Construction machinery is inseparable from the oil cylinder, and the oil cylinder is inseparable from the seal.The common seal is the seal ring, also known as the oil seal, which can isolate the oil and prevent the oil from overflowing or passing through.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.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 mode, it can be divided into snap in type and press in type.The snap in dust ring is the most common. As the name suggests, the dust ring is stuck in the groove on the inner wall of the end cover, which is used for less harsh environmental conditions.The material of snap in dust ring is usually polyurethane, and there are many kinds of structural forms. For example, h and K cross sections are double lip structure, but they are always the same.

 

 
The press in dust ring is used in severe and heavy load conditions. Instead of being stuck in the groove, the polyurethane material is wrapped with a layer of metal to increase the strength and is pressed into the end cover of the hydraulic cylinder.Press in dust ring also has a variety of forms, also divided into single lip and double lip.The piston rod seal ring, also known as the u-cup, is the main piston rod seal. It is installed inside the end cover of the hydraulic cylinder to prevent the leakage of hydraulic oil.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 called retaining ring). The support ring is used to prevent the seal ring from extrusion deformation under pressure.The piston rod seal ring is also available in a variety of variants.As an auxiliary piston rod seal ring, the buffer seal ring is used to protect the piston rod in case of sudden increase of system pressure.There are three common types of buffer seals.Type A is a one-piece sealing ring made of polyurethane. Type B and type C are two-piece to prevent seal extrusion and allow the seal to withstand higher pressure.The guide support ring is installed on the end cover and piston of hydraulic cylinder, which is used to support the piston rod and piston, guide the piston to make linear movement, and prevent metal to metal contact.The materials are plastic, bronze coated with polytetrafluoroethylene, etc.The end cover seal ring is used to seal the cylinder end cover and the cylinder wall. It is a static seal, which is used to prevent the hydraulic oil from leaking out from the gap between the end cover and the cylinder wall.It usually consists of NBR O-ring and support ring (retaining 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.It is usually two-piece, the outer ring is made of polytetrafluoroethylene or nylon, and the inner ring is made of nitrile rubber.There are also a variety of variants, including the use of PTFE coated bronze, and so on. In single acting oil cylinder, polyurethane U-shaped cup is also used.
 
 

2020-07-27

How many kinds of seals are there? What's the use of it?

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