The lubricating oil for air compressor, if the exhaust temperature is too high, will make the oil viscosity decrease, resulting in a deterioration of the performance of lubricating oil, the lubricating oil in the light fraction and rapid evaporation, resulting in "coke" phenomenon. In actual use, when the air compressor exhaust temperature more than 200 DEG C, "coke" is very serious can cause the exhaust valve seat and a spring seat (cutting gear) channel and the exhaust pipe blocked, the channel resistance increased; "coke" can make the piston ring stuck in the ring slot, lost a sealing function; if the electrostatic interaction will make the "coke" explosion, the exhaust temperature of the compressor is powered by the cooling water does not exceed 160 degrees, wind cooling can not exceed 180 DEG C. So if the machine to find the cause of high temperature, and extend the service life of the machine, improve the quality of compressed air.