We experienced an incident with plate heat exchangers (Alfa Laval) which are used to cool Glycol brine to -8 Deg Celsius. The refrigerant used is R22. The Glycol side was coated with deposits which have been sent away for analysis.The heat exchangers did not indicate a high differential pressure, the only indication was a rise in Brine temperature upt -3 Deg C.Preliminary investigations indicate that the heat exchanger was fouled and not blocked. Flushing the heat exchanger with hot water did not remove any of the deposits, however introducing refrigerant(Thermal shock) did dislodge black particulates. The first question is has anyone experienced such a heat exchanger failure and what can cause it. The second is how does one predict a failure besides performing a load test. Please note that 4 heat exchangers are connected in parallel and flow and pressure rates vary as three pumps acn operatre based on plant demand. pumps operate

Hi Desmond,

Fouling is only one of the reasons for loss of heat transfer. You may wish to examine the following possibilities as well.
1. Deposition of salts or other particulate matter on the hot surfaces, providing a thermal insulation layer. In this contect the analysis of the black particles you mention will be useful information.
2. Dissolved gases, e.g., caused by aeration of the coolant can cause heat transfer loss. These gases can come out of solution when heated and 'sit' on the plates, providing a thermal barrier.
3. Coolant velocities that produce non-turbulent flow regimes. Good heat transfer requires turbulent flows.

I amy have missed out some others, but you can make a start with the above list.

V.Narayan.