Seals

Single- and Double-acting cylinder

Single-acting cylinders are economical and the simplest design. Hydraulic fluid enters through a port at one end of the cylinder, which extends the rod by means of area difference. An external force, internal retraction spring or gravity returns the piston rod.

Double acting cylinders have a port at each end or side of the piston, supplied with hydraulic fluid for both the retraction and extension.[10]

Designs

There are primarily two main styles of hydraulic cylinder construction used in the industry: tie rod-style cylinders and welded body-style cylinders.

Tie rod cylinder

A tie rod cylinder

Tie rod style hydraulic cylinders use high strength threaded steel rods to hold the two end caps to the cylinder barrel. They are most often seen in industrial factory appliEions. Small-bore cylinders usually have 4 tie rods, and large bore cylinders may require as many as 16 or 20 tie rods in order to retain the end caps under the tremendous forces produced. Tie rod style cylinders can be completely disassembled for service and repair, and they are not always customizable