt). Avid: Safety: Drilling thrugh any part f the exchanger. Pressure it is essential that the exchanger, as with all pressure cntainers, is prtected frm the effects f any ver pressurisatin shuld a fault in the peratin f the system arise. Prvisin f suitable pressure relief devices such as relief valves, r bursting disks shuld be cnsidered and installed in the pipes clse t the PHE. Pipe wrk: We recmmend the fllwing... 1) that the pipe wrk is fully supprted t avid weight/frces acting upn the unit. 2) the fitting f flexible cuplings if the pipe wrk is subject t vibratin. 3) the fitting f flexible cuplings if perating ver 80 Deg. C. (t absrb expansin). 4) that the pipe wrk is cmpletely flushed befre attaching t exchanger. 5) the fitting f suitable vents & drains. 6) the fitting f islating valves / by-pass valves t facilitate easier inspectins, etc, shuld the need arise. Fittings: Welding: Filtratin: The use f thermmeters and pressure gauges t recrd temperatures and pressures in the inlet and utlet pipes f bth circuits f the PHE is recmmended. Peridic checking f these devices shall allw the perfrmance f the exchanger t be mnitred, plus, give a visual warning that the internal passages are becming fuled up thrugh service. Nne allwed, either nt, r near the exchanger. Unless therwise stated, a filter mesh shuld be used t remve all particles greater than 0.5 m.m. diameter.
5 Cnnectins: AVOID ver tightening nt the threaded cnnectins. Excessive frce shall shear the cnnectin braze. The threads are BSPT. Althugh the best methd is t seal by the use f an O-ring, r a ring gasket lcated at the end f the cnnectin, the threads can be sealed by a suitable tape / paste. Sldering: Steam: Ensure cnnectin and pipe wrk are thrughly cleaned Apply flux t prtect frm xidising & t help cl the temperature PHE t be hrizntal Fill the ther circuit with water (ensure pen t atmsphere). Wrap a wet twel arund the base f the cnnectin t be sldered. Use slder cntaining n less than 45% silver. The steam supply shuld be f gd quality, dry saturated, & at the design pressure. Attentin shuld be paid t the sizing f the steam traps these must be f adequate size (the steam cnsumptin figures are given in the design data sheets), and alng with any strainers, must be lcated belw the lwer mst level f the exchanger. It is essential that nly gd quality steam enters the exchanger - a strainer and trap set shuld be psitined within the steam supply line. See FIG 2 fr suggested system lay ut. NOTE althugh the PHE ffered is safe t use when perated as abve, there is a ptential issue between the differences in the expansin rates f the stainless and the cpper materials. This can result in cracking f the braze which shall lead leakage frm the PHE and a shrter than expected service life f the unit. Fr this reasn, we d nt give any service life guarantee fr the abve equipment when used with steam. Refrigerants: Insulate unit t avid cndensatin freezing n the plate pack fr lw temperature use. Quick acting refrigerant cntrls are best suited fr use with the brazed plate. Evaprating psitin the expansin valve as clse as pssible t the liquid cnnectin. The valve shuld be f a slightly higher capacity than the unit, and shuld have an external pressure equalising cnnectin t avid unnecessary heating. The sensr bulb lcated n the suctin side shuld be well insulated frm the effects f the ambient air temperature, and shuld be sensitive enugh t respnd quickly t changes in the gas temperature. Cndensing regulate and cntrl via, r n the service medium circuit. 3. Cmmissining & Starting :- Shck :- It is essential that the exchanger is nt subjected t thermal r mechanical shck as this culd lead t premature failure. Start up: Fully vent pipe wrk system and the PHE. Clse islatin valves between pump & exchanger. Fully pen valve fitted int return line frm the exchanger. Start the circulatin pump (cldest circuit first). Gradually pen clsed valve fitted t inlet line f exchanger. Vent circuit again if necessary special cnsideratin must be given t discharge f ht fluids. Repeat fr the ther circuit.
