PLATE HEAT EXCHANGER (PHE ) - TROUBLE SHOOTING

PHE is a static piece of equipment ,the heat exchange rate or capacity is dependant on the surface area designed for the heat load .

For units that has been operating a while and one day failed to perform , fouling is the likely
cuase .The unit need to be cleaned or serviced

Another possibility ,check the gasket , if it is very old and flattened  due  overtightening during
maintenance .These gaskets has become too flat , narrowing  the flow passage thus reducing the flowrate

Monitoring the pressure drop is one way to determine if fouling has taken place
Before commissioning the unit ,take note of the pressure at inlet and outlet and record the
pressure drop[ across the PHE.If the pressure drop is high after a while ,then flouling could have set in

The right presure drop /velocity will help in reduction of fouling .The fluid velocity must be good enough to create some turbulence to self cleaned the walls of the PHE

In the case of new units . if the new unit is not working according to the designed parmeter,
check the following
a) is the actual heat load same as the design? calculate the head load l/sec x 4.18 ( specific heat for water and Temperature Difference = Kw , and check against designed temperature profile

b) is the process media flowrate correct? check with a flow meter or simply note the operating pressure and check pump curve for actual flowrate . May also check running ampheres or BHP
the flow is too high ,throttle the flow to designed flowrate

c) Is the flowrate of cooling water sufficient? If the oulet temperature from PHE is too high
this may be an indication that flow(service water ) is too low
check the pump curve

There is also pressure drop across the PHE ,ranging from 0.2 bar to 1.5 bar or higher depending
on factors such viscosity ,sizing of the PHE itself

We came across recently two cases of pmps underdesigned
System head is about 2,5 bar ,whereas the pump head is max 2 bar.This cause the pump
to be operating on the left of the pump curve and thus,.very low flow .
The head loss calculation was not complete ,the head loss of 1.5 bar accoss the PHE was not taken into consideration

The system head

a) static Head : 4 meter
b) head loss (PHE ) : 15 M(left out )
c) head loss ( pipelines ): 3 M
d) Total head : 22 M

Pump Max head : 18 m
Designed Flow : 400 m3/hr
Actual flow : 260 m3/hr

Solution : upgrade pump to 400 m3/hr at 25 M head