Intro4u2u

This low-tech valve may not have changed much in the last 100 years, but the gate valve plays a major role in virtually every refinery, chemical plant and industrial facility in the world.

The most popular style of valve in the world of flow control is the gate valve. They are the on/off switches of the fluid control industry and they are found in every refinery, chemical plant, power plant and industrial facility. Gate valves exist for one primary purpose- to stop flow. Because of this, they are often referred to as “stop” or “block” valves. Gate valves are manufactured in a wide range of sizes- from ¼” through 144”.

It is not recommended to operate gate valves in the partially open position, or to use them in throttling service. When a gate valve is partially open, it closure element (disc or wedge) can vibrate against the seats and become scratched causing them to lose their seating integrity.

The chief advantage of a gate valve is that it offers virtually no resistance to flow in the open position. Only a full port ball valve can equal the gate valve’s flow characteristics. Due to their symmetrical design and equilateral seating, gate valves can be used to stop flow from either direction. They are available in every material from the shiny brass construction of the diminutive ½” water valves on the hardware store shelf, to the exotic high alloy models found in nuclear power installations.

Gate valves have been an important piece of fluid control equipment for over 150 years. In fact, the very first valve patent issued in the United States was for a “gate valve”. Since those humble beginnings in the 19th century, the gate valve has answered the fluid control call with relatively little basic design change.

From the outside, most gate valves look somewhat similar. However, inside there are a host of different design possibilities. Most gate valves consist of a body and bonnet that contains a closure element, called a disc or a gate. The closure element is attached to a stem that passes through the bonnet of the valve, ultimately interfacing with a handwheel or other device to operate the stem. Pressure around the stem is contained through the use of packing material which is compressed into a packing area or chamber.