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The common seal rings used in hydraulic cylinder are as follows: dust ring, piston rod seal ring, buffer seal ring, guide support ring, end cover seal ring and piston seal ring.

Dust ring

The dust ring is installed on the outside of the end cover of the hydraulic cylinder to prevent external pollutants from entering the cylinder. According to the installation method, it can be divided into snap in type and press in type.

Basic form of snap in dust ring

Snap in type dust ring is the most common. As the name suggests, the dust ring is stuck in the groove of the inner wall of the end cover, which is used in less harsh environmental conditions. The material of snap in dustproof ring is usually polyurethane, and there are many variations in its structure. For example, the h-and k-sections are double lip structure, but they are always the same.

Some variants of snap in dust ring

The press in dust ring is used under severe and heavy load conditions. It is not stuck in the groove. Instead, it is wrapped with a layer of metal to increase the strength and pressed into the end cover of the hydraulic cylinder. There are many types of press in dust rings, including single lip and double lip.

Press in dust ring and some variants

Piston rod sealing ring

Piston rod seal ring, also known as u-cup, is the main piston rod seal, which is installed inside the end cover of hydraulic cylinder to prevent hydraulic oil leakage. The piston rod seal ring is made of polyurethane or nitrile rubber. In some cases, it needs to be used together with the support ring (also known as the retaining ring). The support ring is used to prevent the seal ring from extrusion deformation under pressure. There are also many variants of piston rod seals.

Common types of piston rod seal ring

Buffer seal ring

As an auxiliary piston rod seal ring, the buffer seal ring is used to protect the piston rod when the system pressure suddenly increases. There are three common types of buffer seals. Type A is a single sealing ring made of polyurethane. Type B and type C are two-piece type, which are used to prevent seal extrusion and allow the seal to bear higher pressure.

Several common forms of buffer seal ring

Guide support ring

The guide support ring is installed on the end cover and piston of the hydraulic cylinder, which is used to support the piston rod and piston, guide the piston to do linear motion, and prevent metal to metal contact. The materials are plastic, bronze coated with polytetrafluoroethylene, etc

It is respectively used for the guide support ring on the end cover of the hydraulic cylinder and the piston

End cover sealing ring

The end cover seal ring is used to seal the cylinder end cover and the cylinder wall. It is a static seal to prevent the leakage of hydraulic oil from the gap between the end cover and the cylinder wall. It is usually composed of NBR O-ring and support ring (retaining ring).

End cover sealing ring

Piston sealing ring

The piston seal ring is used to isolate the two chambers of the hydraulic cylinder and is the main seal in the hydraulic cylinder. Usually two-piece, the outer ring is made of PTFE or nylon, and the inner ring is made of NBR. Focus on mechanical engineers to acquire more mechanical knowledge. There are also a variety of variants, including the use of bronze coated with polytetrafluoroethylene, and so on. Polyurethane u-cup is also used in single acting oil cylinder.