Hazardous Location? Confusion still exists

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Two years ago this journal published my article titled, “Hazardous Location: How Do We Know That It Actually Is?” and I received a number of positive observations on it.

With the changes to Section 18 in the 2015 edition of the Canadian Electrical Code, Part I (CE Code), I received a number of new comments and questions on installation of electrical equipment in hazardous locations. The majority of these questions relate to the following issues:

  1. Where to find the ultimate expertise for determination of a hazardous location described in Section 18?
  2. Why atmospheres with hazardous concentrations of combustible dusts or ignitable fibres have disappeared from classification of hazardous locations in Section 18?
  3. Why Section 18 has abolished description of Classes of hazardous locations, but such description remains in other Sections of the Code?
  4. Why despite the fact that Section 18 has adopted classification of hazardous locations based on zones (and not on classes), electrical equipment in such location still has to be suitable for the appropriate Class and Division of hazardous location?
  5. What is the intent of Rule 18-068?

Let’s discuss these questions one by one and try to provide some clarification on them.

  1. Where to find the ultimate expertise for determination of a hazardous location described in Section 18?

Subrule 18-000(1) of the 2015 edition of the CE Code states the following:

“18-000 Scope (see Appendices B, F, and J)

(1) This Section applies to locations in which electrical equipment and wiring are subject to the conditions indicated by the following classifications.”

“Hazardous location” is defined in Section 0 of the CE Code as follows:

“Hazardous location (see Appendix B) — premises, buildings, or parts thereof in which

(a) an explosive gas atmosphere is present, or may be present, in the air in quantities that require special precautions for the construction, installation, and use of electrical equipment;

(b) combustible dusts are present, or may be present, in the form of clouds or layers in quantities to require special precautions for the construction, installation, and operation of electrical equipment; or

(c) combustible fibres or flyings are manufactured, handled, or stored in a manner that will require special precautions for the construction, installation, and operation of electrical equipment.”

Rule 18-002 of the CE Code “special terminology” offers the following classification of zones that compose (or make up) hazardous locations:

“Zone 0 — a location in which explosive gas atmospheres are present continuously or are present for long periods.

Zone 1 — a location in which

(a) explosive gas atmospheres are likely to occur in normal operation; or

(b) the location is adjacent to a Zone 0 location, from which explosive gas atmospheres could be communicated.

Zone 2 — a location in which

(a) explosive gas atmospheres are not likely to occur in normal operation and, if they do occur, they will exist for a short time only; or

(b) the location is adjacent to a Zone 1 location, from which explosive gas atmospheres could be communicated, unless such communication is prevented by adequate positive-pressure ventilation from a source of clean air, and effective safeguards against ventilation failure are provided.

Zone 20 — a location in which an explosive dust atmosphere, in the form of a cloud of dust in air, is present continuously, or for long periods, or frequently.

Zone 21 — a location in which an explosive dust atmosphere, in the form of a cloud of dust in air, is likely to occur in normal operation occasionally.

Zone 22 — location in which an explosive dust atmosphere, in the form of a cloud of dust in air, is not likely to occur in normal operation but, if it does occur, will persist for a short period only.”

Rules 18-004 – 18-008 of the CE Code further elaborate on specifics of explosive atmospheres that might comprise a hazardous location (see below):

 “18-004 Classification of hazardous locations (see Appendices B, J, and L)

Hazardous locations shall be classified according to the nature of the hazard, as follows:

(a) explosive gas atmospheres; or

(b) explosive dust atmospheres.

18-006 Locations containing an explosive gas atmosphere (see Appendix B)

 Explosive gas atmospheres shall be divided into Zones 0, 1, and 2 based upon frequency of occurrence and duration of an explosive gas atmosphere.

18-008 Locations containing an explosive dust atmosphere (see Appendix B)

Explosive dust atmospheres shall be divided into Zones 20, 21, and 22 based upon frequency of occurrence and duration of an explosive dust atmosphere.”

So far, so good. But how can the CE Code user determine whether concentration of these gases or dust in the air is, in fact, present in quantities that are sufficient to produce “explosive” gas or dust atmosphere? What if the Code user inaccurately assessed a potential for concentration of such explosive gases or dust in the air and has chosen to apply provisions of Section 18 for selection of electrical equipment and wiring methods where use of Section 18 is not warranted? And what if, on the contrary, the Code user has underestimated a potential for “explosive” gas or dust atmosphere in the air and did not apply requirements of Section 18 for the applicable selection of electrical equipment and wiring methods?

While the former approach will simply make installation unjustifiably more expensive, the latter approach will certainly make such installation unsafe and simply hazardous. Some electrical inspection authorities do not necessarily have sufficient expertise to assess whether the area in question could be, indeed, treated as a non-hazardous or ordinary location, and the inspectors prudently apply more restrictive approach to ensure that the safety is not compromised, unless the determination of area classification is made by the process experts who  are familiar with the relevant NFPA standards and with the appropriate provisions of the National Fire Code of Canada.

