Combustion expert Dick Bennett cautions that when it comes to oven safety, some of us are living in the past, and it can be dangerous.



The National Fire Protection Association (NFPA) recently released the 2003 edition of its Standard for Ovens and Furnaces, NFPA 86. This edition combines all of the material previously published in three separate standards -- NFPA 86, NFPA 86C and NFPA 86D. For those of you not familiar with the old breakdown, NFPA 86 covered Class A and B furnaces and ovens, NFPA 86C covered Class C furnaces and ovens, and NFPA 86D applied to (you guessed it) Class D furnaces and ovens.

Class A units are defined as those that operate at essentially atmospheric pressure and which could contain flammable volatiles or combustible materials that could pose an explosion hazard. One example is a curing oven handling solvent-based finishes.

Class B ovens and furnaces also operate at near-atmospheric pressure but contain no flammable or combustible materials. Dryers used to evaporate water off of cleaned steel parts and aluminum melting furnaces would be good examples.

Class C furnaces and ovens are those that employ a potentially hazardous flammable or special atmosphere for processing their workloads. A common example is an atmosphere heat treating furnace for steel.

Class D furnaces are essentially vacuum furnaces, although recent developments have forced the definition to be stretched to include operating pressures above atmospheric and the use of special processing atmospheres.

Apart from the consolidation of the three standards, a review of the 2003 edition will not yield many new requirements applicable to Process Heating readers. Most of the changes are refinements or clarifications of earlier wordings. In general, existing equipment is grandfathered under the edition in force at the time it was built. So, you're not required to make retroactive alterations to equipment unless required by authorities to forestall an unacceptably hazardous situation, or where the standard specifically says it is retroactive. Two such sections are Section 4.2 and Chapter 14.

To ensure safe operating practices, Section 4.2 requires all operating, maintenance and supervisory personnel to be thoroughly trained in the operation of the equipment. Further, they have to demonstrate their understanding of these subjects, receive regularly scheduled retraining and testing, and have access to operating instructions, equipment documentation and maintenance and emergency procedures.

Chapter 14 is short, but it's loaded with responsibility. It holds the equipment manufacturer responsible for providing the end-user with information and instructions concerning inspection, maintenance and testing of the heating equipment. From that point on, the ball is in the user's court -- he has to set up an inspection, testing and maintenance program and retain records of those activities for one year or until the next inspection, testing or maintenance cycle, whichever is longer.

NFPA 86 includes many other safety-related requirements. One calls for a "…permanent and ready means for testing all fuel gas safety shutoff valves for valve seat leakage…" and requires that leak testing be done at least annually. Use of the new valve-proving systems, where the valve is tested for leakage each time the system is started up, doesn't absolve the user of the responsibility of testing. In fact, the valve-proving system is supposed to be checked at least annually, too.

Another clause says valves are to be provided to shut off fuel in the event of an emergency, and that those valves must be located where fires and explosions at furnaces will not prevent access to them.

Over the years, I've been in plenty of plants, and only a handful have those "permanent and ready means" for leak-testing their safety shutoff valves. If asked, most people would point to the plugged taps in the valve bodies, explaining they could install the lines and petcocks to run the leak tests when it was necessary. They overlooked the fact that their electrical control panels didn't have the special wiring circuit required to carry out the leak test.

In other places, the only gas valve meeting the NFPA definition of an emergency shutoff is at the plant meter, safely padlocked behind a chain link fence. I guess if the key is located where fires and explosions at furnaces will not prevent access to it, they're OK.

So why the bellyaching, you ask? Didn't you say only Section 4.2 and Chapter 14 are retroactive?

Yes I did, but the requirement for annual safety valve inspections dates to 1995, and the emergency shutoff valve and leak test hardware requirements have been in the various versions of NFPA 86 since at least 1990. That's as far back as my archival copies go -- they may even predate that.

The point is, some of us are living in the past, and it can be dangerous.



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