A plug valve is a quarter-turn valve that controls flow by rotating a cylindrical or conically tapered plug inside the valve body. The plug contains one or more passageways running sideways through it, so that the medium can flow through the plug when the valve is open. Luna Flow Control supplies plug valves from DN 15 to DN 600 and from PN 10 to PN 320 / Class 150 to 2500, in straight-through and multi-port designs.
What Is a Plug Valve?
A plug valve is a simple, robust shut-off valve with a one-piece body and a rotating plug. Its leak-tight construction makes it a common alternative to ball valves, and it is particularly valued in services where ball valves lose their effectiveness, such as lines carrying particles, mud and slurry. Plug valves are widely used in natural gas lines.
Working Principle
The plug is rotated through 90° within the body to control the flow. In the open position the passageway in the plug is aligned with the pipeline and the medium passes freely; a quarter turn moves the passageway out of line and stops the flow completely. Multi-port versions have several passageways, allowing the valve to divert or distribute the flow between two to seven ports.
What Does a Plug Valve Do?
Plug valves maintain reliable flow in pipelines containing particles. Particles that would damage other valve types do not affect lubricated plug valves, so the flow can be controlled safely. The design also prevents particles that could block the installation from settling and seizing the valve, which makes plug valves a safe choice for lines transporting mud and slurry.
Types of Plug Valves
- PTFE sleeved plug valves – quarter-turn valves with a PTFE sleeve that provides an excellent level of sealing. They can be used as an alternative to ball valves and perform well in natural gas lines, but they require more frequent maintenance and should be operated with care.
- API plug valves – one-piece cast body, leak-tight design and flanged, threaded or welded connections. They are also available in stainless steel and are widely chosen for natural gas lines.
- Multi-port plug valves – 3- to 7-way designs for diverting and mixing duties.
- High-pressure plug valves – for demanding process conditions.
Size Ranges
| Version | Pressure rating | Size range |
|---|---|---|
| Standard design | PN 10 – 40 / Class 150 – 300 | DN 15 – 500 / 1/2″ – 20″ |
| 3 – 7 way plug valve | PN 10 – 40 / Class 150 – 300 | DN 15 – 500 / 1/2″ – 20″ |
| High-pressure plug valve | PN 10 – 100 / Class 150 – 600 | DN 15 – 500 / 1/2″ – 20″ |
Materials and Actuation
Bodies are available in ductile iron, steel, stainless steel, Monel and Hastelloy, with metal-to-metal or PTFE/PFA sealing. Plug valves can be operated by lever or gearbox, or fitted with electric, pneumatic or hydraulic actuators for automated service.
Advantages
- Fast quarter-turn operation
- Leak-tight shut-off
- Tolerant of particles, mud and slurry
- Multi-port options reduce the number of valves in a system
Selection and Maintenance Tips
Choose the sealing type according to the medium: metal-to-metal seats suit abrasive and high-temperature service, while PTFE/PFA sleeves give excellent tightness in clean gas and chemical service. Sleeved and lubricated designs should be included in a regular maintenance programme to preserve their sealing performance.
