| UNDERSTANDING INTRINSIC SAFE APPROVAL |
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"Yeah, it's intrinsically safe", .... I always answered the same way ...."How Safe is it ?" More often than not the question is followed by a pause that varies in duration, ending with the inevitable "whadaya mean how safe?". If I had to choose one of the most misunderstood topics involving rescue equipment, it would have to be the Classifications for Intrinsic Safe (I.S.) Approval. Everyone knows that you need approved equipment but few realize what the various classifications actually mean .
It all boils down to "peace of mind". I.S. Approvals are structured so that equipment users know where they can (or can't) use equipment safely. Equipment is tested to determine if it has the ability to cause an explosion in an area that contains an explosive or a potentially explosive atmosphere. This topic is of particular importance to confined space rescuers, but is something that all firefighters and first responders should be aware of. Rescuers have enough to worry about without wondering whether or not their equipment has the potential to kill them. The Process To remove some of the confusion surrounding I.S. approvals let's start with a look at the approval process as a whole. It all begins with NFPA 70 National Electrical Code (NEC). The NEC breaks down hazardous locations into three separate types or classes, Class I - flammable gases or vapors, Class II - combustible or electrically conductive dusts and Class III - easily ignitable fibers or flyings. Each Class is divided into two Divisions. Division 1 - where a hazard is present under normal operating conditions and Division 2 where a hazard might become present under abnormal operating conditions. Classes I and II are even further broken down into groups of gasses and dusts (SEE CHART #1). In addition, to the class,division and group most equipment will have a temperature code i.e.T1, T2, T3 etc. This code corresponds to Table 500-3D in the NEC . The code tells you the maximum temperature that the piece of equipment could reach under maximum fault conditions. The temperature code provides you with an actual temperature that you can cross reference with the Automatic Ignition Temperature (AIT) of a particular gas, vapor or dust to ensure safe operation. After the classifications for hazardous areas were identified, methods of testing and test procedures had to be developed so that all equipment, destined for use in a hazardous location could be properly evaluated. The American National Standards Institute (ANSI) authorized the development of these standards. All of the actual equipment testing must be conducted by a Nationally Recognized Testing Laboratory - NRTL (Remember those initials) in accordance with the accepted test procedures and standards. Probably the most familiar NRTL's are Underwriters Laboratories (UL) and Factory Mutual (FM) but there are a number of others that are also authorized to test and certify equipment for use in hazardous locations. While they provide their services to equipment manufacturers for a fee, it is important to note that they only do the testing that is requested by the manufacturer. Manufacturers therefore typically design equipment from the ground up, to meet a specific hazardous location classification or series of classifications depending on the market for their equipment. DON'T MAKE THIS MISTAKE ! Don't make the mistake of assuming that equipment approved for Class I, Division 1 is the best and can go anywhere because that is not the case. Classifications are NOT a method of grading. Class I is not "higher" or "better" than Class II or Class III, only different. It's like saying because a someone got an 'A' in Math, then they automatically get and an 'A' in Gym and Wood Shop, it just doesn't work that way. Each Class, represents a different hazardous location or work environment and the required testing for each Class is completely different. For example, equipment approved for Class I locations can be used safely in a Refinery but not in a Grain Elevator which requires a Class II approval. The opposite is also true. If you wish to use the equipment in both a refinery and a grain elevator it must be tested for each class separately and pass both tests (Class I & II). CHECK IT So how do you tell if equipment is I.S. approved and how safe it is ?...Well that's the easy part!. In North America, all intrinsically safe equipment has to carry a label that lists the hazardous location or hazardous locations, for which it has been tested and approved. Simply put, if it doesn't say it on the label, it's not approved for that location and if there is no label, the equipment is not approved. In instances where physical size prohibits a listing of approved locations, the equipment will have, as a minimum requirement, the mark of the NRTL that did the testing. If there is any question about the approval status for a piece of electrical equipment, request a copy of the certification record or approval agreement from the equipment manufacturer or distributor and keep it on file for future reference. Be Careful Out There The term "Intrinsic Safe" is becoming more and more a generic term and some advertisements for equipment include slogans like ; "Designed to Intrinsic Standards" or "Meets Intrinsic Safe Requirements" or simply "Intrinsically Safe". All of these terms sound great but they could be merely the manufacturers assertions regarding their own equipment. Saying it on a brochure doesn't necessarily mean the equipment has been properly tested and approved by an NRTL. There is one sure way to cut through the marketing garbage and get the information you want... "Check The Label".
