Hazardous Areas are defined as:

premises, buildings, or parts thereof in which there exists the hazard of fire or explosion due to following:

highly flammable gases, flammable volatile liquid mixtures, or other highly flammable substances are manufactured or used, or stored

b) combustible dust or flyings are likely to be present in quantities sufficient to produce an explosive or combustible mixture

For an area to be classified as a Hazardous Area there must be the possibility that the conditions for an explosion or fire may exist as the result of some abnormal occurrence.

Premises or locations Alcohols (production by distillation)Batteries (charging workshops)Acetylene (storage or use of)Acetylene (manufacture of)Use or storage of toxic substances or preparationAcids (use or storage of) Flammable amines, storage Workshops for repair and servicing of motor vehiclesWood or similar combustible materials(workshops where these are worked on) Wood, paper, cardboard or similar combustible materials (deposits of) Candles or other wax objects, etc.(moulding of)Grinding, crushing, etc, of vegetable substances and all organic productsPolymer processingEasily flammable solidsCharcoal (deposits or warehouses of) Shoes or leather/skin products(manufacture of)

Oxidising substances (manufacture, use, storage of)

Detergent (manufacture of products

Liquefied fuel gases (filling stations, or distribution of)

Tar, pitch, resins, etc. (mixture or hot processing of)

Coal, coke, etc (warehouses and deposits of)

Gaseous hydrogen (storage, use of)Flammable liquids (storage and manufactured tank of)

Flammable liquids (installations for blending, processing or use of)

Flammable liquids (filling or distribution stations)Leather goods (workshops)Plastics, plastomers or elastomers(manufacture of)Refrigeration or compression (installations)Sugar factories, sugar refineries, malt houses

Silos and storage installations for cereals, grain, food products or any organic products releasing flammable dustTextile dyeing and printing

Fabrics, knitted articles, tulles,guipure lace, etc (manufacturing workshops

Varnishes, paints, primers, glues, rendering (application, baking, drying of)

Hazardous Locations are classified according to the nature of the hazard, as follows: (as per NEC definitions)a) 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 gas atmospheres;b) Class II locations are those which are hazardous because of the presence of combustible or electrically conductive combustible dusts;

c) Class III locations are those which are hazardous because of the presence of easily ignitable fibers or flyings, but in which such fibers or flyings are not likely to be in suspension in air in quantities sufficient to produce ignitable mixtures.

All three elements must be present for an explosion to occur.For an area to be classified as a Hazardous Location there must be the possibility that the conditions for an explosion or fire may exist as the result of some abnormal occurrence.

For an explosion to take place, all three sides of the triangle,satisfying the following conditions, must be present: There must be a supply of oxygen present. In most situations this is applicable as a result of the oxygen content in the air (21%). There must be sufficient fuel present in the air to form an ignitable mixture. The fuel may be in the form of a gas, vapor, mist or dust. There must be a source of ignition with sufficient energy to ignite the fuel-air mixture. For electrical equipment this may be from an arcing or sparking device or from a hot surface. There may be sources of ignition other than electrical equipment, such as hot exhaust surfaces from internal combustion engines. These devices do not fall within the scope of the North American electrical codes and are normally covered by other codes and standards such as Occupational Health and Safety.,

The basic requirement to classify a Hazardous Location is to ensure that all three sides of the triangle do not exist simultaneously. If any one side of the triangle is not present, an explosion cannot occur. Protection against explosions will therefore require control or elimination of one or more sides of the triangle.

1.0 THE OXYGEN SIDEIn most situations there is sufficient oxygen present in the air (21%) to meet the conditions for an explosion. In some situations however, oxygen may be excluded by blanketing an enclosed area with another gas to ensure there will not be sufficient oxygen present. The blanket gas is normally an inert gas, such as nitrogen, or in some cases it may even be a flammable gas such as methane.How to prevent explosions ?

2.0 THE FUEL SIDE

If avoiding the use of flammable substances is not possible, the fuel side of the triangle is removed by enclosing the gas or dust in piping, or vessels in the case of gas, vapors or flammable liquids, or in enclosed ducts in the case of dust.

