Plug Valve
What is a Plug Valve?
A plug valve is a type of valve that uses a cylindrical or tapered plug that can be rotated inside the pipe to control flow [1]. Plug valves have a passage that, depending on how the valve is oriented, allow flow across the pipe. When the valve is open, the passage is in line with the pipe openings, allowing full flow [1]. When the plug is turned 90 degrees, the passage is perpendicular to the pipe openings, and the fluid is stopped by the solid part of the valve, that is, the valve is closed. There are two types of plug valves: lubricated and non-lubricated.
Lubricated Plug Valve
The valve has a hole on top to allow for injection of lubricant [1]
Lubricant reduces friction in rotating the valve [1]
Lubricants are usually plastic sealants [2]
Plug is more corrosion resistant [1]
Useful in high temperature and pressure applications [1]
Lubricated Plug Valve Components [1] |
 |
|---|
Non-Lubricated Plug Valve
A non-metallic sleeve is used to reduce friction [2]
Require less maintenance
Not useful in high temperature applications
Usually used in low pressure applications
Lift type: external lever is used to disengage plug from seat
Elastomer type: uses a self-lubricated sleeve that is locked in place and surrounds the plug
Fully lined type: uses a ductile iron or cast iron body with the body and plug lined with Teflon
Non-Lubricated Plug Valve [1] |
|
|---|
Multiport Plug Valve
There are many plug valves with two, three, or even four ports. Multiport plug valves are used to direct and divert flow to specific lines, as well as blocking the flow, whereas single port valves can only block flow. There are also multiport valves that do not stop the flow, and can only redirect it [1].
Multiport Plug Valves [1] | Plug Valves with Four Ports [1] |
| |
|---|
Plug Valve Components
A plug valve generally consists of a body, stem, disk, and bonnet. The body houses the inner components of the valve and connects the pipes. The valve stem connects the valve actuator and disk, allowing the disk to be rotated by moving the actuator. The disk is the plug of the valve that allows for the control of flow and is often tapered. The plug valve disk can have many patterns [2].
Diagram of a Plug Valve [3] |
|
|---|
Plug Valve Port Patterns
There are different types of plug valve port patterns for different applications: round, rectangular, standard, diamond, multiport, and Venturi design patterns [2]:
Plug Valve Port Patterns [1] |
|
|---|
Rectangular port patterns are the most common port pattern type and the port opening makes up at least 70% of the pipe's cross-sectional area [1]. Round port patterns come in two types: full bore and reduced bore [1]. Reduced bore round ports are used when flow restriction is not required [1]. Diamond port plug valves are used for throttling flow [1].
Advantages
Few parts [3]
Smaller valves can be easily opened and closed
Maintenance can take place wherever the plug valve is operated
Low resistance to flow
Reliably leak-proof
Disadvantages
Getting the valve to start moving requires a lot of force due to high friction
Some larger valves need a gearbox or actuator
Generally cost more than ball valves
Reducing ports drop more pressure [2]
Applications
Commonly used in low temperature and pressure applications [3]
Some plug valves are used in high temperature and pressure applications
Useful in applications that require control of flow direction
Can be used in moderate vacuum environments
Can be used in gas and liquid fuel applications
Can be used in applications with high temperature flow
Useful in regulating the flow of suspension mixtures such as slurries
Suppliers
Listed below are links to some common plug valve suppliers:
Contributors:
Faculty Advisor: Rachel Malevich (alumni)