Furnace Safety Q&A (part 1)
Most readers are aware that NFPA 86, the Ovens and Furnaces standard, just underwent a major revision, and the new edition will be available in August. The committee addressed nearly 160 proposals and comments in 2009, and only 15% were rejected outright. Several chapters were relocated and a number of major modifications were implemented.
While most furnace users are familiar with the requirements that apply to their specific equipment, some recent changes may need scrutiny. Occasionally, furnace users are not even aware of seemingly “old” changes because they haven’t purchased new equipment in many years and these old requirements are actually too new to apply to their equipment.
This column includes some of the most common questions the author has received as a consultant, a member of the NFPA 86 Technical Committee and an Industrial Heating columnist.
Q: Does NFPA 86 apply to my furnace?
A: If you have a “furnace,” “oven,” “dryer,” “kiln” or “thermal oxidizer,” chances are good that NFPA 86 does apply to your equipment. The primary categories to which the standard does not apply are: boilers, fluid heaters, solid-fuel combustion equipment and listed heating equipment rated for less than 150,000 BTU/hour.
Q: How can I determine whether NFPA 86 applies to my equipment without actually buying the standard?
A: Compared with many other publishers, NFPA’s standards are very inexpensive, so cost should not be an impediment. Also, NFPA actually provides an opportunity to “preview” the content of every document it sells over the Internet using special software. Previewing the “Applicability” statements in Chapter 1 and the related Annex content should provide sufficient information to help a user decide whether or not to buy the document.
Q: How do NFPA, FM, IRI, etc. relate, and which code has authority over the others?
A: Factory Mutual (FM Global) Property-Loss Prevention Data Sheets and XL-Global Asset Protection Service (formerly IRI or Industrial Risk Insurers) GAP Guidelines are generally not considered “national consensus standards,” and they are typically not recognized by the American National Standards Institute (ANSI). Historically, these documents were developed by the insurers for their use in conjunction with their own insured clients. Furnace/oven users and manufacturers are required to comply with all legally enforceable codes adopted in their jurisdiction. Even if a consensus standard is not legally enforceable in a particular jurisdiction, failure to comply with industry-standard safety requirements is not recommended and may constitute a violation of OSHA’s general-duty clause. While many FM Global and XL-GAPS recommendations are virtually identical to NFPA requirements, it is up to the authority having jurisdiction to review any differences and determine whether the implementation selected by the user is acceptable.
Q: Does an existing oven that is relocated have to meet the new standards?
A: This question is addressed in the “Retroactivity” and “Applicability” portions of the standard. In theory, if an oven is simply relocated, without any alterations or extensions to the existing equipment or process, the earlier requirements apply and subsequent changes do not. However, such “grandfathering” may be superseded in cases where the pre-existing situation presents an unacceptable degree of risk.
Q: Does NFPA 87 supersede NFPA 86 for fired-heaters in refineries?
A: NFPA 87 is a new Recommended Practice for Fluid Heaters. Although portions of NFPA 86 could have been applied to fluid heaters in the past if agreed to by a user and manufacturer, NFPA 86 by itself was neither sufficient for nor applicable to fluid heaters. NFPA 86 now explicitly excludes refinery fired-heaters just as NFPA 85 has done for many years.
Q: Please explain the new requirement for explosion relief.
A: NFPA 86 has required explosion relief on most ovens and furnaces for 40 years or more. The 2011 Edition will permit oven manufacturers to compute the required vent area in one of two ways: (a) the traditional guidance in NFPA 86, which calls for 1 ft2 of vent area per every 15 ft3 of furnace volume, or (b) the computational methods given in NFPA 68 – Standard on Explosion Prevention by Deflagration Venting (2007).
Q: Are smokehouse ovens, paint-booth ovens, coffee-bean roasters, textile dryers, laminator ovens, etc. exempt from NFPA explosion-relief requirements?
A: Ovens of light construction are not exempt from the requirement for explosion relief in NFPA 86. Furnaces of “heavy-wall” construction (e.g., vacuum furnaces) are listed as exceptions to the explosion-relief requirement because it is usually impractical to install explosion relief in such equipment, and furthermore, the vessel itself is more capable (albeit seldom fully capable) of containing the pressure buildup from a deflagration than light-construction ovens. Exceptions are itemized in NFPA 86 for low-oxygen atmosphere ovens, thermal oxidizers and the work chambers of indirect-fired ovens. IH