76-500I THE TECHNICAL TIMES HEATING EQUIPMENT IN HAZARDOUS (CLASSIFIED) LOCATIONS When dealing with hazardous (classified) locations, special precautions must be exercised when specifying the proper heating equipment. Merely changing a motor to explosion proof does not always make a unit explosion proof. Modine manufactures products which are specifically designed for use in hazardous environments; however, knowledge of classifications is necessary before equipment can be selected. Hazardous locations are classified by Underwriters Laboratories (U.L.) depending on the properties of the flammable vapors, liquids, gases, combustible dusts, or fibers which may be present, and the likelihood that a flammable or combustible concentration or quantity is present. The National Electrical Code (NEC) has a section devoted to special occupancies, including hazardous (classified) locations, along with definitions and material breakdowns. When an area is identified to use or handle pyrophoric materials, the location shall not be classified. Pyrophoric materials ignite spontaneously upon contact with air. The use of electrical equipment suitable for a hazardous (classified) location will not prevent ignition of this material. In situations containing pyrophoric materials, material handling methods must be designed to prevent contact with air. Figure 1, on top of next column, is a summary chart to be used as a preliminary indication of a locations hazardous classification. The classifying of an area as hazardous is not the responsibility of the equipment supplier, it is done by the architect, electrical inspector, or insurance carrier. Class I locations are those in which flammable gases or vapors are or may be present in the air in quantities sufficient to produce explosive or ignitible mixtures. Class I locations are further broken down to identify the likelihood of presence. A Class I, Division 1 location is defined as an area where the flammable gases or vapors can exist under normal operating conditions, or because of frequent repair or maintenance operations, or when a breakdown or faulty SUMMARY OF CLASSIFICATION CHART Class I. GAS Division 1. HAZARD MAY EXIST May Exist in Atmosphere Under Normal Operating Conditions Group A. Acerylene B. Hydrogen and Manufactured Gases containing Hydrogen C. Perrochemicals (e.g. ethylene) D. Petrochemicals (e.g. alcohol) 2. POTENTIAL HAZARD A. Acerylene A. May Be Present In Atmosphere Only Under Abnormal Circumstances B. Hydrogen and Manufactured Gases containing Hydrogen B. Location Adjacent D. Petrochemicals (e.g. alcohol) C. Perrochemicals (e.g. ethylene) To Division 1 Location II. DUST III. FIBERS 1. HAZARD MAY EXIST May Exist in Atmosphere Under Normal Operating Conditions E. Conductive and Combustible Dust (Resistivity <105 ohms/cm) F. Carbonaceous Dusts (Resistivity) <102 ohm/cm but <108 ohm/cm) G. Non-Conductive Combustible Dust (Resistivity >= 105 ohms/cm) 2. POTENTIAL HAZARD A. May Be Present In Atmosphere Only Under Abnormal Circumstances G. Non-Conductive Combustible Dust (Resistivity >= 105 ohms/cm) 1. PRODUCTION AREAS Easily Ignitable Fibers or Flying 2. HANDLING AND STORAGE AREAS Easily Ignitable Fibers or Flying Figure 1 operation of equipment or a process might release ignitible concentrations of gases or vapors. A Class I, Division 2 location is an area where volatile flammable liquid or gases are handled, processed, or used, but are normally confined within closed containers or closed systems for which presence is only possible in case of accidental rupture or breakdown. By example, if a positive ventilation means is provided which prevents the concentration from becoming hazardous, the failure of this system has the potential of making the area explosive. Another area which carries the Division 2 classification is a location adjacent to a Class I, Division 1 location where ignitible concentrations of gases or vapors might occasionally migrate. The second location classification is Class II. Class II location are hazardous because of the presence of combustible dusts. A Class II, Division 1 location Page 1 of 4 contains combustible dust under normal operating conditions in quantities sufficient to produce explosive or ignitible mixtures. A Class II, Division 2 location is a location where combustible dust is not normally in the air, but combustible dust may be present as a result of infrequent malfunctioning of handling or processing equipment. The last classification used is Class III. Class III locations are those