4 replies to this topic

[venkatesh.b]

Dear all

Can anyone justify the exact difference in CLASS & ZONE teminology used in "Hazardous Area Classification".And where this terminology is appllied??

[breizh]

http://www.hse.gov.u...easareaclas.htm

Hi ,
Let you consider this resource ,it should help.

Breizh

[kkala]

Web reference by breizh reflects present status, in Europe and other countries. UK Health and Safety Executive articles are useful indeed. Following additional information can be also interesting:
1. In 1990s and before, hazardous area classification was per API RP 500, briefly as in http://www.engineeri...tion-d_345.html. Class was referring to the general nature of hazardous substance (flammable vapor, dust, fiber) and Division to the intensity / probability of explosion.
2. ATEX 95 & 137 Directives (with IP15 code) made the European Contribution to the subject, extending the sources of ignition to non electrical sources too. Now there are Zones instead of Divisions, explained in the Web reference of breizh, as well as in http://en.wikipedia....hazardous_areas.
3. Comparison between "old" Classes and "new" Zones can be seen in http://www.isa.org/T...ContentID=27204, with one comment: "Old" Class II areas (combustible dust) are classified into Zones 20, 21, 22, each having exactly the same risk and meaning as the Zones 0, 1, 2 of flammable fluids. It is Division (not Class) that is compared to Zone.
I do not know whether "old" Class III material (ignitable fibers) is now considered as combustible dust (advice welcomed).
4. API RP 505 is based on concepts similar to European (para 2 above). Mentioned Zones are used (at least for flammable fluids), but it seems that Classes have remained. See http://www.ehawke.co...ical/amhaz.html. Divisions in North America may be replaced with Zones (at least for "old" Class I), see http://www.ehawke.co...ical/amhaz.html.
5. Rougly, Division 1 includes the Zones 0 (more risky) & 1, Division 2 includes the Zone 3. Experts say the Division 2 is not always identified with Zone 3 , although this is assumed in most urgent local studies.

Edited by kkala, 17 September 2011 - 01:11 PM.

[demank]

Different of Class and Zone terminology,
I was confused also for the first time.
Then I read thoroughly of API 500 (Div) dan API 505 (Zone).

There is one statement in API 505 of this dual classification.
"A Zone 2 location is allowed to abut, but nor overlap Division 2 location.
A Zone 0 or Zone 1 is not allowed to abut a Division 1 or Division 2 location."

A location may be classified in accordance with either the Zone or the Division concept but not both.

[breizh]

Additional info .

Hope this helps

Breizh