Recently, Schubert & Salzer Control Systems have developed a universal sealing disc for sliding gate valves. Two sliding discs slide against each other at the heart of the valve to form a seal. One sealing disc is permanently fixed in the valve body and the other is mobilizable.

 

The selection of the ideal material pairing for these sealing discs depends on the following factors:

•Friction coefficient, which has a direct influence on the level of the force needed to actuate the valve.

•Leakage rate.

•Chemical resistance.

•Suitability for high differential pressures.

•Edge stability.

•Operation in cavitation.

•Long service life and low replacement costs.

 

The traditional materials for the mobilizable sealing disc based on carbon or stainless steel with a hard alloy based on cobalt and chromium are now replenished by a diamond like coating known as slide friction coating (SFC).

 

The SFC is used to a stainless steel dealing disc and brings together the stability of the stainless steel base body, the very low friction coefficient of the carbon and the extreme robustness of the diamond like coating layer. Therefore, mobilizable sealing discs coated with SFC can withstand high differential pressures while actuation forces for the moving seal discs are still very low. This makes it possible to have smaller, more cost-effective actuators.

 

In addition, the SFC forms an surrounding hard layer around the base material, protecting it from chemical and mechanical attacks by the medium or contaminants. Sealing disks with an SFC coating can be used for media temperatures from -60 °C to +300 °C.