Oil Cooling Methods and Oil - changing Operation Procedures for Screw Compressors

2025-02-25

I. Common Oil Cooling Methods for Screw Machines

(1) Water - cooled Oil Cooler

The water - cooled oil cooler is a horizontal shell - and - tube heat exchanger. Oil is outside the tubes, and water is inside the tubes. The tube bundle is fixed on the tube plates at both ends.

Oil Cooling Methods and Oil - changing Operation Procedures for Screw Compressors1740496415743

There are baffles in the cylinder of the oil cooler, which can improve the heat exchange between oil and cooling water. The inlet water temperature of the oil cooler's cooling water should be less than 32°C, and the unit's oil temperature is controlled between 40 - 65°C.

(2) Thermosiphon Oil Cooler

The structure of the thermosiphon oil cooler is similar to the principle of the water - cooled oil cooler. It is a horizontal shell - and - tube type, with oil outside the tubes and refrigerant inside the tubes. The temperature of the oil cooled by the thermosiphon oil cooler is generally 10 - 20°C higher than the condensing temperature.

(3) Liquid Injection Cooling

In units with liquid injection cooling, high - pressure refrigerant liquid led out from the condenser or liquid receiver passes through a filter, a throttle valve or a high - temperature expansion valve, and then is sprayed into a certain intermediate orifice of the compressor. This serves to absorb the heat of compression and cool the oil temperature.

(4) Air Cooling

The air - cooling system is an indirect cooling method. It cools the oil in the oil cooler through the ambient air.

II. Operation of Lubricating Oil Replacement

Recover the system refrigerant to the condenser side, exhaust the refrigerant in the compressor, and drain the refrigeration oil from the oil - drain angle valve of the compressor.
Drain the lubricating oil of the compressor from the oil - drain valve on the oil filter. When the lubricating oil is almost drained, introduce a certain amount of nitrogen from the high - pressure side detection joint of the compressor. Use pressure to accelerate the discharge of the lubricating oil. Stop injecting pressure and close the oil - drain valve. Then, remove the oil filter of the compressor, drain all the lubricating oil in the oil sump, clean the oil filter, and reinstall it and tighten it.
Add lubricating oil according to the standard amount of the compressor. At the same time, evacuate the system. It is recommended to select the high (low) - pressure side angle valve or other relatively high - position points as the connection point of the vacuum pump to prevent damage to the vacuum pump by sucking in the refrigeration oil.
When conducting vacuum pressure - holding or leak - checking, observe whether the pressure rebounds.
Inject lubricating oil. Connect a clean plastic tube to the oil - drain valve, and place the other end of the plastic tube at the bottom of the oil drum. When injecting oil, the oil drum should be sealed to reduce the pollution of the oil by air.