3.0 THE IGNITION SIDEThe electrical equipment installed in Hazardous Locations forms the ignition side of the triangle. The various designs used for electrical equipment ensure there will not be a simultaneous occurrence of all three sides of the triangle. The specific design of an electrical device for use in a Hazardous Location will depend on the amount of time it will be exposed to flammable concentrations of flammable material. In other words, the design must be suitable for the classification of the area in which it is installed..

The most important characteristics of flammable substances in regard to ignition are: Upper Flammable Limit Lower Flammable Limit Flash Point of the flammable material Auto-Ignition Temperature Vapor Density1.0 UPPER EXPLOSIVE LIMIT (UEL)is the highest percentage by volume of gas or vapor in a gas-air mixture that will form an ignitable concentration. Above that concentration there is too much gas or vapor in the mixture and the gas-air mixture is too rich to ignite.2.0 LOWER EXPLOSIVE LIMIT (LEL)is the lowest percentage by volume of gas (or vapor) in a gas-air mixture that will form an ignitable concentration. Below that concentration there is insufficient gas or vapor in the mixture and the gas-air mixture is too lean to be ignited.

The mixture of gas and air must be between the Upper and LowerFlammable Limits for a fire or explosion to occur.

3.0 FLASH POINT OF THE FLAMMABLE MATERIALSFlash point is the minimum temperature of a liquid at which sufficient vapor is given off to form an ignitable mixture with air, near the surface of a liquid. Liquids with a flash point belowFlammable limits are normally given at 25C; an increase in temperature widens the flammable limits.As a general rule, 12C below flash point results in a flammable vapor concentration of 50% of the lower flammable limit Class I Flash PointGroup Substance F CC IIB Acetaldehyde -38 -39D IIA Acetic Acid 103 39D IIA Acetic Anhydride 120 49D IIA Acetone -4 -20

4.0 AUTO-IGNITION TEMPERATUREThe ignition temperature of a gas, sometimes referred to asauto-ignition temperature, is the lowest surface temperature which will ignite the flammable atmosphere (independent of any externally heated element). This becomes important when determining the temperature rating, or T-rating, of an enclosure or component. Published values of ignition temperature are determined by injecting a gas sample into a heated flask to determine the minimum temperature at which ignition takes place.Class I Auto-Ignition Temp.Group Substance F CC IIB Acetaldehyde 347 75D IIA Acetic Acid 867 464D IIA Acetic Anhydride 600 316D IIA Acetone 869 465D IIA Acetone Cyanohydrin 1270 688

VAPOR DENSITYThe vapor density of a gas sometimes referred to as relative vapor density, is the weight of a volume of a vapor or gas with no air present compared to the weight of an equal volume of dry air at the same normal atmospheric temperature and pressure. Vapor densities greater than 1.0 indicate the vapor or gas is heavier than air and will tend to settle towards the ground. Vapor densities less than 1.0 indicate the vapor or gas is lighter than air and will tend to rise.Class I Vapor DensityGroup Substance (Air Equals 1.0)C IIB Acetaldehyde 1.5D IIA Acetic Acid 2.1D IIA Acetic Anhydride 3.5D IIA Acetone 2.0When selecting hazardous area electrical apparatus, ensure that the gas grouping is appropriate to the area classification and that the temperature classification of the equipment is not higher than the auto ignition temperature of the surrounding gas or vapor

The gases are divided into groups with similar characteristics based on two main factors: The requirements for constructing an explosion proof or flameproof enclosure to contain an explosion of the gas or vapor, and The minimum current (amperage) required to ignite the gas or vapor. This is the basis for gas grouping relative to intrinsically safe circuits.The North American Division system groups gases into four Groups; A, B, C and D, where A is the most critical group. The IEC system groups the gases into only three Groups; A, B and C, with C as the most critical group.

Explosion proof or flameproof enclosures are constructed to withstand an internal gas explosion without damage to the enclosure and to cool the hot gases produced by the explosion as they exit the enclosure along the flame paths.

The gases in the most critical gas groups (i.e. Groups A, B or IIC) require longer flame paths to cool the gas and sometimes thicker walls to contain the increased pressure of the internal explosion.