that are hazardous because of the presence of easily ignitible fibers or flyings, but are not likely to be in suspension in the air in quantities sufficient to produce ignitible mixtures. A Class III, Division 1 location is a location where easily ignitible fibers or materials are handled, manufactured, or used. Where easily ignitible fibers are merely stored the classification is Class III, Division 2. Each class and division is further broken down by groups to indicate the type of gas, vapor, dust, fiber, or flyings which are contained in the atmosphere. Each room, section, or area shall be considered individually in determining class, division, and group. Equipment that has been approved for a Division 1 location shall be permitted in a Division 2 location of the same class and group. In addition to the previously stated definitions for determining location classifications, Class I equipment shall not have any exposed surface which operated at a temperature above the ignition temperature of the specific gas or vapor. Class II equipment shall not have an external temperature higher than that specified in Table 1. Class III equipment shall not exceed the following maximum surface temperatures: ° ° For a more detailed explanation of hazardous (classified) locations, contact your local electrical inspector or refer to Chapter 5, in the National Electrical Code Handbook. Once a basic understanding of hazardous location classifications is known, this knowledge can be used to assist in heating equipment selection. A combustible or ignitible atmosphere is capable of explosion by a sudden spark, such as from the arc created when electrical contacts make and break; open flames, as found on all gas or oil-fired equipment; and from surface temperatures exceeding the ignition temperatures of a given gas, dust, or fiber. Modine offers two basic types of unit heaters which can be utilized in a hazardous location. They are the steam/hot-water unit heater equipped with explosionproof motor and the electric unit heater for hazardous (classified) locations. Both units are designed to operate in specific environments. Modine steam/hot-water unit heaters can be classified explosion proof with the addition of an explosion-proof motor and explosion-proof junction box. These units are then suitable for Class I, Group D; Class II, Groups F and G; and Class III atmospheres. Canadian Standards Association (CSA) requirements state that explosionproof units may not be used with a fluid temperature in excess of 329°F or 100 psi and still maintain their explosion-proof rating. 165°C (329°F) for equipment not subject to overloading. 120°C (248°F) for equipment (such as motor or power transformers) that may be overloaded. TABLE 1 MAXIMUM MECHANICAL EQUIPMENT SURFACE TEMPERATURES CLASS II HAZARDOUS LOCATIONS EQUIPMENT (SUCH AS MOTORS OR POWER TRANSFORMERS) EQUIPMENT THAT IS NOT THAT MAY BE OVERLOADED SUBJECT TO OVERLOADING NORMAL OPERATION ABNORMAL OPERATION DEGREES DEGREES DEGREES DEGREES GROUP C F C F C F E 200 200 105 392 392 329 200 150 120 392 302 248 200 200 165 392 392 329 GLASS II DEGREES DEGREES F G Explosion-Proof Electric The newest addition to the Modine family of explosion-proof units is the electric unit heater for hazardous (classified) locations. These units are suitable for operation in Class I, Group D; and Class II, Groups E,F, and G locations. These are the only products which are explosion proof. Page 2 of 4 To our knowledge no one manufacturers an explosion-proof gas-fired unit heater. Putting an explosion-proof motor on a gas, oil, or standard electric unit heater does not make that unit explosion proof. These units contain a heat exchanger whose surface temperature very often exceeds the ignition temperature very often exceeds the ignition temperature of many gases, dusts and fibers. Gas and Oil units also contain an open flame, used to fire the heat-exchanger, which may ignite the hazardous atmosphere. Gas, oil, or electric units contain electrical components which produce enough voltage and spark to cause ignition. When you are not sure if an area is classified as hazardous, you can do a few things to determine it. First, look to see if lights or other electrical components are explosion proof. Also, check to see if the area contains special precautions or warning signs which might indicate a hazardous classification. Third, check with the building owner or architect. If the building permits have been issued, they should note when an area is hazardous. Make certain