Copyright Goodheart-Willcox Co., Inc.
136 Hydraulic Systems for Mobile Equipment
Rod Rings and Seals
Cylinder glands contain several seals and rings. The rod seal is located
inside of the gland. The rod seal keeps the pressurized oil retained inside the
cylinder. This seal is a dynamic-type seal and must hold pressure as the rod
moves in and out of the cylinder. A lip-type seal is commonly used in rod seal
applications. This single-acting seal performs well at retaining high pressure
during cylinder operation. Refer to Figure 6-17 and Figure 6-13.
The gland uses a wiper to remove any contamination from the surface
of the rod. The wiper is the external seal that protrudes out of the cylinder’s
gland. It is also known as a scraper. If the wiper fails to remove outside con-
taminants, the intrusion of dirt will cause the rod seal to fail. If a cylinder’s rod
has oil seepage, the leakage is a direct result of a failed rod seal. The rod seal
failure might be the result of a bad wiper. However, a wiper does not have the
responsibility to retain the high internal cylinder pressure. Some glands use a
dual-purpose seal that includes both a wiper and a rod seal in one ring.
Figure 6-18. A pipe wrench is sometimes used to remove the cylinder’s gland.
Figure 6-17. Opposite ends of two different cylinder glands are shown here. The glands contain external seals, an internal
seal, and an internal wear ring. The red gland has two notches for the placement of a spanner wrench during disassembly.
External O-ring seals
Internal wear
ring seals
Rod seal Rod seal
Wiper/scraper