Plug valve, also called cocks, generally are used for the same full flow service as gate valves, where quick shut off is required. They are used for steam, water, oil, gas and chemical liquid service.
Plug valves are not generally designed for the regulation of flow. Full flow is obtained when the opening in the tapered plug represent the essential features in plug valves. Careful design of the internal contours of the valve produces maximum flow efficiency.
The port in the tapered plug is generally rectangular. However, valves are also available with round ports. Major valve patterns or types are identified as regular, venturi, short, round port and multi-port.
The regular pattern employs the tapered form of port openings, the area of which is from 70 to 100 percent of the internal pipe area. In some cases, the face-to-face lengths are greater than those of standard gate valves. The venturi pattern provides streamlined flow and thus permits reduction in the port size. The port opening area is approximately 35 percent of the internal pipe area.
The round-port full-bore pattern has a circular port through the plug and body equal to or grater than the inside diameter of the pipe or fitting. Operating efficiency is equal to or greater than that of gate valves of the same size.
Major types of plug valves involve lubricated major types of plug valves involve lubricated and non-lubricated designs. Lubricant-seal plug valves are less subject to seizing or wear and may exhibit somewhat greater resistance to corrosion in some service environments.
Non-lubricated plug valve is used where maintenance must be kept to a minimum. Both types of valves provide a bubble tight closure and are of compact service applications. Also, plug valves are available with a wide variety of linings suitable for many chemical service applications.
What is Plug valve symbol
Below is the plug valve symbol used in P&ID