MTS Landmark Floor Standing - Manual (Page 110)

k) Lightly lubricate the filter O-ring with clean hydraulic fluid, install it on the replacement filter, and insert
the filter into the housing.
l) Lightly lubricate the filter plug O-rings with clean hydraulic fluid, install them on the filter plug, and install
the filter plug.
m) Secure the filter cover plate to the housing using the four socket head screws and washers removed
in Step f. Tighten each socket head screw until it is firmly seated against the filter cover plate. Using
the appropriate sequence, tighten the socket head screws to 4.5 N·m (40 lbf·in). Continue using the
sequence and tighten the socket head screws to a final torque of 9.60 N·m (85 lbf·in).
2. Turn on electrical and hydraulic system power.
3. Apply low hydraulic pressure to the servovalve so that hydraulic fluid gradually fills the filter cavity.
4. Apply high hydraulic pressure and check for leaks.
Adjusting 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
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.
During the servovalve mechanical null adjustment procedure, the actuator must be able to move through full
displacement in either direction without contacting a reaction surface.
Valve Balance Adjustments
MTS controllers have an electronic mechanical null adjustment called valve balance. The valve balance
adjustment is a convenient way to compensate for a servovalve that needs a mechanical null adjustment.
The adjustment introduces an electrical offset signal that causes the servovalve to hold the position of the
actuator when a zero command is issued.
Adjust the Mechanical Null
Warning:
Sudden and unexpected actuator rod movement can cause serious injury to personnel and/or
damage to equipment.
Do not perform the following procedure without clearing the path of motion of the actuator.
Ensure that all personnel, specimen/structures, and tools are away from the path of motion of
the actuator (crush zone).
110 MTS Landmark™ Floor Standing Load Units Product Information
Maintenance