Influence of Zone Classification on Elect. Equip. Installation in Hazardous ATM

Just make the whole world be Zone 0, and be happy! (But broke.)

It won't set off an explosion if the electrical equipment installed in the zone is suitable for it.

Do not proceed further without having received proper training on the topic.

Then the Wikipedia page on the topic is overdue bedtime reading material.

I am almost done with wiki, I thought of clearing this query as it is just mentioned in Wiki and also in www.hse.gov.uk/ as,

"Division 1 or Zone 1 area Gas, vapor or mist will be present or expected to be present for long periods of time under normal operating conditions. As a guide for Zone 1, this can be defined as 10-1000 hours/year or 0.1-10% of the time."

Is there any further definition which tells the frequency of release in addition to the above statement?

I am bit confused if above said duration is continuous or Intemittent.

The expected frequency of release is in that statement and no further definition is required.

http://en.wikipedia.org/wiki/Electrical_equipment_in_hazardous_areas

Hello,

Thanks for your reply,

As per my understanding, what is given the definition is total duration for presence of explosive mixture in a year. If an explosive mixture lasts for 20hrs continuously in a Zone 1 area would it be still safe considering the equipments selected for the Zone?

Please correct me if I am wrong.

Yes, it would. Zoning is to do with the normality/abnormality of the presence of the flammable atmosphere:

• 20h/year around a tank vent would be zone 1.
• 20h/year around a pump seal might be zone 2.

Try concentrating less on initial zone classification and more on the differences between equipment designed for the different zones. Afterall the hazardous area zoning should be done by an expert, all you need to do as a supplier/contractor/site owner/etc is insure the right zoned equipment goes into or is used in the right zoned area.

Try this website (for example) for more information including what's available in the way of off-the-shelf or custom built equipment to meet your hazardous area needs.

Link.

Additional information can also be obtained from the relevant hazardous area standards (although they are expensive and hard to read) or off the internet in the form of hazardous area guides or application notes.

Let the learning begin.

Agreed, but I think AP#1 raises a relevant point.

If there's a possibility of a flammable mixture why should equipment protection depend on the likelihood of it occurring? Protection increases for kit rated Zone 2, 1, 0 and if Zone 2 kit is installed and there is an explosion it's not much comfort to know it was in theory less likely to happen.

Of course for instrumentation, can make it IS and that covers all cases, but not a option for motors.

Motors don't go in zone 0!

Explosion does not occur if the electrical equipment is correctly selected and installed for the appropriate zone. Confirmation of this is determied by type-testing the equipment at nationally-accredited laboratores. That is what the certification warrants.

I didn't actually refer to motors in Zone 0, though to be honest I didn't appreciate it wasn't allowed, so I've learnt something.

But it doesn't alter what I was saying, which applies to any ignition source. If something is designed for say Zone 2, as flammable mixture is expected to be infrequent, if such a mixture does occur and there's an explosion, it's still a problem. It can either ignite the mixture or it can't, the way I see it.

I can see that in practice over a long time the lower the frequency of a flammable mixture the fewer explosions there will be, which might justify use of a lower standard of protection, but the logic seems a bit odd.

If equipment is designed for zone 2, and installed correctly in accordance with its certification in zone 2, then no explosion will occur as a result of the use of the electrical equipment whether or not a flammable atmosphere happens to be present at any particular instant. Removing the numbers for a moment:

• Zone 2: "from time to time under abnormal operation, a flammable atmosphere may be present and if it exists, it will only be there for a short time".
• Zone 1: "from time to time under normal operation, a flammable atmosphere may be present and if it exists, it will only be there for a short time".
• Zone 0: "a flammable atmosphere is more-or-less continuously present".

Let's move on <sigh>.

Not liking an on-topic comment in response to a post is insufficient justification for marking a comment off topic, and singularly inappropriate.