Tips and Tricks Hydraulic Cylinder Repair

Hydraulic cylinders produce the actual work in a hydraulic system (or circuit). Very small hydraulic cylinders are installed to make a car's hatchback or hood open and stay elevated. Larger cylinders are used to move bulldozer blades, lift dumpsters into garbage trucks and even maneuver rockets on the launch pad. All hydraulic cylinders, however, share the same basic components, and the maintenance and repair procedures are similar.

Piston
Hydraulic fluid forced into the cylinder moves the piston out, and when the fluid is removed the piston returns into the cylinder. The piston is usually exposed to the environment and can easily become dented or fractured, causing reduced cylinder pressure. Repairing the piston usually involves removing it from the cylinder and performing metal work repairs. It's a good idea to have easy access to a replacement piston so as not to cause work to stop for too long. If the piston is dented, raised metal may surround the dent and the cylinder seals can be damaged.

Seals
The cylinder must be sealed tightly to not only keep the hydraulic pressure contained, but also to keep contamination from entering the cylinder. If there are inordinate leaks of hydraulic fluid, check the seals around the end of the cylinder where the piston actuates. Don't try to repair a seal--replace it. Once a seal is leaking, its lost its integrity to control and seal the tremendous pressure inside the cylinder.

Fittings
Another source of leaks and loss of pressure are the fittings attaching the hydraulic lines (tubing or hoses) to the cylinder. Check the fittings for a tight seal. Swaged fittings should have no play, and threaded fittings must be torqued to the correct weight. Don't tighten a threaded fittings too much--interior seals can be compressed and damaged. Always make necessary connections to the manufacturer's recommended torque wrench settings. Also, if fittings are damaged, they should be replaced.

Cylinder
The hydraulic cylinder is a metal tube closed at one end with the hydraulic fittings attached, and open at the other to allow the piston to actuate. Repairing seals and fittings is the best way to maintain proper fluid pressure. If the cylinder wall is damaged, repair is a very suspect procedure; welds and other repairs may not have the strength to contain the hydraulic pressure. For the most part, when the cylinder itself is damaged the best "repair" is replacement. {source : www.ehow.com}