Thermo Scientific 42iQTL, Instruction Manual

Page: 225 / 310

Servicing
Vacuum Pump Diaphragm and Valve Replacement
Thermo Scientific 42iQTL Instruction Manual 7-21
carefully use a small flat-bladed screwdriver to pry-off the housing
cover.
5. Install the two PTFE (white color) diaphragms together with one TFM
(translucent) diaphragm as shown in Figure E-1. Install with the ridges
of the diaphragm convolutions as shown in the diaphragm stack cross-
section inset.
6. Temporarily insert two of the head screws through the diaphragms and
screw into the pump body to keep the position of the diaphragms as
the clamping disc is tightened. Any stress applied re-aligning the
diaphragm in the process of assembling the head will significantly
reduce diaphragm life
7. Check the threads of the clamping disc to insure that they are clean and
free of debris. Apply a small amount of the breakable thread adhesive to
the clamping disc threads and install.
8. Rotate the counterweight until the connecting rod is in mid-stroke and
then tighten the clamping disc. Do not over tighten the clamping disc.
Note Over tightening of the clamping disc will significantly reduce
diaphragm life. Tighten enough to avoid contact with the head. If a
significant amount of torque is required to tighten, first re-check to see if
the threads are clear, then check that the connection rod support disc (“H”)
is properly seated on the connection rod. Over-torque of the clamping disc
must never be a way to avoid contact with the head.
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9. Remove the two temporary aligning screws and re-install the heads on
to the pump body. The correct head bolt torque range is 20-30 inch-
pounds.
10. Turn the counterweight (“M”) through at least one full revolution to
check for smooth operation.
11. Re-install the housing cover and check the pump for correct
performance.