Hazardous-Area-Classification.pdf

Hazardous Area Classification

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WARNING: This guide is not intended to replace published standards, codes of practice or other relevant publications. This is for External used only.

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Hazardous Area Classification Definitions of hazardous Area Definition 1: Petroleum Rule, 1976 An area shall be deemed to be hazardous area where petroleum having flash point below 65°C or any flammable gas or vapour in concentration capable of ignition is likely to be present. Definition 2: IS 5572 Hazardous area is an area in which an explosive gas atmosphere is present or likely to be present, in quantities such as to require special precautions for the construction, installation and use of electrical apparatus. Q. Why Zoning is required? Ans: To provide or decide the protection and selection. i. Leak Potential & Presence of Ignition Sources. ii. Hazardous properties of hydrocarbons. Safe selection (& optimisation) of Electrical Equipment. iii. Hazardous areas are defined by three main criteria: The type of hazard The likelihood of the hazard being present in flammable concentrations The ( auto) ignition temperature of the hazardous material

• • •

The hazard will be in the form of a gas, vapour, dust or fibre. Hazardous Area Classification (HAC) is as follows: Definitions of hazardous area are different as per IEC and NEC. NEC

IEC Zone 0

Highly Flammable for long period

DESRIPTION

Zone 1

Flammable during normal operation

Flammable atmosphere present intermittently (Typical 10 & 1000 hours / year).

Most Safer Zone

Flammable atmosphere present abnormally (typically as a result of a process fault condition) (Typically less than 10 hours / year).

Div 1

Div 2

Ex

• • • • Ex

Zone 2

DEFINITION Flammable atmosphere present continuously (Typically 1000 hours / year).

Zone 0 – Typical Areas (Continuous grade) Closed process vessels Storage tanks Closed containers Areas containing open tanks of volatile, flammable liquid Q. How to identify Zone 1 areas? Ans: 1. Flammable gas or vapour concentration is likely to exist in the air under normal operating conditions. 2. Flammable atmospheric concentration is likely to occur frequently because of maintenance, repairs or leakage. 3. Flammable liquid or vapour piping system (containing valves, meters, or screwed or flanged fittings) is in an inadequately ventilated area. 4. The area below the surrounding elevation or grade is such that flammable liquids or vapors may accumulate.

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Ex

Zone 1 – Typical Area • • • •

Imperfectly fitting peripheral seals on floating roof tanks. Inadequately ventilated pump rooms for flammable gas or volatile, flammable liquids. Oily waste water sewer / basins Loading / unloading gantries of hazardous products. Zone 2 – Typical Areas (Secondary grade)

Ex

•

• • • Ex

• • • • •

The system handling flammable liquid or vapour is in an adequately ventilated area and is so designed and operated that the explosive or ignitable liquids, Vapours or gases will normally be confined within closed containers or closed systems from which they can escape only during abnormal conditions such as accidental release of a gasket or packing The flammable vapours can be conducted to the location as through trenches, pipes or ducts Locations adjacent to Zone 1 areas Pressurized rooms where flammable gas / vapour can enter in the case of failure of positive mechanical ventilation Safe Areas – Typical areas The following locations are considered safe from the point of view of electrical installation Area where the piping system is without valves, fittings, flanges or similar appurtenances. Areas where flammable liquids or vapors are transported only in suitable containers or vessels. Areas where permanent ignition sources area present like area where combustion gases are present, for example flare pits,tips,other open flames 7 hot surfaces. Diesel Generator shed room /shed having adequate ventilation GT installation meeting the ventilation (12 ACPH), pressurization (0.5 mbar) and flange (not more than one pair of flanges inside the turbine room) requirements.

HAC Comparison

Ex

•

•

North America (NFPA / API/ NFPA 70E or NEC) • Hazardous Areas: • Division I- Z0 + Z1 • Division II- Z2 •

Hazardous Locations • Class I-Flammable Gases / Vapour • Class II- Combustible dust • Class III- Combustible fibers or flyings

•

Gas / vapour grouping • A, B, C, D, E, F & G

Japan • Hazardous Areas - Classes 1, 2 & 3 •

Gas / vapour groups - G1, G2, G3, G4, G5 & G6

An experienced process engineer’s judgement in visualizing leak scenarios and classifying hazardous areas is the most CRUCIAL factor in the HAC exercise

