Hazardous Location Information

[DM2]

I've seen several manufactures that publish technical info on Hazardous locations, state that the difference between Class 1, Division 1 and 2 depends on the number of hours the combustible vapor is present and use 1000 hours.

I've seen this for "Zones" in API 505, but not of the "Class" and "Division" method.

Can anyone give me some direction here?

Regards,
Dan Marr

 

[georgeshall]

Class 1, Zone 0, 1, and 2 locations have time constraints for the presence of ignitable concentrations of gases or vapors.

Class 1, Div 1 and Div 2 locations are defined based solely on the presence of ignitable concentrations of gases or vapors.

Do you have access to the NEC? If so check out article 500 and 505.

 

[DM2]

Georgshall,
I do have a copy of NEC and have reviewed article 500 and 505. I also took a look at NFPA 30 but didn't see anything in there.

Would I find the requirements for "Time" in one of the IEC 60079 standards?

 

[georgeshall]

That IEC standard would be a place to start, but I don't have access to it so I don't know if it defines the time. The NEC article 505 has a couple of other standard references as well.

From what I've read in various IEEE articles (based on API RP 505), if the gas is present for more than 1000hr/year it's a zone 0 location, if the gas is present between 10 and 1000hr/year it's a zone 1 location, if the gas is present between 1 and 10hr/year it's a zone 2 location, less than 1hr/year is unclassified.

I may be able to email you one of the articles I have if you'd like for reference.

 

[georgeshall]

I left out the class/division times based on the same article:

If the gas is present more than 10hr/year it's a Class1Div1 location, if the gas is present between 1 and 10hr/year it's a Class1Div2 locations, less than 1hr/year it's unclassified.

Hope this helps.

 

[rbalex]

One of the key differences between the NEC and the "classic" IEC classifications, if you read the actual definitions carefully, is that Divisions are defined by possibilities and Zones are defined by probabilities. Unfortunately, the NEC muddies the issue in Article 505.

IEC has no specific “time limits” either. The hours listed in API 505 come from the [British Institute of Petroleum’s] IP 15.

See

http://www.ieee-pcic.org/archive/PCIC 1997-5.pdf