A question we are very often asked in Tempco is if during maintenance and regeneration operations on plate heat exchangers the gaskets have to be all replaced every time. The answer is… yes and no. Which means that sometimes the substitution is necessary, sometimes not, and it depends on the kind of application involved.
First of all let’s divide two cases, the first one being heat exchangers for heating that work using vapour. In this case, it is very likely that the exchanger will have gaskets in Ethylene-Propylene Diene Monomer (EPDM). This kind of gasket will result very stressed by the vapour at high temperatures. When opening the exchanger, it will be clear to see that gaskets are stressed, because EPDM has a lower elastic return coefficient than Nitrile or Vition. So that after 2 or 3 years of operations it looses the elastic return of a brand new gasket. If we don’t replace them after having washed the plates and re-assembled them, we will probably encounter leaks on the exchanger. It is then suitable to replace all of the gaskets while at it.
Otherwise, if we have a plate heat exchanger working with cold water, for example coming from a cooling tower at 30° C or from a refrigerating group, after 3 or 4 years of operations the plates will be dirt and to be washed, but gaskets will probably look as new. It is then very likely that it will be possible to keep and re-use them, especially in case of clip-on gaskets that don’t require the use of glue.
Of course, some good common sense must be used here also. If the regeneration intervention involves a huge plate heat exchanger, with for example a frame of 200 plates with a 0,4 sm surface each and nozzles with 100-150 diameters… the operation will clearly have a high cost, maybe after 4 years of operations. The cost of a replacement of the gaskets will thus have a partial impact on it too, but very much worth it if the exchanger, once washed and re-assembled with the old gaskets still on it and not replaced, will start leaking.
The tip is then to ask experts to have a look on it, which means that in Tempco when we open a plate heat exchanger, we prepare a proposal for the customer that includes the cost of new gaskets, even splitted. And then contacting the customer telling him if it’s better to effectively replace them or, otherwise, if the old gaskets can undergo a further working cycle.
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