Analysis and Suggestions on Oil Leakage of Hydraulic Cylinder
External Leakage from Hydraulic Cylinder
The external leakage of hydraulic cylinders generally has the following situations.
(1) Oil leakage between relative movement surface of the piston rod and guide sleeve.
If the hydraulic cylinder reciprocates without any oil leakage, the surface of the piston rod and the seal will be in a state of dry friction, which will increase the wear of the seal,greatly shorten its service life.Therefore, a certain degree of oil leakage between the surface of the piston rod and the seal is allowed, In order to play the role of lubrication and reduce friction, but it is required that the piston rod cannot leak oil when it is stationary.
Every time the piston rod moves 100mm, the oil leakage should not exceed two drops, otherwise it will be regarded as serious leakage. The leakage along the piston rod and the inner seal of the guide sleeve is mainly caused by the damage of the (commonly used YX type) seal ring installed on the guide sleeve and the strain on the piston rod, grooves and pits.
(2) Oil leakage along the cylinder tube and the outer seal of the guide sleeve. The seal between the cylinder barrel and the guide sleeve is a static seal. The possible causes of oil leakage are: poor quality of the sealing ring; insufficient compression of the sealing ring; scratched or damaged sealing ring; Cylinder tube quality and the guide sleeve seal groove surface rough machining.
(3) Oil leakage caused by defects in the hydraulic cylinder body and its mating parts. If the hydraulic cylinder body has defects in its cooperation, it will gradually expand under the action of the pressure pulsation or shock vibration of the hydraulic system and cause oil leakage. For example, the cast guide sleeve has oil leakage caused by defects such as casting pores, sand holes and shrinkage; or oil leakage caused by defects on the cylinder body; or oil leakage caused by defects on the cylinder end cover.
(4) Oil leakage between the cylinder body and the fixed mating surface of the end. Oil leakage will occur when the 0-type sealing ring on the mating surface fails or has insufficient compression, aging, damage, unqualified accuracy, poor processing quality, irregular products, or repeated use. Just choose the right O-ring to solve the problem.
Internal Leakage in Hydraulic Cylinder
There are two oil leaks inside the hydraulic cylinder. One is the static seal between the piston and the piston rod. As long as you choose a suitable O-ring, you can prevent oil leakage; the other is the dynamic seal between the piston and the cylinder wall. . Causes of leakage in the hydraulic cylinder;
(1) Suitable for bending of the plug rod or poor coaxiality of the piston rod. When the coaxiality between the piston and the cylinder barrel is too poor, the gap between the outer edge of the piston and the cylinder barrel sound is reduced, causing eccentric wear on the inner diameter of the cylinder and oil leakage. In severe cases, it will cause the cylinder to pull and increase internal leakage.
(2) Damage or failure of seals. When the material or structure type of the seal is inconsistent with the conditions of use, it will cause internal leakage. For example, if the sealing material is too soft, the seals of the hydraulic cylinder can easily squeeze into the sealing gap and be damaged; the seals fail, the compression is not enough, aging, damage, geometric accuracy is not qualified, processing quality is poor, irregular products, seals The hardness, pressure rating, deformation rate and strength range of the seal are unqualified; if the seal is improperly installed, the surface is worn or hardened, and the service life expires but is not replaced in time, it will cause internal leakage;
(3) Iron filings and hard foreign matter enter the hydraulic cylinder. There is generally a gap of 0.5mm between the outer circle of the piston and the cylinder. If iron filings or foreign matter are embedded in it, it will cause the cylinder to pull and cause internal leakage.
(4) There are problems with the design, processing and installation of the sealing ring. If the design of the seal ring does not meet
According to the specifications, the size of the sealing groove is unreasonable, the accuracy of the seal fit is low, and the fit gap is too poor, which will cause damage to the seal and cause internal leakage; It will cause the seal to operate and cause internal leakage; if the assembly is not careful, the joint surface will be dusty or large plastic deformation due to operation will also cause internal leakage.
(5) The piston radius or roundness of the hydraulic cylinder is out of tolerance, the piston has burrs or depressions, and the chrome plating falls off, which will cause internal leakage.