3 GAS DETECTOR HEAD INSTALLATION
3.1 Siting the Detectors
Mounting positions for the gas detectors need to be considered individually, Status Scientific
Controls will offer advice and assistance with regard to the siting of detectors in varying
environments. Some initial points for consideration are:
• Ensure all gas detectors are mounted to allow routine calibration and maintenance to be
carried out as required.
Note: The sensors used within the gas detectors have a finite life. Pellistors have an
expected life span in excess of two years, whilst electrochemical sensors have an
expected life span of approximately two years.
• Ensure the proposed site will not interfere with movement of existing equipment, e.g. cranes,
doors etc
• Install all cables neatly and securely.
• Detectors for gases that are lighter than air should be positioned at a high level.
• Detectors for gases that are heavier than air should be located at below head height.
• Avoid siting the gas detectors adjacent to potential sources of radio frequency interference,
e.g. radio transmitters, control switchgear, motors etc.
• Ensure the detectors are mounted with sufficient space to allow air movement around the
sensor section, and the opening of the front hinged lid.
Mounting details for Status Scientific Detector Heads are located in section 8.6 within the
appendix.
3.2 Installation in a Non-Hazardous Area
Where gas detector heads are to be installed in an area where there is no potential of an
explosive gas hazard present, the cable lengths are limited solely by the resistance of the cable.
The FGD2 or FGD3 gas detectors fitted with either oxygen or toxic sensors require a minimum of
6V at its terminals to operate correctly. The maximum cable loop resistance is therefore
(20-6)/25mA i.e. 560.
Cable resistance values depend upon the size of the cable. Typical resistance values are:
1.0mm
2
solid core 40/Km loop.
1.5mm
2
solid core 25/Km loop.
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