Hazardous Areas Zoning

[bs123]

We are currently building a coal handling system for a Power plant.
The hazardous zoning on the conveyors has a Class II Div 1 zone within the conveyor cover (not dust tight) and unclassified on the walkway with no Div 2 boundary. To justify this, they have referenced NFPA120: 6.2.1.1 "where coal dust is dispersed to open atmosphere the area is unclassified". My interpretation of NEC120 is that it is restricted to coal mines and non-coal mining activities are excluded.

I am arguing that NFPA 499 should have been used.
With respect to conveyors (Clause 6.8.6), “Tight equipment, ventilated hoods and pick up points, good maintenance and good housekeeping practices” can limit Div 1 locations to inside process enclosures and transfer points, and limit the Div 2 location that surrounds the Div 1 location.

based upon this point, the Div 2 location can be limited, not eliminated, by the cover.

Can someone please clarify/confirm this?
I am new to the NEC (used to IEC). When designing the areas can one just jump in and out NFPA articles that fit there usage?

Thanks in advance.

 

[rbalex]

Was the first phrase of NFPA 120, Section 6.2.1.1 ignored: "Plant areas of open construction ..."? I agree with your understanding of the limits of NFPA 120's Scope [Section 1.1; especially 1.1.1 and 1.1.2]

NFPA 499 is the preferred NEC general reference Standard for dusts, NFPA 120 isn't one of the Standards referenced in NEC, Section 500.4(B).

Unlike Class I, Class II does not require a Division 2 envelope around Division 1. The real concern is housekeeping and how much dust accumulates around potential sources of ignition.

With respect to NFPA Documents, the last sentence of the 2014 NEC, Section 90.1(A) probably applies universally,