What will be the impact of the poor oil return of the screw air compressor?
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Update time : 2022-02-24 16:17:53
If the oil return of the screw air compressor is not smooth, it will cause a large amount of lubricating oil in the equipment to stay in the evaporator pipeline. When the oil film increases by 0.1mm, it will directly affect the cooling of the system. On the other hand, other parts of the machine cannot operate normally due to lack of oil. , It is necessary to continuously replenish lubricating oil, which will lead to the accumulation of lubricating oil in the system, resulting in a vicious circle, increasing operating costs and reducing operating reliability. In general, it is permissible for the oil-air mixture to circulate in the system with a flow rate of less than 1% of the refrigerant gas.
There are two ways to return oil to the compressor, one is to return oil to the oil separator, and the other is to return the oil to the air return pipe. The oil separator is installed on the exhaust pipeline of the compression house, which can generally separate 50-95% of the rush oil. The oil return effect is good and the speed is fast, which greatly reduces the amount of oil entering the system pipeline, thus effectively prolonging the operation without oil return. time. For cold storage refrigeration systems with particularly long pipelines, flooded ice-making systems, and freeze-drying equipment with very low temperatures, it is not uncommon to see no oil return or very little oil return for ten or even tens of minutes after starting the machine. A bad system will cause the compressor to shut down due to low oil pressure. The installation of a high-efficiency separator in this refrigeration system can greatly prolong the operation time of the compressor without oil return, so that the compressor can safely pass through the crisis stage of no oil return after startup.
The lubricating oil that is not separated will enter the system and flow with the refrigerant in the tube to form an oil circulation. After the lubricating oil enters the evaporator, on the one hand, due to the low temperature and low solubility, part of the lubricating oil is separated from the refrigerant. . The lower the evaporating temperature, the more difficult it is to return the oil. This requires the design and construction of the evaporation pipeline and the return pipeline to be conducive to oil return. The common practice is to use a descending pipeline design and ensure a large airflow velocity. For refrigeration systems with particularly low temperature, in addition to the selection of high-efficiency oil separators, special solvents are usually added to prevent lubricating oil from blocking capillary tubes and expansion valves, and to help oil return. When someone replaces the external oil separator with the built-in oil separator of the air conditioner, the cost is saved on the surface, but in terms of the use cost of the system, it will only greatly increase the operating cost. The efficiency of the system will get worse and worse.