Gear Pump High Pressure, Teflon Shaft Seal Bears Over-pressures Of Over 210 Bar
A system of radial sealing at the shaft that can bear enormous internal over-pressures without resulting in damage. This radial sealing is particularly useful in single direction hydraulic motors when, in certain conditions of use, high over-pressures will be generated at the motor output.
With bi-directional motors, the area adjacent to the seal ring of the drive-shaft is maintained at atmospheric pressure by the drainage circuit. In single-direction motors, this area is directly connected to the output so any over-pressure impacts directly on the seal ring, causing the lip to turn over or the ring to be expelled from its seat with a consequent leakage of fluid.
Validation tests have revealed that the system is able to work on a continuous basis at a constant pressure of 30 bar (430psi) without the spilling of fluid and without the ring and the shaft exhibiting wear.
Tests performed at higher pressures also demonstrated the possibility of the system functioning for short periods of time (several minutes) with over-pressures of up to 140 bar (2,030psi).
If the operating conditions must be maintained with extremely high over-pressure values (80-100 bar / 1,160 – 1,450psi) for prolonged periods of time (over 30 minutes), the heat generated by the friction between the ring and the shaft can result in temperatures of over 300°C.
This inevitably plays a part in deteriorating the structure of the P450 material used in the seal ring, as well as compromising the ground profile on the shaft, and thereby reduces its sealing function.
In the presence of pressure peaks, for example caused by errors of manoeuvre or an incorrect timing of the valves of the hydraulic circuit, or in static conditions, with the shaft immobile, this sealing system can bear over-pressures of over 210 bar (3,050psi) without leading to any loss of fluid or deformation of the components.
One of many excellent features of the wide range of gear pumps available from jbj Techniques Limited; www.jbj.co.uk/MarzocchiTeflonSeal.html
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