Types of Hydraulic Cylinder Seals
In many build styles, the cylinder head contains a seal gland that houses specific types of hydraulic seals to prevent pressurized oil inside the barrel from leaking past the interface between the rod and the head. The advantage of a seal gland is easy removal for seal replacement.
Seal glands typically contain a primary seal, secondary seal/buffer seal, bearing elements, wiper/scraper, and static seal. In some cases, especially in small hydraulic cylinders, the rod gland and bearing elements are made from a single integral machined part.
Hydraulic seals, like the hydraulic cylinder itself, are specified based on cylinder working pressure, cylinder speed, operating temperature, and application. Seals used on hydraulic cylinders are dynamic and must be able to stand up to the wear of the piston rod extending and retracting.
Seals are generally made from nitrile rubber, Polyurethane or Teflon, and are best in lower temperature environments. higher temperatures, hydraulic seals made of Fluorocarbon are a better option. Metallic seals are also available and commonly use bronze for the seal material. Wipers are often made from polyurethane and are used to eliminate contaminants such as moisture, dirt, and dust, which can cause extensive damage to cylinder walls, rods, seals, and other internal components.