Servo Valves

Servo valve driven hydraulic systems provide exceptional control over very large forces. The valves themselves are not very expensive, but the processes they control are often the most mission critical in the plant.

Common servo valves consist of a two-stage spool whose position is controlled by electromagnetic coils. Energizing the coils allows fluid flow (which translates as a velocity in actuator movement) in one direction or the other depending on the input signal.

Servo valve tolerances are extremely small, ranging from the sub-micron size to tens of microns. As such, they are extremely prone to contamination, particularly adhesive oxide insolubles which gum up the valve. When sticky varnish builds inside the servo, the valves stick shut in either an open or closed position or become unresponsive.

The net result is production downtime. Sticking servos can shut down paper lines and bring calendaring machines out of tolerance, resulting in poor product quality. Servo problems can lead to shutdowns of steam turbines and poor yields on precision machine tools.

ISOPur® has many demonstrated successes purifying oil systems, and as a result, eliminating servo valve sticking. Read the following case studies to see how ISOPur BCA® has successfully solved servo valve problems.