The main factor in grouping gases for the design of explosion proof enclosures is the Maximum Experimental Safe Gap (MESG). MESG for a given gas is the maximum gap or opening (expressed in mm), for a 25 mm-wide flame path, which does not propagate an explosion of that gas.

Minimum Ignition Current (MIC) is determined in a laboratory and provides comparative values for the purposes of grouping only. Gases in the higher gas groups will ignite with lower currents, and as a result, intrinsically safe circuits for these groups will be restricted to lower currents than in the lower groups. For the IEC, gases and vapors are subdivided according to the ratio of their minimum igniting currents (MIC) to that of laboratory methane.

NORTH AMERICAN VS IEC PRACTICES The North American Division system groups gases into four groups while the IEC system groups the gases into only three groups. Table 2.4.1 shows a comparison of the two systems, a typical gas for each group and the MESG and MIC for each of the gases.Table 2.4.1Comparison of North American and IEC Gas GroupingsMESG MIC GroupingTypical NAGas (mm) IEC (mm) IEC* NA IECAcetylene 0.25 0.8 A IICHydrogen 0.28 0.8 B IICEthylene 0.65 0.5-0.9 108 0.45-0.8 C IIBPropane 0.97 >0.9 146

For the purpose of flameproof enclosures and intrinsic safety, gases and vapors have been classified according to the groups or subgroups of apparatus required for use in the particular gas or vapor atmosphere. The groups of the apparatus are:

GROUP I : FOR MINING APPLICATIONS

GROUP II : APPLICATION IN OTHER INDUSTRIES

For group II apparatus is subdivided according to the requirements appropriate to the nature of the flammable, atmosphere for which the apparatus is intended.

These sub groups with a representative gas and the design parameters are as follows:APPARATUS SUB GROUPREPRESENTATIVE GAS

II APROPANE

II BETHYLENE

II CHYDROGEN

Various gases & vapours, for which a particular group of enclosure is suitable are listed in IS : 9570-1980

The selection of electrical equipment for use in hazardous areas must ensure that the maximum surface temperature of any part of the apparatus exposed to the potentially explosive atmosphere, does not exceed the auto ignition temperature

(i.e., the temperature at which the substance when heated will ignite spontaneously).

Temperature classifications according to the North American and IEC 79-0 standards are detailed in Table A.

The reference ambient temperature of 40C will be assumed unless otherwise stated on the apparatus labeling .

The T-Classification allocated to Certified Electrical Apparatus is based on normal temperature at the most difficult operating conditions. For example, the most onerous condition for an increased safety, Ex-e, terminal box would be an enclosure fitted with the maximum permitted number of terminals with every terminal carrying its maximum rated current and maximum cable lengths connected to each terminal .

Table AT-numbers for North America and IECMaximumTemperature Surface TemperatureClassification North America IECT1 450C 450CT2 300C 300CT2A 280C -T2B 260C -T2C 230C -T3 200C 200CT3A 180C -T3B 165C -T3C 160C -T4 135C 135CT4A 20C -T5 100C 100CT6 85C 85C

FOLLOWING ARE MAIN STANDARDS IN AREA CLASSIFICATION

1.0 IEC 2.0 NEC

THE AREA CLASSIFICATION IN NEC IS BASED ON DIVISION SYSTEM & IN IEC THE SAME IS IN ZONE SYSTEM

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CLASS IDIVISION SYSTEMDESCRIPTIONZONE SYSTEMCOMMENTS

GASES & VAPORSDIVISION 1Hazardous under normal operationZONE 0Division 1 is split into Zone 0 and 1. Zone 0 is a small % of locations usually confined to inside vented tanks.

