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3098 Technical Manual Maintenance & Fault Finding
5-7
5.2.3 Reference Chamber Diaphragm removal (Figure 5-3)
The diaphragm that regulates the sample gas pressure to that of the reference chamber is held in between the welded
assembly and the base plate. The following procedure shows how to access and service this part.
(The figure below shows two views for clarity with top plate and pipework not shown).
Diaphragm
Base Plate
Reference Chamber
Figure 5-3: Reference chamber diaphragm section
1. As the diaphragm produces a gas tight seal for the reference chamber, before any servicing of this part is done, the
REFERENCE CHAMBER MUST BE VENTED TO ATMOSPHERIC PRESSURE.
2. With the 3098 out of its enclosure (see procedure 5.2.1) remove the three unit feet and stand the metalwork upright.
3. Using a 9/16” spanner, undo and remove the two gas pipes that connect the base plate to the top plate.
4. Gently rest the 3098 on its side and undo the six M6 bolts that lock the base plate to the reference chamber.
Note: Care must be taken not to bend or damage the three gas pipelines that originate from the base plate.
5. The diaphragm is exposed once the base plate has been removed.
6. As the diaphragm is a single moulded piece part, servicing consists of either changing the sealing O-ring or changing
the diaphragm itself.