Owner's manual

Series 322 Load Unit

Maintenance

D. Lightly lubricate the filter with clean hydraulic fluid and insert the

filter into the housing.

E. Secure the filter cover plate to the housing using the four socket head

screws and washers removed in Step A.

For the Series 252.3x Servovalve proceed as follows:

A. Remove the four socket head screws and washers that secure the filter

cover plate to the filter housing as shown below.

B. Remove the filter plug by threading one of the socket head screws,

removed in Step A, into the filter plug and pulling it out of the filter

housing. Remove the filter cover plate.

C. Remove the filter plug O-rings from the filter plug.

D. Remove the filter O-ring from the filter.

E. Remove the filter.

F. Lightly lubricate the filter O-ring with clean hydraulic fluid, install it

on the replacement filter, and insert the filter into the housing.

G. Lightly lubricate the filter plug O-rings with clean hydraulic fluid,

install them on the filter plug and install the filter plug.

H. Secure the filter cover plate to the housing using the four socket head

screws and washers removed in Step A. Tighten each socket head

screw until it is firmly seated against the filter cover plate. Using the

sequence shown in the previous figure, tighten the socket head screws

to 4.5 N·m (40 lb·in). Continue using the sequence and tighten the

socket head screws to a final torque of 9.60 N·m (85 lb·in).

11. Turn on electrical and hydraulic system power.

12. Apply low hydraulic pressure to the servovalve so that hydraulic fluid

gradually fills the filter cavity.

13. Apply high hydraulic pressure and check for leaks.

252 Servovalve: Adjust the Mechanical Null

This procedure describes how to adjust the mechanical null for the Series 252

Servovalve. The mechanical null adjustment aligns the servovalve spool to a

position that allows little or no actuator movement when there is no control

signal.

Prerequisites MTS Systems Corporation recommends that you read this procedure before

attempting to adjust the mechanical null. The mechanical null adjustment is quite

sensitive, and you should be familiar with the hazards that can be encountered

when performing the procedure.

Perform the servovalve mechanical null adjustment after the valve balancing

procedure (electrical compensation) has been completed and the results are

judged unsatisfactory.