500 – Hazardous (Classified) Locations, Classes I, II, and III, Division 1 and 2
500.7(K) – Combustible Gas Detection System as a Protection Technique
Change at a Glance:
The requirements for a combustible gas detection system as a protection technique was sufficiently revised and expanded to provide more specific detail for the installation and operation of a gas detection system.
500.7 Protections Techniques. Section 500.7(A) through (L) shall be acceptable protection techniques for Electrical and electronic equipment in hazardous (classified) locations shall be protected by one or more of the techniques in 500.7(A) through (P).
(K) Combustible Gas Detection System. A combustible gas detection system shall be permitted as a means of protection in industrial establishments with restricted public access and where the conditions of maintenance and supervision ensure that only qualified persons service the installation. Where such a system is installed, equipment specified in 500.7(K)(1), (K)(2), or (K)(3) shall be permitted.
(1) General. Any gas detection system utilized as a protection technique shall meet all of the requirements in 500.7(K)(1)(a) through (K)(1)(e).
(a) The gas detection equipment used shall be listed for Class I, Division 1 and listed for the detection of the specific gas or vapor to be encountered.
(b) The gas detection system shall not utilize portable or transportable equipment or temporary wiring methods.
(c) The gas detection system shall only use pointtype sensors. The system shall be permitted to be augmented with open-path (line-of-sight)–type sensors, but open-path–type sensors shall not be the basis for this protection technique.
(d) The type of detection equipment, its listing, installation location(s), alarm and shutdown criteria, and calibration frequency shall be documented where combustible gas detectors are used as a protection technique.
(e) The applications for the use of combustible gas detection systems as a protection technique shall be limited to 500.7(K)(2), or (K)(3), or (K)(4).
[see NEC for (4) Informational Notes here] (1)(2) Inadequate Ventilation. (2)(3) Interior of a Building or Enclosed Space. (3)(4) Interior of a Control Panel.
(see NEC for complete Code text)
500.7(L), (M), (N), and (O) – New Protection Techniques for Electrical and Electronic Equipment
Change at a Glance:
Four new protection techniques were added protection of electrical and electronic equipment in hazardous (classified) locations.
500.7 Protections Techniques. Section 500.7(A) through (L) shall be acceptable protection techniques for Electrical and electronic equipment in hazardous (classified) locations shall be protected by one or more of the techniques in 500.7(A) through (P).
(L) Inherently Safe Optical Radiation “op is.” This protection technique shall be permitted for equipment in Class I or II, Division 1 or 2 locations for which the equipment is identified.
Informational Note: The identified class and division depends on the intended explosive atmosphere and the number of faults applied as part of the protection technique evaluation.
(M) Protected Optical Radiation “op pr.” This protection technique shall be permitted for equipment in Class I or II, Division 2 locations for which the equipment is identified.
Informational Note: The identified class and division depends on the intended explosive atmosphere as part of the protection technique evaluation.
(N) Optical System With Interlock “op sh.” This protection technique shall be permitted for equipment in Class I or II, Division 1 or 2 locations for which the equipment is identified.
Informational Note: The identified class and division depends on the intended explosive atmosphere and the number of faults applied as part of the protection technique evaluation.
(O) Protection by Skin Effect Trace Heating “IEEE 844.1.” This protection technique shall be permitted for skin effect trace heating equipment in Class I, Division 2; Class II, Division 2; or Class III, Division 2 for which it is listed.
(see NEC for complete Code text)