A Process Industry Stalwart - The Plug Valve

Flowserve Durco lubricated plug valve
Lubricated plug valve.
(Flowserve Durco)
This article will focus on one of the oldest and most reliable (when properly applied) industrial valve types - the plug valve.

Fluid process control operations commonly employ pumps, piping, tanks and valves as the means of transporting, containing and controlling the fluid movement through a system.

Valves, of which there are many types, provide control over the flow rate, direction and routing of fluids in a processing operation. Flow can be started, stopped or modulated between zero and full rate using a properly sized and configured valve. Some valves enable media flow to be diverted to a selection of outlets, in lieu of a single inlet and outlet pair. Specialized valves regulate inlet or outlet pressure, or prevent fluid flow from going in an undesirable direction. All of these capabilities are packaged into differing valve product offerings that present a very large selection array to a process designer or engineer.

Floserve Durco non-lubricated plug valve
Non-lubricated plug valve.
(Flowserve Durco)
Industrial flow control valve types are generally classified according to the structure or arrangement contained within the valve body that provides obstruction to fluid flow. Some of the common types are ball, butterfly, gate, globe, and plug. Surely, there are more valve types, and this article is not intended to list them all. Some of our previous blogs have discussed selection considerations for gate, ball and butterfly valves.

Plug valves, like ball and butterfly valves, span from fully open to fully closed positions with a shaft rotation of 90 degrees. The “plug” in a plug valve is installed in the flow path within the valve body and rotated by means of a stem or shaft extending to the exterior of the body. Plugs are tapered toward the bottom and are fitted to a seating surface in the valve body cavity that prevents fluid from bypassing the plug. An opening through the plug, the port, can be shaped to provide particular flow characteristics. There are two main types of basic plug, lubricated and non-lubricated. Lubricated plug valves have a cavity into which a sealant is injected. The sealant provides a renewable seal between the plug and the body, prevents internal leakage, and protects the seating surfaces against corrosion. Non-lubricated plug valves utilize an elastomeric body liner or a sleeve in the body cavity that is pressed in to the body of the valve by the plug's wedge-like shape,  with the result of reducing the friction between the plug and the body.

Plug valve considerations:
  • 90 degree rotation from open to closed provides fast operation.
  • With proper configuration, can be well suited for frequent operation.
  • Availability of corrosion resistant liner may provide comparative cost savings because valve body can be constructed of less expensive material.
  • Design is simple and employs a low parts count.
  • Valve can be serviced in place.
  • Generally, low resistance to flow when fully open.
  • Reliable leak-tight service due to tapered plug wedging action, replaceable sleeve, and injection of lubricant in some variants.
  • Potential issues of concern for plug valve application include a short list of items.
  • Higher friction in the plug closure mechanism may require comparatively higher operating torque than other valve types.
  • Without a specially designed plug, generally not well suited for throttling applications.
  • Rapid shutoff delivered by plug design may not be suitable for some applications where hammering may occur.
Share your fluid control application challenges with a valve and automation specialist. Leverage your own knowledge and experience with their product application expertise to develop an effective solution.

A Peek Inside a Valtek Mark One Control Valve with Piston Actuator

Valtek Mark One Control ValveThe video below provides a look inside the Flowserve Valtek Mark One control valve and identifies its major components.

The Flowserve Valtek® Mark One globe control valve is designed for liquid and gaseous services, and for permitting easy, fast and inexpensive maintenance.

The spring-cylinder actuated Mark One valve provides stiffness and maintains high positioning accuracy, repeatability, controlled high speed, and faithful response. The Mark One valve handles up to 150 psig supply air and has the thrust to shut off against much higher fluid pressures.

The Mark One valve is designed so the spring, supply air pressure and fluid pressure itself combine to produce exceptionally tight shutoff. A self-aligning seat ring further enhances the shutoff capability of the valve.

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Jorlon™ Structurally Modified Pure PTFE Diaphragm for Control Valves and Gas Regulators

Jorlon™
Jorlon™ Diaphragm
Jorlon™ is structurally modified pure PTFE. It is manufactured by a proprietary technique where PTFE layers are combined and formed in a unique process to reduce the creep and cold flow associated with conventionally formed solid, or laminated PTFE or Teflon.

Jorlon™ is featured in all of Steriflow's valve product lines:
  • Mark 978 Control Valves
  • JSHM Manual Metering Valve
  • Mark 96 Pressure Regulating Valves
  • Mark 95 Back Pressure Regulating Valves
  • Mark 96A, 96AA, 95A, 95AA Air Loaded Regulators
  • J Series Clean Gas Pressure and Back Pressure Regulating Valves
Lifetime Warranty
Jorlon™ is warranted for a lifetime of use on our Mark 95, Mark 96, Mark 96AA, Mark 95AA regulators, MK978 Series control valves, J-series regulators, and the JSHM metering valve.

Product Applications
JorlonTM has been specified in biopharm applications including WFI, clean steam (up to 100 psig), buffers, acids, cryogenic liquids, clean utility gas, biological intermediates and final process fluids.

Customer Use
Since its inception, thousands of Steriflow valves with Jorlon™ diaphragms have been installed in systems which have been validated by the FDA.

Cycle Testing
Jorlon™ has been tested on a variety of Steriflow control valves on 45 psig (3 bar) continuous steam service to over 1 million full stroke cycles. One of those valves was further tested with an additional 100 Steam and vacuum cycles without failure.

Lab Testing
Lab tests comparing Jorlon™ to 316L diaphragms have shown continued life after exceeding the SST failure cycle count by more than 100 times.

Jorlon™ Material
Jorlon™ has been used by Steriflow for over 15 years. To date, not one valve has been returned due to diaphragm failure when operating within its use parameters. Jorlon™ has been nitrogen pressure tested to over 1200 psi without failure.