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HAC-RELEVANT INTERNATIONAL STANDARDS • • • • •

Ex

API RP 500- Area Classification of Petroleum Installations IEC 79-10 :1995 -Electrical Apparatus for Explosive Gas Atmospheres, part 10 Classification of hazardous areas IP Part 15, 1990- Area Classification Code for Petroleum Installations BS EN 60079-10, : 1996 -Electrical Apparatus for Explosive Gas Atmospheres, part 10 Classification of hazardous areas BS 5345, 1983-Selection, installation and maintenance of electrical apparatus for use in potentially explosive atmospheres (other than mining applications or explosive manufacturing), part 2, Recommendations for particular industrial situations

SELECTION OF ELECTRICAL EQUIPMENT IN HAZARDOUS AREAS •

Selection Criteria –

Gas Grouping (based on ignition energy)

–

Temperature Classification

–

Classified Zones

IEC Gas Grouping Mining

Surface Industry

Group I

Group II IIA

IIB

IIC

Propane

Ethylene

Hydrogen/Accetylene

180 Microjoules

60 Mircojoules

20 Mircojoules

Group A

Group B

Group C

Group D

Acetylene

Hydrogen

Ethylene

Propane

20 Mircojoules

20 Mircojoules

60 Mircojoules

180 Mircojoules

Methane

NEC Gas Grouping

Temperature Classes: Hot surfaces can ignite explosive atmospheres. To guard against this all Electrical Equipment intended for use in a potentially explosive atmosphere is classified according to maximum surface temp. it will reach in service. This temperature is normally based on a surrounding ambient temperature of 40°C (102°F).This temp. can then be compared to the ignition temp of the gas(es) which may come into contact with the equipment & a judgment reached as to the suitability of the equipment to be used in that area

T-Class

Max. Surface temperature in °C

T1

450°C

T2

300°C

T3

200°C

T4

135°C

T5

100°C

T6

85°C Dattatray K. Nikam Instrument Engineer

EX d typical marking: EEx d IIB T5 The bigger the T-number the lower is the ignition temperature of the hazard. So equipment to be installed in hazardous areas where the hazard has temperature class T5 or T6 must be ensured not to get hot. Electrical equipment is marked with a T-Class. The T-Class on the equipment states that the equipment will not provide an ignition capable surface hotter than the temperature represented by the stated T-Class. For equipment in hazardous areas, the bigger the T-Number on the equipment the less hot it will get. Ex

RECOMMENDED PROTECTION METHODS • TYPES OF PROTECTION EXPLOSION-PROTECTION METHODS / EQUIPMENT -Popular types

Ex-proof (Flameproof )(EX d) Intrinsically Safe (Ex i ) Increased Safety (Ex e ) Non-Sparking (Ex n ) Pressurization (Ex p )

-

OTHER TYPES OF EXPLOSION-PROTECTION –Not so Popular types

Powder filled Ex ‘q’ type Oil immersed Ex ‘o’ type Special Ex ‘s’ type

•

DEFINITIONS OF DIFFERENT PROTECTIONS 1. Ex‘d ‘Flameproof Equipment A type of protection in which the parts can ignite an explosive atmosphere are to be placed in an enclosure, which can withstand the pressure developed during internal explosion of an explosive mixture, and which prevents the transmission of the explosion to the explosive atmosphere surrounding the enclosure. US- Explosion-Proof, UK- Flame-Proof, GERMANY - Pressure-Proof - Assumption: • Flammable gases / vapours, if present in atmosphere will enter the enclosure • The apparatus will be selected, installed, operated and maintained within the acceptable ratings. The maintenance and use of FLP equipment shall be so that its safety will not be impaired, is the responsibility of the user • The electric circuit of the FLP equipment will have all required protection devices • Sparking which will ignite a flammable gas or vapour, may occur at any part of the equipment contained in the enclosure in normal operation due to an internal fault due to insulation failure, etc.

