In screw refrigeration units, refrigeration oil plays a vital role. It is not only a lubricant for the moving parts inside the compressor, reducing friction and wear between the screw rotor and the housing, and improving mechanical efficiency, but also plays a sealing role. By forming an oil film between the screw gaps, gas leakage is reduced. In addition, the refrigeration oil also undertakes the cooling task and absorbs a large amount of heat generated during the compression process.
The oil circuit system of the screw refrigeration unit is designed to ensure that the compressor and its related components are properly lubricated, cooled and cleaned. The following are the main components of the screw refrigeration unit oil circuit system:
Oil reservoir: It is a place where lubricating oil is stored. It plays the role of storing and buffering lubricating oil in the screw refrigeration unit. The oil reservoir is generally equipped with an observation window or oil level gauge to facilitate the operator to check the oil level.
Oil temperature sensor: It is used to monitor the temperature of the lubricating oil. It is part of the control system and helps to maintain the lubricating oil within an ideal temperature range. The oil temperature sensor transmits the detected temperature signal to the control system. The control system can adjust the working state of the cooler according to the change of oil temperature, or trigger an alarm. Common oil temperature sensors are thermocouples and thermal resistors (such as PT100), which generate corresponding electrical signals according to temperature changes.
Oil separator: mainly used to separate lubricating oil from compressed gas to prevent lubricating oil from entering the refrigeration system, and also to recover lubricating oil for reuse. Common oil separators include cyclone separators, centrifugal separators, and fiber filter separators.
Oil heater: used to heat lubricating oil before starting the compressor to reduce the viscosity of the lubricating oil, make it easier to circulate, and reduce friction loss during startup. Especially in cold seasons, it should be confirmed that the heater can effectively heat the lubricating oil to avoid starting difficulties. The oil heater is usually an electric heating element that is directly immersed in the lubricating oil in the oil tank or installed on the wall of the oil tank. When the system is in standby mode, the oil heater will automatically turn on and raise the oil temperature to the set value. Oil heaters can be divided into direct heating and indirect heating types. Direct heating heaters heat the lubricating oil directly, while indirect heating heaters increase the temperature of the lubricating oil by heating the air around the oil tank.
Oil filter: is to ensure the cleanliness of the lubricating oil, prevent impurities from entering the compressor and other key components, and thus protect the entire system from wear. Oil filters are available in various forms, such as paper filters and sintered metal filters. Oil filters should be replaced at the intervals recommended by the manufacturer to ensure the cleanliness of the lubricating oil. If the differential pressure switch before and after the oil filter alarms, the filter may be dirty and blocked and needs to be replaced immediately.
Oil cooler: The oil cooler is a key component used to cool the compressor lubricating oil. The lubricating oil will heat up due to friction during the operation of the compressor. Excessive oil temperature will affect the viscosity of the lubricating oil, thereby affecting its lubricating effect and even causing the compressor to overheat and malfunction. Therefore, the role of the oil cooler is to cool the lubricating oil to a suitable temperature range to ensure the best performance of the lubricating oil.
