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What Is An Eccentric Plug Valve?

There is a wide range of valves available in the market for different purposes and applications. But when it comes to handling liquids with suspended solids, there is no better option than the Eccentric plug valves.

These valves are considered to give high performance and are designed with high safety standards, yet they are economical. They also have higher rangeability, precise control, and higher flow capacity.

So, in this article, let’s find out about Eccentric Plug Valve, how it works, its unique features, installation tips, and a wide range of applications.

What Is An Eccentric Plug Valve?

As the name suggests, Eccentric plug valves are quarter-turn rotary control valves. The plug of these valves follows an eccentric path as it rotates for opening and closing.

The uniqueness of the valve lies in the fact that the eccentric valve plug has no contact with the seat until it reaches near the shut-off position. Once the valve is fully shut off, the valve plug rests on the seat. Due to the above facts, they are also known as Rotary globe valves.

Eccentric plug valves are provided in sizes ranging from 3 to 72 inches with a cold working pressure of 150 to 175 psi depending on the size and can handle flow up to 2.4 m/sec.

How Does An Eccentric Plug Valve Work?

The quarter-turn action of the eccentric valve leads to the open or shut position of the valve. The eccentric plug valve shaft is rotated using a handle or through automatic actuation from open to closed position.

The plug moves into a raised eccentric seat during this process and sits firmly on the seat once the 90o rotation is achieved. This gives a tight sealing obstructing the flow of the fluid.

As the plug moves to the closed position, it moves in an eccentric path towards the seat without coming in contact with the seat or body walls. It is only when the valve is fully closed; the valve and the seat are in contact with each other. Thus, there is minimum friction between the plug and seat during operation.

Moreover, in an open position, the plug is out of the flow path, which ensures a smooth and streamlined flow. Finally, the resilient plug face makes a full uniform, firm contact with the seat to form a bubble-tight shut-off.

Important Installation Tips

It is to be noted that the valve must be installed in such a way that flow direction is with plug seat upstream. This ensures the long life of the valve. Because of the unique shape of the plug, it allows usage of the valve for any type of abrasive fluid medium.

There are two positions in which the valve can be installed (i.e., horizontally or vertically). However, special precautions must be taken during the installation of the valve in either of the two directions as it affects the valve’s life.

  • In the case of horizontal installation, the operating shaft should always be in a horizontal position, and the plug should always be on the top of the pipe (as shown in the figure) in open condition.
  • In the case of vertical installation, regardless of the flow direction, the seat end should be at the upper side so that the deposits do not get collected when the valve is in the closed position

Features And Benefits Of Eccentric Plug Valve

Eccentric plug valves are heavy-duty valves used for on/off or throttling operations. The key features and benefits of these valves are as follows:

  • Superior design allows higher flow capacity for a given size of valve.
  • Tight shut off even after a prolonged operation and usage of the valve.
  • Ease of automated pressure and flow control due to quarter turn operation
  • When applied, rubber coating or glass lining the valve can also handle highly abrasive liquids. As a result, these Valves are a highly dependable service in slurry applications.
  • Seat ring and Retainers can be protected by utilizing erosion-resistant materials and can be easily maintained.
  • The end post shaft is accurately machined, perfectly aligned, and retained positively on the valve body to ensure smooth and precise movement.
  • The improved design of the shaft makes it safer and more reliable. It enhances the lifetime of the valve by reducing the bearing wear and avoiding valve failure.
  • Design of the valve and direction of flow assists movement of the valve plug to a safe position in case of automation failure of the actuator.

Eccentric Plug Valve Application

Due to the Superior design, ease of operation and automation, and capability to handle suspended solids in the flowing media, Eccentric plug valves are used in a wide range of industries, such as:

  • Mining industry
  • Petroleum and Gas Refinery
  • Chemical Industry
  • Power plants
  • Pulp and Paper industry
  • Sewage and Sanitation fittings
  • Wastewater Management
  • Fertilizers industry

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