New universal sealing disc for sliding gate valves

One sealing disc is permanently fixed in the valve body and the other is movable

One sealing disc is permanently fixed in the valve body and the other is movable

At the heart of a Schubert & Salzer Control Systems’ sliding gate valve lie two slotted discs sliding against each other, and forming a seal. One sealing disc is permanently fixed in the valve body and the other is movable. The selection of the ideal material pairing for these sealing discs depends on many factors. In addition to the friction coefficient, which has a direct effect on the level of the force needed to actuate the valve, there are other aspects such as leakage rate, chemical resistance, suitability for high differential pressures, edge stability as well as operation in cavitation, which are all critical parameters in the choice of material or coating for the sealing discs. Moreover, the desired service life and replacement costs have to be considered.

The conventional materials for the movable sealing disc based on carbon or stainless steel with a hard alloy based on cobalt and chromium (Stellite®) are now supplemented by a diamond-like coating known as SFC (slide friction coating).

The SFC is applied to a stainless steel sealing disc and brings together the stability of the stainless steel base body, the very low coefficient of friction of the carbon and the extreme robustness of the diamond-like coating layer. Thus, movable sealing discs coated with SFC can withstand high differential pressures while, at the same time, the actuation forces for moving the sealing discs remain extremely low. This makes it possible to have smaller, and hence much more cost-effective valve actuators. Insensitivity to pressure shocks, operation near the closing point with improved edge stability and the relatively low leakage rate round off the advantages of this sliding disc coating.

The SFC coating not only improves the frictional properties of the base body but also forms an enveloping hard layer around the base material and protects it from chemical and mechanical attacks by the medium or by contaminants. Sliding gate valves with an SFC-coated sealing disc are ideal not just for shutting off and controlling high differential pressures at low actuation forces but they also present an easy solution for dealing with carrier fluids, saturated steam, acids and caustic solutions. Furthermore, a sealing disc with an SFC coating can be used for media temperatures from – 60 °C to + 300 °C.

Schubert & Salzer UK Limited
Tel: 01952 46 20 21
www.schubert-salzer.co.uk


Published: 13th May 2014

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