ZONE 1

DIVISION 2Not normally HazardousZONE 2Zone 2 and Division 2 are essentially the same

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CLASS IDIVISION SYSTEMDESCRIPTIONZONE SYSTEMCOMMENTSCLASSIFIED AREATIME THAT HAZ. GASES PRESENT IN INGNITABLE CONCENTRATIONSESTIMATED % OF DIVISION AREAS IN NORTH AMERICAESTIMATED % OF DIVISION AREAS IN EUROPE

GASES & VAPORSDIVISION 1Hazardous under normal operationZONE 0Division 1 is split into Zone 0 and 1. Zone 0 is a small % of locations usually confined to inside vented tanks.Zone 0Div. 1Continuously Normally Presently< 5 %< 2 %

ZONE 1Zone 1Occasionally in normal opeartions> 60 %

Zone 2Div. 2Not normally present> 95 %< 40 %

DIVISION 2Not normally HazardousZONE 2Zone 2 and Division 2 are essentially the same

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DEFINITION OF DIVISIONS:

North American Hazardous Locations are divided into Class and Divisions:

Class I, Division 1 :

A Class I, Division 1 location is one where an explosive atmosphere is presumed to be present in normal operation either all or part of the time. These are typically manufacturing areas such as a pharmaceutical plant where volatile gases escape from vessels during fermentation. In theory, Division 1 locations encompass both Zones 0 and 1 as designated in IEC Standards.

Class I, Division 2 :

A Class I, Division 2 location is one where volatile flammable liquids or flammable gases are handled, processed or used, but which are normally enclosed in containers from which they can only escape in the case of accidental rupturing or abnormal operation of equipment. This classification approximates Zone 2 in IEC Standards

DEFINITION OF ZONES:

The Zones are divided in three types based upon frequency of occurrence and duration of an explosive gas atmosphere as follows:

ZONE 0:

Zone 0, locations in which explosive gas atmospheres are present continuously or are present for long periods;

Zone 0 locations are those where there is a flammable mixture exists typically more than 1,000 hours per year.

Zone 0 locations typically do not exist outside of enclosed spaces except for the area immediately around vents which are venting from a Zone 0 location.

ZONE 1

Zone 1, comprising locations in which:Explosive gas atmospheres are likely to occur in normal operation; orZone 1 locations are those where there is a flammable mixture more than 10 hours per year and less than 1,000 hours per year.

Zone 1 locations normally occur around vents or in enclosed areas where there are intermittent or continuously open processes

The areas where Explosive gas atmospheres may exist frequently because of repair or maintenance operations or because of leakage;

The area where location is adjacent to a class I, Zone 0 location, from which explosive gas atmospheres could be communicated .

ZONE 2

Zone 2, comprising Class I locations in which, Explosive gas atmospheres are not likely to occur in normal operation and, if they do occur, they will exist for a short time only; orExplosive gas atmospheres will not occur in the air except as the result of an abnormal situation such as a failed pump packing, flange leak, etc. Also when an abnormal situation does occur it will be corrected within a short time .

Zone 2 locations are those where explosive gas atmospheres will exist for less than 10 hours per year

ZONE CLASSIFICATION SUMMARYThe primary activity for Area Classification is to list the process equipment in the area under consideration and identify all potential sources of flammable material. An estimate must be made of the duration and frequency of each release in order to classify the emission as Continuous, Primary or Secondary and the rate of potentially explosive atmosphere into the surrounding area. Continuous Grade (1000 hours/year) leads to a Zone 0. Primary Grade (100 hours/year) leads to a Zone 1. Secondary Grade (10 hour/year in total) leads to a Zone 2.

EXAMPLES OF HAZARDOUS AREA ZONE CLASSIFICATION

ZONE 0:

Areas within process equipment developing flammable gas or vapors. Areas within enclosed pressure vessels or storage tanks. Areas around vent pipes which discharge continually or for long periods. Areas over or near the surface of flammable materials

ZONE 1

Areas above roofs outside storage tanks. Areas above floating storage tanks. Areas within a specified radius around the outlet pipes and safety valves. Rooms without ventilation openings from a Zone 1 area. Areas around flexible pipelines and hoses. Areas around sample taking points. Areas around seals of pumps, compressors and similar primary sources.

Typical Zone designation.Zone 0 is inside the vented tank and near the vent. Zone 1 is a perimeter around the vent.Zone 2 is the area outside the tank.

