GENERAL PURPOSE EQUIPMENT IN HAZARDOUS AREA

[bobziva]

Analyzer Building, project what I started a some time ago, provides better ventilation system and reduction of classified area from Division 2 Group B to Division 2 Group D. Building is very old with some existing equipment as "general purpose equipment" ( lighting, fans) i.e. with unclassified equipment inside hazardous classified zone.
I have to STAMP this project as P.Eng. but I am refusing.
Please your comments !

 

[dpc]

I'm not sure how ventilation could change the Group designation. I thought that was just based on the type of gas or dust.

I think it is possible to go from Div 1 to Div 2 by means of ventilation.

 

[GordS]

I think you are right - it does not make sense to have unclassified equipment in a classified Div 2 area. There is some wiggle room for motors ( in Canada) as long as items such as space heaters are investigated as to safe application. But items such as lighting definitely need to be suitable for the area.

 

[jbartos]

Suggestion: Some rooms, e.g. battery rooms, are often brought to a normal nonhazardous environment by the ventilation. However, the ventilation functionality has to be monitored or redundant, e.g. two exhaust fans.

 

[Elecme]

Jbartos: is it a must to have that redundant operation of the ventilation,cause i doughpt that it has to be . as you said.

Elecme

 

[jsummerfield]

Don't sign.

Study the entire NEC article 500 topics and related API topics regarding groups. You do not move from group B to D but the room might be overclassified unless there is lots of hydrogen. There are several things that you should consider. Move the sample systems and cylinders outside. Restrict the calibration and sample gas flow with excessive flow fittings from Swagelok. Pressureize the room with NFPA HVAC units that get air from outside the hazardous area. Minimize the group B content to permit classifying group D. Design and select the installation materials to otherwise comply with group B.

Obtain support from the analyzer manufacturers if necessary.

John

 

[jbartos]

Suggestion: Reference: IEEE Std 484-1987 Section 5.1.4 Ventilation. It does not explicitly call for a redundancy; however, to meet the standard and the single failure criterion, the redundancy in the ventilation system is justified.

 

[dwraith]

Hazardous area classification and selection of equipment is a specialist area. Although I am not aware of relevant legislation in your Country/State, it seems to me that as a PE you cannot sign off the installation as you do not have the relevant experience and competence. This is not a criticism of you personally as you cannot be expected to know everything. Make your employer get in a specialist.

 

[jbartos]

Comment: The originator of this thread has enough expertise and competence to work on the project. In fact, the posting the problem in this Forum evidences it. The problem being faced is not simple. The building should be renovated to be in compliance with safety codes to eliminate any potential hazards.

 

[alehman]

I doesn't matter if it's group B or D. Unclassified equipment can't be in a Cl.2 area (except motors without arc producing contacts). I agree with dpc.

 

[jbartos]

Suggestion: The electrical installation should comply with electrical safety code hazardous environment requirements.

 

[alehman]

One other thought - perhaps this change from group B to group D is due to presence of multiple hazardous gases. The referenced improved ventilation perhaps being able to remove one of the gases (e.g. hydrogen - lighter than air) while not removing another (e.g. propane - heavier than air). In this case it is conceivable the ventilation would allow part of the area to become unclassified while other parts remain Div.2.

Suggest thorough review of NEC 500-501 and applicable sections of NFPA.

 

[resqcapt19]

aleham,
"I doesn't matter if it's group B or D. Unclassified equipment can't be in a Cl.2 area (except motors without arc producing contacts). I agree with dpc."
I don't agree. In general the NEC permits the use of nonclassifed equipment in Class 1 Division 1 areas as long as there are no arc producing contacts and the normal operating temperature of the equipment is 80% or less of the ignition temperature for the gasses involved. See 501.3(B).
Don

 

[dpc]

Well, I don't see that I said much of anything previously.

But I wonder if resqcapt has a typo in the last post. For a Class 1, Div 1 area, the NEC has some very specific requirements even for non-arcing devices such as meters, transformers, etc. Maybe you are referring to Class 1, **Div 2**, where NEC allows general purpose enclosures for non-arcing equipment.

What I actually said in my first post was that it is not possible to re-classify an area that would normally be Div 2 to unclassified by means of ventilation. It is possible to re-classify an area from Div 1 to Div 2 by means of ventilation.

This is how I recall it, but it has several years since I actually had to think about it, so I could certainly be mistaken.

 

[resqcapt19]

dpc,
Yes, I do have a typo in my previous post. It should read Class 1 Division 2, not Division 1. Sorry.
Don

 

[alehman]

resqcapt,
Yes there are exceptions. I assumed the discussion pertained to equipment in the space that would be required to be explosionproof if the space is Div 2.