Installation of Combustibe gas monitors in hazardous areas to manage area classification problems

....continued

1. If the area to be so protected has an area classification of a higher level (like Zone 1) only because of a lack of ventilation.

2. If the area is part of an industrial or work area which would have very little public access.

3. If fixed type combustible gas detectors are used to detect the presence of combustible mixtures of gas or vapors, in the same area, near which the equipment is sought to be installed.

4. The fixed combustible gas detector is itself certified to be used in the hazardous area under the same classification.

5. The fixed combustible gas detector is selected, installed and mounted as per prevailing standards and regulations.

6. The fixed combustible gas detector is regularly calibrated and tested for correctness of its indication, which means its integrity is never in question at any time.

7. The fixed combustible gas detector is capable of giving out a high level alarm signal (audio/visual) on detecting explosive levels of gas or vapor mixtures in the surroundings and this alarm or trip signal should also switch off the power to the equipment in the area.

8. The gas detector should cover the entire area which is sought to be protected.

The above are just broad guidelines and you should consult the appropriate national or international standards (or legal regulations), that apply to your installation.

Why not use it throughout the plant?

This method of protection cannot be used all over the plant. The reasons are many, but we enumerate a few below:

a) Modern plants may cover large land tracts. To cover this entire area (even just the hazardous areas) would require probably hundreds of fixed gas detectors. The costs of doing this would be huge. Again remember the ALARP principle.

b) The total cost of ownership also has to be considered. Each detector would have to have itself subject to periodic calibration & inspection, maintenance & repair.

c) It may not be practical to shut down entire plants just because of some gas leakages in certain portions of the plants.

d) Some equipment requires itself to be up and running, even in case of leakages or in presence of explosive gases or vapors. For example, alarm hooters, scrubber pumps, etc.

Conclusion

Merely having a higher level of area classification does not automatically preclude you from installing equipment of a lower area classification. A workaround for this situation is now available and consists of installing a suitable fixed type combustible gas detector, which continuously monitors the ambient air for any explosive or flammable levels of gas or vapor and takes adequate automatic alarm and trip actions to safely shut down the equipment in the hazardous area.

Further information

For further information on Hazardous Areas or Gas Monitors, please take a look at some excellent e-learning courses on these topics by us. These courses can be taken online at anytime and are very comprehensive.

Please visit our Gas Detectors training course page and Hazardous Area Instrumentation training course page for more details.

For an excellent guide to Area Classification, please download the Practical Guide to Hazardous Area Classification now!

If you have any comments or questions, or you would like to know something more about e-learning, please send us an email to mail@abhisam.com

We will be glad to assist you!

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