Developing NFPA Safety Standards
The NFPA 86 Report on Proposals (ROP) was recently published on the NFPA website (www.nfpa.org), and the period for public comment has begun. Comments must be submitted on a standard NFPA form (see page 7 of the ROP document) and the deadline for submission of comments is 5:00 p.m. EDT on Friday, Sept. 4, 2009.
Of the 110 proposals received, only 20 were rejected outright and just 42 were accepted without change. The balance were accepted in principle, which means that the proposal was either modified before being approved or that another parallel proposal was accepted instead.
Of the 90 proposals accepted, about two-thirds addressed requirements in the introductory chapters, which consist of Chapters 1-8 and 14 (in the 2007 edition). These requirements apply generally to all furnaces and ovens, unless exceptions are stated or when explicitly superseded by different requirements in one of the “equipment” chapters (9-13).
The committee accepted several new terms and modified definitions, including pipe burner, equipment isolation valve, safety shutdown and readily accessible. Also, the term “LFL” (Lower Flammable Limit) replaced the term “LEL” (Explosive), and the term “Interlock” replaced the term “Controller.”
A number of paragraphs were relocated from the introductory chapters to a particular equipment chapter to keep related material together. For example, approximately 50 requirements for vacuum furnaces were moved from Chapters 5 and 6 to the Class D section (formerly Chapter 13).
Text was added to clarify that discharging furnace exhaust directly into the building may be permissible in some instances. New requirements were added for gas and oil manual valves to accomplish equipment isolation and emergency shutoff, including location, accessibility, handle function, position indication and maintenance. The requirement that radiant tubes be tested for explosion resistance was relaxed to apply only to non-metallic radiant tubes.
Due to a clerical error, the requirement for manual intervention to re-open the main fuel safety shut-off valve was removed from the 2007 edition. Because it was not the committee’s intent to remove this requirement, they accepted a proposal to re-insert this requirement for the next (2011) edition. Additionally, a requirement was added for proof-of-closure switches to be installed only in listed safety shut-off valves.
A new requirement was accepted to require the installation of safety shut-off valves in thermal oxidizers (and other equipment) that utilize “direct fuel injection” and to require that such valves be listed for dual service if they also act as modulating valves.
New design alternatives were approved involving explosion relief and programmable logic controllers. In both cases, the committee essentially left unchanged the previous design options and added a new compliance option.
For the explosion-relief requirement, the committee did not change any of the exceptions currently in place, and they continue to permit the use of the formula of “1 square foot of vent area per 15 cubic feet of oven volume,” which is based on industry experience. As an alternative, the committee approved the scientifically based formula(s) for vent area specified in the NFPA 68 Standard for Explosion Protection by Deflagration Venting (2007).
For logic systems, the committee added a fourth option to the three existing choices. Currently, manufacturers can provide a logic system based on hard-wired relays and switches, a PLC listed for combustion-safety service or a general-purpose PLC providing it is equipped with a long list of added safeguards as enumerated in the standard. As a fourth alternative, the committee approved the use of a safety-rated PLC providing it meets certain minimum performance requirements, among which is a “safety integrity level” of 2.
A major restructuring of the Class A oven chapter was accepted, with clearer methods for computing “safety ventilation” when combustible solvents or powder-coating materials are dried and cured.
The Class C atmosphere-furnace chapter also underwent a major revision in structure and content. In addition to specific new requirements for bubbler bottles, burn-off pilots and ignition sources for burn-in procedures (among others), the requirements for safe handling of special atmospheres in a furnace were significantly changed. The committee’s intent was to replace the older prescriptive operating instructions with a sequence of clear performance-based requirements.
Please note that this column is not long enough to contain a complete review of all the committee actions. In order to examine all of the accepted changes, readers are encouraged to obtain a copy of the ROP directly from NFPA’s website.
Industrial Heating magazine recently sponsored a webinar that also addressed many of these changes. The NFPA 86 committee welcomes comments on these and all proposed revisions to the Ovens and Furnaces standard. IH
Industrial Heating’s NFPA 86 webinar has been archived for one full year. You can go to http://webinars.industrialheating.com and listen to it in its entirety. Don’t miss the Q&A.