MKS Instruments UK Ltd
Cirrus2 Hardware Manual – SP101017.100 June 2011
32
Capillary Inlet
Before carrying out ANY operations that involve the capillary system, 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.
The Cirrus2 system uses a capillary inlet to admit sample gas into the chamber for analysis. MKS Spectra produce a
variety of capillary inlets but the Flexil capillary is dealt with in this manual.
The Flexil capillary inlet assembly consists of a white PTFE tube containing a fine bore stainless steel tube, down the
centre of which is threaded a 0.32mm I.D. fused silica tube.
You may need to replace the fused silica capillary tube which forms part of the capillary inlet assembly, if it has been
damaged or becomes blocked.
1. Shut down the Cirrus 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. In the oven compartment, use a 5/16 inch spanner to undo the nut on the inlet flange and slide it, and the ferrule,
along the fused silica tube towards the front of the oven.
5. Carefully slide the fused silica tube
down the capillary assembly away from
the inlet flange and remove the nut and
ferrule.
Once the fused silica capillary appears at the high pressure end you can pull it out of the assembly.
6. Take the cassette of fused silica tubing and carefully feed one end down the capillary assembly from the high
pressure end. The fused silica tubing is quite fragile but should slide freely down the inner bore of the capillary assembly.
Continue to feed the tube down the capillary until it emerges inside the oven.
7. Thread the Swagelok nut and then the ferrule onto the silica tubing as shown in the picture above.
8. Thread the fused silica tube into the Swagelok reducer and continue until you feel it butt up against the vacuum
chamber inlet, then withdraw the fused silica tube by 5mm.
Slide the ferrule into place then tighten the nut FINGER TIGHT. With a 5/16 inch spanner tighten the nut a further 1/4
TURN only.
9. At the high pressure end of the capillary, carefully cut the fused silica tube flush with the end of the 1/4 inch stainless
steel tube. Ensure the cut is clean and the tubing has not been crushed.
10. You will now need to leak check the inlet, see Leak Checking before refitting the oven lid.