Waters Xevo TQD Operator's, Overview And Maintenance Manual page 181

Caution:
exhaust flange must not be overtightened; ensure that only
approximately 1 mm of thread is exposed beyond the nut when it
is tightened.
3. Use the 10-mm wrench to fit and tighten the nut that secures the oil
demister element to the exhaust flange.
4. Ensure that the inscription "TOP" is at the top of the oil demister
element, and, using both hands, carefully fit the oil demister element
and exhaust flange to the roughing pump.
Caution:
roughing pump must each be sequentially and incrementally
tightened until they are all fully tight.
5. Use the 6-mm Allen wrench to fit the 4 bolts securing the exhaust flange
to the roughing pump.
The nut that secures the oil demister element to the
The bolts securing the source exhaust flange to the
Replacing the roughing pump's oil demister element 4-105
1 mm exposed thread
after tightening
TP02686