EXAMPLES OF HAZARDOUS AREA ZONE CLASSIFICATION

ZONE 2

Areas around flanges and connecting valves. Areas outside Zone 1 around outlet pipes and safety valves. Areas around vent openings from Zone 2. See file hazardous area examples.doc

Ex-d is a type of Ex Protection in which the parts that can ignite an explosive gas air mixture are placed in an enclosure which can withstand the pressure developed during an internal explosion, and which prevents transmission of the explosion to the surrounding external atmosphere. (IS : 2148-1981)

Flameproof enclosures contain the explosion and allow gases to cool as they escape across the joints.

Flameproof protection is often used for motors and switchgear. Since very little heat is generated in switchgear, the surface temperature of the enclosure is only slightly higher than the surrounding atmosphere. In most cases the switchgear satisfies the temperature classes T5 and T6.Motors dissipate more heat. In order not to exceed the permissible limiting temperature, it may be necessary to lower the rated output of a flameproof motor as compared to a standard motor.

Examples of components requiring flameproof protection: Motors with slip rings and commutators Three-phased squirrel cage motors Switchgear with opening and closing contacts such as motor protection switches, circuit breakers and air break contactors Fuses Transformers Lighting fixtures Communication equipment measuring instruments

The definition of Type e Protection is where increased measures are taken to prevent the possibility of excessive heat, arcs, or sparks occurring on internal or external parts of the apparatus in normal operation.

The increased safety concept can be used for electrical equipment such as terminal boxes, lighting, transformers, instruments, and motors.Ex-e prevents the possibility of excessive heat, arcs or sparks from occurring on internal or external parts of the apparatus in normal operation.

The increased safety concept is only suitable for non-sparking apparatus and is commonly used in Zone 2 designated hazardous areas. (IS : 6381 1972)

Whereas the other protective techniques use mechanical means to prevent ignition from electrical faults, intrinsic safety, Ex-ia is an electrical protective measure.

This protective technique removes ignition from the explosion triangle. Intrinsic Safety, used in both Zones 0 & 1 and Division 1, prevents high fault currents and voltage from occurring in control circuits.

Intrinsic Safety is normally applied to sensing or control circuits which are 24 VDC/AC or less..

EX-ia LIMITS THE ENERGY

Voltage and current limitations are determined by ignition curves, as seen in Fig. 4. A circuit with a combination of 30 V and 150 mA would fall on the ignition level of some gases. This combination of voltage and current could create a spark with enough energy to ignite the mixture of gases and oxygen.

Intrinsically safe applications always stay below these curves. Ex-ia prevents excess voltage and current from creating sparks with enough energy to ignite gases.(IS : 5780- 1980)

Pressurization, which is a similar to purging, removes fuel from the explosion triangle by passing a quantity of protective gas through the enclosure. (IS : 7389 (PART 1) 1976)

This ensures that any potentially explosive mixture that may be present inside the system is expelled, and the mixture reduced to a concentration well below the lower flammable limit.

It guards against the ingress of the external atmosphere into an enclosure or room by maintaining a positive pressure above that of the external atmosphere. Normally air is the protective gas used provided that the oxygen content is not more than 21%. Alternatively, an inert gas such as nitrogen may be used.

Ex-p pressurization by continuous dilution of air removes fuel from the enclosure.Pressurization is used to overcome installation problems in hazardous areas where other explosive protected techniques would be difficult or too expensive

Type n apparatus is standard industrial equipment which in normal operation will not produce arcs, sparks or surface temperatures high enough to cause ignition.

The apparatus has an IP rating called Ingress Protection which is similar to NEMA enclosure ratings such as NEMA 4. Ex-n prevents or limits electrical apparatus sparking in Zone 2.( IS : 8289 1976)

This protection method is typically only used for small transformers, capacitors and on electrical components that have no moving parts.

The protection consists of a sealed enclosure (normally with a vent) containing quartz sand (the origin of the q description), powder or glass beads. The enclosed electrical components are covered and surrounded by the filling medium. This ensures that under normal use no arc can be created which is able to ignite the explosive mixture inside the enclosure and the surrounding hazardous area.

(IS : 7224-1975)

The Oil Immersion Ex-o concept has historically been used for heavy duty switchgear, motor starters and transformers.

The standard for design and testing of Ex-o type electrical apparatus is IEC 60079-6. (IS : 7693-1975)Ex-o immerses electrical apparatus in oil to prevent arcs or sparks from igniting volatile gases.

