How to handle plate heat exchangers when using them with steam? In case of plate heat exchangers that can be inspected there are no problems, because it’s always possible to maintain and repair them. In case of hammering pressures, steam peaks or condensate that damages the gaskets, it’s indeed possible to open the exchanger, replace the gaskets, closing the exchanger and make a pressure test, and the heat exchanger is ready back to work. A different story with brazed plate exchangers, that cannot be repaired when they get broken.
The main problem with plate heat exchangers using steam happen when there is not a proper condensate discharge, so that condensate remains inside the exchanger. When new steam enters the exchanger in presence of stagnant condensate, the condensate suddenly evaporates and noises such as clicks and cracks can be heard. These are caused by the sudden evaporation of the condensate which leads to very high pressure peaks, that can damage the exchanger irreparably.
An efficient condensate discharge must then be installed, ensuring that the discharge pipeline have no counter pressures, in order to achieve a complete draining. A vacuum breaker valve should be installed as well, on the outlet circuit of the steam regulating valve, working in fact as a backwards restraint valve: when the steam flow stops, the vacuum breaker valve opens letting air in, ensuring the complete draining of the exchanger, forcing air and condensate out of it through the condensate discharge.
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