61
The sensors used in
Xgard
have limitations common to all such gas
sensors, and users should be aware of the points listed below. Crowcon
can advise on particular situations and suggest alternative sensors if the
instrument is likely to experience extreme conditions.
•
Electrochemical sensor performance changes at extremes of
temperature; consult Crowcon if the detector will be exposed to
ambient temperatures below 20°C or above +40°C (4 and 104°F).
•
Extreme levels of humidity can also cause problems. The sensors are rated
for an (average) ambient of 1590% R.H. However they are used from the
tropics to deserts to tundra without this normally presenting a problem.
•
Water, contaminants or paint should not be allowed to impede the
sensor, as this will prevent gas diffusion. Detectors should be
mounted with the sensor pointing down to help prevent this.
•
Persistent exposure to certain compounds may contaminate the
sensors. Calibration checks should be performed in accordance with
the instructions for each detector type to ensure that the sensor is
working correctly.
•
Persistent exposure to high levels of toxic or flammable gas will
shorten the life of the sensor. If the high level gas is corrosive (e.g.
hydrogen sulphide) damage may occur over time to metal
components.
•
Sensors may be cross sensitive to other gases. If unsure, contact
Crowcon or your local agent.
•
Storage Instructions:
Electrochemical sensors used in Xgard Types 1
and 2 have a maximum nonpowered storage life of 3 months.
Sensors stored within a detector for longer than 3 months prior to
commissioning may not last for the full expected operational life. The
warranty period for all sensors begins from the date of shipment from
Crowcon. Detectors should be stored in a cool and dry environment
where temperatures remain within the 020°C range.
There are no rules which dictate the siting and location of detectors,
however considerable guidance is available from BS EN50073:1999
‘Guide for Selection, Installation, Use and Maintenance of Apparatus for
the Detection and Measurement of Combustible Gases or Oxygen’.
Similar international codes of practice may be used where applicable. In
addition certain regulatory bodies publish specifications giving minimum
gas detection requirements for specific applications.
The detector should be mounted where the gas is most likely to be
present.
Appendix: Sensor limitations
