What is in this article?:
- Multi-element sealing system improves performance in high-load hydraulic applications: web exclusive
- Sealing reduces friction
Sealing reduces friction
Due to the intermediate pressure between the primary and secondary seal, friction and wear of the primary seal is reduced. Tests show that despite the higher friction of the pressure-loaded secondary seal, the friction of the sealing system in total is decreased. This leads to lower wear and longer operating time. The friction tests were done with the test rig shown in Figure 4. The intermediate pressure were varied in defined steps from 0 to 15 MPa while the friction was measured at different stroke speeds, as seen in Figure 5.
- System pressure: 7 / 12 / 15 MPa
- Intemediate pressure: 0 – 15 MPa
- Velocity: 2 mm/s
This means that the increasing load on the secondary seal with a direct related increase of friction force will be compensated by the improved lubrication and pressure balance of the primary seal. With an optimized choice of seal geometry and compound, the increase of friction in a sealing system due to intermediate pressure can not only be kept neutral but reduced.
The secondary seal is designed for a low increase of friction depending on pressure load so that the benefit of friction and balance on the primary seal is bigger than the increase of the special designed secondary seal. Figure 8 shows that the friction decreases considerably at higher speed and at higher intermediate pressure.
Lower wear means increased operating time
|• Temperature||T|| |
|• Rod diameter||50||[mm]|
|• Surface coating||chrome|
|• Medium||HLP 46|
Without intermediate pressure the seal profile made of filled PTFE material shows typical deformation and extrusion for these test conditions, Figure 10, unlike the direct comparable test with intermediate pressure that shows significant better results, Figure 11.
Because the intermediate pressure is limited to an allowed rate, the secondary seal also shows no wear.
A sealing system with a pre-lubricated primary seal and integrated check valve in combination with an optimized secondary seal can improve the service time and reliable functionality of a sealing system by far. The reduction of the friction as an additional feature also opens new possibilities for special demands. The choice of specialized elements in a sealing system enables sealing systems for much higher demands.