Hi all --
There was a fire alarm this morning. The Fire Department responded and
were met by SNF staff. The problem was a heat exchanger in the
basement, which overheated - the steam set off the smoke detectors. The
alarm has been cleared and the building is OK to reoccupy. Apologies for
any inconvenience.
Your SNF Staff
Preliminary findings:
ReplyDeleteThe heat exchanger that failed was HTX-1 (65 C) and not HTXC-2 (80 C) The likely causes of the coolant boil over were 1) a water flow switch that is stuck ON. 2) a weak pump.
The thermocouple that controls the temperature is located in the return manifold. The coolant that was being heated to 65 C continued heating past its setpoint and boiled over because of the lack of coolant flow to the return manifold due to the weak pump. The flow switch would have normally shut the exchanger down but the switch was also stuck in the ON state.
Permanent fix:
ReplyDeleteThe coolant pump and flow switch has been replaced but still unable to restore flow to the system because the coolant lines are badly clogged. Fortunately, the chamber wall temperature is not critical to the process. We turned off the heat exchanger heater and set the temperature to 36C (ambient). All the system recipes had already been setup to run with the heat exchanger temperature set to 0 C (which essentially mean you don't care)