However, who are the ultimate process experts on this subject, and does the CE Code address the criteria in accordance with which, such determination should be made? Appendix B Note on Rule 18-000 of the CE Code offers the following information on this subject:

“Appendix B Note on Rule 18-000

 Through the exercise of ingenuity in the layout of electrical installations for hazardous locations, it is frequently possible to locate much of the equipment in a reduced level of classification or in a non-hazardous location and thus to reduce the amount of special equipment required.

    To assist users in the proper design and selection of equipment for electrical installations in hazardous locations, numerous reference documents are available. Tables A, B, and C list the documents most commonly referenced.”

   Is this information sufficient? Not really.

Absence of information on this matter—in order to help the Code users consistently determine hazardous locations (and, particularly, accuracy in assessment of applicable Zones in a hazardous location) — has created not only a huge void in clear understanding of the criteria for determination of the areas of hazardous locations, but it has become a subject of numerous arguments between various AHJs, designers and installers.

It has been recognized in discussions between the CSA technical management and the members of the CSA Strategic Steering Committee on the Requirements for Electrical Safety that while the CE Code users clearly understand how to apply the requirements of Section 18 for selection of electrical equipment and wiring methods for the determined hazardous areas, the electrical safety practitioners don’t have sufficient expertise in understanding specific processes that can lead to the presence of explosive gas atmospheres. Thus, the CSA is considering developing a guide that could be referenced by Section 18 of the CE Code and that could provide basic assistance to the CE Code users in criteria for determination of hazardous locations. Meanwhile, only the process experts should be engaged in the determination of hazardous locations, and such process experts are not necessarily electrical engineers involved in electrical design.

 

  1. Why have atmospheres with hazardous concentrations of combustible dusts or ignitable fibres disappeared from classification of hazardous locations in Section 18?

As it was indicated in the discussion on question 1 above, Section 18 has been revised to apply only to zone-based classification of hazardous locations, and Rule 18-004 classifies the nature of hazard based on presence of “explosive gas” or “explosive dust” atmospheres. However, the definition of “dust” in Rule 18-002 (see below) also includes “combustible dust,” “non-conductive dust,” and “combustible flyings”:

 “Dust — generic term including both combustible dust and combustible flyings.

Combustible dust — dust particles that are 500 μm or smaller (material passing a No. 35 standard sieve as defined in ASTM E11) and present a fire or explosion hazard when dispersed and ignited in air.

Conductive dust — combustible metal dust.

Non-conductive dust — combustible dust other than combustible metal dust.

Combustible flyings — solid particles, including fibres, greater than 500 μm in nominal size that may be suspended in air and can settle out of the atmosphere under their own weight.”

Furthermore, definition of hazardous location in Section 0 (see discussion on question 1 above) includes “combustible dusts” and “combustible fibres and flyings.”

In addition, Appendix B Note on Rule 18-008 references “readily ignitable fibres and flyings”:

 “Appendix B Note on Rule 18-008

 Readily ignitable fibres and flyings include rayon, cotton (including cotton linters and cotton waste), sisal or henequen, istle, jute, hemp, tow, cocoa fibre, oakum, baled waste kapok, Spanish moss, excelsior, and other materials of similar nature.”

  So, for the purpose of Rule 18-004(b), “explosive dust atmospheres” include the presence of “combustible or electrically conductive combustible dusts,” or “ignitable fibres or flyings” in the air in quantities sufficient to produce “explosive dust atmosphere,” and the revision to Section 18 still recognizes the fact combustible dusts or ignitable fibres and flyings in air could become a source for an “explosive dust atmosphere.”

 

  1. Why has Section 18 abolished the description of Classes of hazardous locations, but such description remains in other Sections of the Code?

It is true that certain Rules in Sections 20 and 22 still reference Class and Zone location system. However, this fact is attributed to a simple editorial inaccuracy, and this inaccuracy has been noted by the Chairs of Sections 20 and 22 S/C’s and by the CSA editors accordingly, and the necessary changes will be made.

Why, despite the fact that Section 18 has adopted classification of hazardous locations based on zones (and not on classes), do the electrical equipment in such location still have to be suitable for the appropriate Class and Division of hazardous location?

The fact that the electrical equipment must be suitable for the appropriate Class and appropriate Division of a hazardous location has nothing to do with the revisions in Section 18 in the 2015 edition of the CE Code. Such requirements have existed in the 2012 edition (and in earlier editions) of the CE Code, as the CSA safety standards for electrical equipment (CSA Part II standards) may apply to equipment intended for use in hazardous locations based on “Class”  and “Division” classification. In fact, Appendix J18 of the CE Code is based on Class and Division type of classification of hazardous locations, and application of such classification is reflected in Subrules 18-000(3) and (4) as follows:

“Rule 18-000(3) For additions, modifications, renovations to, or operation and maintenance of existing facilities employing the Division system of classification, the continued use of the Division system of classification shall be permitted.

Rule 18-000(4) Where the Division system of classification is used as permitted by Subrule (3), the Rules for Class I, II, and III locations found in Annex  J18 of Appendix  J shall apply.”

