Construction machinery is inseparable from the oil cylinder, and the oil cylinder is inseparable from the seal. The common seal is the sealing ring, also known as the oil seal, which acts to isolate the oil and prevent the oil from overflowing or passing through.
Commonly used seals for hydraulic cylinders are the following types: dust seals, piston rod seals, buffer seals, guide support rings, end cap seals, and piston seals.
The dust ring is installed on the outside of the end cover of the hydraulic cylinder to prevent external pollutants from entering the cylinder. The installation method, it can be divided into the snap-in type and press-in type.
The basic form of snap-in wiper
Snap-in wipers are the most common and, as the name suggests, snap into grooves on the inner wall of the end cap and are used in less severe environmental conditions. The material of the snap-in wiper is usually polyurethane, and there are many variants of the structure, such as the H and K sections are double-lip structures, but the same is true.
Press-fit wipers are used under severe, heavy-duty conditions. They do not get stuck in the groove but are wrapped with a layer of metal in polyurethane material to increase strength and are pressed into the end cap of the hydraulic cylinder. Press-fit wipers are also available in various forms, also single-lip and double-lip.
Piston Rod Seal
The piston rod seal, also known as the U-cup, is the main piston rod seal and is installed on the inside of the hydraulic cylinder end cover to prevent hydraulic oil from leaking out. 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), which is used to prevent the sealing ring from being squeezed and deformed under pressure. Piston rod seals are also available in several variants.
Common Piston Rod Seal Forms
The bumper seal acts as an auxiliary piston rod seal to protect the piston rod in the event of a sudden increase in system pressure. There are three common types of buffer seals. Type A is a one-piece sealing ring made of polyurethane. Types B and C are two-piece to prevent seal pinching, allowing the seal to withstand higher pressures.
guide support ring
The guide support ring is installed on the end cover of the hydraulic cylinder and the piston to support the piston rod and the piston, guide the piston to perform the linear motion and prevent metal-to-metal contact. Materials include plastic, Teflon-coated bronze, etc.
For guide, support rings on the cylinder head and piston, respectively
end cap seal
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 backup ring (retaining ring).
The piston seal 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 Teflon or nylon and the inner ring is made of nitrile rubber. There are also several variants, including Teflon-coated bronze, and more. On single-acting cylinders, there are also polyurethane U-cups.
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