oil pressure control switch (oil pressure switch) oil pressure control switch serves to cut the compressor to stop working When the pressure of the lubricant is lower than the specified to prevent the compressor from being damaged due to lack of lubrication low pressure switch, low pressure switch It acts to control the pressure on the low side not to be too low. By relying on the pressure of the low pressure liquid through the contacts. Cut off the compressor to stop working when the pressure is below set. High pressure control switch High pressure control switch Acts to control the pressure on the high side not to be too high By relying on the pressure of the high-pressure liquid acting through the contacts. Cut off the compressor to stop working when the pressure is too high. 

pressure relief valve (safety valve or reliet valve) pressure relief valve It acts like a fusible plug. Suitable for use with large systems Working when the pressure in the system is too high The liquid will push through the spring lift valve, allowing the liquid to drain. Until the pressure decreases, the spring will press the tongue to close it back. The solution will not completely drain like a system that uses a fusing plug.