The first step in preparing to disassemble a hydraulic cylinder is to clean off the unit to prevent the unnecessary incursion of dust, oil, grease, and similar debris into the cylinder unit. Also keep in mind that repairs need to be performed in a clean space if at all possible; while there are times when emergency repairs may need to be performed in the field, it is always preferable to take care of maintenance and repair in an area as free of dust and moisture as possible.
Once the unit is clean, the hoses can be disconnected and both the ports and hoses should be plugged securely. From that point, you can open the cylinder ports and allow the hydraulic fluid to drain.
Hydraulic Cylinder Repair
There are different types of cylinders, and the repair process depends on which type is involved. The most common types of cylinders are either wire ring or threaded head (and in the case of a threaded head cylinder, there will be either a set screw or a locking ring). Note that, during the repair process, all components should be cleaned in a petroleum-based solvent, blown dry via compressed air and, before they are installed, coated with hydraulic fluid.
Disassembling a Wire Ring Cylinder
For a wire ring cylinder, the rod assembly should be retracted and the external steel wire ring removed. A mallet and punch can then be used to push the head into the cylinder tube until the internal groove is exposed and the internal wire ring is moved into a position to be removed.
Common Aspects of Hydraulic Cylinder Repair
The details for repairing threaded head cylinders differ in certain respects from the process for a wire ring cylinder. There are, however, certain things that both procedures have in common. For example, if you find it difficult to push the cylinder back in due to pressure, it is highly likely that the input valves need to be slightly loosened. Also, polished surfaces do need to be inspected carefully, seals should always be replaced once they have been removed, and specific torque values need to be used when tightening critical components. Finally, incorrectly reassembling the hydraulic cylinder or failure to correctly install seals can result in serious, expensive damage.