It should be noted that Appendix B Note on Rule 18-000 also clarifies extent of application of electrical equipment “suitable” for Class and Division type classification of hazardous location under a Zone based classification system in Section 18(see below):

“Appendix B Note on Rules 18-000, 18-006, and 18-008

The Zone and Division systems of area classification are deemed to provide equivalent levels of safety; however, the Code has been written to give preference to the Zone system of area classification. It is important to understand that while the Code gives preference to the Zone system of area classification, it does not give preference to the IEC type of equipment. Equipment approved as Class I or Class I, Division 1 will be acceptable in Zone 1 and Zone 2, and equipment marked Class I, Division 2 will be acceptable only in Zone 2. See Rules 18-100 and 18-150 and the Table in Appendix J, Section J1.2.

The Scope of this Section recognizes that there are cases where renovations or additions will occur on existing installations employing the Class/Division system of classification. It is expected that such installations will comply with the requirements for Class I installations as found in Appendix J.”

Thus, there is no reason for any concerns regarding so-called inconsistency between classification of hazardous locations in Section 18, and the requirements for suitability of the electrical equipment in such locations.

 

  1. What is the intent of Rule 18-068?

While conditions under which this Rule is intended to be invoked appear to be quite transparent (see below), the practice has demonstrated that this Rule is misapplied by the CE Code users:

“Rule 18-068 Combustible gas detection (see Appendices B and H)

Electrical equipment suitable for non-hazardous locations shall be permitted to be installed in a Zone 2 location, and electrical equipment suitable for Zone 2 locations shall be permitted to be installed in a Zone 1 location, provided that

(a) no specific equipment suitable for the purpose is available;

(b) the equipment, during its normal operation, does not produce arcs, sparks, or hot surfaces capable of igniting an explosive gas atmosphere; and

(c) the location is continuously monitored by a combustible gas detection system that will

(i) activate an alarm when the gas concentration reaches 20% of the lower explosive limit;

(ii) activate ventilating equipment or other means designed to prevent the concentration of gas from reaching the lower explosive limit when the gas concentration reaches 20% of the lower explosive limit, where such ventilating equipment or other means is provided;

(iii) automatically de-energize the electrical equipment being protected when the gas concentration reaches 40% of the lower explosive limit, where the ventilating equipment or other means referred to in Item (ii) is provided;

(iv) automatically de-energize the electrical equipment being protected when the gas concentration reaches 20% of the lower explosive limit, where the ventilating equipment or other means referred to in Item (ii) cannot be provided; and

(v) automatically de-energize the electrical equipment being protected upon failure of the gas detection instrument.”

Apparently the wording of this Rule has created confusion and inconsistency among the Code users. Many Code users (including inspection authorities) consider that the relaxation allowed under specific conditions of this Rule to the electrical equipment must be also extended to the wiring methods for the referenced equipment; as such approach is logical from the perspective of safety and consistency of electrical installations. These Code users indicate that in many cases, where the existing area classification has to be changed from ordinary location to hazardous location, the existing electrical equipment in the area does not have to be upgraded to be suitable for the appropriate hazardous location, and could be continued to be used (provided that it meets all conditions listed in this Rule). As well, these Code users are also of the opinion that the relaxation under conditions listed in Rule 18-068 is intended to cover wiring methods to the existing equipment subjected to such relaxation in accordance with this Rule. These Code users indicate that under no condition will electrical and fire safety be compromised if the requirement for use of wiring methods and electrical equipment will be consistent.

If, for instance, the existing equipment in such reclassified area (i.e., in the area that used to be classified as ordinary location, but has to be re-classified as Zone 2 hazardous location) is no longer suitable for this newly established hazardous location, such equipment is permitted to continue to be used in Zone 2 location under all listed conditions of Rule 18-068.

These Code users state that there have been numerous cases, when the existing lighting, ventilation, fire alarm systems and emergency lighting equipment suitable for ordinary location had to operate in the existing industrial facility which was re-classified from a medium hazard industrial occupancy to a high hazard industrial occupancy (or from F2 to F1 – from the perspective of the National Building Code of Canada), when let’s say a boutique distillery moved into the industrial tenant space previously occupied by a small manufacturing tenant, and the already existing equipment and wiring methods to this equipment were not available for Zone 2 hazardous location.

However, these Code users don’t realize that Rule 18-068 was placed into Section 18 (it was numbered differently at the time of its placement into the Code) after a CSA standard for Class I, Division 2 ignition systems was finalized.  At that time most engines were in Class I, Division 1 locations but there wasn’t (and still isn’t) a standard for a Class I, Division 1 ignition system. There were also many ignition systems that were not approved to the new CSA standard, and as such, Rule 18-068 was intended to allow use of a very specific equipment that was originally suitable for ordinary location only (and which is not available for use in Zone 2 hazardous location) for installation in Class I, Division 2 locations.  Although, in order to prevent misapplication, the wording of this Rule clearly states that it could be applied where “No specific equipment suitable for the purpose is available,” confusion in this regard still exists, and the proposal has been recently sent to Section 18 S/C  to clarify this Rule.

Hopefully, this follow-up article on hazardous locations provides the answers to the questions posted at the outset of the article. However, as usual, the local AHJ must be always consulted for specific issues related to each particular installation.