Gas Detection

There are no specific standards governing gas detector location (unlike fire detection systems); there are however general guidance documents. Two examples which give information on locating detectors and also selection of sensor technologies are: BS EN 50073:1999: Guide for selection, installation, use and maintenance of apparatus for the detection and measurement of combustible gases or oxygen and IEC60079-29-2 Ed1.0: Explosive atmospheres – Part 29-2: Gas detectors – Selection, installation, use and maintenance of detectors for flammable gases and oxygen.

To quote BS EN 50073:1999 “Sensors should be located in positions determined by those who have knowledge of gas dispersion, the process plant systems and equipment involved and in consultation with both safety and electrical engineering personnel”.

The following information is required in order to identify the correct gas detector type and locations for any application:

The most suitable detectors to provide fast and reliable operation
The limitation of detectors (for example cross-sensitivity to other gases which may be present)
Detectors must be accessible for testing and maintenance
Detectors and cables must be protected against mechanical damage

Other important factors to be considered:

The sensor technology selected must not be adversely affected by other substances in the environment (eg catalytic bead sensors must not be used in areas that may contain lead, sulphurs or silicones). Detector accessories must be selected to ensure suitability for operation in the environment: spray deflectors should be used in wet areas, sun shades must be fitted if detectors are exposed to direct sunlight in hot countries, collector cones can be used to aid detection of lighter than air gases When installing gas detectors it is advisable to ensure that the sensor orifice is not exposed to liquid or dust contamination by positioning the unit downwards. Spray deflectors should be used when detectors are installed outdoors, or in indoor areas subject to wash-down operations.

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