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Plug Valve

Plug Valve


What is plug valve?

Plug valve is used to control and regulate the flow of liquids and gases in a piping system. They are usually mounted horizontally on manways, valves, or other vertical surfaces with the outlet end below the inlet.

Plug Valve is used to control the flow of fuel, air, or any other fluid.
A plug valve, also known as a stop-cock valve, is a device that controls the passage of fluid from one part of a system to another.

A plug valve is shaped as a cylindrical or cone and can be rotated inside the valve body to control flow of fluid. Plug valves are usually connected to a hollow passageway sometimes situated horizontally to allow easier passage through the valve with their open ends. Lubricated plug valves work well in processes using fluids which carry mildly abrasives such as dirty upstream applications. Eccentric plug valves for large ranges of flow management and isolation applications include clear and dirty water, sewage sludge and liquid slurries, air and other services. Expanding plug valve uses multiple elements that allow the valve to mechanically expand and gives it full double- block and bleed functions in one.

The plug valve Round Port (RSP) plug is a fast, efficient, and low-cost way to control and meter liquid flow. The port valves are a popular choice for many industries because it’s so easy to install.

Difference between plug valves and ball valves

Ball valves and plug valves are two types of quarter turn valve having similar functions and are frequently used interchangeably. But even in terms of their structurality they differ in every respect. Inadequate valves can make a system less efficient or even dangerous especially when they apply to applications that are highly critical. This blog will help you understand the differences between plug and ball valves. So you can make an informed decision about which would be right for your application. Read the blog to learn more about these special valve sizes. Click Here To read the latest articles on The Daily Mail Online for the week here.

Type of Plug Valves

A Plug Valves is a device that allows water to flow in one direction. They are mainly used under tanks and boilers to allow water to flow from a vessel to an outlet.

Lubricated plug valve

The plug on a lubricated plug valve has a cavity in its middle along its axis. At the bottom a reservoir of lubricant is provided and sealing stent injection fittings are supplied to assure that the liquid remains lubric. The lubricant is designed to reduce the power to open or close the valve and allows the plug to move freely. Most valve plugs are of allmetal construction. The narrow gap around the plug allows leakage, and when you cut the gap further it increases friction and sometimes the plug is plugged into the valve body. The lubricated plugs are available in the larger sizes and are suitable for the high-pressure cooling services.

Lubricated plug valves is an important part of the machine that regulates the release of a liquid or gas. It is used to control the amount of liquid or gas coming out of a pipe.

A plug valve assures that no liquid leaks into the tube when under high pressure and temperature conditions.

A lubricated plug valve uses a one-way bushing which ensures quick and safe flow in low pressure and temperature conditions by increasing fluid capacity through capillary action. When using lubrication, the fluids flow easily along billions of tiny channels between the surfaces without any friction.

Non-lubricated plug valves

Valve is a device that consists of two or more movable parts, such as disks, and used to regulate the flow of fluid

Non-lubricated plug valves have a screw thread that screws into the body. The plug is usually connected to the outlet pipe and often has a valve seat. A non-lubricated plug valves can be used in any case where it is desirable to have an airtight seal with no leakage of fluid passing through valve.

The valve assembles itself into a non-metallic elastomeric sleeve. The polished tapered plug acts as a wedge and presses the sleeve against the body. This nonmetallic sleeve reduces friction between the valve plug and the plug body. Non-lubricating connector valve requires minimal maintenance. This valve is not used for high temperature services. Lubricating and nondoing valves provide a bubble-tight closing function and have a small size. Lubed or nonleasable valves provide bubble tight shut off. This can be easily avoided.

Plug valve parts

The typical plug valve consists of body, bonnet, stem and plug. The seat makes up its own body. For non-metallic types a metallic seat is used to maintain leaky seal of the valve.


The valve sealing surface is much wider than in a ball valve. The cylindrical or conical plug in the valve has a larger surface area to give better seals. However, larger surface area also results in an increased torque. The torques are terribly high making the valve inflexible and difficult in operation. Ball valves ensure torque control. Smaller surface areas can bring a low seal performance but advances in chemical sealant and seal injection technologies mean ball valves can easily overcome this difficulty. Since plug valves use a larger solid disc the weight is also heavier and can become quite heavy as well.

Type of plug valve disks

The plugs are usually rounds or tapered cylindrical. They do have several types and shapes of ports each with varying depth of opening. The plugs are available in rectangular, round & diamond shaped ports. Every day, many different types of plugs are being used in a variety of industries. These range from round and taper cylinder types, to straight or tooling plug valves.


Click here for information about the other valve types. Your book will be opened in another tab. Use the Weekly Newsquiz to test your knowledge about the stories you saw on CNN eReport.


Ball valves are more flexible than plug valves in the design possibilities. Plug valves may also be customized but only on limited capacity. Multiple-ports valves start out at 2 ports and go up to 5 ports. All other customizations to plug valves such as the addition of pneumatic or electric valves or anti-friction systems are extremely costly. The sheer range of ball valves available on the market has many feature features you can choose from. Ball valves are usually unidirectional, bidirectional or multidirectional. The cables come in either a one or two part body and can contain multiple ports.

Application of Plug Valves

A plug valve is a quarter turn valve. It has a curved cylindrical stem that has an inlet and outlet at each end, and a threaded annular seat in the middle. The stem connects to a tubing using either an O-ring or tapered seals. Each of these connections forms a seal and prevents fluid from flowing through the tubing without first passing through the valve.


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