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- REQUIREMENTS: •

Contain internal explosion

• •

Explosion cannot be transmitted outside enclosure External temperature of enclosure below ignition temperature of surrounding gases

•

Similar to NEC® "explosion proof"

• •

Cable fittings must have 5 threads engaged Internal and external ground screw EX d typical marking: EEx d IIB T5

- Enclosures

Round junction box with cable Round junction box with cable glands glands

32 Amp 380v receptable

Control station start-stop

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2. Ex ‘e’ INCREASED SAFETY EQUIPMENT Electrical apparatus produces no sparks in normal operation and is conservatively designed to reduce changes of abnormal occurrences which could cause sparks of temperatures with sufficient energy to ignite a specific flammable atmosphere. - Construction Method: Stringiest construction methods to ensure that no sparks, excessive temperature are produced • Careful terminal design • Use of good quality insulation material • Use of special materials to protect the enclosure against impact, ingress of dust & moisture • Can be used for I, II A, B, C gas groups • Permitted for us in T1, T2, T3 classes only • Terminal with minimum IP 54 ingress protection - Requirements:







Must use high impact resistant materials FRP, or GRP will not hold static charge Cannot produce arcs or sparks Has special air and line leakage and creepage distances Use I EC non-loosen connection Minimum IP 54 ingress rating Control internal and external temperature. External should not exceed T6 (85°C) EX d typical marking: EEx e IIA T3

Increased safety fixture 18, 36 or 58

Round junction box with cable glands

16 amp, 24 v receptacle

Control station, start-

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JUNCTION BOX

Approved cable

Weatherpro of seal in

Approved locking type terminals

SPECIAL TERMINAL BOX No. of terminals is restricted by dissipated power per ckt.

Approved internal ground screw (4)

STRIPPING A CONNECTION THE CONDUCTORS

TERMINAL LOCK Torque in unlocked position

INCORRECT

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3. Ex ‘i’ INTRINSICALLY SAFE EQUIPMENT & CIRCUITS Electrical apparatus and its associated wiring which is located in the hazardous area has insufficient electrical or thermal energy under normal of abnormal condition to ignite the specific hazardous atmospheric mixture. “Simple Apparatus” is defined as an apparatus which does not generate power exceeding 1.2 V, 100mA, 25 mW or 20 µ J, such as thermocouples, RTD, Contact, terminal strips, junction boxes, etc. They are not required to be certified and connected to the intrinsic safety loops without approvals. Method:
Only electrical protective measure (protection technology by way of power limitation), the other protective techniques use mechanical means to prevent ignition from electrical faults (max. 30 volts or 50 mA)
Ex ‘i’ apparatus is the one which has all the circuits within intrinsically safe
Ex ‘i’ circuit is the one which has intrinsically safe barriers with Zenner diodes for power limitation
Minimum IP 20 ingress protection Ex ib: Equipment shall be incapable of causing ignition in normal operation, with a single fault and with the following safety factors: – –

1.5 in normal operation and with one fault 1.0 with one fault, if the equipment contains no unprotected switch contacts in parts likely to be exposed to a potentially explosive atmosphere and the fault is self-revealing

Ex ia: Equipment shall be incapable of causing ignition in normal operation, with a Two fault. EX i typical marking: EEx ia IIC T5

4. Ex ‘p’ PRESSURIZATION TYPE By maintaining positive pressure of clean air or inert gases inside an instrument enclosure with respect to an external atmosphere, the external atmosphere can not come in contact with sources if ignition inside. - PRESSURIZATION TYPE (Ex ‘p’) TYPES


Dynamic Pressurization (DP) or pressurization by continuos circulation of protective gas (purging) DP is a method of maintaining pressure in an enclosure in which after purging the protective gas is passed continuously through the enclosure at a pressure above that of the specified minimum and discharged to the outside atmosphere

Static Pressurization or pressurization with leakage compensation Air supplied & pressurized continuously from a non-hazardous area to avoid ingress of flammable gases / vapour inside the enclosure - Pressurized Equipment
Ingress protection minimum IP 4X
Over pressure 1.5 times or 0.2 kPa
Material of construction should be flame retardant, self- extinguishing and should not be affected by protective gas.


