Servovalve Installation Instructions

The Servovalve may be mounted in any position provided the servovalve pressure, piston, and return ports match the respective manifold ports. The servovalve should be mounted with 5/16-18 x 3 inch long socket head cap screws. Apply a light film of oil to screw threads and torque to 120 in lbs.

Mechanical Null-adjustment

It is occasionally required to adjust the flow null of a Servovalve independent of other system parameters. The “mechanical null adjustment” on Electro-hydraulic Servovalves usually allows a minimum of 20% adjustment of flow null.

The “mechanical null adjustor” is an eccentric bushing retainer pin (null pin), located above the return port designation (R) on the valve body which, when rotated, provides control of the bushing position. Mechanical feedback elements position the spool relative to the valve body for a given input signal. Therefore, a movement of the bushing relative to the body changes the flow null.

Adjustment Procedure

1. Using a 3/8 inch offset box wrench, loosen the self-locking fitting 1/2 to 1 full turn, but no more than 1 full turn. Do not remove the self-locking fitting.
   
   
2. Insert a 3/32 inch Allen wrench into the null adjustor pin and rotate the mechanical null adjustor to obtain desired flow null. Do not rotate the pin more than 180 degrees in any one direction.
   
   
3. Tighten the 3/8 inch self-locking fitting until a torque of 10-12 in-lbs is obtained.

NOTE: Clock wise rotation of null adjustor pin increases flow from port No. 2. You must disconnect the servovalve from its electrical source BEFORE you adjust the null.

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