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External Seat Wear Indicator

The position stop plate provides external indication of seat wear.  As the seats wear, the stop plate moves closer to the valve cover.  Operators can easily determine when contact is made, indicating the seats should be replaced.

Design and Construction

Permaseal® Plug Valves are designed for on-off and diverting applications in the chemical, power, mining and paper industries.  They are designed to handle clean, viscous and corrosive liquids, clean and corrosive gases, and low pressure steam.

The unique design of SMG Valves’ Permaseal® Plug Valve includes a non-lubricated, tapered plug and two individual seats that provide a double seal and bi-directional shutoff.  Ranging in sizes from ½”–6" (15–150mm), they offer corrosion resistance and temperature ratings to 1000°F (540°C).  Pressure ratings include ANSI Class 150 for applications to 285 psi (1960 kPa) and ANSI Class 300 for services to 740 psi (5100 kPa).

Permaseal® Plug Valves are available in 316 stainless steel, carbon steel, Alloy 20, Monel, Hastelloy C, Inconel and other alloys.  Several body designs are available for various process applications including 2-way, 3-way, jacketed, flush-through and double block and bleed valves.  The Permaseal® Plug Valve is also available with modified construction for chlorine service and bellows stem seals for controlling fugitive emissions.

A variety of actuator options are available including lever, handwheel, double acting cylinder, spring return cylinder and electric motor.

Pressure Relief Design Offers Automatic Flushing

The self-adjusting plug in the Permaseal® valve features a pressure relief hole in the plug that allows flushing of the lower cavity.  When the valve is being opened or closed, flow is created through the pressure relief hole in the bottom of the plug and out the downstream port.  Accumulation of contaminants is eliminated by this flushing action during normal valve actuation.  Elimination of contamination problems is especially important on radiation and molten sulfur applications.

Seat Wiping Action Prevents Material Build-Up and Wear

Wiping action of the plug on the raised seats prevents the build-up of material that can cause excessive wear and shorten life.  This is especially beneficial in crude oil applications that contain sand or other entrained materials.

Dynamic Stem Seal Assures Long Life and Reduced Maintenance

Thrust from the Belleville washers provides a live-loaded, self-adjusting stem seal. Uniform pressure on the multiple ring packing continuously adjusts for wear to assure a long-life stem seal and reduced maintenance.

Self-Adjusting Plug Compensates for Wear

Compressed Belleville washers provide positive contact between the tapered plug and the seats.  The Belleville washers are located between the plug and the bonnet, distributing a constant thrust on the plug to compensate for seat wear, thermal expansion and contraction. The Permaseal® design does not rely on line pressure for tight sealing.

Top Entry Design Allows Ease of Maintenance

Top entry design allows periodic maintenance to be performed with minimum downtime required for disassembly and reassembly.  Top entry design also means the seats can be replaced without removing the valve from service.  Using common hand tools, worn seats can be removed and new seats inserted in as little as ten minutes without ever removing the valve from the pipeline.

Self-Aligning Double Seat Seals Both Ports Simultaneously

The tapered plug design provides automatic self-alignment of the two separate seats.  The unique seat design, combined with the self-adjusting plug, seals both ports at the same time and provides bi-directional shutoff to achieve full ANSI ratings.

High Flow Capacity Minimizes Turbulence

Straight-through flow and a large port minimize turbulence and pressure loss.

Variety of Body and Plug Materials Available

A choice of body and plug materials include: 316 stainless steel, carbon steel, Alloy 20, Monel and Hastelloy C.  For economy and corrosion resistance, a nickel plated ductile iron plug is available.  Other body and plug materials available on request, including Inconel.

Variety of Seat Materials Available for Multiple Applications

Seat options meet a wide range of application requirements.  Seat materials include PTFE, reinforced PTFE and UHMW (ultra-high molecular weight) polyethylene, all of which provide drip-tight shutoff.  A carbon graphite seat provides ANSI Class IV shutoff for high temperature applications.  Seat materials are engineered to application requirements for temperatures to 1000°F (540°C).  (See pressure/temperature capability curves for limitations.)

Variety of Body Designs and End Connections

The Permaseal® design offers a variety of models including two-way and three-way flow patterns; partial, full and bolt-on jackets; double block and bleed; and flush-through valves.  Modified construction is also available for chlorine service.  End connection options include threaded, flanged, socket weld and butt weld.  Raised face flanges are standard for all ratings and materials.

Low Torque Allows Use of Smaller Actuators

Because the Permaseal® plug contacts only the seats and not the body walls, torque is much less than a sleeved or lined valve.  The lower torque allows the use of smaller, less expensive actuators.

Actuator Flexibility Options

Permaseal® Plug Valves are available with a variety of actuator options including levers, handwheels, spring diaphragm, double-acting and spring return cylinders, or electric motors.  All actuator top mounting pads/adapter brackets are compatible with the ISO-5211/1 standard, making actuators interchangeable with other rotary control valves.


Permaseal® valves can be furnished with a variety of special accessories and options to meet specific application requirements.  Accessories available include air filter regulators, solenoid valves, mechanical or proximity switches, potentiometers and position transmitters.  Other accessories available on request.