Selection and maintenance of cascade low temperature unit

Update:29 Jan 2019
Summary:

Deep refrigeration compressors generally have: piston, […]

Deep refrigeration compressors generally have: piston, screw and other types, ultra-low temperature units should be preferred screw-type refrigeration unit, the main reasons:
(1) There are few moving parts and it is safe and reliable to use. Because the screw compressor has no vulnerable parts such as valve plate, piston ring and crankshaft connecting rod, the structure is relatively simple, and its main moving part, the screw rotor, runs smoothly, and the trouble-free running time can reach more than 80,000 hours, so it is more reliable to use. It is more in line with the demanding requirements of reaction temperature control in the synthesis of antibiotics.
(2) Energy can be adjusted steplessly. Because the demand for cooling in the production process is dynamic. Therefore, the refrigeration unit is required to be able to perform energy adjustment efficiently. Generally, the piston compressor is gradient adjustment, that is, the adjustment of the cooling supply is realized by the unit opening and stopping mode. The frequent starting of the unit is easy to cause damage to electrical and mechanical components, and at the same time, due to the large motor power, the motor Frequent start-up is easy to impact on the safe operation of the grid: the screw compressor uses a slide valve to adjust its energy level, which can achieve stepless adjustment between 10% and 100%, so it is superior to other forms in energy consumption and stability of the unit. unit.
(3) During the operation of the cascade ultra-low temperature unit, the high temperature partial evaporation temperature is about -30 °C, and the low temperature partial evaporation temperature is about -80 °C. During operation, there may be a part of unvaporized liquid refrigerant, for the piston compressor. It is easy to produce liquid hammer, which causes the compressor to be scrapped in severe cases, while the screw compressor is not sensitive to a small amount of liquid.

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