Plug Valves Advantages and Disadvantages

May. 20, 2024

Plug Valves Advantages and Disadvantages

A Plug Valve is a quarter-turn rotational motion Valve that use a tapered or cylindrical plug to stop or start the flow. In the open position, the plug-passage is in one line with the inlet and outlet ports of the Valve body. If the plug 90° is rotated from the open position, the solid part of the plug blocks the port and stops the flow. Plug valves are similar to Ball valves in operation.

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Type of Plug Valve

lubricated plug valve
non-lubricated plug valve
eccentric plug valve
lift-type plug valve

Plug Valve Application

Plug valves are a type of flow control valve that allows the user to increase or decrease flow by rotating the handle or other similar operation. The user may have to adjust the valve to the desired flow rate, with the valve able to hold the flow rate consistently and reliably.

Other popular flow control valves include needle and fine metering valves, but they generally have more moving parts than plug valves, which makes them more expensive and harder to maintain.

Plug valves are typically used in applications where flow must be controlled and changed on a regular basis and where the user must have access to the valve.

Plug valves should not be used in applications where a constant, steady flow is required or where the valve does not need to be readily accessible.

Quarter-turn plug valves are the most common and involve a simple quarter turn on a handle to open and close the valve. They are economically priced and are commonly used for applications involving low-pressure throttle.

Advantages of Plug Valve

one-piece valve body, top-loading design, simple structure, convenient maintenance, no leakage, supporting higher-strength pipe system.
The medium in the chemical process has strong corrosion resistance. In the chemical field, corroded valve body often can be seen. Therefore, the valve in the application of chemical process must have strong permeability and resistance to intergranular corrosion. The body of plug valve should be high-level casting, with casting quality of class II and precision of grade V.
Really simple internals. The plug is completely covered by the bushing. Body and plug have no wear. Replacing simple and economic bushing or top sealing device can complete the maintenance and update of the valve. Plug valve can reach long-term use requirement of 300 ℃, which has a considerable competitive edge compared with a ball valve that belongs to this application.
Top surface and flange are all the processing surface of the plug valve. Other parts are all one-time casting molding. The inside of the valve body has no processing. Comparing with the ball valve, it has the advantages of lower machining allowance. Especially, when the material is INCONEL, MONEL, HARTZ alloy, plug valve has the distinct advantage of price.
According to the user’s demand, various designs of plug valve can achieve a specific function. Plug valve is the best one of customized products. Plug valve is easy to cater to custom design, can be made into three-way, four-way, five-way and six-way valve; double valve group or valves group; all kinds of jacket requirements, etc. For example, the six-way distribution valve used in the polyester industry is designed according to the requirements of patent owners, while the ball valve is difficult to make in line with custom design.
Now, no clearance and face sealing is still the unique features of the plug valve. Although it has the design of the clearance like ball valve’s, the clearance just can be reduced to 1 ~ 3 mm at the most, which can’t achieve the application advantages of coated surface sealing. This characteristic of plug valves enables it to deal with a lot of harsh media, such as easy crystal and viscous fluid or those medium containing catalyst particles and deposit.
Coated bushing provides the characteristics of face sealing. It can be strictly controlled in accordance with the test requirements of zero leakage of API 598 soft sealing valve seat, achieving or sealing requirements of a stem of TA Luft or ISO 15848.
Comprehensive characteristics of plug valve are long service life, high reliability. It is a good choice for a lot of corrosive, abrasive and toxic fluid as well as continuously operated device. It has the application advantages and extensive applicability in the field of chemical industry.

Disadvantages of Plug Valves

The design of face sealing improves the requirements for driving torque. In the case of needing to be equipped with pneumatic actuators, compared with ball valve, it will cost much more. Such as the PP process, the main shut-off valve of it is the plug valve, rather than the ball valve, but the high-frequency switching valve is a ball valve. Therefore, basically, the pneumatic plug valves are applied to the key cut-off position. Plug valve is not recommended to apply it to the occasion of adjustment since the high-frequency switching is not the advantage of it. It is the cut-off valve of high reliability.
In some applications, the incorrect choice of bushing material or improper design of the release area of bushing deformation may cause swelling for PTFE bushing materials, leading to the change of driving torque for several times.
Though the investment of plug valve is more than ball valve, as its advantages of reliability and the total cost of the life cycle are gradually accepted by users, more and more users will continue to use the plug valve.

