Types of Cylinder Seals and Factors Affecting Sealing Performance

Cylinder sealing, an important parameter of air cylinder, is related to the technical condition of cylinder block, cylinder head, cylinder gasket, piston, piston ring, inlet and exhaust valves and other parts

Figure 1: different types of air cylinder sealing part.

Cylinder sealing is an important parameter to characterize the technical condition of engine. Cylinder sealing is related to the technical condition of cylinder block, cylinder head, cylinder gasket, piston, piston ring, inlet and exhaust valves and other parts.

Types of Sealing Part

There are various sealing parts of air cylinder, and different parts have different characteristics.

Compression Sealing Ring

It can resist high temperature, featuring small deformation in permanent compression.
The greater the amount of pre-compression is, the better the sealing performance is, yet the greater the friction is.
It can be sealed in both directions.
The friction force will increase if it is placed for a long time.

It varies according to the specific application. For general static seal, in order to obtain better sealing performance, larger compression amount can be selected; for dynamic seal, in order to reduce resistance, smaller compression amount can be selected.

compression can resist high temperature, featuring small deformation in permanent compression. The greater the amount of pre-compression is, the better the sealing performance is, yet the greater the friction is

Figure 2: The appearance of O-shaped compression sealing ring.

NLP Compression Sealing Ring

It occupies a small space and has a small sliding resistance. It can be lubricated without oil, and the resistance is reduced under low pressure.

Gas Pressure Sealing Ring

The higher the air pressure is, the better the sealing performance is and the greater the friction resistance is.
It can only be sealed in one direction, and two ones must be installed on the piston of double acting SMC cylinder.
The lip has a certain self-compensating effect on wear.
It has small amount of pre-compression and good performance of small action under low pressure.
U, Y-shaped air pressure sealing ring: The sealing groove has a simple structure, reliable sealing and a wide range of operating pressures.
Air pressure sealing ring for buffer: used at the buffer sleeve of the air buffer motorcycle cylinder.
Air pressure sealing ring for dust prevention: prevent dust and junks from entering the cylinder.

Figure 3: The appearance and design code of gas pressure sealing ring.

Manifestations of Poor Sealing of Air Cylinder

The manifestations of poor sealing include difficult or even impossible to start the engine, not reaching the maximum speed, prolonged acceleration time, reduced capacity for maximum climbing, increased fuel and oil consumption, increased smoke exhaust with abnormal smell.

Influencing Factors

Uneven Cooling of Cylinder Surface

Heat in part areas will also cause additional internal stress in the cylinder itself, which will lead to cracks in the cylinder head. If the operating temperature exceeds the normal temperature, it will cause serious effects.

Heat in part areas of cylinder surface will also cause additional internal stress in the cylinder itself, which will lead to cracks in the cylinder head

Figure 4: The surface of air cylinder.

Slight Beat of Cylinder Head

The slight beat of the cylinder head will cause the relaxation and compression of cylinder head gasket, thus accelerating the damage of the cylinder head gasket and affecting the sealing performance.

Incorrect Disassembly and Assembly Method of Cylinder Head

Whether the cylinder head is disassembled and assembled correctly plays an important role in prolonging the service life of the cylinder gasket and preventing the deformation of the rodless cylinder head. When disassembling and assembling the cylinder head, it should be carried out in the cold engine state, rather than in the hot state, so as to prevent the cylinder head from warping.

Too Large Plane of Cylinder Head or Cylinder Block

If the cylinder head is deformed, it will not be tightly combined with the plane of the cylinder block, which will affect the sealing quality of the cylinder.

Incorrect Installation and Use of Cylinder Gasket

The cylinder gasket, installed between the cylinder block and the cylinder head, ensure the sealing of the combustion chamber and prevent blowby of fuel gas, cooling water and lubrication.