The latest process chiller maintenance service visit for a customer of ours in the North West. We carry out 4 visits a year to 12 chillers of 300kw to 500kw capacities. Read on to find out the issues we have found with a selection of these chillers…
News Article No.31
Chiller 1 during Process Chiller Maintenance Service
This is an old chiller, but due to our maintenance we have extended its life.
The chiller has had both condensers retrofitted in the past due to the tubes having been found to be work hardened and corroded. Repairing them would have led to reoccurring leaks on the condenser.
A compressor had also failed previously, but as the chiller is oversized for the process that it is feeding, the customer has decided not to replace it.
Condenser Fan Failure
There are a multitude of chiller condenser fan types, each having different blade profiles, different sizes and different mounting plate dimensions. This is to achieve the correct air flow rate through the condenser fins. Therefore, we have a supplier that can source or retrofit any fan. One of the fans was identified as having seized on this visit. All three of the fans on each system run at the same time which means that the failed fan was causing air to recirculate. The recirculating air means that the condenser pressure goes up. This in turn causes the program to bring on more fans which uses more electricity. The fan deck replacement is scheduled to be carried out before the summer.
Chiller 6 during Process Chiller Maintenance Service
This chiller was found to have no power to the display. Our engineer followed the fault finding procedure until he found a blown control circuit fuse. The control circuit is 24v and runs around the various safety devices in the chiller. It also powers the chiller controller. He used his diagnosis procedure to follow the fault through to the controller. Volts were found to be leaking across to earth on the internal PCB (Printed Circuit Board) A replacement controller was ordered and fitted on a subsequent visit.
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Chiller 8 during Process Chiller Maintenance Service
A condenser fan had also failed on this chiller. This fault was a difficult one to diagnose as it was intermittent. It had been occurring for a long time and was known both to the onsite engineers and to our engineers. It would occasionally throw the breaker, then run okay for weeks. From our experience, when fans seize, they do so completely. However, our engineer caught this fan in the act: the bearings were found to be partly worn and momentarily locked up. We have arranged the fan deck replacement on a subsequent visit.
Chiller 10 during Process Chiller Maintenance Service
This is the chiller featured in the photo. The customer had bought it a year ago and were anxious that we carry out a thorough maintenance. This was to bring the chiller up to the level of service as carried out by Maximus Chillers. We are primarily a chiller service and maintenance company as we specialise in reducing the customer’s carbon footprint by improving chiller efficiency.
The chiller had been maintained during the warranty period, but the condenser was found to be heavily blocked. This is a major reason for a chiller’s increased high energy consumption. A blocked condenser means higher system pressures, more fans running and higher amps of the compressors.
Coefficient of Performance
The blocked condenser meant that the coefficient of performance was found to be dramatically reduced. The COP is the ratio between the Kw of electricity used, versus the Kw of cooling capacity supplied to the process. At the beginning of the maintenance, the chiller was found to have a COP of 2:1 and at the end we had improved it to 4:1. Just by the effect of having one of our engineers carry out the maintenance, we dramatically reduced the customer’s electricity costs.
Flow Switch not Functioning
Another issue our engineer found during the maintenance was that the flow switch failed to stop the chiller when it was tested. This is the most critical safety device on the chiller because it prevents freeze ups in the evaporator which will ruin a chiller. We have submitted a price to replace the plastic flow switch with our high quality reliable flow switch.
As you can see from the photo, there are panels around the chiller which cover the internal components. Not all of these panels need to be removed during the maintenance. The ones that do need to be removed have been secured with one bolt which is finger tight. The spare bolts have been placed in the panel to be used as spares during the chiller’s life.
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Chiller 12 during Process Chiller Maintenance Service
This is a reliable chiller in a dusty environment.
Head Pressure Control
The chiller had preciously tripped out on high pressure as the fan speed controller had failed. We decided to fit a fan switch as the efficiency is around the same as an FSC. Also, the carbon footprint of a fan switch is dramatically lower than the thyristors (solid state soft starters) which are found in a fan speed controller.
We stock our own range of crankcase heaters in our stores at Head Office in Droylsden, Manchester. We selected a 240v wrap around crankcase heater of the correct Wattage to replace the blown one in the chiller. It comes with an adjustable strap which fits most scroll compressor types. The fuse protecting the rest of the chiller was found to have blown because the old heater had burned out to earth. A straight forward job to remove and replace.
Process Chiller Service
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