Introduction
A gate valve is a type of valve used to allow or stop the flow of fluids through a pipeline. It employs a sliding gate or wedge-like disc that moves perpendicular to the flow of the liquid to either fully open or fully close the gateway. This operation is in contrast to globe valves or ball valves, which use a spherical element for the control of flow.
Gate valve suppliers provide valves that are widely used in oil and gas, power generation and desalination, and industrial, civil, and municipal applications. They are the go-to solution for applications that require reliable and quick shut-off and isolation of liquids. They have been in operation longer than most types of valves, and are expected to stay as a robust and cost-effective solution for fluid regulation.
How Does A Gate Valve Work?
Gate valves generally 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 connecting to a handwheel or other manual or automated actuation device to engage the stem. Pressure around the stem is contained with a packing material that is compressed into a packing area or chamber.
Gate valves differ from ball, plug, and butterfly valves in that the closure element, called the disc, gate, or obturator, rises on the base of a stem or spindle completely out of the way of the fluid flow and into the valve top, called the bonnet. This is done by means of multiple turns of the spindle or stem. They use a straight-line motion also called multi-turn or linear valves, as opposed to quarter-turn styles, whose stems rotate 90 degrees and generally don’t rise.
At the heart of the gate valve is the design of the closure element. This can either be a wedge or parallel seat. The wedge design is the most popular and has been around since it was invented in 1843. The wedge style uses a slightly angled disc mating with the same angled valve body seats to affect a tight closure. These valves are seated by applying torque to push the disc firmly into the seats.
Gate valves are constructed of castings, forgings, or weld-fabricated assemblies, although casting designs are the most common in operations. They come in a wide range of sizes, from NPS ½ inch, through NPS 144 inch. Standards for the design and construction of gate valves are published by the American Petroleum Institute (API), Manufacturers Standardization Society (MSS), American Waterworks Association (AWWA), and the American Society of Mechanical Engineers (ASME).
Advantages and Disadvantages of Gate Valves
In addition to their ease of operation, one of the most critical aspects of gate valves is their ability to open fully and leave the flow bore virtually free of encumbrances or friction. An open gate valve offers about the same amount of resistance to flow as a section of pipe of the same port size. As a result, gate valves are still strongly recommended for blocking or on/off applications.
Gate valves are generally bad choices for regulating flow or operating in any orientation other than fully open or fully closed. Using a partially open gate valve for throttling or regulating flow can result in turbulence and cause banging of the seating surfaces against each other, and resulting in either damage to the disc or the body seat rings.
Conclusion
Gate valves are integral components in a variety of industries due to their reliable shut-off capabilities and ease of operation. Gate valves are still the primary choice for many service applications. Their cost of manufacture to value ratio is still very high. Gate valve suppliers like Gerab National Enterprises, generally find that on typical petrochemical and refining projects today, the percentage of gate valves on requisition orders is about 60%, making them the most relied-on type of valve in the industry.