MTS Series 646 Hydraulic Collet Grips - Manual (Page 62)

Series 646 Hydraulic Collet Grips 62 Operation
Note A knocking noise coming from the grip when a cyclic load is being
applied to the specimen indicates:
Hydraulic pressure—to the grip might not be set high enough. Increase
the grip pressure at the hydraulic grip supply until the knocking stops. Do
not exceed a grip pressure of 45 MPa (6500 psi ).
Specimen in the lower grip—is not making contact with the preload
platen. Unlock the lower grip and screw the threaded insert further up
onto the specimen, and then lock the grip.
Adjust Water Cooling Flow
Water flow through the grips must be sufficient to prevent damage to the grips.
Minimum cooling water requirements are for 4 L/min (1 gpm) flow at 0.275 MPa
(40 psi). The temperature of the outer surface of the grip body should not exceed
121°C (250°F) under any circumstances.
The water cooling manifold includes water flow switches that will generate an
interlock in the furnace controller if the water flow is below a safe level. It will
not allow the furnace to be turned on without the proper amount of water cooling.
Adjusting the water cooling to the procedure below will ensure adequate water
cooling. It will also ensure that the flow rate is not needlessly high, which wastes
water.
To set the water cooling:
1. Open both needle valves all the way
2. Activate the furnace controller, but command a furnace temperature lower
than the ambient temperature to keep the furnace from turning on.
3. Adjust one needle valve down until the furnace controller indicates an
interlock.
4. Open the needle valve one full turn and ensure that the furnace controller
does not interlock
5. Repeat steps 2-4 with the other needle valve.
6. Leave the water on for a period of time to ensure that water supply pressure
fluctuations do not cause a controller interlock.
7. If an interlock occurs, open both needle valves 1/2 turn and repeat step 6
until no interlock occurs.
Do not interrupt water flow to the grips during operation.
If water flow is interrupted, grips and exceed safe operating temperature
causing specimen and equipment damage.
Ensure that the cooling water to the grips is continuous during operation at
elevated temperatures.
CAUTION