The basic principle is to immerse the electrical parts in mineral oil, which will prevent any exposure of the arcing or sparking to the an explosive atmosphere. It will also quench arcs and limit the temperature rise on electrical parts.Standards for oil immersion protection, Ex-o, require that all parts capable of producing arcs or sparks must be immersed in the oil at a depth not be than 25 mm. A method to check the oil level must be provided, e.g., by a sight glass or by some other reliable method.

Some mineral oils used in switchgear apparatus produce acetylene and hydrogen gas when arcing occurs. Because of the risk of fire or an explosion with oil immersion, this application for apparatus in hazardous areas has been generally restricted. In the Petro-Chemical industries there are very few examples of Ex-o certified products installed in hazardous areas even though the standards permit its use in Zones 1 and 2.

Encapsulation is a type of protection whereby parts that are capable of igniting an explosive atmosphere, by either sparking or heating, are enclosed in a compound is such a way that the explosive atmosphere cannot be ignited under operating or installation conditions.

The selected compound may be any thermosetting, thermoplastic, epoxy, resin (cold curing) or elastomeric material with or without fillers and/or additives, in their solid state. Ex-m encloses all ignitable component parts in resin, preventing contact with explosive gases

Enclosures are designed to protect components mounted inside from the outside environment. When these enclosures contain electrical equipment, the degree of protection is critical to shield the components from moisture and dusts that could contaminate and damage the equipment.

The North American Electrical Manufacturers Association (NEMA) have designated numbers to describe the protection that the enclosure will render. Likewise the IEC Standard IEC 60529 provides a means of classifying the degree of protection from touch, dust, water and impact.The IEC designation of the ratings is known as Ingress Protection or IP.

The IP is followed by 2 numbers with the first number providing the degree of protection against solid objects and dust, and the second number the degree of protection against water

FIRST NUMERAL Protecting against solid bodies0 - No Protection1 - Objects equal to or greater than 50 mm2 - Objects equal to or greater than 12.5 mm3 - Objects equal to or greater than 2.5 mm4 - Objects equal to or greater than 1.0 mm5 - Dust Protected6 - Dust-tightSECOND NUMERAL - Protecting against liquid0 - No Protection1 - Vertically Dripping Water2 - 75 to 105-Angled Dripping Water3 - Spraying Water4 - Splashing Water5 - Water Jets6 - Heavy Seas, Powerful Water Jets7 - Effects of Immersion8 - Indefinite Immersion

A commonly asked question is what IP number is equivalent to NEMA. While there may be differences in the intricacies of the testing program such as nozzle size and water velocity, following Table provides conversion of the NEMA type numbers to IP ratings.

NEMA vs. IP Ratings

Type Number IP Designation1 IP102 IP113 IP543R IP143S IP544 and 4X IP565 IP526 and 6P IP6712 and 12K IP5213 IP54

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ZONES & EQUIPMENTS

EQUIPMENTZONE 0ZONE 1ZONE 2

1MOTORSNo motor shall be used in this areaa) Motors with type of protection 'd'a) Motors suitabe for ZONE 1

a) Motors with type of protection 'p'b) Motors with type of protection 'n' & 'e'

However all normally sparking parts such as slip-rings and brushes shall be provided with type of protection 'd' or 'p'

Motors provided with a combination of the above forms of protection, e.g , slip ring motors in which the main enclosures and windings are of type 'e' but the normaly sparking parts of type 'd' protection

2Transformers & CapacitorsNo Transformer or capacitor shall be used in this areaa) All power and distribution transformer and capacitors with type 'd' protectionTransformers and capacitors suitable for Zone 1 areas

b) For control and instrumentation purpose, type of protection 'i'Transformers and capacitors that are dry type or containing liquids that need not have any special enclosure provided and the following requirements are satisfied:

a) Cable boxes shall be suitable for specified level of current and fault clearing time.

