Reducing Your Oven's Hazards, Part 1
The NFPA 86 Standard for Ovens and Furnaces, 2003 Edition, addresses the safety aspects of the design, construction and operation of gas- and oil-fired ovens and furnaces. NFPA 86 provides the requirements for preventing fire and explosion hazards associated with the processing of materials in ovens, furnaces and related equipment. NFPA 86 states: The heat processing of materials involves serious fire and explosion hazards that can endanger the equipment, building or personnel.
This series of columns is intended to summarize key points of the requirements for safety-shutoff valves in combustion systems. It is not a comprehensive summary of all NFPA requirements for oven and furnace applications. The NFPA 86 standard, which applies to new installations or to alterations or extensions to existing equipment, also includes retroactivity clauses that may require compliance for existing equipment. In addition, NFPA 86 defines an “Authority Having Jurisdiction (AHJ)” as “An organization, office or individual responsible for enforcing the requirements of a code or standard, or for approving materials, and installation, or a procedure.” The AHJ for your location could be your insurer or the local fire marshal, for instance. Whoever it is, the AHJ should be the point of definitive reference for all compliance matters.
NFPA 86 is very specific about system selection and configuration of the number and type of safety-shutoff valves for fuel-gas ovens and furnaces. (Fuel-oil systems have different requirements and are not discussed here.) The standard states: Safety-shutoff valves shall be utilized as a key safety control to protect against explosions and fires.
Here is a summary of general safety-shutoff valve requirements.
- All safety-shutoff valves must be listed for the service intended. (Ref: 7.2.1)
- All safety-shutoff valves must be complemented with manual valves for leak-tightness tests. (Ref: 126.96.36.199)
- All safety-shutoff valves must be tested for leak tightness at least annually. (Ref: 188.8.131.52)
- Each independently operated burner and/or pilot must be equipped with two safety-shutoff valves piped in series. (Ref: 184.108.40.206)
- Each independently operated burner of capacity between 150,000 and 400,000 BTU/hr requires two safety-shutoff valves, each equipped with open- and closed-position indication. (Ref: 220.127.116.11 & 18.104.22.168)
- Each independently operated burner of capacity greater than 400,000 BTU/hr requires two safety-shutoff valves (see figure), where one safety-shutoff valve is equipped with open- and closed-position indication and one safety-shutoff valve is equipped with proof-of-closure switch and with open- and closed-position indication. (Ref: 22.214.171.124 & 126.96.36.199)
This series will continue in the October 2004 issue of Process Heating. PH