that explosion-proof equipment is always used when an area is classified hazardous. Equipment must be selected to suit the environment for which it is installed. Not all explosion-proof equipment can be installed in all hazardous locations. Explosion-proof equipment serves a unique market segment, and it is crucial that equipment meet very stringent specifications. APPENDIX A The following information is included to give a quick reference of definitions of hazardous locations. This information is limited and only includes definitions for classifications which Modine products meet. For a more complete listing of Hazardous Location Definitions see NEC Handbook, Chapter 5. HAZARDOUS LOCATION DEFINITIONS HAZARDOUS LOCATIONS - Areas where the possibility of explosion or fire exists because of the presence of flammable gases, vapors, or dusts, etc. DIVISION I - Locations where the hazard is expected to be present during normal production operations, or during frequent maintenance and repair activities. DIVISION II - Locations where the hazards would only exist as a result of an accident or other abnormal event such as a rupture or spillage. CLASS I - Areas where sufficient quantities of flammable gases or vapor exist in the air to be explosive or ignitible. * * * * * * Offshore and land based drilling rigs, petroleum exploration and testing facilities. Petroleum refineries, gasoline storage and dispensing areas. Industrial firms that use flammable liquids dip tanks for parts cleaning or other operations. Dry cleaning plants where vapors from cleaning fluids can be present. Aircraft hangars and fuel servicing areas. Utility gas plants and operations involving storage and handling of liquefied petroleum gas or natural gas. GROUP D - Gases or vapors with specific explosive characteristics grouped together including: Acetone Acrylonitrile Ammonia Allyl Alcohol Amyl Acetate Benzene Blast Furnace Gas 1, 3 - Butadiene Butane n-Butyl Acetate Iso-Butyl Acetate Cyclohexane Ethane Ethanol Ethyl Acetate Ethylene Dichloride Ethyl Alcohol Ethyl Nitrite Gasoline Heptane Hexane Isoprene Methane Methanol Methyl Acetate Methyl Isobutyl Ketone Methyl Ethyl Ketone Naphtha Natural Gas Iso-Octane Pentane Propane Propylene n-Propyl Acetate Styrene Toluene Vinyl Acetate Vinyl Chloride Xylene Page 3 of 4 CLASS II - Areas which are made hazardous by the existence of combustible dusts. * * * * * * TYPICAL HAZARDOUS ATMOSPHERES Class I & II, Groups D, E, F & G Coal preparation plants and other carbon handling or processing areas. Grain elevators, flour and feed mills. Plants that manufacture, or use or store magnesium or aluminum powders. Plants that have chemical or metal-lurgical processes . . . producers of plastics, medicines and fireworks, etc. Producers of starch or candies. Spice grinding plants, sugar plants and cocoa plants. NEC CODE NO. T1 GROUP E - Powdered metals such as aluminum and magnesium, and other metal dusts with similar characteristics. GROUP F - Dusts such as carbon black coke, and coal dust. 800 790 790 780 413 775 413 405 775 761 404 402 399 759 756 750 385 343 363 350 725 650 685 662 300 572 Ethyl acetate Isobutyl acetate N-butyl acetate 2-Methyl-1-propanol (isobutyl alcohol) 1-propanol (propyl alcohol) Ethylene dichloride 2-butanol (secondary butyl alcohol) Methyl ethyl Ketone Vinyl acetate 2-propanol (ispropyl alcohol) Methanol (methyl alcohol) 1-butanol (butyl alcohol) Ethanol (ehtyl alcohol) 3-methyl-1 butanol (isomyl alcohol) 1-pentanal (amyl alcohol) T2A 288 288 280 550 550 536 Butane Petroleum naptha Gasoline (56-60 octane) T2C 243 470 Pentanes T2D 225 220 437 428 Hexanes Isoprene T3 206 204 200 403 399 392 Octanes Heptanes Metal & Coal Dust T3B 165 329 Grain Dust T2 The atmosphere given are those found in NFPA 427m, 1986 & NFPA 325m, 1984. For other hazardous atmospheres not listed above, consult NFPA 497m and 325m. 1 1500 DeKoven Avenue Racine, Wisconsin 53403-2552 Phone: 1.800.828.HEAT Fax: 1.262.636.1665 www.modine.com © Modine Manufacturing Company 2002 ATMOSPHERES Ammonia Methane (natural gas) Benzene Styrene Acrylonitrile Toluene Ethane Vinyl Chloride Acetone Acetic Acid (glacia) Xylenes Gasoline (100 octane) Propylene Propane Methyl Isobutyl Ketone 427 421 421 416 GROUP G - Dusts, including flour, starch, spices, and grain dust. Commercial HVAC&R Division Modine Manufacturing Company IGNITION TEMPERATURE °C °F 498 928 630 999 498 928 490 914 524 975 480 896 472 882 472 882 465 869 464 867 464 867 456 853 455 851 450 842 440 840 3/02 - Litho in USA Page 4 of 4