What Determines Div 1 or Div 2 (Class I)?

[DM2-Inc]

Some time ago I had read in a Killark catalog, in the "Technical" section, that the dividing line between what is considered Division 1 and Division 2 (Class 1) areas, is the number of hours that gas may be in the area. I want to say that Less than 1000 hours / Year, was Div 2, and 1000 or more was Div 1.

I called Killark up several years ago to try and find out where they got this but didn't get a response. I've looked at the NEC, Chapter 5, but can't seem to find it there. I looked through NFPA 30, but either I skipped over it, or it's not there.

Can someone point me in the right direction for some education?

 

[sgunsel]

Classification of areas is a complex issue, but I doubt that anyone advocates 1000 hours per year as a criteria. Suggest you search this site as area classification has been addressed many times. Also strongly suggest you leave this to someone with adequate knowledge and experience to do it right.

 

[petersonra]

I have seen something like that as well, but it was a lot less then 1000 hours/year.

 

[rbalex]

This is "residue" from when Killark was in bed with Stahl and pushing Zone rated equipment. However, even then it was improperly referencing IEC (usually European Union CENELEC) rather than NEC practices. (US “Zones” and IEC “Zones” are not the same)

The root IEC Zone definitions are based on “probability,” the root NEC Zone (and Division) definitions are based on “possibility.” CMP14 "force-fit" the IEC definitions into NEC Division format.

The number of hours/year though is applied in some IEC jurisdictions; but it is not a fixed practice. It is common practice in most IEC (usually European CENELEC) locations to base “Zones” on a logarithmic scale:

1000hrs or more / year is Zone 0
100 to 1000 hours/ year is Zone 1
10 to 100 hours/ year is Zone 2.

This is not a universal practice though, nor is it statutory in any of the CENELEC jurisdictions I’m familiar with. It is vaguely referenced in the British Institute of Petroleum’s IP15 Area Classification Code for Petroleum Installations, IP 15, which is also referenced in NEC Section 505.2(A)FPN and 505.2(B)FPN No. 2. It also shows up in API RP-505 Tables 2 & 3 (Page 15) but read the surrounding text VERY carefully.

 

[Coyote]

I seem to remember reading that if the explosive substance was present during
normal operation in a CL I area it was Div I, if only during a break down it was Div II.

 

[Smart $]

...

Can someone point me in the right direction for some education?

I seem to remember reading that if the explosive substance was present during
normal operation in a CL I area it was Div I, if only during a break down it was Div II.

Here's a publication that may help...

http://literature.rockwellautomation.com/idc/groups/literature/documents/wp/800-wp003_-en-p.pdf

 

[rbalex]

Here's a publication that may help...

http://literature.rockwellautomation.com/idc/groups/literature/documents/wp/800-wp003_-en-p.pdf

I didn't go through the whole document but if the rest is as accurate as "Appendix A" it's pretty bad. It was obviously not written by someone actually familiar with IEC practices.

 

[Smart $]

I didn't go through the whole document but if the rest is as accurate as "Appendix A" it's pretty bad. It was obviously not written by someone actually familiar with IEC practices.

I trust your interpretation, as I'm not at all familiar with IEC classification. Nevertheless, I have to ask why the concern with IEC, being we are here in the U.S.? I thought IEC was basically European-only practice.


Perhaps you can provide an opinion on this publication:

http://www.appletonelec.com/PDF/IEC_NEC.pdf

 

[puckman]

I though that the differrence between div1 and div2 was that the haszard in div 2 was sealed in containers or enclosed in vessals and became a problem when there was a leak or uncontrolled release .

 

[jdsmith]

I though that the difference between div1 and div2 was that the hazard in div 2 was sealed in containers or enclosed in vessals and became a problem when there was a leak or uncontrolled release .

You are essentially correct - the big caveat is that while we can summarize area classification in one sentence, actually classifying an area is not a simple task and has significant safety ramifications if done incorrectly. My one sentence explanation is: Class 1 Div 1 areas will have hazardous vapors under circumstances when equipment is not in an abnormal condition, and Class 1 Division 2 areas will only have hazardous vapors present is some sort of equipment has failed or is in an abnormal condition.

We have areas in the refinery that would be classified Class 1 Div 2 according to API RP 500, but we know from experience that there is something leaking most of the time that is waiting until an outage to be repaired - that makes it Class 1 Div 1 according to our judgment even though the standard doesn't require it.