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Detailed analysis of three cases of hydraulic cylinder buffer device failure and seven causes of leakage

Hydraulic cylinder is the executive component of hydraulic transmission system. There are often various faults in the operation process. This paper shares the causes and solutions of the failure and leakage of the buffer device of hydraulic cylinder.
1、 Buffer failure
1. buffer action is excessive.
(1) The orifice opening of the buffer regulating valve is too small.
(2) Buffer plunger "no force" (such as too small clearance between plunger head and buffer ring, piston tilt or eccentric).
(3) There is dirt between the plunger head and the buffer ring.
(4) The clearance between the plunger head and the bushing of the fixed buffer is too small.
terms of settlement:
(1) Adjust the throttle to the proper position and tighten.
(2) Take apart and clean properly and increase the clearance. Unqualified parts should be replaced.
(3) Deburring and cleaning.
(4) Increase the clearance properly.
2. buffer function fails.
(1) The buffer regulating valve is in full open state.
(2) The inertia energy is too large.
(3) The buffer regulating valve cannot be adjusted.
(4) The check valve is in full open state or the seat of check valve is not tightly closed.
(5) The seal on the piston is damaged. When the pressure of buffer chamber increases, the working liquid flows back from the chamber to the working pressure side, so the piston does not slow down.
(6) There are scars on the inner surface of the plunger head or bushing.
(7) The buffer ring that is inserted on the cylinder head falls off.
(8) The length and angle of the conical surface of the buffer plunger are not suitable.
terms of settlement:
(1) Adjust to the right position and tighten.
(2) Suitable buffer mechanism shall be designed.
(3) Repair or replace.
(4) Check the size, replace the cone valve core or steel ball, replace the spring, and match the research and repair.
(5) Replace the seal.
(6) Repair or replace.
(7) Replace the new buffer ring.
(8) Amendment.
3. the "crawl" appears in the buffer travel section.
(1) The machining is not good, such as cylinder head, the verticality of piston end face is not required, the clearance between piston and cylinder barrel is uneven in the whole length, and the cylinder head and cylinder cylinder are not concentric. The deviation between the inner diameter of cylinder barrel and the center line of cylinder head is large, and the verticality of piston and nut end face is not satisfied, which causes the piston rod to bend.
(2) Poor assembly, such as eccentric or inclined holes in the matching holes of buffer plunger and buffer ring.
terms of settlement:
(1) Every part shall be carefully inspected and unqualified parts shall not be used.
(2) Reassembly to ensure quality.
2、 There is an external leak
1. poor assembly.
(1) When the hydraulic cylinder is assembled, the end cap is installed in a wrong way, and the piston rod is not concentric with the cylinder barrel, which makes it difficult to extend the piston rod and accelerate the wear of the seal.
(2) The poor parallelism between the hydraulic cylinder and the guide rail surface of the workbench makes it difficult for the piston to extend out and accelerate the wear of the seal.
(3) The installation of the seal is wrong, such as scratch or cutting of the seal, reverse installation of the sealing lip, broken lip or wrong dimension of the shaft chamfer, and wrong or missing installation of the seal.
(4) The gland is not installed.
① Gland installation deviation.
② The fastening screw is not evenly stressed.
③ The fastening screws are too long to hold the gland down.
terms of settlement:
(1) Disassemble and reassemble.
(2) Remove inspection, refit and replace seal.
(3) Replace and refit the seal.
(4) Re install and tighten the screw to make it bear even force; Screw length shall be selected reasonably according to the depth of screw hole.
2. quality problems of seals.
(1) The storage period is too long, and the seal will be aged and invalid naturally.
(2) Poor storage, deformation or damage.
(3) The performance of the rubber is poor, and the oil resistance or compatibility between the rubber material and the oil is poor.
(4) The product quality is poor, the dimension is not correct, and the tolerance is not in conformity with the requirements.
terms of settlement:
3. poor quality of piston rod and groove processing.
(1) The surface of piston rod is rough, and the chamfer of piston rod head is not in conformity with requirements or not chamfered.
(2) The groove size and precision are not in conformity with the requirements.
① There is a mistake in the design drawing.
② Groove size processing does not meet the standard.
③ The groove has poor precision and many burrs.
terms of settlement:
(1) Surface roughness shall be Ra0.2 μ m. Chamfer according to the requirements.
(2) ① design the groove according to relevant standards.
② Check dimensions and correct to required dimensions.
③ Correct and deburring.
4. the viscosity of oil is too low.
(1) The wrong oil was used.
(2) There are other grades of oil in the oil.
terms of settlement:
Replace the appropriate fluid.
5. oil temperature is too high.
(1) The hydraulic cylinder inlet resistance is too high.
(2) The ambient temperature is too high.
(3) There is a problem with the pump or cooler, etc.
terms of settlement:
(1) Check whether the oil inlet is smooth.
(2) Take insulation measures.
(3) Check the cause and remove it.
6. high frequency vibration.
(1) The fastening screws are loose.
(2) Loose pipe joints.
(3) The installation position produces movement.
terms of settlement:
(1) The screws should be tightened regularly.
(2) The joints shall be tightened regularly.
(3) The mounting screws should be tightened regularly.
7. piston rod is pulled.
(1) Dust ring aging, failure to invade sand chip and other dirt.
(2) The fitting between guide sleeve and piston rod is too tight, which causes overheating of movable surface, resulting in chromium layer falling off and pulling damage on piston rod surface.
terms of settlement:
(1) Clean and replace the dust ring and repair the surface of piston rod.
(2) Check and clean, and use scraper to repair the inner diameter of guide sleeve to reach the matching clearance.


Contact: David Song

Phone: 8615376198599

Tel: 053187101088

Email: hxl@huachen.cc

Add: Room 603,Xinsheng building 2#, Xinluo Road, Gaoxin district, Jinan, Shandong province, China

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