MTS Series 647 Hydraulic Wedge Grips - Manual (Page 73)

6.
Warning:
Performing the next step can apply a force greater than the force train capacity.
Exceeding the tensile load capacity of any element in the force train can cause personal injury
or equipment damage.
It is necessary to temporarily exceed the tensile load capacity to achieve the requirements of
the next step. This is accomplished by increasing the output pressure of the HPU.
Apply a static tensile force 10 to 20% higher than the maximum force to be applied during testing.
7.
Caution:
If the spiral washers are not sufficiently tightened, the connector stud can break when subjected
to cyclic loads.
Improper preloading of the connector stud can cause eventual fatigue resulting in connector
stud breakage.
Make sure that the spiral washers are sufficiently tightened.
Using spanner wrenches, rotate the two halves of the spiral washers in opposite directions to tighten them.
The opening between the washers must not exceed an arc of 30° from the closed position.
If more than a 30° arc is created, remove the tensile load from the specimen. Remove the specimen (see
appropriate procedure) and tighten the grips on the mounting studs, taking care not to misalign the wedge
openings. Repeat Step 5 through Step 7 of this procedure.
8. Reduce tensile force to zero and remove the specimen.
9. Remove system hydraulic pressure.
Ensure that system hydraulic pressure has been reduced to zero before proceeding. To do this, turn off
the hydraulic power unit and exercise the actuator until it stops moving.
Connector Stud and Spiral Washers
Series 647 Hydraulic Wedge Grips Reference Manual 73
Installation