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Closing Soft Seat Valves

My UniPro™ Operating Manual says not to turn down the operating pressure to close tank car valves with soft seats. That’s how competitive actuators do it. Why not the UniPro™?

Answer:

It’s true that reducing the air pressure to the UniPro™ Pneumatic Actuator will reduce the torque that it produces. But air motors used in valve closure actuators, including the UniPro™ and its competitors, have what is called a "threshold pressure." This is the pressure below which the motor might not start to turn when activated. In order to reduce the torque produced by the UniPro™ Standard actuator (and its competitors) to a level that will not harm the soft valve seats, the pressure must be turned down to a level below the threshold pressure of the air motor, thus introducing the possibility of a failure to operate when activated.

To eliminate this possibility, the UniPro™ Torque Limiting Valve Adapter for soft seat valves is designed to be interchangeable with the High Torque Valve Adapter used on ACF valves. The two can be interchanged in seconds simply by pulling a hitch pin and installing the replacement. The UniPro™ Torque Limiting Valve Adapter has an internal clutch that disengages at a pre-set torque which is below the level that will harm the soft valve seats, but is enough to completely close and seal the valve in an emergency. This is true even at the recommended operating pressure of 90 psig. Both the Torque Limiting and the High Torque valve adapters are designed so that they cannot be installed on the wrong valve handle, eliminating the possibility of mounting the Torque Limiting Valve Adapter on an ACF valve and visa versa.

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