What is a Plug Valve and What is it Used for

For any sector that relies on hydraulic systems in their operations, gas plug valves are an essential component for the smooth and efficient running of the systems. Usually available in cylindrical or conical shapes, plug valves are quarter-turn manual motion valves used for stopping or starting the flow of fluid. They offer on-off, diverting, as well as basic moderate throttling services.

Read on for an overview on plug valves, along with their types and applications.

How Does a Plug Valve Work?

A plug valve is based on a plug with a hollow passage in the valve body. The quarter-turn motion creates an alignment between the pipe and the hole, leading to an open state. When turned to a 90-degree angle from the open position, the valve sits across the pipe leading to a closed state.

See the animated video below that explains how a plug valve works.

Plug valves are available in a variety of different styles and port openings through the plug.

Goto kairuite to know more.

Two-Way Plug Valves: The design allows for a closure element in the middle (a plug and a sleeve), along with a straight through, two-way service for the open and close function.
Three-Way Plug Valves: These valves include a third port, which typically sits at a right angle from the inlet. These plug valves can help in diverting flow (entry from inlet directed between one or both outlets) or combining flow (entry from the two inlets channeled into a single outlet).

What is a Plug Valve Used for?

Plug valves are an excellent option for many commercial and light industrial applications, including directional flow control, handling of gas or liquid fuels, regulating fluids with suspended solids, such as slurries, or handling low-pressure, low-temperature services. Due to their smooth design, inline maintenance capabilities, leak-tight service, minimal resistance to flow, and multi-port design options, gas plug valves find application across a multitude of sectors and systems.

What are the Different Types of Plug Valves?

Lubricated Plug Valves

Highly suitable for dirty upstream applications, the cast iron lubricated plug valves can handle abrasive or corrosive materials and do not get clogged. These plugs require frequent resealing for maintaining optimum effectiveness.

Non-Lubricated Plug Valves

Used in settings that prioritize low-maintenance applications, non-lubricated plug valves include elastomer sleeved, lift-type, and fully lined plug valves.

Expandable Plug Valves

These valves comprise multiple components and a complex rotation motion that helps in avoiding wear or abrasions to the seals. They are a good fit for preventing product contamination in applications that do not require double isolation.

Eccentric Plug Valves

Ideal for applications that need a higher seating force and minimal friction from open to closed position, eccentric plug valves find a place in a wide range of isolation or flow control systems. This includes sewage, sludge and slurries, air, and other services.

Advantages and Disadvantages

Besides being compact and using up less space, gas plug valves offer the following advantages:

Flow Regulation – Tight shut-off, quick opening and low-pressure drop.
Fire-safety and Durability – Reduced likelihood of corrosion or erosion as the actual plug and body seating surface do not get exposed to the line fluid.
Versatility – You can use plug valves with large flow rates as well.

A few disadvantages of plug valves are:

They are not suitable for throttling applications.
They require greater force for actuation due to high friction.
They present the possibility of galling.
The tapered plug design basically leads to a reduced port.

Learn more about plug valves by reading our next article: Plug Valves vs. Ball Valves: What are the Differences?

Find the Right Plug Valves for Your Application

Whether it is gases, liquids, non-abrasive slurries, fuel gas piping systems, chemical industries, fly ash applications, or vacuum to high pressure applications, plug valves play a key role in an extensive range of applications and industries.

At Norgas, our team of experienced professionals has a deep understanding of the HVAC, propane, industrial, and combustion markets. We can help you find the best gas plug valves among reputable brands such as Milliken Hattersley plug valves or flow regulation solutions for your specific project or application.

Contact us at 888-427-7347 for more information on our gas plug valves or if you have questions about our other products such as our gas regulators and gas flow meters.

Additional reading:
cryogenic valves buying guide, its uses, and benefits