Achieving precise control of large valves
30 August 2011
A control valve positioner package from Samson Controls achieves precise control of large valves. Exact positioning with fast response times over the entire operating range is possible, thanks to a package consisting of a positioner and a special hook up of several volume boosters with different air output capacities. Closing and opening times of less than two seconds can be achieved over the entire positioning range.
Larger valves tend to be fitted with pneumatic actuators. The positioner is used to position the valve by filling the actuator with the corresponding amount of air, or by venting from the actuator. However, the air output capacity required to achieve fast positioning in larger actuators (with diaphragm areas of 1,400cm2 up to 2,800cm2) is simply too much for normal positioners and so accuracy can be compromised. Also, an added complication in these situations is that the positioner controls a volume booster which achieves a much higher air capacity than the positioner and consequently results in an overshoot on responding to small signal changes.
The Samson control valve positioner package volume boosters with different air output capacities overcomes this problem.
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