Plug Valve

China plug valve manufacturer, factory and supplier, mainly produce lubricated plug valve, non-lubricated plug valve, sleeved plug valve, eccentric plug valve, fully lined plug valve, 2 way,3 way,4 way plug valve, lift plug valve, jacketed plug valve, DBB plug valve, pneumatic,electric plug valve or plug valves.

Plug valve uses a cylinder or tapered plug that can be rotated at a right angle inside the valve body to control the flow of fluids. The plug may have one or multiple passages often placed horizontally to allow ease of flow.The most common type is the two-port type valve which has a single passage.

The purpose of the plug valve is to stop, start and regulate the flow of fluids by creating a partial or full obstruction in the path of flow. Sometimes the quick and frequent start-stop flow of fluids is desired in certain operations, and Plug valve is best suited for such operations.

In this post, we will learn about plug valve, their types, how they function, their distinctive characteristics, limitations, a selection guide, and a broad range of applications to help you choose the right type of plug valve for your needs.

 

Plug Valve Specification

Size Range : NPS 1/2 to NPS 56
Class Range : 150LB to 2500LB
Design Standard : API6D / API599 or Others
End Connection : RF / Threaded / BW
Operation  : Manual Lever / Pneumatic / Electrical
Pressure Testing : API 598 / API 6D / EN 12266-1/ISO 5208
Temperature Range : -29°C to +180°C for soft seated design, -46°C to +450°C for metal seated design
 

Plug Valve Construction

Plug valve construction is mostly common and similar to that of other types of industrial valves. Most of the components are similar to other valves, some of those are:

Body: The plug valve body, also known as the housing, houses the valve’s intake and outlet ports as well as the rest of the plug valve’s components in a single unit. Valve bodies are made of steel, brass, bronze, carbon steel, stainless steel, aluminium, PVC, or PVDF, among other materials. The material used is determined by the operational circumstances to which the valve will be subjected.

Plug: The valve plug is the element that acts as the plug valve’s flow control mechanism; it functions similarly to the ball in a ball valve, blocking or allowing fluid flow based on how the valve ports in the plug are connected with the channel in the valve body. Some plug valves feature tapered plugs, while others have cylindrically formed plugs.

Stem: The plug valve stem connects the valve plug to the valve (or actuator) handle and allows the plug to revolve when the handle is rotated, causing the valve stem to rotate as well. The stem connects to the exterior of the valve body through the bonnet or cover, which incorporates seals and packing to prevent fluid leakage.
Valve Port: The valve port is the hole in the valve plug that is carved out. The opening is most commonly rectangular in shape, but it can also be diamond-shaped or round.

How Does A Plug Valve Work？

Types Of Plug Valve

Lubricated Plug Valve
Plug valve is generally of all-metal type construction. The narrow gap around the plug and the housing can allow leakage. If the gap is reduced by shrink fitting the plugin the body, it will result in a considerable increase in operational torque. As a solution to this situation, a number of grooves are made around the body and plug where grease is applied through passageways to ease up the motion and seal the gaps between the plug and the body. This type of plug valve is termed as lubricated plug valve.

These plug valves can be as big as 24 inches and may handle pressure up to 6000 psi. They are generally made up of cast iron and steel and are able to withstand considerably high temperatures than the non-lubricated plug valves. This type of plug valve performs well in processes that carry mild abrasive particles such as gas pipe stations, blowdown valves, etc.

Non-Lubricated Plug Valve
This type of valve has a polymer sleeve against the body cavity of the plug. The plug acts as a wedge and presses the polymer against the body cavity to reduce friction and provide ease of movement. Non-lubricated plug valves find their application where Maintenance is to be kept at a minimum.

These are also used where the fluid or chemicals flowing have a tendency to get trapped and potentially jam the valve.  Non-lubricated plug valve nonmetallic parts are susceptible to damage on exposure to high temperature and corrosive chemicals.

Further, there are three types of non-lubricated plug valve:
  Lift-type plug valve
Elastomer sleeved plug valve
Fully lined plug valve   

3 Way Plug Valve

3 way plug valve is very common, with a third port typically at a right angle from the inlet. With the three-way design, the closure element is used to divert or combine the flow. Similarly, customized design of four ports, five ports can also be achieved.

3 Way Plug Valve has two types:
Diverting Flow: The fluid enters through the inlet port and passes through the plug, having an inbuilt passage that diverts the flow to one of the two outlets. When the plug is turned 90°, the flow is directed outward to the other outlet. If the plug is positioned midway, the flow will be equally divided to both outlets.
Combining Flow:This is the exact opposite of diverting flow wherein flow from two inlets enters the valve, passes through the plug, and channels to forms one outlet.

Eccentric Plug Valve

This type of plug valve uses a half plug which has a high seating force with minimum friction for open and close positions. In addition, an eccentric plug valve demonstrates superior shut-off capabilities. Eccentric plug valve has a variety of uses in flow control and isolation application, such as sewage pipes, sludge, slurries, grits, etc.
 

Expanding Plug Valve

These are valves superior design plug valves that use many components that allow the valve to mechanically expand in place during operation and provide a double block and bleed function in a single valve.

These plug valves use a mechanism that makes the valve swing between the open and closed positions and protects both the seals from the flow path. It ensures no contact between the body and the seal in the closed position to avoid causing any wear or abrasion in the seals.They are often used to prevent product contamination in applications where double isolation is not required.

Advantages And Disadvantages Of Plug Valve

Advantages Of Plug Valve

Now let us have a look at the advantages which make Plug Valve different from other industrial valves.
1.Simple design with a one-piece, top entry body of the plug and few parts makes it easy to use and maintain.
2. Ease of operation with minimum force applied. It can meet a long-term service requirement under a high-temperature environment up to 300 degrees.
3. Easy and in-situ Maintenance and repairs possible. All parts are one piece cast-off in this type of valve except the top flange and the cylindrical or taper plug.
4. They have a low resistance to the flow of fluid.
5. Also, these valves can be customized as per the user’s requirements with various designs available and can be made into two, three, or multi-port units.
6. Reliable leak proofing is achieved. The cover seal plug valve can achieve a 1-3mm gap between the body and the plug, which makes it suitable for harsh media like fluids containing catalytic particles, highly viscous, etc.
 

Disadvantages Of Plug Valve

Plug valve also has some limitations, such as:
1. They cannot be used for throttling. This is because the lining material exposed to the flowing medium will reduce the PTFE liner’s swelling, which damages the valve.
2. DN 100 and larger valves require a gearbox or an actuator larger than that of the ball valve.
3. Plug valve transition narrows flows due to conical plug.
4. The cost of installing these valves is higher than that of the ball valve, but in the long run, they are more economical because of their high reliability and less maintenance cost.
 

Where Is A Plug Valve Used？

1. These plug valves efficiently handle gas and liquid fuel, so they find a wide variety of use in petroleum, gas, power plants, and the marine industry. They can handle working temperatures up to 300o C, like in the case of boiler feed water, condensate, etc.
2.Since the plug valve can withstand control and regulate the flow of fluids with suspended solids like sewage, sludge, etc., it is greatly used in the Chemical industry and sewage, sanitation fittings.
3.They are widely used in AC and Refrigeration plants, especially the HVAC, to control and regulate the flow of refrigerants. 2 ports, 3 ports, or multi-port valves are especially used in this type of application.

4.Commonly used in low pressure and/or low-temperature services, some high pressure and/or high-temperature designs too exist. Thus, it finds a wide variety of usage in different pharmaceutical, food processing, and beverage industries.