How does plug valve work

Plug valve comprises a body with tapered or parallel seating into which a plug fits. The plug is formed with a port, the position of the port controls the amount of opening through the valve. Ports are known as the openings in the valve body through which fluid can enter or leave.

A 90 degree of plug fully opens or closes the fluid flow. Plug valve is not as efficient as ball valves and can only operate fully open or closed.

When the opening in the plug is in line with the inlet and outlet ports, flow continues through the valve. A pressure drop occurs through the reduced area of the plug port. However, with a full-area cylindrical plug the pressure drop is minimal. When the full quarter-turn rotation is reached, the port is completely perpendicular to the flow stream, creating complete shutoff. In throttling situations, where the plug is placed in a midturn position, the plug takes a double pressure drop.

The flow then moves into the full-port area inside the plug, where a pressure recovery takes place, followed by another restriction at the outlet port. Leakage is prevented through the seat by the compression of the plug against the sleeve or other sealing mechanism, while the packing or the collar—diaphragm assembly prevents leakage through the stem.

With three-way valve arrangements requiring diverting flow, flow enters at the inlet and moves through the plug, which channels the flow to one of the other two outlets. At a midway position, flow may be equally diverted to both outlets. With combining flow, flow is directed from two inlets to a single outlet.

With larger plug-valve sizes [3 in DN 80 or larger], the torque required for seal breakout may become somewhat excessive. This is caused by the larger contact surface between the plug and sealing device as well as any adverse operating conditions, such as a high process pressure, temperature extreme, corrosion deposits, etc.

In this case, hand-levers are typically replaced with geared handwheels, which reduce the torque requirement significantly. The simple plug valve is suitable for low pressure, low-temperature applications and is made in large sizes of to mm. The main limitation of the plug valve is that if wide variations in fluid temperature are involved then differential expansion is inevitable, leading either to undue stiffness of operation or loss of pressure-tightness.

The plug may be tapered, parallel and the movement may be plain or lubricated. Another variation is known as the ball plug valve, in which the plug is spherical, having circular ports rotating between circular seats of the concave section. These valves use lubricants or sealants to ease their operation over a wide range of operating pressure. The lubrication film which is used between plug and body provides a seal and that requires periodic lubricant injection. The sealant must be like that it does not get washed away with the fluid as the fluid can get contaminated and it should be able to withstand line temperature.

These lubricants in plug valves are mostly plastic sealants. The use of effective sealant with properties such as proper elasticity, resistance to chemicals, and its ability to form an impervious seal around each body part is essential.

Close Privacy Overview This website uses cookies to improve your experience while you navigate through the website. Out of these cookies, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. We also use third-party cookies that help us analyze and understand how you use this website.

These cookies will be stored in your browser only with your consent. You also have the option to opt-out of these cookies. But opting out of some of these cookies may have an effect on your browsing experience. Necessary Necessary. Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website.

These cookies do not store any personal information. Non-necessary Non-necessary. Lubricating and non-lubricating valves are capable of providing a bubble-tight shutoff and are of compact size. Here you can see the 3-way multiport plug valve. The top image is of 3-way 3-port design and the bottom is 3-way 2-port design. Multiport valves are used in transfer lines and for diverting services.

A single multiport valve may serve the purpose of three or four gate valves or other types of the shutoff valve. However, sometimes the multiport valve does not completely shut off flow. Great care should be taken in specifying the particular port arrangement for proper operation. The typical plug valve is consisting of a body, bonnet, stem, and plug.

The seat is an integral part of the body in case of a lubricated type. For a non-lubricated type, a non-metallic seat is used to improve leak tightness of the valve. Plugs are either round or taper cylinder. Non-lubricated plug valves are often used instead of lubricated ones in applications where maintenance needs to be kept to a minimum, such special services in sulphur, hydrogen fluoride, or where liquids could be trapped or solidify and potentially jam the valve.

However, non-lubricated plug valves are limited by temperature and chemical compatibility of the non-metallic materials they are made of. The design of this plug valve uses a half plug that is advantageous for applications needing a higher seating force with minimal friction from open to closed position. The torque seated valves also feature improved shut off capabilities.

Eccentric plug valves are used for a wide range of flow control and isolation applications including clean and dirty water, sewage, sludge and slurries, air, and other services. This complex plug valve uses multiple components that allow the valve to mechanically expand and give it a true double block and bleed function in one valve.

The plug valve uses a mechanism that rotates between the open and closed position and protects both seals from the flow path. During rotation there is no contact between body and seals, and slips expand onto the body seat when the valve is closed to avoid causing any wear or abrasion to the seals. They are often used to prevent product contamination in applications that do not require a double isolation.

In conclusion, plug valves have a number of useful applications, and new technology and designs are sure to give them an even wider variety of applications within many processes. And if you need more information on different types of valves, check out this piece on check valves or the rest of the site. A recent visitor to our facility described the lengthy process that entails when a power failure occurs and what that….

Water is such a fundamental necessity for life that it is often taken for granted. In modern industrial societies, the water from every tap is….