The hydraulic cylinder is one of the indispensable components of construction machinery. Common working pressures range from just a few MPa to several tens of MPa.
Although specific structures vary, the principle is the same: using fluid pressure energy to generate linear motion (sometimes combined with rotary motion). Because the principle never changes, the main causes of failure are generally the same. The most common problem is oil leakage — either external or internal.

1. External leakage
External leakage is obvious at a glance (if you can’t recognize it, maybe you had too much to drink at lunch). But the cause is not simply seal failure. Apart from incorrect installation, external leaks almost always accompany internal leaks.

External leakage doesn’t just waste hydraulic oil. Its bigger problem is that during the piston rod’s return stroke, contaminants are carried back into the hydraulic system, causing greater pollution and accelerated wear.