Industrial Process Chillers

Case Study of Industrial Process Chillers

We recently attended a call out to a plastic injection moulding factory. The chiller had gone off and before the maintenance engineers noticed, the water system had got up to 91°C 

Water System Draining

Before fault finding could be carried out, the water system had to be drained down and refilled. The fridge system was found to be short of gas.

Leak Detector for Industrial Process Chillers

No leak could be found on the pipework or the condenser, but still the nitrogen pressure test was going down. Our engineer decided to remove the inlet and outlet to the evaporator, blank one end off and fit a blank with a gauge fitting on the other. His suspicions were confirmed when the gauge went up water side as nitrogen was added fridge side. The evaporator had failed.

Replacement Evaporator and Dehydration

A replacement evaporator was sent to site next day and the dehydration process was started. This is a necessary part of the chiller repair so as to remove water from the system.

Pressure Testing on Industrial Process Chillers

The system was then pressure tested according to standard industry guidelines. Each side of this pressure test was witnessed by the customer and added to our Pressure Test Certificate.

Recharge of Refrigerant

Half the charge of the refrigerant was then charged to the parts of the system where refrigerant is in its liquid state. The remaining refrigerant will be trimmed during commissioning…

Commissioning for Industrial Process Chillers

The chiller was then started and a high superheat and low pressure condition was present which was expected. The remaining refrigerant charge was added away from the compressor until the superheat and subcooling values came to within standard industry guidelines. Compressor failure will occur if liquid refrigerant is charged through the compressor as a compressor cannot compress a liquid.

Fault Finding on Industrial Process Chillers

An electrical fault occurred on the PLC (programmable logic controller) The difference in temperature between the evaporator Inlet and Outlet were the same. The sensors were located and they were found to have not been pushed far enough into the sensor pockets. A special heat transfer paste was added and the sensors were located correctly.

Reset and Timer

The reset procedure was followed on the PLC and the chiller went through a timer. The timer is a safety measure to allow engineers time to get out of the way if the chiller was started by another engineer. At Maximus Chillers, our two man teams always communicate to each other before a start up is carried out. Another reason for the timer is to allow the compressor temperatures and pressures to stabilise to prevent compressor damage.

Evaporator Adjustment

A full load condition was supplied to the chiller so effective run testing could be carried out. The evaporator water system pressures were compared to the Evaporator Technical Sheet and adjustments were made to the pump and other components on the water system.

Electrical Readings

The volts and amps were monitored and compared to our previous Tick Sheets to make sure that the energy consumption was the same as before.

System Temperatures

The temperatures of the discharge, suction and crankcase were monitored around the compressor. All of these readings were okay, so the superheat and subcooling values were worked out using an app on our engineer’s phone.