Here are three common causes of hydraulic cylinder failure: 

Ballooned Tubes 

Ballooning of the cylinder tube is usually caused by excessive honing or insufficient wall thickness and/or material strength for the cylinder's operating pressure. 

Once the tube balloons, the correct tolerance between the piston seal and tube wall is lost, and high-pressure fluid bypasses the seal. This high velocity fluid can erode the seal and localized heating caused by the pressure drop across the piston reduces seal life. 

Insufficient Bearing Area 

If the internal bearing areas in the gland and on the piston are insufficient to carry the torsional load transferred to the cylinder, excessive load is placed on the rod and piston seals. This results in deformation and ultimately premature failure of the seals. 

Rod Finish 

The surface finish of the cylinder rod can have a dramatic effect on the life of the rod seal. If the surface roughness is too low seal life can be reduced through inadequate lubrication. 

If the surface roughness is too high, contaminant ingression is increased and an unacceptable level of leakage can result. 

Keep in mind that not all hydraulic cylinders are made equal. So if you have hydraulic cylinders that suffer recurring failure, it's likely that modifications to the cylinder are required to break the vicious circle of failure and repair.

Craig Cook