In the commonly used hydraulic torque wrench set, hydraulic wrench is one of them, and there are also hydraulic torque wrench body, hydraulic torque wrench special pump station, etc. Hydraulic wrench can be divided into drive type and hollow type, and there are three pollution sources, external, internal and system itself.

　　1) External intrusion pollutants: the external pollutants mainly include sand or dust in the air, which are usually penetrated into the system through the air holes in the oil tank of hydraulic wrench, the sealing shaft of the cylinder, the pump and motor. The main purpose is to use the environmental impact.

　　2) Internal pollutants: the pollutants left in the processing, installation, commissioning, packaging, storage, transportation and installation of hydraulic wrench components;

　　3) Pollutants in hydraulic wrench system: particles occurred near the system due to the wear of components, sand particles falling off on castings, metal particles falling off from pumps, valves and joints, particles and colloids caused by oxidation and differentiation of oil in the pipeline, Even the system pipeline has not passed the scour before it is put into operation.