The exhaust oil content of refrigerated air dryer is different. For example, the exhaust oil content of domestic piston oil-lubricated air compressor is 65-220mg/m3, the exhaust oil content of low-oil lubricated air compressor is 30-40mg/m3, and the exhaust oil content of domestic so-called oil-free lubrication air compressor (actually semi-oil-free lubrication) is also 6-15mg/m3; Sometimes, due to the damage and failure of the oil and gas separator in the air compressor, the oil content in the air compressor exhaust will be greatly increased. The compressed air with high oil content will be covered with a thick oil film on the surface of the copper tube of the heat exchanger after entering the freeze dryer. Because the heat transfer resistance of the oil film is 40~70 times greater than that of the copper tube, this will greatly reduce the heat exchange performance of the precooler and evaporator, and in serious cases, it will make the freeze dryer unable to work normally. The specific performance is that the evaporation pressure decreases and the dew point rises instead, the oil content in the exhaust of the freeze dryer increases abnormally, and the automatic drain is often blocked by oil dirt. In this case, even if the oil removal filter is constantly replaced in the pipeline system of the refrigerated air dryer, it will be useless. The filter element of the precision oil removal filter will soon be blocked by oil dirt after maintenance. The good way is to repair the air compressor and replace the filter element of the oil-gas separator so that the oil content in the exhaust gas reaches the normal delivery index.)