6 Checks: 1) Check fr pressure pulses in system caused by the pumps r cntrl valves. If fund, stp peratin, and rectify. Cntinuus pressure pulses will result in fatigue failure f the plates. 2) Check that all pump vents are clsed t prevent air being sucked int system. Steam: Use nly slw acting cntrl valves and mechanisms. Befre start up :- a) ensure that the steam cntrl valve is fully clsed. b) ensure that the exchanger, and supply line, is fully drained f cndensate. Start cld circuit first, then the steam side. Open steam cntrl valve slwly - this prevents water hammer f any cndensate in the steam line, and reduces the pressure / thermal shck t the exchanger. Ensure that the steam trap is crrectly sized t allw full cndensate discharge - this prevents water clgging inside the exchanger. 4. Shutting dwn the Exchanger :- Warning: Water hammer & thermal shck can damage the exchanger resulting in lss f fluid frm ne, r mre, f the liquid circuits. Water hammer ccurs when a flwing liquid is suddenly halted. Pressure waves then travel alng the pipes creating a hammering effect as they bunce ff any restrictins within the pathway. Thermal shck ccurs when the bulk temperature f the exchanger is suddenly raised r lwered. The resulting expansin r cntractin f the unit can result in damage t the plate pack. Bth water hammer & thermal shck can be avided by nt using fast acting cntrl valves, therefre, sufficient cnsideratin shuld be given t prtecting the heat exchanger when designing the assciated cntrl systems. Shut dwn: SLOWLY clse the cntrl valve n the ht circuit whilst maintaining the full flw n the cld circuit. (shut dwn cld side first if ht side liable t freeze) Switch ff ht circuit pump. SLOWLY clse the cntrl valve n the cld circuit. Switch ff the cld circuit pump, and clse all islating valves. Strage: If the unit is t taken ff line fr an extended perid f time, then the fllwing prcedure can be fllwed :- Allw unit t cl, and then drain bth circuits after the release f any pressure. Flush thrugh with clean water, drain and then seal the cnnectins (if pipes remved).
7 5. Cleaning f the Exchanger :- A reductin in the perfrmance f the exchanger especially cmbined with an increase in the pressure drp acrss either circuit indicates that the heat transfer surfaces have becme fuled. The chemicals selected is the chice f the peratr f the plant, and shall depend n the type f depsit we recmmend that the services f a cleaning specialist cmpany be emplyed fr further advise. This type f rganisatin shall be able t determine the nature f the depsit t be remved, and shall furnish the crrect slvents, and equipment, plus cmply with all Health & Safety regulatins. Suggested cleaning fluid: 5% phsphric acid, r 5% xalic acid circulated at ambient temperature, fllwed by large amunts f fresh water t flush. Safety: Rinsing: Wear glves & eye gggles when using cleaning detergents. After using any type f cleaning agent, always rinse thrughly with fresh water. Circulate fresh water fr at least 10 mins. 6. Truble Shting :- Excessive pressure drps: 1) Liquid flws higher than design :- check & adjust 2) Plate channels blcked :- back flush r C.I.P. 3) Inaccurate measurement :- check pressure gauge fr accuracy :- ensure measurement des nt include any bend, valve / fitting, & pipe run lsses. 4) Liquid temp. belw design. :- viscus media generate higher resistance t flw at lwer temperatures. 5) Media used nt as per design :- the additin f glycl r ther additives can increase the pressure drp. Leakage: 1) crss cntaminatin r leaks :- plate pack failure frm the plate pack replace exchanger as repairs nt pssible. Decrease in the perfrmance: 1) plate surfaces require cleaning r de-scaling. 2) pumps r assciated cntrls have failed r faulty 3) plate channels blcked. 4) liquid flws nt as per the design specificatin. 5) assciated chiller / cling twer / biler under sized r faulty. 6) cling water flw temperature t the exchanger is higher than design. 7) heating media temperature lwer than design figures. 8) steam flw nt sufficient - cntrl valve malfunctin r starvatin. 9) steam trap defective - this can cause the unit t fill with cndensate. 10) unit running in c-current flw, instead f cunter current - check with cntract drawing and alter pipe wrk if necessary., and check directin f pump flws. 11) air lck has develped in the plate pack. Bulges / distrtins In back plate: 1) Unit has been subjected t a pressure shck investigate system and remve / dampen surce f pressure wave / spike if unit still intact then it can be cntinued t be used. Repeated shcking shall destry the exchanger.
FIG 2: Recmmended Steam system incrprating steam feed line drainage trap set. 8