2205B0JE-DA-J-N_2014.05.
1 Safety
Screw Compressor J-series
1.4 Safety Devices
1-11
1.4.3 Compressor Protection Devices
Overview/Function/Purpose
To protect the compressor, the following safety functions of the CP4 controller are used.
Protection from High discharge temperature
This function stops the compressor when the discharge temperature exceeds the set value.
A temperature sensor is installed in the oil separator.
Protection from High oil temperature
This function stops the compressor when the oil temperature exceeds the set value.
A temperature sensor is installed in the package lubrication piping after the oil cooler.
Protection from abnormally High pressure
This function stops the compressor when the discharge pressure abnormally rises due to
compressor misoperations or stoppage of cooling water supply to the condenser.
This function prevents explosion of the equipment and components.
A pressure sensor is installed in the oil separator.
Protection from abnormally Low suction pressure
This function stops the compressor when the suction pressure is below the set value.
A pressure sensor is installed in the suction piping.
Protection from abnormal oil pressure
This function stops the compressor when oil supply is not sufficient, the oil filter is clogged, too
much refrigerant in oil, or oil supply pressure difference (from suction pressure) is below the set
value. This is to protect the compressor from wear and seizure.
A pressure sensor is installed after the oil filter.
Protection from oil filter Differential pressure
This function stops the compressor when the differential pressure between discharge and
lubrication pressure is below the set value due to clogging of filters or other reasons.
The discharge and the oil pressure sensors are used.
Protection from Low oil level
[Case 1 Differential pressure oil supply system]
This function constantly detects the oil level in the oil separator and stops the compressor when the
oil level is below the lower limit.
Oil level sensor is installed in the oil separator.
[Case 2 Forced oil supply system]
When the oil level gets lower and the oil pump takes in the refrigerant gas, the differential pressure
between before and after the oil pump decreases. When the differential pressure between before
and after the oil pump is less than the specified value, the system will stop the compressor
operation.
Protection from motor over-current
This function controls the unloader of compressor when current exceeds the set value (upper limit).
In some cases, it stops the compressor.
The current value is monitored by the CP4 controller.