avoid having to classify area?

[WPS]

I am rehabing a groundwater remediation system, pump & treat realated to a gasoline release. While there is little chance for fumes/vapors to accumulate at explosive concentration, my understanding is the inside of the equipment shed has to be classified because fluid valves/meters are within the shed. Can I avoid having to classify enclosure if I install LEL monitors that would automatically shut system down if 10 or 20% LEL is detected?

 

[petersonra]

Re: avoid having to classify area?

Do the valves and meters have some kind of flammable liquid inside them? presumably that is your issue.

You might be able to get by with appropriate ventilation but I suspect you would need to have such a thing determined by an engineer with experience in such things.

It might end up being more cost effective to just go forth assuming it is division 1 rather than paying an engineer and adding whatever equipment might be encessary.

I am not so sure just having piping and valves inside a shed constitutes a division 1 area anyway, even if the fluid inside them is flammable.

Bob Alexander would actually know the asnwer to this question though.

<added>
I reread what you said and it mentioned an enclosure. If all you are worried about is the enclosure, you can get a pressurization system for that.

[ July 26, 2005, 10:44 AM: Message edited by: petersonra ]

 

[WPS]

Re: avoid having to classify area?

So, the LEL monitoring idea would not fly the, to avoid having to classify? By enclosure, I am referring to the inside of equipment shed.

 

[rbalex]

Re: avoid having to classify area?

Originally posted by petersonra:
...Bob Alexander would actually know the asnwer to this question though.
...

Such confidence

WPS,

Prior to the 2002 NEC, combustible gas detection was not a recognized protection technique at all; although it is now recognized in a few limited applications [See 500.7(K)]. None of the three applications describes your installation.

The problem is that using a gas detector is tacit recognition that the area between the potential source and the detector is Division 2 at a minimum; otherwise, you wouldn?t need the detector at all.

The issue in your case is a matter of maintenance and/or ventilation.

NFPA 497
3-3 Unclassified Areas.
3-3.1 Experience has shown that the release of ignitable mixtures from some operations and apparatus is so infrequent that area classification is not necessary. For example, it is not usually necessary to classify the following areas where combustible materials are processed, stored, or handled:
(a) Areas that have adequate ventilation, where combustible materials are contained within suitable, well-maintained, closed piping systems
(b) Areas that lack adequate ventilation, but where piping systems are without valves, fittings, flanges, and similar accessories that may be prone to leaks
(c) Areas where combustible materials are stored in suitable containers

Note a significant difference between 3-3.1 (a) and (b). Subsection (a) does not say there are no ??valves, fittings, flanges, and similar accessories??as does (b), rather it is simply a well maintained, closed system with adequate ventilation.

?Adequate ventilation? is occasionally difficult to establish in small rooms. NFPA 497 defines it as ?A ventilation rate that affords either 6 air changes per hour, or l cfm per square foot of floor area or other similar criteria that prevent the accumulation of significant quantities of vapor-air concentrations from exceeding 25 percent of the lower flammable limit.?

Edit: originally omitted the "6" in the definition

[ July 26, 2005, 04:29 PM: Message edited by: rbalex ]