NFPA 59A 'Ignition Source'

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nhee2

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NFPA 59A is the standard for installation of LNG plants. This question is related to 59A and not the NEC but maybe other codes have similar wording.

NFPA 59A has a table which defines electrical classifications around various equipment and is pretty straightforward. Area classifications and boundaries are consistent with NFPA 497.

Separately, NFPA 59A says:
Fired equipment and other sources of ignition shall be located at least 50ft (15m) from any impounding area or container drainage system.

An source of ignition is defined in NFPA 59A as:
Appliances or equipment that, because of their intended modes of use or operation, are capable of providing sufficient thermal energy to ignite flammable gas–air mixtures. [54, 2012]

So if I want to install a circuit breaker or contactor or other arc producing equipment 25' from an impounding area, the electrical classification guidance in NFPA 59A would allow a general purpose enclosure. But would this be considered an 'ignition source'? And therefore be prevented from being installed at that location? Do people have experience with other codes with similar requirements? Why not just make a 50' Div. 2 area requirement?

I always interpreted the 'ignition source' to be fired equipment and not electrical in this instance. But now I am not certain.
 
You have stumbled on one of the subtle differences between North American and international classified location practices. It isn’t explicit, but it is hinted at in the Informational Note (IN) to Article 500 by reference to NFPA 497 and 499. (It’s just before the Scope statement, Section 500.1) Within the titles of those Standards is the phrase “… Locations for Electrical Installations in Chemical Process Areas.” It is explicit in the Scope statements of NFPA 497 and 499, identified as Reference Standards in Section 500.4(B) that:
1.1.2 This recommended practice provides information on specific flammable gases and vapors, flammable liquids,and combustible liquids, whose relevant combustion properties have been sufficiently identified to allow their classification into the groups established by NFPA 70, National Electrical Code®(NEC®), for proper selection of electrical equipment in hazardous (classified) locations...
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It is also emphasized in another primary document, API RP-500, also referenced in 500.4(B), which says
1.1.1 The purpose of this recommended practice is to provide guidelines for classifying locations Class I, Division l and Class I, Division 2 at petroleum facilities for the selection and installation of electrical equipment.
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In other words, in common North American practice, Divisions only identify electrical area classifications. In International practice, it is area classification and all sources of ignition are relevant to the classification document.

In North American practice non-electrical ignition sources have to be identified/located with respect to emission sources within their relevant installation documents, such as NFPA 59 A; several others are listed in Section500.4(B) informational notes. Circuit breakers are indeed “other sources ofignition.”
 
Thanks rbalex for the reply.

So in my hypothetical case, where I want to install a circuit breaker or disconnect switch 25' from an impoundment area, NFPA 59A (and NFPA 497) would tell me the area is non-classified, suggesting a general purpose device.

An alternate section of NFPA 59A would tell me it cannot be installed at that location, because it is an ignition source. Would this mean no disconnect switch could be installed at that location? Or that only an explosion-proof disconnect switch could be installed there? If an explosion-proof switch is installed, do Chapter 5 sealing methods apply (I'd assume yes for seals at the disconnect, but what about boundary seals - we're not going into or out of a (electrically) classified area.

I understand (or think I do) that international and North American standards will differ. It is when there are different rules within the same NFPA 59A document that it gets confusing. It seems as though the Div 2 electrical area classification within 59A would be extended to 50' for consistency with other requirements within the document.
 
I can’t necessarily explain the contradictions/ambiguities in many NFPA documents – even those where I participated in their development.

The NEC Technical Correlating Committee(TCC) oversees/coordinates the various NEC Code Making Panels (CMP), NFPA 497,499 and a few other NFPA documents. It’s a tough job; especially since the documents aren’t developed on the same schedule. It becomes even more difficult when the Technical Committee (TC) of a still relevant, but foreign, document, such as NFPA 59A, isn’t obligated to observe their leadership. For those cases, coordination is referred to the Standards Council (SC). There are a couple of TCC members that operate from the test lab point-of-view that are very sharp as far as installation applications in classified locations are concerned; but, in my opinion, are less familiar with determining practical classified boundaries.

Since the NFPA 59A TC isn’t obligated to follow NEC rules in the first place, they may develop what appears to be inconsistencies with respect to emission/ignition boundaries and the SC is reluctant to enforce non-required practices. (This is why we have AHJs)

Note that NFPA 59A is also a reference document in Section 500.4(B). Also note 500.4(A) requires that classified locations be properly documented.

In my opinion, you are still required to document whatever boundary the impounding area would create by conventional methods. You are also obligated to accept the restrictions/definitions of NFPA59A if it applies. That is, if the equipment is not rendered a non-ignition source, it would still be required to be 50’ away.
 
rbalex said:
In my opinion, you are still required to document whatever boundary the impounding area would create by conventional methods. You are also obligated to accept the restrictions/definitions of NFPA59A if it applies. That is, if the equipment is not rendered a non-ignition source, it would still be required to be 50’ away.
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Would you consider installation of arcing/sparking device using within XP or purged enclosure, or IS (if low power circuit) as a reasonable (acceptable) method of 'rendering a non-ignition source'?
 
In my opinion those should be fine as well as any other appropriate protection technique for Class I, Division 2 listed in Section 500.7. I said "appropriate" because I don't believe any of the Subsections of 500.7(K) apply.

NOTE: Nonincendive (NI) can substitute for Intrinsically Safe (IS) in Division 2. Neither IS nor NI solve nearly as many problems as some seem to think they do, but they would work.
 
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