Steam Boiler Area Classification 1

[wjc123]

OSHA regulations seem clear that if a flammable gas is present in the piping, an area must be Class I, Div 2. However, our steam boiler area (natural gas feed) is not a classified area. When I asked our EE about this, he said that all steam boilers are sold with general purpose instruments. Is there an exclusion for steam boilers or natural gas?

 

[EEIre]

In Europe (IEC Regs) gas fired boilers are fitted with a gas detection system and a slam shut valve on the natural gas supply.

This precludes the need to classify the boiler area as a hazardous area

Regards

Sean

 

[peebee]

This is almost the same question as thread184-57562 .

Gas furnaces, water heaters, stoves, etc., are in common use in residential, commercial, and industrial facilities all over the world, and not one of those installations are considered hazardous to the best of my knowledge.

What's the OSHA regulation you're referring to? Can you post an excerpt?

 

[wjc123]

OSHA 1910.399 gives definitions for hazardous classification of areas. (This would apply only to general industrial settings, so home water heaters, etc. would be exempt.) Unless there is an exemption for natural gas or steam generation, it would appear, from this definition, that instrumentation around such a boiler would need to meet the Class I, Division 2 standard.

(ii) "Class I, Division 2. " A Class I, Division 2 location is a location: (a) in which volatile flammable liquids or flammable gases are handled, processed, or used, but in which the hazardous liquids, vapors, or gases will normally be confined within closed containers or closed systems from which they can escape only in case of accidental rupture or breakdown of such containers or systems, or in case of abnormal operation of equipment; or (b) in which hazardous concentrations of gases or vapors are normally prevented by positive mechanical ventilation, and which might become hazardous through failure or abnormal operations of the ventilating equipment; or (c) that is adjacent to a Class I, Division 1 location, and to which hazardous concentrations of gases or vapors might occasionally be communicated unless such communication is prevented by adequate positive-pressure ventilation from a source of clean air, and effective safeguards against ventilation failure are provided.

 

[peebee]

Sounds like OSHA copied those definitions straight out of NFPA, and I suspect that they would defer to NFPA. Here's some other insights directly from NFPA:

NFPA 86
Standard for Ovens and Furnaces 1999 Edition
A-1-4.3.3
Unless otherwise required by the local environment, ovens and furnaces and the surrounding area are not classified as a hazardous (classified) location. The primary source of ignition associated with an oven installation is the oven heating system or equipment or materials heated. The presence of these ignition sources precludes the need for imposing requirements for wiring methods appropriate for a hazardous (classified) location. Refer to Section 3-3 of NFPA 497, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, and Section 3-3 of NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, regarding equipment with open flames or other ignition sources. In addition, ovens or furnaces are considered unclassified internally because safety depends upon ventilation.

NFPA 497
Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas
1997 Edition
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

3-3.3
Open flames and hot surfaces associated with the operation of certain equipment, such as boilers and fired heaters, provide inherent thermal ignition sources. Electrical classification is not appropriate in the immediate vicinity of these facilities. However, it is prudent to avoid installing electrical equipment that could be a primary ignition source for potential leak sources in pumps, valves, and so forth, or in waste product and fuel feed lines.

 

[wjc123]

That makes sense. (Wow, I don't say that very often about codes and standards.) The flame and temperature of the boiler would make the instrument classification ratings moot.

Thanks for your help!