Before the resilient seated gate valve was introduced to the market, gate valves with a metal seated wedge were widely used. The conical wedge design and angular sealing devices of a metal seated wedge require a depression in the valve bottom to ensure a tight closure. Herewith, sand and pebbles are embedded in the bore. The pipe system will never be completely free from impurities regardless of how thoroughly the pipe is flushed upon installation or repair. Thus any metal wedge will eventually lose its ability to be drop-tight.A resilient seated gate valve has a plain valve bottom allowing free passage for sand and pebbles in the valve. If impurities pass as the valve closes, the rubber surface will close around the impurities while the valve is closed. A high-quality rubber compound is soft enough to absorb impurities, yet strong enough to wash the impurities through when the valve is opened again. This means that the rubber surface will regain its original shape securing a drop-tight sealing.
Rising stems are fixed to the gate and they rise and lower together as the valve is operated, providing a visual indication of the valve position and making it possible to grease the stem. A nut rotates around the threaded stem and moves it. This type is only suitable for above ground installation.Non-rising stems are threaded into the gate, and rotate with the wedge rising and lowering inside the valve. They take up less vertical space since the stem is kept within the valve body.
We offers gate valves with a factory-mounted indicator on the upper end of the stem to indicate the valve position. Gate valves with non-rising stems are suitable for both above ground and underground installations.