Manage Hazardous Areas effectively using Gas Monitors

Zone 2 equipment in Zone 1 areas?

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?

Let us examine your options
a) Install it anyway!-Not recommended at all, as it would not only violate the law, it could cause a disaster.

b) Re-classify it, until you get an answer you like!
(Try to get the area re-classified by another expert, to check if the area really merits a Zone 1 designation, or you can get it designated as Zone 2, or even better, a safe area!)
This option is also not recommended, since if the original design engineer has done the job well, there is no reason why he would have been wrong. You will waste time, money and energy on a futile project.

c) Look for another less-taxing job?-Not necessary, there is a fourth option, read on below!

Installing Zone 2 equipment in a Zone 1 area-Your options

Yes, you guessed right. You can install a Zone 2 certified equipment, in an area reserved for only Zone 1 equipment, legally in many countries, provided certain conditions are met. What are these conditions? Before proceeding further, let us go back to basic concepts. What is really the difference between a Zone 1 and a Zone 2 area? If you remember your fundamentals of area classification, recollect that the only difference, is in the probability of an explosive mixture of vapor/gas/dust being present.
In Zone 1, it is more probable, in Zone 2, it is less probable.  It is as simple as that.

Option 1

You can try to reduce the classification of the hazardous area from Zone 1 to Zone 2, by changing certain environmental conditions, like improving ventilation in the area. Improving ventilation will ensure that enough dilution air is always present at all times, so that explosive limits of vapors/ dust concentrations are never reached. This would reduce the classification itself to Zone 2, so the problem gets solved.

You may now think, that this is exactly what was offered as an option in the previous section, where we ruled it out, why repeat it now?
This is not so. Note, that in order to really change the classification of the area, we cannot merely study it again and again and hope to get a different answer every time. We will have to change the nature of that area, by reducing the hazards present. In the option that we are discussing now, we are not merely studying the classification again, we are going to physically change the characteristics of the classified area to make it safer.

In this case by having better ventilation of fresh air into the area.

For studying the second option, let us first study the basic idea behind area classification. The idea was to segregate areas, that were at risk of having explosive vapor or gas mixtures for longer periods of time, from other non hazardous areas. Again, further sub-dividing the hazardous areas into zones (Zone 0, Zone 1 and Zone 2) gives us finer choices, for selecting certain methods of protection over others, in a cost effective way. This is in keeping with the general principles of risk reduction, using ALARP (As Low As Reasonably Possible). This basically means, that we can spend truckloads of greenbacks on installing explosion protected equipment everywhere, even in safe areas, (to really really protect ourselves), but then the cost of doing so would drive us out of business. Thus we follow the ALARP principle.

For example, Increased Safety (Ex-e) as a method of protection, is allowed in Zone 2, but not in Zone 1. Thus we can have equipment that is appropriate for use in the area without overdesigning it or being unsafe.

However, what if we could continuously measure the so called hazardous area and check if there really are explosive gases or vapors present? Of course, we can and to do this correctly, we can install a fixed (not portable) combustible gas detector(s) in the hazardous area and monitor it in real time, if hazardous levels of vapors are present.

Option 2

You could install a combustible gas detector, that will detect the presence of combustible gas or vapor in the area and give warning alarms, or shut off the equipment immediately, in case flammable gas is detected.
Is this allowed? Yes of course, provided certain conditions are met. This protection method is known as “Combustible gas detector method of  protection”

Note: You can take a look at the Abhisam Gas Monitors e-learning course to learn everything about gas detection including explosive gas detectors, toxic gas detection, oxygen detectors and more. Also get certified.