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What are the common sealing rings of hydraulic cylinders?

October 29, 2021


Which cylinders are commonly used in the market?


For example: piston type, plunger city, swing type.


1. Piston rod diameter;


2. Oil cylinder stroke;


3. Cylinder pressure; the working pressure of the cylinder is often calculated by using the test pressure,


which is lower than 16MPa multiplied by 1.5, and higher than 16 multiplied by 1.25


4. Inlet and outlet diameter and thread parameters.


5. Whether there is cushioning; according to the working conditions, the extension and contraction


of the piston rod should generally be cushioned if the impact is large.


Machinery is inseparable from the cylinder, and the cylinder cannot be separated from the seal.


A common seal is a sealing ring, also called an oil seal, which acts as a barrier against oil and prevents


oil from overflowing or passing through. The dust ring, piston rod sealing ring, buffer sealing ring,


guide support ring, end cover sealing ring and dust ring are installed on the outside of the hydraulic cylinder


end cover to prevent external contaminants from entering the oil cylinder. They can be divided according to the


installation method. Snap-in and press-in. The basic form of the snap-in dust ring is the most common.


   As the name suggests, the dust ring is stuck in a groove on the inner wall of the end cover and


is used in less harsh environmental conditions. The material of the snap-in dust ring is usually polyurethane,


and there are many variants of the structure. For example, the H and K-shaped cross-sections


have a double lip structure, but some variants of the snap-in dust ring are inseparable from the press-in type.


   The dust ring is used under severe and heavy load conditions. It is not stuck in the groove,


but is wrapped with a layer of metal to increase the strength of the polyurethane material and pressed


into the end cover of the hydraulic cylinder. There are also many types of press-in dust rings,


which are also divided into single lip and double lip. Press-in dust rings and some variants of piston


rod seals are also called U-shaped cups. They are the main piston rod seals and are installed inside


the end cover of the hydraulic cylinder to prevent leakage of hydraulic oil. The piston rod sealing ring is


made of polyurethane or nitrile rubber. In some cases, it needs to be used together with a support ring


(also called a retaining ring). The support ring is used to prevent the sealing ring from being in


the pressure buffer. The sealing ring is used as an auxiliary piston rod sealing ring.


   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-piece sealing ring made of polyurethane.


Type B and Type C are two-piece, used 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 the hydraulic cylinder to support the piston


rod and piston, guide the piston to move linearly, and prevent metal-to-metal contact.


   There are plastics, bronze coated with PTFE, etc. on the materials. The end cover sealing ring is


used to seal the cylinder end cover and the cylinder wall. It is a static seal to prevent hydraulic oil from


leaking from the gap between the end cover and the cylinder wall. Usually consists of a nitrile rubber O-ring


and a 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. Usually two-piece, the outer ring is made


of PTFE or nylon, and the inner ring is made of nitrile rubber. There are also many variants,


including the use of bronze coated with PTFE, and so on.


  On single-acting cylinders, there are also polyurethane U-shaped cups.