The causes of leakage outside the piston rod of the hydraulic cutting machine hydraulic cylinder are as follows:
a; The shaft assembly seal structure is unreasonable.
At present, the main sealing structure of the piston rod is dust ring + low pressure seal (Y-ring) + high pressure seal (combination seal for shaft). After years of research, the Y-ring is a relatively mature structure, plus the application of imported Y-rings. There is basically no problem with the low pressure seal quality. The price of the composite sealing member for the shaft is relatively high, and the design angle of the sealing lip of the domestic component is unreasonable, which easily causes the material flow problem in the high temperature state of the lip, which causes the size and shape of the sealing lip to change, resulting in failure of the sealing performance. The pressure is concentrated at the low-pressure seal Y-ring, so that the early piston rod leakage problem occurs. From the hydraulic cylinders that were dismantled, the above problems were found to exist. 20181229
b; the matching clearance between the piston rod and the guide sleeve is unreasonable.
According to the hydraulic cylinder design principle of the hydraulic cutting machine, the fitting tolerance of the piston rod and the guide sleeve is H9/f8. However, in practical applications, if the two are matched to the minimum tolerance value, due to the long-term overloading of the construction machinery, the material expands under high temperature conditions, which easily causes the oil film on the surface of the piston rod to sharply decrease, the lubrication effect of the sealing lip is reduced, and the local temperature exceeds the seal. The allowable temperature of the ring causes the sealing ring to age at a high temperature and lose the sealing effect. The market user feedback blackening problem on the surface of the piston rod is caused by the above reasons.
From the investigation and analysis of the causes of the leakage of the piston rod of the hydraulic cutting machine hydraulic cylinder for several consecutive years, the above problems are the main reason for the early leakage of the piston rod in the hydraulic cylinder, and the proportion is over 60%.