Safety Shutoff-Valve Compliance

Each independently operated burner of capacity greater than 400,000 BTU/hr requires two safety-shutoff valves, where one safety-shutoff valve is equipped with an open- and closed-position indicator and one safety-shutoff valve is equipped with proof-of-closure switch and with open- and closed-position indication.
The NFPA 86 Standards for Ovens and Furnaces, 2003 Edition, address the safety aspects of the design, construction and operation of gas- and oil-fired ovens and furnaces. The standard provides the requirements for preventing fire and explosions associated with the processing of materials in ovens, furnaces and related industrial heating equipment.

NFPA 86 states: The heat processing of materials involves serious fire and explosion hazards that can endanger the equipment, building or personnel.

This is the third in a four-part series intended to summarize the key points of the requirements for safety shutoff valves in combustion systems. It is not a comprehensive summary of all NFPA requirements for ovens and furnaces.

In Part 1 (September 2004, p. 25), some of the requirements summarized for fuel-gas safety shutoff valves referred only to independently operated burners, as follows:

  • Each independently operated burner and/or pilot must be equipped with two safety-shutoff valves piped in series. (Ref: 7.7.2.1)

  • Each independently operated burner with capacity between 150,000 and 400,000 BTU/hr requires two safety-shutoff valves, each equipped with open and closed position indication. (Ref: 7.7.1.9 and 7.7.2.2)

  • 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 an open- and closed-position indicator and one safety-shutoff valve is equipped with proof-of-closure switch and with open- and closed-position indication. (Ref: 7.7.1.9 and 7.7.2.2)

    The above synopsis simplifies the explanation of the safety-shutoff-valve requirements by only considering their application to an independently operated burner. The summary does not indicate that these requirements also apply to a burner system.

    NFPA 86, 3.3.6 Burner System, addresses one or more burners operated as a unit by a common safety-shutoff valve(s). To be inclusive of both independently operated burners and simultaneously operated burners arranged in a burner system, the above synopsis can be modified as follows:

  • Each main and pilot fuel-gas burner system must be equipped with two safety-shutoff valves piped in series. (Ref: 7.7.2.1)

  • Each main and pilot fuel-gas burner system of capacity between 150,000 and 400,000 BTU/hr requires two safety shutoff valves, each equipped with open- and closed-position indication. (Ref: 7.7.1.9 and 7.7.2.2)

  • Each main and pilot fuel-gas burner system of capacity greater than 400,000 BTU/hr requires two safety shutoff valves (see figure) where one safety-shutoff valve is equipped with an open- and closed-position indicator and one safety-shutoff valve is equipped with proof of closure switch and with open- and closed-position indication. (Ref: 7.7.1.9 and 7.7.2.2)

    The above three items highlights the difficulty in providing a summary that covers all aspects of the NFPA 86. One word can change the requirement, so care must be taken by the user to gain an understanding of the entire standard as well as any other standard or code referred to by the governing standard.

    Thus far we have only discussed fuel-gas applications. The requirements for safety-shutoff valves for fuel-oil systems are similar to those for fuel gas but not exactly the same. Here is the exact language of the standard regarding fuel-oil safety shutoff-valve requirements.

    7.7.3 Oil Safety-Shutoff Valves

  • 7.7.3.1 Two safety-shutoff valves shall be provided under any one of the following conditions:

    (1) Where the pressure is greater than 125 psi (862 kPa).

    (2) Wherever the fuel-oil pump operates without the main oil-burner firing, regardless of the pressure.

    (3) For combination gas and oil burners, where the fuel-oil pump operates during the fuel-gas burner operation.

  • 7.7.3.2 Where none of the conditions of 7.7.3.1(1) through 7.7.3.1(3) apply, a single safety-shutoff valve shall be permitted.

  • 7.7.3.3 Where two safety-shutoff valves are required by 7.7.3.1, at least one of the two safety-shutoff valves shall be proved closed and interlocked with the pre-ignition purge interval.

    Please note that the requirements of 7.7.1.9 for local visual indication of valve position for inputs in excess of 150,000 BTU/hr also applies to fuel-oil safety shutoff valves and that the requirements of 7.7.3.3 are not predicated on any particular BTU/hr capacity as for fuel-gas applications.

    There are other requiremnts for safety shutoff valves that will not be covered in Safety Zone, so please refer to Chapter 7.7 Safety Shutoff Valves (Fuel Gas or Oil) in the 2003 edition of NFPA 86. PH

    Each main and pilot fuel-gas burner system of capacity greater than 400,000 BTU/hr requires two safety shutoff valves (see figure) where one safety-shutoff valve is equipped with an open- and closed-position indicator and one safety-shutoff valve is equipped with proof of closure switch and with open- and closed-position indication. (Ref: 7.7.1.9 and 7.7.2.2)
    Given the complexity and diversity of combustion applications, this article is not intended to relieve any user or company from taking it upon themselves to gain a thorough understand of NFPA codes and standards and the requirements for compliance of their own operation. As such, the author and North American Mfg. Co. Ltd. disclaim liability for any personal injury, property or other damages of any nature whatsoever, whether special, indirect, consequential or compensatory, directly or indirectly resulting from the publication, use of, or reliance on this article.