What is a Gate Valve?

Gate valves are widely used in all types of applications, both above and below ground. Especially for underground installations, it is crucial 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 isolation valves and should not be used as control or regulating valves. The operation of the gate valve performs a clockwise closing (CTC) or clockwise opening (CTO) rotational movement of the valve stem. When the stem is operated, the gate moves up or down on the threaded portion of the stem.

1. Where is the gate valve used?

Gate valves are typically used when minimal pressure loss and free orifice are required. When fully open, a typical gate valve has no blockage in the flow path, resulting in very low pressure losses, a design that makes it possible to use pipeline cleaning pigs. A gate valve is a multi-turn valve, which means that the operation of the valve is done through a threaded rod. Slow operation also prevents water hammer, as the valve must be turned several times to go from the open to the closed position.

2. Parallel and wedge gate valve

Gate valves can be divided into two main types: parallel and wedge. Parallel gate valves use a flat gate between two parallel seats, and the popular type is the knife gate valve designed with a sharp edge on the bottom of the gate. Wedge gate valves use two sloped seats and a slightly mismatched sloped gate.

Most gate valves are solid wedge designs, but we also offer knife gate valves for wastewater treatment and parallel spool valves for air supply.

3. Metal seat and resilient seated gate valve

Metal seated gate valves were widely used before resilient seated gate valves were introduced to the market. The tapered wedge design and corner seal of the metal seat wedge require a recess in the bottom of the valve to ensure a tight shutoff. Therefore, sand and pebbles are embedded in the holes. No matter how thoroughly the pipes are flushed during installation or repair, the piping system will never be completely free of impurities. Therefore, any metal wedge will eventually lose its ability to prevent dripping.

Resilient seated gate valves have a common bottom that allows free passage of sand and pebbles in the valve. If impurities pass through when the valve is closed, the rubber surface will close around the impurities when the valve is closed. The premium rubber compound absorbs impurities when the valve is closed and is washed away when the valve is opened again. The rubber surface will return to its original shape, ensuring a drip-proof seal.

The vast majority of gate valves are resiliently seated, but metal seated gate valves are still required in some markets.

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