What is a gate valve?
Gate valves are widely used for all types of applications and are suitable for both above-ground and underground installation. Not least for underground installations it is paramount to choose the right type of valve to avoid high replacement costs.
Gate valves are designed for fully open or fully closed service. They are installed in pipelines as isolating valves, and should not be used as control or regulating valves.
Their are two main types of steam in gate valve:
Resilient steam gate valve: where rubber are used in this type. You can find this type used in 16 bar pressure
Metal steam gate valve : the steam used in this type is usually brass. This type of gate valves are used in 25, 40 bar pressure.
Gate valves are used when minimum pressure loss and a free bore is needed. When fully open, a gate valve has no obstruction in the flow path resulting in a very low pressure loss. A gate valve is a multi turn valve which the operation of the valve is done by means of a threaded stem. As the valve has to turn multiple times to go from open to closed position, this slow operating system also prevents water hammer effects.
Metal seated vs resilient seated gate valves
gate valves with a metal seated wedge (brass) were widely used before the resilient seated wedge gate valves are shown. 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.
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 found in A.1 Jordan valve 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.
Gate valves with rising vs non-rising stem design
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.
the only difference between these two gate valves is the application; Rising steams gate valves are found in fire resistance systems, while the non-rising steam are used in water networks.