Let our experts help you choose the right actuated valves for your process application. Valve actuation is the use of a mechanical device to open, close or throttle a valve. This can be achieved by the use of either an electric or pneumatic actuator. We’ve worked extensively with all types of actuators, and we not only help you make the right choice, we also use industry best practices to calibrate and test each valve before it leaves our automation center. Every valve receives a serialized stainless steel tag that is kept at Process Supply to allow for full traceability.
There are two main styles of rotary pneumatic actuators for use on quarter turn ball, butterfly and plug valves:
- Rack and pinion
- Scotch yoke
Both operate by converting the linear motion of a piston in the actuator into the rotational motion of the valve stem drive. Both types are available in two designs:
- Double acting
- Spring return
In a double acting actuator, the instrument air is directed by the use of a solenoid that moves the valve clockwise and counterclockwise. The motion is air to open and air to close. Instrument air is directed by the use of a solenoid to move the valve in the clockwise position, which puts the valve in the open position. In a spring return actuator, internal springs in the actuator return the valve to the fail close position. The motion is air to open and spring to close, and it can be reversed to air to close and spring to open.
A limit switch used in conjunction with a pneumatic quarter turn actuated valve can prove the open or closed position of the valve using a beacon visual indicator. A limit switch also sends an electrical signal to the Programmable Logic Controller (PLC) or the Distributed Control System (DCS) via a mechanical or proximity limit switch that allows the facility’s computers to know if the actuated valves are in the open or closed position.
A valve positioner is an integrated control device that is mounted to any type of valve used for proportional process control known as a “final control element”. A positioner is directly connected to the valve trim via a shaft or linkage. This allows the positioner to physically respond to actual valve position. A positioner receives a control signal (set point) from the control system, then interprets the signal to provide a proportional output to the valve actuator to drive the valve to set point. The linkage provides a mechanical feedback of actual valve position. When the valve has traveled to the desired position it is “at set point”. Whenever the set point changes, the positioner will move the valve to the new set point. If the valve trim moves because of dynamic process conditions, the positioner will move the valve back to the correct set point.
Positioners are also able to provide an output signal that can be read by the control system to confirm valve position. Positioners can operate on many types of signals, including:
- 3-15psi, 5-27psi, 6-30psi Pneumatic input/Pneumatic output (P/P)
- 4-20mA/24VDC Analog Current input/Pneumatic output (I/P) 2 wire loop powered, or 4 wire independent power
- 0-10VDC/24VDC Analog Voltage input/Pneumatic output (V/P) 4 wire
- Digital signals such as HART, FOUNDATION fieldbus, Profibus, Digital input/Pneumatic output (digital, or smart)
- Digital signals such as HART, Founddation FieldBus, ProfiBus. Digital input/Pneumatic output (digital, or smart)
Solenoid valves are electro/pneumatic valves that are assembled onto a pneumatic actuator that moves the actuator and valve when energized to the clockwise position and then to the counterclockwise position.
- 3-way solenoids are used on spring return actuators
- 4-way solenoids are used on double acting actuators