1. Causes of leakage of hydraulic system of Valve Test Bench

Many components in the hydraulic system of Valve Testing Machine widely use clearance seal, and the sealing of clearance seal and clearance size (leakage and clearance of the cube into positive), pressure difference (leakage and pressure difference is proportional), sealing oil length (leakage and length is inversely proportional), processing quality and oil viscosity and so on. Due to poor lubrication between motion pairs, improper material selection and poor machining, assembly, installation accuracy, it will lead to early wear, increase the gap, increase the leakage. Secondly, the system is also widely used in the hydraulic components of the seal, the sealing effect of the seal and seal material, seal surface quality, structure and so on. In the Portable Valve Grinding Machine system, if the sealing material is inferior, the physicochemical property is not stable, the mechanical strength is low, the elasticity and the wearability are low and so on, then leaks because of the poor sealing effect; Installs the seal the groove size design not to be reasonable, also has the size accuracy and the roughness difference, the pre-compression quantity is small but the seal is not good also can cause the leakage. In addition, the surface roughness of the joint surface is poor, the flatness is bad, the deformation after compression and the tightening force is uneven; Components oil drainage, return pipeline is not smooth; If the oil temperature is too high, the oil viscosity drops or the selected oil viscosity is too small; The system pressure is adjusted too high, the seal pre-compression amount is too small; Defects in the shell of hydraulic parts will lead to increased leakage.

2. The Valve Test Bench hydraulic system to reduce internal leakage and eliminate external leakage measures

A. The motion pair with clearance seal shall be strictly controlled for its machining accuracy and matching clearance. 

B. Sealing with seals is an effective means to solve the leakage. However, if the seals are excessively sealed, although the leakage is solved, it will increase the friction resistance and power loss and accelerate the wear of seals. 

C. Improve unreasonable hydraulic system, simplify hydraulic circuit as much as possible and reduce leakage; Improve the sealing device, such as the piston rod in the "V" seal to "Yx" seal ring, not only low friction and sealing reliable. 

D. The amount of leakage is inversely proportional to the viscosity of oil. The viscosity is small and the amount of leakage is large. 

E. Controlling temperature rise is an effective measure to reduce internal and external leakage. Pressure and flow are the two most basic parameters of the hydraulic system. These two different physical quantities play different roles in the hydraulic system, but there are certain internal relations. Mastering this basic principle is necessary for correct debugging and troubleshooting of the system.