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Several major factors that affect the sealing performance

Update:11 Jul 2017

1.Movement speed Movement speed is very low (<0.03m […]

1.Movement speed
Movement speed is very low (<0.03m / s), to consider the smooth operation of the equipment and whether the "crawling" phenomenon. When the movement speed is high (> 0.8m / s), the oil film which is lubricated may be damaged, and the seal can be frictional heat due to the lack of good lubrication, resulting in a significant reduction in life.
It is recommended that the polyurethane or rubber seal work in the range of 0.03m / s ~ 0.8m / s.
2. Temperature
Low temperature will make the polyurethane or rubber seal elasticity reduced, resulting in leakage, and even the entire seal becomes hard and brittle High temperature will make the oil seal volume expansion, soft, resulting in movement when the friction frictional resistance increased rapidly and pressure resistance decreased. Recommended polyurethane or rubber seal continuous working temperature range -10 ℃ ~ +80 ℃.
3.Work pressure
The seal has a minimum service pressure requirement. Low-pressure work to be selected low friction performance, start the resistance of small seals. In the 2.5MPa below, the polyurethane seal is not suitable; high pressure to consider the case of compression deformation of the seal, the need to use anti-extrusion ring, groove processing also has special requirements.
In addition, the seals of different materials have different optimum working pressure ranges. The optimum working pressure range for polyurethane seals is 2.5 to 31.5 MPa.
The effects of temperature and pressure on the sealing performance are interrelated and therefore considered. See table:
Imported polyurethane PU material
Maximum working pressure
Maximum temperature range Temperature range
Movement speed -25 ~ +80 -25 ~ + 110
0.5m / s 28MPa 25MPa
0.15m / s 40MPa 35MPa
4. Working medium
In addition to strictly in accordance with the recommendations of the manufacturer to select the working medium, to maintain the cleaning of the working medium is essential. The aging or contamination of the oil will not only cause the components in the system to fail, to speed up the aging and wear of the seal, and the dirt may scratch or insert the seal to render the seal ineffective. Therefore, the quality of the oil and its cleanliness must be checked regularly and the oil filter or oil can be replaced according to the maintenance specifications of the equipment. In the oil tank in the oil in the air by high pressure compression will produce high temperature so that the oil seal burned, or even carbonization. To avoid this, the exhaust system should be operated at the beginning of the hydraulic system. The hydraulic cylinders should also run at low pressure for several minutes to confirm that they have drained the residual air in the oil before they can work properly.
5. Lateral load
Pistons must be installed on the bearing ring, to ensure that the cylinder can withstand greater load. Seals and support rings play a completely different role, the seal can not replace the support ring load. A hydraulic cylinder with lateral force must be equipped with a support ring with a strong load capacity (metal ring can be used during heavy load) to prevent the seal from working in eccentric conditions causing leakage and abrasion.
6. Hydraulic shock
There are many factors that produce hydraulic shocks, such as excavator bucket suddenly hit the stone, lifting the crane or put the weight of the moment. In addition to the factors, the high pressure large flow hydraulic system, the implementation of components (hydraulic cylinders or hydraulic motors, etc.) when the commutation, if the valve performance is not very good, it is prone to hydraulic shock. The instantaneous high pressure of the hydraulic shock may be several times the system working pressure, so that the high pressure will tear or seal the oil seal into the gap in a very short time, causing serious damage. Generally the hydraulic shock of the cylinder should be installed in the piston rod buffer ring and retaining ring. Buffer ring in the front of the oil seal to absorb most of the impact pressure, retaining ring to prevent the oil seal in the high pressure squeezed into the gap, the root was bitten bad.