Let me talk about it. Hydraulic cylinder What should be noted throughout the entire disassembly process?
 

　　(1) Before disassembling or assembling a hydraulic cylinder, the hydraulic control circuit must be depressurized. Otherwise, when the high-pressure hose connected to the cylinder is loosened, the high-pressure oil in the control circuit will rapidly spray out. To depressurize the hydraulic control circuit, first unscrew the spindles or adjusting screws at locations such as the flow‑control valve to relieve the pressure on the working fluid, then turn off the power supply or disconnect the power unit to stop the hydraulic equipment from operating.

　　(2) During disassembly, care must be taken to avoid damaging the threads at the top of the hydraulic cylinder, the threads of the oil ports, the piston surface, and the inner bore of the cylinder liner. To prevent bending or deformation of slender components such as hydraulic cylinders, use shims to provide balanced support during placement.

　　(3) Disassembly and reassembly should be carried out in the prescribed sequence. Since hydraulic cylinders vary in design and dimensions, the disassembly order may differ slightly from one model to another. Generally, first drain the hydraulic fluid from both chambers of the cylinder, then remove the cylinder head, followed by the piston rod and the cylinder body. When dismantling the cylinder barrel, use standard tools to remove internal key‑type retaining keys or circlips; never use a chisel. For the bearing end caps of poppet check valves, use a screwdriver to gently push them out—do not strike them with a hammer or pry them forcefully. If the piston rod or cylinder cannot be withdrawn, do not attempt to force it out; first identify the cause before proceeding with disassembly.
 

　　(4) During disassembly and assembly, make full use of the specific characteristics of each component to prevent hydraulic cylinder parts from being contaminated by dust and debris in the surrounding environment. For example, all operations must be performed in a clean, controlled environment; after disassembly, all components should be covered with plastic film, and must not be shielded with cotton cloth or other work‑clothing fabrics.

　　(5) After disassembling and reassembling the hydraulic cylinder, a thorough inspection should be conducted to determine which components are fit for service, which can be reused after repair, and which must be replaced.

　　(6) Prior to installation, all components must be carefully cleaned.

　　(7) The sealing structures at all locations must be assembled accurately.

　　① When assembling the O-ring, do not stretch it to the point of deformation, nor roll it while fitting it onto the groove; otherwise, distortion may occur, leading to oil leakage.

　　② When assembling Y‑shaped and V‑shaped sealing rings, pay close attention to their installation orientation to prevent oil leakage caused by incorrect mounting. For rubber seals, the lip serves as the return‑oil port; moreover, be sure to distinguish between shaft‑type and bore‑type seals to avoid misinstallation.

　　(8) When tightening threaded fasteners, use a dedicated wrench, and ensure the torque meets the specified requirements.

　　(9) After the piston rod and hydraulic cylinder have been installed, every effort must be made to accurately measure their parallelism and to verify whether there is any deviation in parallelism over the entire length.

　　(10) After installation, when the piston rod assembly is moved, there should be no sense of obstruction or uneven frictional resistance.

　　(11) Be sure to install and securely fasten a sealing ring in the middle of the hydraulic cylinder’s oil inlet and outlet fittings to prevent oil leakage.

　　(12) After installation as required, several reciprocating strokes should be performed at low voltage to vent air from the cylinder.

　　That concludes the information shared today. We hope it has been helpful to you.