Types of Electrical Equipment Here are some examples of commonly used electrical equipment used by rescuers in hazardous locations; lights, gas detectors, two-way radios, hardline and sound powered communication systems, PASS devices, pagers, generators and ventilation equipment. However, it doesn't end there... electrical equipment is defined by Factory Mutual Research in their Approval Standard 3600 as ; "All items applied as a whole or in part for the utilization of electrical energy. These include, among others, items for the generation, transmission, storage, measurement, regulation, conversion, and consumption of electrical energy and items for telecommunications". Maintain the Approval Some types of equipment require periodic calibration or servicing to maintain their intrinsic approval. Service and Repair of approved equipment is usually done by a certified repair facility or the manufacturer of the equipment. The best course of action in this situation is to consult the equipments operation manual or contact the manufacturer before any work is done. It's also important to note that when replacing batteries you use the correct type and style of battery cell, recommended by the manufacturer. If you don't it could void the approval. The right type and style of battery will be specified on the approval label and\in the operating manual. Just like any piece of rescue or specialized equipment, it must be maintained properly, so it can be relied on, if things go sour.
European and Canadian Intrinsically Safe Approvals Equipment certified Intrinsically Safe by Test Laboratories in Europe and other parts of the world are not typically acceptable for use in the U.S.A. unless they carry a separate U.S.A. approval. The exception to this is equipment approved by the Canadian Standards Association (CSA). The approved equipment must actually have "NRTL" on the printed label (below to CSA logo). This denotes that the equipment has been tested following approved U.S. test procedures and is recognized by OSHA as safe for use in the United States.
The Last Word Rescuers, don't normally have the luxury of knowing the location they will be called upon to work in next. For rescue use, electrical equipment should be approved for the widest variety of hazardous locations. Equipment that carries low level approval or No approval must be identified so that it's users are aware of the limitations of their equipment for their own safety as well as the safety of those around them. A good understanding of the classification structure will take the guess work out of the selection and deployment of electrically powered equipment, it can also have an impact on the equipment budget. There are definite logistical and cost advantages in having one piece of equipment approved for multiple locations rather than multiple pieces of equipment approved for individual locations. The bottom line is, if you use non-approved or inadequately approved equipment in a hazardous location and it causes an explosion, not only could people get injured or killed, it could expose your department or organization to a lot of uncomfortable questions from safety / compliance officers and insurance investigators, not to mention the friends and families of those involved. Authors Note This article, or for that matter, this entire magazine is not big enough to include all of the pertinent documentation on intrinsic safe approval standards, testing procedures, hazardous location identification and classification information etc. The information covered here is to raise the awareness of this issue. When in doubt, consult the NEC and /or your safety officer. The classification and grouping systems in the NEC also apply to electrical equipment that incorporates the following types of protection - Explosion Proof, Non-incendive circuits, Pressurized, Purged or Dust-Ignition proof. But, that's another story.... CHART #1 National Electrical Code (NEC) classifications for hazardous locations.
Class I Locations where there is a danger of explosion due to flammable Gases or vapours present in quantities sufficient to produce explosive or ignitable mixtures. Class II Locations where there is a danger of explosion due to the presence of combustible or electrically conductive dust. Class III Locations where there is a danger of explosion or flash fire due to the presence of easily ignitable fibres or flyings. Classes are separated into Divisions 1 & 2
Div I Locations where the gases, vapors, conductive dust, combustible dust, flyings and/or fibres are present in the air in potentially flammable concentrations continuously, frequently or intermittently under normal operating conditions. Div II Locations where the gases, vapors, conductive dust, combustible dust, flyings and/or fibres might become hazardous in the event of mechanical breakdown, accident, failure or the abnormal operation or equipment. The Classes are further divided into Groups ;
Class I Group A Acetylene
Group B Butadiene, Hydrogen, Ethylene Oxide, Propylene Oxide & Acrolien
Group C Acetaldehyde, Ethylene, Ether Vapours,
Group D Acetone, Ammonia, Benzene, Butane, Cyclopropane, Gasoline, Hexane, Methane, Methanol, Natural Gas, Naptha, Propane,
Class II Group E Combustible metal dust including Aluminium, Magnesium and thier Commercial Alloys
Group F Combustible carbonaceous dusts including Carbon Black, Coal, Charcoal,
Group G Combustible dusts not listed in groups E or F including Flour, Grain, Wood, Plastic
Class III No Groups Note: Refer to the National Electrical Code Articles 500,501,502,503 for a complete description of Hazardous Area Classifications and Group descriptions. CHART #2 Examples of Classifications and Corresponding Rescue Sites;
Class I, Div 1 & 2 Petroleum Refineries, Dry Cleaning Plants, Petrochemical Plants, Hospitals, Utilities, Aircraft Hangers, Paint Manufacturers, Dip Tanks Containing Flammable or Combustible Liquids, Spray Finishing Areas
Class II, Div 1 & 2 Grain Elevators, Flour and Feed Mills, Confectionary Plants, Fireworks manufacturing and storage, Grain Ships, Areas for packaging and handling of pulverized sugar and cocoa, Manufacturing and Storage of Magnesium or Aluminium, Spice grinding Mills, and some Coal handling plants,
Class III, Div 1 & 2 Wood Working Plants, Textile Mills, Cotton Gins, Cotton Seed Mills, Flax producing Plants , Knitting Mills, Weaving Mills
NOTE: The above is meant as an example only, Individual group classifications also apply to the above and were omitted for brevity. To determine Classifications for specific locations consult with your safety officer.
