Koso REXA Electraulic Xpac, Installation And Operation Manual

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REXA
Electraulic Actuators & Drives
Xpac
Installation Manual -- Version 5.1 (5/08)
41
In most cases, lateral alignment is corrected by stroking the actuator
with the mounting or mating connection in a loosened condition.
This will allow the connection to self-align. If there is insufficient
clearance, then the appropriate bore diameters must be increased.
7.3.2 Longitudinal Misalignment
LINEAR
Failure to reach full stroke is caused by a mechanical limitation
within the actuator or driven device. Incorrect yoke leg lengths or
thread engagement in the stem coupling may reduce the travel. In
most cases, the required adjustment is small and can simply be made
by changing the length of thread engagement of the stem coupling.
Further adjustment can only be made by changing the length of the
yoke legs.
ROTARY (<90° Rotation)
Failure to reach the full 90° rotation is usually not binding, but rather
an installation problem. With the actuator separated from the driven
device, rotate the driven device to the closed position. Move the
actuator in the same direction until the end of rotary piston travel is
reached. The connections between the driven device and the actuator
should be within 2-4 degrees. If a large discrepancy exists between
the mating connections, the adapter may be incorrect.
7.4 Tuning
With a user selectable deadband as low as 0.05%, the
Xpac
can usually
position the driven device finer than the instrumentation can detect.
If the process does not demand this level of control, ease up on the
deadband. Make sure that the control signal is driving the actuator
and not random noise (section 7.2).
Oscillation about the target position can occur on high speed units that
have a low deadband setting. This motion does neither the actuator
nor the process any good. The Acceleration Sub-menu is designed
to eliminate this motion. Proper operation for such cases is a single
overshoot, followed immediately by a
Low Acceleration (see section
6.3.2) reversal to the correct position.