We’ve previously discussed how to select specific valves for improving production time and MTBF and thought it would be a good time to review one of the most simple and economical valves available: the plug valve.
Plug Valve Basics
A plug valve is shaped like a cylinder or cone and can be rotated inside the valve body to control flow of fluids. Plug valves have one or more hollow passageways often placed horizontally to allow ease of flow through the valve when open. The most common type of plug valve is the 2 port model with an open and closed position. The two ports are usually located on opposite sides of the valve with one passageway leading from inbound to outbound and the stem and handle located on the top. A plug valve also uses a quarter turn valve, which is useful where quick and frequent operation is essential. The valve ends can be flanged, hub type, or butt weld.
Plug Valve Types and Their Uses
Although there are many types of plug valves, there are four general categories, each with their own benefits.
1. Lubricated Plug Valve
As the name suggests, a lubricated valve uses a lubricant usually made up of a base oil and viscosity improver (like amorphous or fumed silica) that is injected under pressure between the plug face and body seat to reduce friction and seal ports. Valve manufacturers generally recommend lubricant suitable for the process fluid, and the valves often must be resealed after only a few cycles, and in some cases, after every cycle. Considered a high maintenance plug valve, they are often used in applications that have infrequent operations. Lubricated plug valves perform well in processes that utilize fluids which carry mildly abrasive particles such as dirty upstream applications, gas pipeline systems that need bypass valves, and as blow-down valves on valve stations and kicker valves.
2. Non-Lubricated Plug Valve
This plug valve utilizes a tapered or cone-shape that acts as a wedge and presses a polymeric sleeve against the body cavity. The use of the sleeve reduces friction between the plug mechanism and body. Non-lubricated plug valves are often used instead of lubricated ones in applications where maintenance needs to be kept to a minimum, such special services in sulphur, hydrogen fluoride, or where liquids could be trapped or solidify and potentially jam the valve. However, non-lubricated plug valves are limited by temperature and chemical compatibility of the non-metallic materials they are made of.
The three main types of non-lubricated plug valves are:
Lift-type plug valve
Elastomer sleeved plug valve
Fully lined plug valve
3. Eccentric Plug Valve
The design of this plug valve uses a half plug that is advantageous for applications needing a higher seating force with minimal friction from open to closed position. The torque seated valves also feature improved shut off capabilities. Eccentric plug valves are used for a wide range of flow control and isolation applications including clean and dirty water, sewage, sludge and slurries, air, and other services.
4. Expanding Plug Valve
This complex plug valve uses multiple components that allow the valve to mechanically expand and give it a true double block and bleed function in one valve. The plug valve uses a mechanism that rotates between the open and closed position and protects both seals from the flow path. During rotation there is no contact between body and seals, and slips expand onto the body seat when the valve is closed to avoid causing any wear or abrasion to the seals. They are often used to prevent product contamination in applications that do not require a double isolation.
In conclusion, plug valves have a number of useful applications, and new technology and designs are sure to give them an even wider variety of applications within many processes. And if you need more information on different types of valves, check out this piece on check valves or the rest of the site.
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A plug valve is a simple type of valve that allows or blocks the flow of a liquid through a pipe. The plug itself is often shaped like an upside-down ice cream cone or a cylinder. A handle on top allows the user to turn the plug valve so it rotates and stops or starts the flow of liquid. A minimum of two holes, known as ports, must exist in the plug for liquid to flow. The ports are located on opposite sides of the plug, and when the plug is turned to the open position it creates a passage for the liquid to flow through.
This arrangement of two ports is known as a 2-port valve. The pipe in which the plug valve is installed has an area for liquid to flow in and another for liquid to flow out. When the 2-port plug valve is turned on, the ports line up with the holes in the pipe and the liquid flows straight through as if the plug valve was not there. Other, more complex plug valves known as 3-way valves allow liquid to flow to a combination of different ports. One port may connect to either of the opposite two ports, or all three may connect at once.
Two major categories of vales exist: stop valves and check valves. Stop valves follow a basic design structure to turn the flow of liquid on and off, or allow partial flow. Check valves, in contrast, allow liquid to travel only one way and often do not have a handle. Plug valves fall into the stop valve category.
Other stop valve types include gate valves and ball valves. Though similar to plug valves, the shape of the parts and how they work to stop the flow of liquid typically determines the specific group they belong to. Regardless of group, stop valves typically control liquid through the use of a handle.
Operation of a plug valve is simple, making it a common valve choice. The user twists the handle and the ports are moved away from the opening in the pipe. In certain valves, a full turn is not required. Quarter-turn valves, for example, only require the user to make a short, quarter turn to stop the flow of liquid. Often, plug valves can lessen the flow without turning off completely if the user turns the valve half-closed but leaves it open wide enough for some liquid to make it through the ports.
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- Size Range: 1/16″ thru 1″
- 316 SS, Carbon Steel, Brass, and Exotic Metals
- Pressure Range: 1000 PSI thru 10,000 PSI
- Full-Flow Quick Connects
- Double Block and Bleed Valves
- Swing-Out Ball Valves
- Rising Plug Valves
- Toggle Valves
- Needle Valves
- Relief Valves
- Hose Adapters
- Metering Valves
- Purge Valves
Sourced by ekomeri.com