Construction machinery is inseparable from the oil cylinder, and the oil cylinder is inseparable from the seal.
Common seal is sealing ring, also called oil seal, which plays a role of insulating oil and preventing oil from overflowing or passing through.
Common seals for hydraulic cylinders include the following 6 types:
- Dust seals
- Piston rod seals
- Buffer seals
- Guide support rings
- End cap seals
- Piston seals
1. 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. It can be divided into snap-in dust ring and press-in dust ring according to the installation method.
Snap-in dust ring
The snap-in dust ring is the most common.
As the name implies, the dust ring is stuck in the groove on the inner wall of the end cover for less severe environmental conditions.
The material of the snap-in dust ring is usually polyurethane, and there are many variants of the structural form.
For example, the H and K type cross sections have a double-lip structure, the changes may vary, but the principle is the same.
Some variants of the snap-in dust ring
Press-in dust ring
The press-in dust ring is used under severe and heavy load conditions and does not get stuck in the groove.
Instead, a layer of metal is wrapped around the polyurethane material to increase strength and pressed into the end cap of the hydraulic cylinder.
There are also many types of press-in dust wipers, which are also divided into single and double lips.
Press-in dust ring and some variants
2. Piston rod seal
The piston rod seal , also called U-cup, is the main piston rod seal and is 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 with a supporting ring (also called a retaining ring). The support ring is used to prevent the seal ring from being deformed under pressure. There are also many variations of piston rod seals.
Common form of piston rod seals
Some variations of piston rod seals
3. Buffer seal
Buffer seals are used as auxiliary piston rod seals to protect the piston rod when the system pressure suddenly increases.
There are three common types of buffer seals.
Type A is a one-piece seal made of polyurethane.
Types B and C are two-pieces designed to prevent seal squeeze and allow seals to withstand higher pressures.
Several common forms of buffer seals
4. Guide support ring
The guide support ring is installed on the end cover and piston of the hydraulic cylinder, it is used to support the piston rod and the piston as well as guide the piston to perform linear movement to prevent metal-to-metal contact.
Materials include plastic, bronze coated with Teflon, etc.
Guide support rings used for the end cover and piston of hydraulic cylinder respectively
5. End cover seal
The end cover seal is used to seal the cylinder end cap 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.
It usually consists of a nitrile rubber O-ring and a support ring (retaining ring).
End cover seal
6. Piston packing ring
The piston packing ring is used to isolate the two chambers of the hydraulic cylinder and is the main seal in the hydraulic cylinder.
It usually has two-piece, the outer ring is made of Teflon or nylon and the inner ring is made of nitrile rubber.
There are also many variations, including the use of Teflon-coated bronze, etc.
On single-acting cylinders, there are also polyurethane U-cups.
Several common forms of piston packing seals