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Screw compressor oil cooling method and oil change method

December 15, 2021

1. Common oil cooling methods of screw compressors

   (1) Water-cooled oil cooler

   water-cooled oil cooler is a horizontal shell and tube heat exchanger, the oil is outside the tube, and the water is inside the tube. The tube bundle is fixed on the tube plates at both ends, and there are baffles in the cylinder of the oil cooler, which can improve the heat exchange between oil and cooling water. The cooling water inlet temperature of the oil cooler should be less than 32℃, and the unit oil temperature should be controlled at 40~65℃.

   (2) thermosiphon oil cooler

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

   (3) spray cooling

In a unit with spray cooling, there is a high-pressure refrigerant liquid drawn from a condenser or a liquid receiver, which is sprayed into an intermediate port of the compressor after passing through a filter, a throttle valve or a high-temperature expansion valve to absorb the heat of compression and cool the oil The role of temperature.

   (4) air cooling

   The cooling method of air cooling system is indirect cooling, which cools the oil in the oil cooler through the ambient atmosphere.

2. Oil change method of screw unit

   (1) How to change the oil

   1. Shut down, then cut off the power supply.

2. Close the suction check valve before the compressor and the exhaust check valve at the outlet of the oil separator. If the unit is equipped with a liquid injection device and an economizer, the liquid injection solenoid valve and the valve before the air supply port should also be closed. Shut-off valve.

  3. Drain the refrigerant from the vent valve of the oil separator.

  4. Drain the oil from several drain plugs at the bottom of the oil separator.

  5. Drain the oil in the oil filter. If there is an oil cooler in the unit, drain the oil in it.

  6. Clean or replace several filters or filters listed in the maintenance schedule.

  7. Vacuum.

  8. Refuel the unit.

   9. Open the suction and exhaust check stop valves, open the spray solenoid valve and the stop valve in front of the air supply port.

   10. Turn on the power and turn on the machine.

   (2) Oil filter element replacement and oil coarse filter cleaning

   1. Shut down, then cut off the power supply.

   2. Close the stop valve before the crude oil filter and after the oil filter, and close the check valve between the oil outlet of the crude oil filter and the fuel injection port of the compressor.

   3. Open the oil filler valve on the crude oil filter to balance the pressure in the oil filter with the atmospheric pressure. Slightly loosen the nut on the flange cover of the oil filter, so that the pressure in the oil filter is slowly released and reduced to balance with the atmosphere.

   4. Remove the flange cover, replace the filter element in the oil filter, and clean the filter screen in the crude oil filter.

   5. Flange cover with coarse oil filter.

6. Fill the oil filter with filtered refrigerating oil, install the flange cover of the oil filter, open the shut-off valve before the oil filter, use the oil filter to empty, open the oil filter The check valve between the fuel injection port and the compressor and the stop valve behind the oil filter.