Double Offset Air Torque Actuated Butterfly Valves

The valve is suitable for almost all chemical applications. Send in an email of pick up the phone. One of our super tech guys will check it over for you.

A standard valve has the disc centered in the pipe. In a double offset design, the stem is located behind the disc and slightly to one side of the center. This creates a "camming" action.

It certainly does. All of our PTFE butterfly valves come complete with a full set of operations and maintenance manuals from the manufacturer.

Yes, significantly. For double offset valves, there is a "preferred" flow direction.

• Seat Integrity: These valves are designed so that the process pressure pushes the disc into the seat for a tighter seal. If installed backwards, the pressure works against the seat, which can lead to premature leaking.

• Stem Position: It is generally recommended to install the valve with the stem horizontal rather than vertical if the fluid contains solids. This prevents sediment from settling into the bottom stem bearing, which could seize the valve over time.

Air torque actuators use a rack and pinion mechanism powered by compressed air. When air enters the chambers, it pushes internal pistons; these pistons move the "rack," which rotates the "pinion" gear attached to the valve stem.

It mostly comes down to cost versus sealing requirements.

• Double Offset: Usually features a high-grade polymer seat (like PTFE). It provides excellent "bubble-tight" shutoff for most chemicals, water, and steam at moderate temperatures.

• Triple Offset: Uses a metal-to-metal seat for extreme temperatures or high-pressure steam where a polymer seat would melt or deform. If you don't have extreme heat, the double offset is a more cost-effective choice.

While these are generally "low maintenance," they aren't "no maintenance." You should regularly check:

• Air Quality: Ensure the compressed air is dry and lubricated (if required) to prevent the actuator seals from cracking.

• Stem Packing: Look for leaks around the valve stem. High-performance valves often have adjustable packing glands to stop minor leaks.

Yes. Because air is a compressible fluid, you can control the speed by installing flow control mufflers or needle valves on the actuator's exhaust ports.

You can’t just match the actuator size to the pipe size; you have to look at the torque demand of the valve. This is influenced by:

• Operating Pressure: Higher pressure pushes the disc harder against the seat, requiring more force to "break" it open.

• Media Type: Lubricating fluids (like oil) require less torque, while dry powders or abrasive slurries increase friction.

• Safety Factor: It is industry standard to add a 20% to 30% safety buffer to the valve's rated torque to ensure the actuator can handle "stiction" after the valve has been sitting closed for a long time.