What is plug valve :-
A plug valve is a rotational motion valve used to stop or start fluid flow. The name is derived from the shape of the disk, which resembles a plug. A plug valve is shown in Figure . The simplest form of a plug valve is the petcock. The body of a plug valve is machined to receive the tapered or cylindrical plug. The disk is a solid plug with a bored passage at a right angle to the longitudinal axis of the plug.
In the open position, the passage in the plug lines up with the inlet and outlet ports of the valve body. When the plug is turned 90° from the open position, the solid part of the plug blocks the ports and stops fluid flow. Plug valves are available in either a lubricated or nonlubricated design and with a variety of styles of port openings through the plug as well as a number of plug designs.
Plug Valve Working Principle:
Plug valve is the oldest member of valve family and used to start or stop fluid flow. It is a rotational motion valve. Body, plug (tapered or cylindrical) and cover are the basic parts of plug valve. The plug is a solid disc with a bored passage at a right angle to the longitudinal axis of the plug. It turned through 900 to allow fluid passage or to present a blank fuse to prevent flow.
In an open position, the bored passage in the plug lines up with inlet and outlet ports of the valve body. When the plug turned 900 from the open position, solid part of the plug blocks the ports and stops fluid flow. Because of their design, these offer quick action, simple operation, minimum installation space, and less pressure drop.
The two-port plug is the simplest and common type of plug valve with two positions, open to allow flow and close to stop the flow. Three-way plug valves are also available. In this type, fluid flow from one port could be directed to either second or third port and even connect all three ports together. Three-way plug valve also shifts flow between three ports.
Plug valve port designs:-
Plug valve ports are available in disc, rectangular, round and diamond shapes. Disc port plug is either round or cylindrical with the taper depend upon selection. A rectangular port plug is commonly used that represents at least 70% of the equivalent pipe cross-sectional area. In round port plug, it has round opening through the plug. If the round port plug size is equal or greater than pipe inner diameter, it refers as a full port. On the other hand, if the port opening is smaller than the pipe inner diameter, the port refers as a standard port. Valves having standard round ports used only where flow restriction is not essential. Diamond port plug designed for throttling purpose. Diamond port plug valves are venturi restricted flow type.
Plug Valve Parts :-
Typical plug valve is composed of body, bonnet, stem and plug. The seat is an essential part from the body in situation of lubricated plug valve. For non-lubricated plug valve, a non-metallic seat can be used to enhance leak tightness from the valve.
Plug valve disk: Plugs are either round or taper cylinder. They may have various types of port openings, each with a varying degree of the opening area.
Plugs are available with
- Rectangular Port
- Round Port and
- Diamond Port
Below in the photo are the list of taper plug with Rectangular, Round, and Diamond Port design.
Multi-Port Plug Valves :-
Below is the photo of 3-way multiport plug valve. The top image is of 3-way 3-port design and bottom is 3-way 2-port design.
Plug valve applications:
Plug valves use for low pressure, low temperature. While some high pressure, high-temperature designs are also available. These valves permit easy lining of the body with corrosive chemical materials such as polytetrafluoroethylene (PTFE), sulfur and hydrogen fluoride. These are ideal for on off, moderate throttling and diversion applications. They are applied in liquid and gas, vacuum, food processing, non-abrasive slurry and pharmaceutical services. Abrasive and sticky fluids can also handle with special design.