Class II Div 2 requirements

[petersonra]

So one of our guys got a job that has some stuff inside of a CIID2 area. Mostly PB stations.

He was thinking IS barriers.

I am thinking dust tight enclosures is all that is required for the PB stations.

Am I missing something here?

 

[rbalex]

I had to go back and refresh my memory a bit with Article 504. While it could be used in Class II, it practically assumes a Class I environment with the clause about not needing seals to be explosionproof or flameproof. [Section 504.70] Sealing in Class II is really simple - but it still must comply with the rest of Section 502.15.

In any case, by the time all the other Article 504 and ANSI/ISA RP-12.06.01 bells and whistles are complied with, it's hard to see what IS buys beyond dusttight. [Section 502.10(B)(4)]

BTW, because ANSI/ISA RP-12.06.01 is ANSI sanctioned it is OSHA enforceable.

 

[petersonra]

Whatever sealing is required is someone else's problem.

Our side of it is providing the control equipment which would include intrinsic safety barriers if they were required for use with the push button stations. I'm not even sure why it's been classified. It was originally unclassified and then somehow it became Class II Division 2.

I don't touch on Class II areas very much so I'm kind of amazed with how relaxed the requirements seem compared to class I.

OTOH, if the customer wants intrinsic safety barriers and is willing to pay for them he can have them.

 

[petersonra]

One other thing. As I understand it their plan is to drop these push button stations down as pendants hanging on a cable and using SO cord to go up to the ceiling where they will terminate in the control box. It doesn't seem to me like there's any place to put a seal other than right at the push-button station. Is a cord grip an acceptable seal for such a thing?

ETA: I am told the division 2 area extends only to 10 feet above the floor and the control box is above 10 ft.

 

[rbalex]

A proper cable gland at a dusttight pushbutton enclosure would alleviate any real need for a seal at all. See Sections 502.140 and, for practical matters, the last sentence of Section 502.130(B)(4).

As an aside. The philosophy for Class I and II are opposites. It's recognized you can't keep gases and vapors out of an explosionproof enclosure but you can reasonably keep dusts out of a dusttight enclosure. With regard to the "seals" themselves the rules for Class II, Divisions I and 2 are identical - and they aren't too difficult. See Section 502.15.