VALVE POSITIONERS
Valve positioners are compact, modular feedback instruments for both rotary and linear type actuators, double or single acting. They have independent zero and span adjustments, making calibration very simple. External access for zeroing is generally standard. The corrosion resistant coatings and seals meet NEMA 4X as well as the sealing requirement IP 66. Most positioners are furnished with four standard port connections for gauges and threaded openings for venting the positioners exhaust. Feedback signalling offers pneumatic or electro-pneumatic options from 3-15 psi or 4-20mA.
WHAT WE KNOW
There are many permutations of signalling feed back options and communication protocols such as HART, Fieldbus, Profibus and not to mention wireless alternatives as opposed to conventional networks. Talk with TVL and let us help you decide.
A VALVE POSITIONER AND ITS PURPOSE
A valve positioner is an intelligent device that adjusts the valve actuator’s position based on a control signal. These positioners are best used in control applications because of their precision.
Valve positioners are usually mounted on a valve yolk or upper casing of a pneumatic actuator for linear control valves, it can also be positioned toward the end of the shaft for rotary control valves. For either configuration, the positioner is connected mechanically to the valve stem or valve shaft via a feedback arm and allows for the valve’s position to be compared with the position requested by the controlling system or network. When a control signal differs from the valve actuator’s position, the valve positioner sends the necessary feedback signal to energise the actuator until the correct position is reached.
