MTS Series 242 Actuators - Manual (Page 32)

Series 242 Actuator Product Information 32
242 Actuator Operating Considerations
Operation
242 Actuator Operating Considerations
Piston rod banding
Piston rod banding can occur if the actuator is operated for a long period of time
at a moderate to high frequency, with short stroke displacement and loads of 25%
or more of the actuator capacity. Piston rod banding is the aggravated erosion of
the piston rod chrome plating in a band slightly wider than the width of the seal
encircling the circumference of the piston rod.
If the actuator is being used for this type of testing, the starting position of the
actuator piston rod should be changed approximately every one million cycles.
This will extend the life of the piston rod and minimize the possibility of
banding. If the system configuration allows it, the piston rod starting position can
be changed by using the displacement transducer conditioner zero control and
repositioning the load frame crosshead or fixture.
Sideload forces
To avoid damaging the actuator bearings and to ensure proper actuator operation,
tests that subject the actuator to nonaxial loads require special consideration.
Nonaxial loading can occur from sideload forces applied directly to the piston
rod (P in the figure) and from moments caused by off-center loads (F in the
figure).
There are four things that must be considered to determine the suitability of an
actuator for nonaxial loaded tests:
• Bearing pressure generated during the test
• Piston rod stress caused by sideload
• Maximum allowable piston rod velocity
B
F
P
C
Sideload Forces