ZONES & EQUIPMENTS

EQUIPMENTZONE 0ZONE 1ZONE 2

b) Only off-circuit manually operated tap changers shall be allowed with provision for locking the opearting handle in position.

c) Auxiliary devices shall be intrinsically safe or if they have sparking contacts, these shall are

1) type 'd' or hermatically sealed

2) under adequate head of oil

3) of enclosed break type

Or alternatively , auxiliary devices may be deleted or installed in a safe zone rendered safe by pressurisation.

d) Any other sparking accessories or swutch shall comply with the requirements for Zone 1 area

Where oil-filled transformers are used, necessary precaustions against spread of fire shall be complied with (IS 1646 -1961)

3Lighting fittingsNo lighting fittings shall be used.All lighting fittings shall be type 'd'. If necessary a suitable guard shall be provided by means of cable in screwed steel conduits. Provision against internal displacement necessary.a) Lighting fittings for Zone 1

b) Lighting fittings with type of protection 'e' or 'n'

4Switchgear & ControlgearNo Switchgear & Controlgear shall be used. When not practicable use type 'i' protection.All switches, circuit-breakers, fuses and other equipments, enclosure together with the enclosed apparatus shall be type 'd' protection.All equipments where arcing may occur under normal condition shall be type 'd' unless the interruption of currents ocuurs in a hermatically sealed chamber, and the equipment is provided with a general purpose.

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ZONES & EQUIPMENTS

EQUIPMENTZONE 0ZONE 1ZONE 2

1MOTORSNo motor shall be used in this areaa) Motors with type of protection 'd'a) Motors suitabe for ZONE 1

a) Motors with type of protection 'p'b) Motors with type of protection 'n' & 'e'

However all normally sparking parts such as slip-rings and brushes shall be provided with type of protection 'd' or 'p'

Motors provided with a combination of the above forms of protection, e.g , slip ring motors in which the main enclosures and windings are of type 'e' but the normaly sparking parts of type 'd' protection

2Transformers & CapacitorsNo Transformer or capacitor shall be used in this areaa) All power and distribution transformer and capacitors with type 'd' protectionTransformers and capacitors suitable for Zone 1 areas

b) For control and instrumentation purpose, type of protection 'i'Transformers and capacitors that are dry type or containing liquids that need not have any special enclosure provided and the following requirements are satisfied:

a) Cable boxes shall be suitable for specified level of current and fault clearing time.

ZONES & EQUIPMENTS

EQUIPMENTZONE 0ZONE 1ZONE 2

b) Only off-circuit manually operated tap changers shall be allowed with provision for locking the opearting handle in position.

c) Auxiliary devices shall be intrinsically safe or if they have sparking contacts, these shall are

1) type 'd' or hermatically sealed

2) under adequate head of oil

3) of enclosed break type

Or alternatively , auxiliary devices may be deleted or installed in a safe zone rendered safe by pressurisation.

d) Any other sparking accessories or swutch shall comply with the requirements for Zone 1 area

Where oil-filled transformers are used, necessary precaustions against spread of fire shall be complied with (IS 1646 -1961)

3Lighting fittingsNo lighting fittings shall be used.All lighting fittings shall be type 'd'. If necessary a suitable guard shall be provided by means of cable in screwed steel conduits. Provision against internal displacement necessary.a) Lighting fittings for Zone 1

b) Lighting fittings with type of protection 'e' or 'n'

4Switchgear & ControlgearNo Switchgear & Controlgear shall be used. When not practicable use type 'i' protection.All switches, circuit-breakers, fuses and other equipments, enclosure together with the enclosed apparatus shall be type 'd' protection.All equipments where arcing may occur under normal condition shall be type 'd' unless the interruption of currents ocuurs in a hermatically sealed chamber, and the equipment is provided with a general purpose.

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Example of New ATEX markings NEW ATEX MARKING REQUIREMENTS

Each piece of equipment must be marked with the following minimum data: Manufacturers name and address CE marking Series and model number Year of construction The letter G for group II for explosive areas containing gases The letter D for areas where an explosive atmosphere can occur from dusts. The Ex symbol showing the equipment is explosion protected. Other details which are required for safety of operation.

ATEX CONCEPT CATEGORIES

In the ATEX Directive (94/9/EC) categories distinguish between safety of equipment and locations of use.

Category 1 Zone 0 Category 2 Zone 1 Category 3 Zone 2