When considering a seal, a maximum pressure of up to 0.5 bar is considered. However, there are many applications where the working pressure can be much higher, as is the case with Epidor SRT pressure seals. In general, the pressure load (P) and the peripheral speed (v) will determine the range of use of the seals. When the respective limit values are exceeded, wear will be premature and will lead to a reduction in the service life of the seal, unless a pressure seal. Conventional seals are designed for service at atmospheric pressure or for very low relative pressures (between 0.2 and 0.5 bar).
Characteristics of pressure seals
The lip of the lip seal is oriented to the pressurized side The lip of the seal is pressed against the shaft by the fluid; therefore, any seal under pressure must be secured on the side opposite to the direction of pressure to prevent it from being pushed out of its housing. To achieve this, the following are used support rings, The seals are designed for each model of oil seal. There are oil seals that already incorporate in their design the support ring and that can work up to 5 bar of pressure.
In addition, lip length should be as short as possible to reduce friction with the shaft. A shorter lip (with less contact surface) will exert a greater radial force and will be less affected by pressure than a longer lip. Low friction coefficient materials are recommended.
The lip seal“ type seals”, The lip seals, capable of withstanding pressures up to 10 bar, are designed for process pumps, hydraulic motors, screw compressors, agitators or hydrodynamic clutches. Lip seals consist of a metal housing containing a very short and at the same time very flexible sealing lip. The lip is manufactured in PTFE and in Restructured PTFE, with a low coefficient of friction. This design minimizes the increase in sealing lip contact pressure and thus the friction between the sealing lip and the shaft.
In the sealing sector, various lip and pocket configurations are developed in order to offer the most suitable solution for each need. For example, there are lip seals that have two lips in tandem or “back-to-back” in the same pocket.
It uses the tandem lip design when it is anticipated that heavy wear may occur, once the first lip breaks, the fluid encounters the second lip. On the other hand, the “back-to-back” design is recommended for use when pressure variations may occur on one side of the lip seal. If necessary, a dust lip can also be added.
Likewise, a lip seal with a suitably reinforced housing can work up to pressures of 25 bar. For higher pressures, the dynamic tightness of the equipment is achieved with more complex solutions such as a mechanical seal.
If you want more information about pressure seals, please consult our seals catalog o contact with us.