- Leak testing may be achieved by pinching the sample line and squeezing the aspirator bulb; the bulb should not expand as long as the sampling line is pinched.
- To avoid the effect of gas flow rate, take a reading when there is no flow, i.e. between two squeezes of the rubber aspirator bulb.
- Use of dilution tubes which enable catalytic filament indicators to measure concentrations in over-rich hydrocarbon gas/air mixtures is not recommended.
- Only instruments fitted with flashback arresters in the inlet and outlet of the detector filament chamber should be used. The arresters are essential to prevent the possibility of flame propagation from the combustion chamber; a check should therefore always be made that they are fitted properly in their place.
- Certain designs of CFCG indicators should have their PVC covers fitted around meters with aluminium cases to avoid the risk of incandescent sparking if the case impacts on rusty steel. These meters shall always be used with their covers in place.
- When hydrocarbons are being measured no filters should be used other than the cotton filter inserted in the gas inlet of the detector to remove solid particles or liquid from the gas sample, although a water absorbent material or water trap may be necessary in the sampling line if the gas is very wet.
Leave a Comment