Plug valves are used in many commercial and industrial applications. They are a quarter-turn rotary design valve and provide an efficient and effective means of controlling flow, ensuring that the entire system works efficiently.
Plug valves have a cylindrical or conically tapered ‘plug’ that can be turned to either start or stop the flow of fluids. The plug also has one or more hollow internal passages running through it. When the valve is open, these internal passages are inline with the flow, allowing the fluid to flow through the plug. When the plug is rotated 90 degrees, the solid part of the plug stops the flow.
Plug valves come in a lubricated and non-lubricated design. As the name implies, a lubricated valve uses a lubricant such as a grease or sealing compound to reduce friction and seal the ports. Non-lubricated valves do not use a lubricant for sealing and are used in applications requiring minimum maintenance. They typically feature a thermoplastic or non-metallic sleeve fitted to the body cavity of the valve to reduce friction between the plug and the body and to also assist with sealing.
What is a plug valve used for?
Plug valves are generally employed for isolating purposes. Special 3-way or 4-way ‘multiport’ valves are also available to control the direction of the flow through multiple port openings within the body of the valve.
Plug valves are widely used when dealing with mud, slurries, and sewage applications because they provide an unrestricted opening for the fluid to flow through.
These valves are also used in natural gas and oil piping systems, pharmaceutical services, food-processing industries, and other high-pressure applications.
How does a plug valve work?
A plug valve consists of three main components:
- A valve body that has parallel or tapered seating into which the plug is fitted.
- A plug which is cylindrical or tapered in shape which can be rotated inside the valve body.
- An operator, which is a manual hand-wheel or lever used for opening or closing the valve. Some valves have an actuator in place of a handwheel. An actuator is a device that controls the opening and closing of the valve with the help of electrical energy.
There are one or more hollow ports inside the plug. The fluid starts flowing through the valve when the hollow ports in the plug are inline with the ports in the body. Rotating the plug 90 degrees blocks the port opening in the body with the solid portion of the plug, thereby closing the valve.
The most basic form of a plug valve is a 2-way bi-directional valve that can be opened and closed to regulate the fluid flow.
Plug Valve Working Principle
The plug valve has a simple and robust structure. Because of its full open port design, the fluid does not come into direct contact with the seating surfaces of the valve’s body. So, the valve does not get damaged easily. For this reason, the plug valve has a longer life than many of its counterparts.
The valve can readily be opened or closed with the help of a handwheel, lever or an actuator. Turning the handwheel by 90-degrees will fully open or close the valve.
- When the handwheel is turned 90-degrees, the pipe and the hole are aligned, and the valve is in the open position.
- When the valve is open, the fluid flow will be straight.
- When the handwheel is turned 90-degrees from the open position, the solid section of the plug sits across the pipe, and it gets closed.
Some plug valves may have multiple hollow ports, and these types of valves are referred to as multi-way valves. These valves are used to divertthe flow of the fluid. The direction of the flow can be changed by turning the handwheel at a 90-degree angle. Generally, multi-way plug valves are used in place of a number of gate valves to regulate the flow’s direction. A single multi-way plug valve requires less space and is more economical than having to install a number of gate valves to achieve the same purpose.
Advantages and Disadvantages
Plug valves are easy to use and have a long service life. Moreover, these valves can have multiple ports that help simplify the piping design and reduce the usage of valves. Let us look at the advantages as well as disadvantages of plug valves.
Advantages:
- The plug valve has a tight shut-off, which implies a high sealing ability. Moreover, it opens up quickly and has a low-pressure drop. Valves with a low-pressure drop need less energy to maintain the desired flow within a system.
- As the body seating faces on a plug valve are not directly exposed to the fluid flow, these valves are less likely to erode and, therefore, have more durability.
- Plug valves are relatively lightweight with a simple design that makes them easy to use.
- Because of their more straightforward design, the maintenance of these valves can be done onsite.
- They do not produce any vibration and noise during operation.
- Using a multiple port design plug valve will help to simplify piping layouts and reduce the number of valves required.
Disadvantages:
- Plug valves need more force to operate as they have higher friction between the plug and the body.
- Large plug valves cannot be operated manually, so an actuator is required.
- The plug valve is costlier than a ball valve for the same application. Therefore, if there is a budgetary constraint, a ball valve may be a more suitable choice depending on the application.
- Plug valves are not suitable for throttling applications.
Summary
Various industries require valves that function well under a high-demand environment. A well designed and planned plug valve can survive wear and tear and last long under different circumstances. John Valves have been in the valve supply and manufacturing business for nearly 125 years and provide high-quality plug valves that last longer. Although it is more expensive than a ball valve, a plug valve is more reliable and lasts longer. So, what are you waiting for? Buy a plug valve from dependable plug valve manufacturers.