The NEC contains a listing of reference standards from the NFPA, American Petroleum Institute and the Instrument Society of America, some useful reference materials include;
- NFPA 497M-1991 " Manual for Classification of Gases and Vapors and Dusts for Electrical Equipment in Hazardous (Classified) Locations". - NFPA 497A-1992 Classifications of Class I Hazardous (Classified) Locations. - NFPA 497B-1991 "Classification of Class II Hazardous (Classified) Locations" - NFPA 820-1995 "Recommended Practice for Fire Protection in Waste Water Treatment and Collection Facilities". - NFPA 325-1994 " Guide to Fire Hazard Properties of Flammable Liquids, Gases and Volatile Solids". - ANSI-API 500-1992 " Classification of Locations for Electrical Installations at Petroleum Facilities" ZONES The 1996 version of the NEC, includes Article 505 - Class I, Zone 0,1, and 2 Locations. This article specifies an alternative hazardous location identification scheme for "Class I" environments only. It must be noted that the Zone system does not replace the aforementioned classification system. Zones are common classifications elsewhere in the world and it's inclusion in the NEC could be considered a step toward harmonization with other countries I.S. approval standards.
Appeals to delete article 505 and related issues in articles 501 and 502 were filed at the time of 1996 printing, however, the appeals have since been denied and Article 505 and all related references will stand.
Class I - Zones * Zone 0 Location in which ignitable concentrations of flammable gases and vapors are present either continuously or for long periods of time. Zone 1 Location in which ignitable concentrations of flammable gases or vapors that are likely to exist under normal operating conditions or may exist frequently because of repair maintenance, leakage or breakdown. Or the location is adjacent to a Class I, Zone 0 from which ignitable concentrations could be communicated, unless prevented by adequate positive pressure ventilation and safeguards are in place to prevent ventilation failure.
Zone 2 Location in which ignitable concentrations of flammable gases or vapors are not likely to occur in normal operation and if they do occur will exist only for a short period of time. An area where liquids gases or vapors are normally confined in closed containers or systems that could escape due to an accidental rupture, breakdown or abnormal operation of equipment. Or where the ignitable concentrations are normally prevented by positive mechanical ventilation but could become hazardous due to the failure or abnormal operation of the ventilation equipment. Or the location is adjacent to a Class I, Zone 1 from which ignitable concentrations could be communicated, unless prevented by adequate positive pressure ventilation and safeguards are in place to prevent ventilation failure.
Groups - Equivalents Zone System Current System
Class I, Group IIc = Class I, Groups A & B
Class I, Group IIb = Class I, Group C
Class I, Group IIa = Class I, Group D
* The above is a abbreviated version of the Zone/Group system and is for information purposes only, refer to the NEC Article 505, for complete descriptions of Class I, Zones and Groups.
Special Precaution : NEC Article 500-3 states that; if article 505 is used, area classification, wiring and equipment selection must be done under the supervision of a qualified Registered Professional Engineer.
GLOSSARY Auto Ignition Temperature ; The temperature at which a gas, vapor or dust can ignite without the presence of a flame. National Electrical Code * - NEC * ; the national code for the safe installation of equipment utilizing electricity .
* Registered trade marks of the National Fire Protection Association Intrinsically Safe - Put simply, Intrinsically Safe is an electrical protection technique § that relies on the actual design of the equipment rather the equipment's enclosure to safeguard against ignition in a hazardous atmosphere.
§ Other Electrical Protection Techniques - Explosion Proof, Intrinsically Safe, Non-incendive circuits, Pressurized, Purged, Hermetically Sealed, Oil Immersion.
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