Valve positioners control a valve's position (ball, butterfly, and globe) such that a given process will achieve specific desired flow parameters. They perform this by determining the error between the optimum valve position and actual valve position. With specialized sensors mounted on the valve stem or actuator shaft, these sensors compare the magnitude of error between the setpoint from the control system and the actual process value. The positioner's corrective output is sent electrically or pneumatically to a valve actuator, which moves the valve in the corrective direction.
As a control valve accessory and the interface between the control system and valves, positioners play a vital role in ensuring the process loop's performance. The valve positioner adjusts the valves' opening, thereby varying the valve's flow rates, from completely shut or wide open to anywhere in between. An example of this type of positioning control will include mixing hot and cold water to achieve a specified downstream temperature requirement. By controlling the valve's opening and closing, process control parameters such as flow, pressure, level, and temperature are maintained
Piping Specialties / PSI Controls offers a full range of positioning equipment, including pneumatic, electro-pneumatic, intrinsically safe, explosion-proof, and Smart type positioners.
