MKS Instruments UK Ltd
Cirrus2 Hardware Manual – SP101017.100 June 2011
33
Replacing the Orifice Disk
Before carrying out ANY operations that involve the orifice disk, take precautions to prevent contact with any
hazardous substances that may have been sampled.
Allow all parts of the inlet and oven to cool before commencing.
You may need to replace the orifice if it becomes blocked or, more likely, you wish to fit a different size orifice in order to
monitor an environment operating at a different pressure.
The orifice is a small disc, with a number of holes in it, which is fitted into a holder machined into the CF flange.
The inlet flange is mounted on the end of the quadrupole vacuum chamber opposite to the analyser flange. The flange is
held in place by eight M8 stainless steel bolts.
The analyser in your Cirrus2 will almost certainly be fitted with a PVD source, so there will be a ceramic coupling which
mates with the gas inlet tube on the top of the analyser. You may wish to remove this to get easier access to the orifice
holder, although it is not essential.
1. Shut down the Cirrus2 by following the instructions in Shutting Down then disconnect from the mains supply. Remove
the outer cover.
2. Disconnect the high pressure end of the capillary from the gas source. If there is a shut off valve remember to close it.
3. Remove the oven lid.
4. Remove the capillary inlet as described on the previous page
5. Using both a 5/8” and ¾” spanner, separate the bypass joint on the cold side of the oven.
