How to make use of Gas Monitors and gas detectors to have safety in hazardous areas

EXECUTIVE SUMMARY

Hazardous areas are those locations that could have hazardous levels of explosive gas, vapor or dust mixtures present that could potentially ignite and cause fires or explosions. Such locations are normally found in oil & gas processing, chemical & petrochemical plants, shipping terminals, warehouses , aircraft fueling depots and similar locations. Electrical equipment that is to be installed in such locations is different from general purpose electrical equipment. It has to be explosion protected and certified for the area in which it is to be used.

Thus Electrical equipment installed in hazardous areas, necessarily has to conform to the area classification for that area. However, frequently, practical problems arise, where the specified equipment may not be easily available. For example, an area classified as Zone 1 under the IEC system, theoretically can accept only Zone 1 equipment. However sometimes, especially in case of specialized equipment, Zone 1 certified equipment of that type may not be available.

In such cases what could be done? This paper presents the background of such situations, possible solutions and current international practices regarding this issue.

Introduction

Places containing combustible or flammable mixtures of vapors, gases and dusts are generally classified according to the likelihood of the flammable mixture being present and the nature of the mixture so present. Hence these areas are known as Hazardous Areas (Classified locations). Typically these locations would be chemical plants, oil refineries, gas processing plants, tank farms, grain storage silos, etc.

These places are generally classified on the basis of two widely applied systems, one is the North American system ( Class, Division & Group based) and the other one is the European/ IEC system (based on Class, Zone, Group). Various National as well as International standards follow either one of these two systems.

Area Classification

Based on the location of your plant or facility, either one of the two systems above would be used to do the area classification. This holds true all over the world. This means, that though each country would have its own national standard ( and a law that basically says that the particular national standard has to be adhered to), in principle, all of the national standards follow either one or the other of the two systems.

Now let us take an example of an upcoming petrochemical manufacturing plant in Happyville. The entire plant is supposed to process petrochemicals and has several areas classified as hazardous. The plant is presently under the engineering design stage. During this stage, it is classified by the engineering and safety gurus/ consultants and the local authorities as "hazardous". It has been agreed by the owners and the engineering consultants, to use the IEC system for Hazardous Areas.

Thus, various markings on engineering layout drawings now show the various locations as Zone 1, Zone 2 and so on. Then during the next stage of the project, suitable equipment is ordered, the plant is constructed and commissioned and starts producing petrochemicals safely.

What next?

The fairy tale ending of "Everyone lived happily ever after" does not happen.

Why? Let us move a little further ahead in the lifecycle of this plant, say two years, after it has been commissioned.

Zone 2 equipment in Zone 1 areas? Sacrilege !?

Suppose there is an equipment in this plant that is certified for Zone 1 and which is installed, also in an area designated as Zone 1. Now after two years of running, it has a major failure and needs replacement. You are the Plant Engineer and are assigned the task of replacing it. You look up the spec sheet and try to contact the original equipment manufacturer. You learn that the manufacturer has stopped producing that kind of equipment because of tough competition and no longer can supply it. He however, helpfully gives you the name of another manufacturer, who makes similar equipment. You are glad to get the information and contact the new guy.

Whew! What a relief! You learn that he can supply his model which will suit your purposes admirably well, except for one (minor?) detail. The equipment is not certified for use in Zone 1, but only for use in Zone 2.

Thus , it can only be installed in Zone 2.

You now have a problem. You understand that you cannot install an equipment that has been certified as suitable for Zone 2, into a Zone 1 classified area, as it would be violating the law, good engineering practice, safety standards and so on. So what do you do?

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