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5. Ex ‘n’ NON-SPARKING TYPE EQUIPMENT Nonincendive circuits may contain components which spark under normal operation, but the energy released by such components limited in normal operation to values incapable of causing ignition. Non-sparking circuits contain no open sparking components (such as provided with hermetic sealing) during normal operation. In short SUBSTANTIAL COST SAVING Equipment construction in such a way that in normal operation, it is incapable of igniting a surrounding explosive atmosphere and a fault incapable of causing ignition Hermetically sealed type Restricted breathing type Careful design of terminals Applications – Tools – Equipment








6. Ex ‘q’ POWDER FILLED TYPE EQUIPMENT
Equipment enclosure filled with quartz /sand so that in normal operating condition, any arc occurring within the enclosure of electrical equipment will not ignite the surrounding atmosphere


No ignition shall be caused either by flame or by excessive temperature of the surfaces of the enclosure




Enclosure constructional features: o High mechanical strength o Ingress protection o Powder filled o Insulation of enclosed equipment

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7. Ex ‘o’ OIL IMMERSED TYPE EQUIPMENT
Protection technique in which the equipment or its parts are immersed in oil in such a way that an explosive atmosphere which, may be above the oil or outside the enclosure cannot be ignited.


Oil used shall be mineral oil confirming to relevant standards




Constructional features: − Fully enclosed, leak-proof enclosure − Oil level indicator Transformers, Switch gears, Control gears




8. Ex‘s’ SPECIAL TYPE EQUIPMENT
This is a concept that has been adopted to permit the certification of those types of equipment which by their nature, do not comply with the constructional or other requirements specified for equipment with established types of protection but which, nevertheless, can be shown, wherever necessary, by test to be suitable for use in hazardous areas in prescribed zones
This concept permits flexibility on the part of certifying and assessment authorities in their approach to applications for certification of equipment the use of which would otherwise not permitted in hazardous areas on account of non-compliance with the requirements of standards for established types of protection. This allows flexibility of approach to innovative ideas and new designs, the development of which otherwise be obstructed.
Examples: − Factory sealed hand lamps, Encapsulation (Ex ‘m’ type), Gas detection apparatus

Equipment Code

Description

Suitable for zones...

Ex ia

Intrinsic safety 'ia'

0, 1, 2

Ex ib

Intrinsic safety 'ib'

1,2

Ex ic

Intrinsic Safety 'ic'

2

Ex d

Flameproof protection

1,2

Ex p

Purge/pressurized protection

1,2

Ex px

Purge/pressurized protection 'px'

1,2

Ex py

Purge/pressurized protection 'py'

1,2

Ex pz

Purge/pressurized protection 'pz'

2

Ex e

Increased safety

1,2

Ex m

Encapsulation

1,2

Ex ma

Encapsulation

0,1,2

Ex mb

Encapsulation

1.2

Ex o

Oil immersion

1,2

Ex q

Sand / powder (quartz) filling

1,2

Ex n

Type - n protection

2

Ex s

Special protection

Normally 1 and 2

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•

INGRESS PROTECTION (IP)

Ingress Protection (IP)

0 1 2 3 4 5 6 7 8

First Digit Protection against solid bodies No Protection Objects greater than 50 mm Objects greater than 12 mm Objects greater than 2.5 mm Objects greater than 1 mm Dust- Protected Dust- Tight -

Second Digit Protection against Liquid No Protection vertically dripped water Angled dripped water sprayed water splashes water water jets Heavy seas Effective immersion ( 1 meter ) Indefinite immersion.

NEMA Standards Type Type 1 Type 2 Type 3 Type 3R Type 3S Type 4 Type 4X

Description General Purpose – Indoor Drip - proof - Indoor Dust - tight, Rain - tight and Sleet (Ice) - resist - Outdoor Rain - proof and Sleet (Ice) - resistant - Outdoor Dust - tight, Rain - tight and Sleet (Ice) - proof-Outdoor Water - tight and Dust - tight - Indoor and Outdoor Water - tight Dust - tight and Corrosion resistant - Indoor and Outdoor

Type 5 Type 6

- Superseded by Type 12 for control apparatus Submersible, Water - tight, Dust - tight and Sleet (Ice) - resistant - Indoor and Outdoor Class I, Group A, B, C or D - Indoor Hazardous Locations, Air Break Equipment Class I. Group A, B, C or D - Indoor Hazardous Locations, Oil - immersed

Type 7 Type 8 Type 9 Type 10 Type 11

Class II, Group E, F or G - Indoor Hazardous Locations, Air Break Equipment Bureau of Mines Corrosion - resistant and Drip - proof Oil - immersed - Indoor Equipment

Type 12 Type 13

Industrial use, Dust - tight and Drip - tight - Indoor Oil - tight and Dust - tight - Indoor

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Indian Standards for Various Protection Techniques IS 5571 Guide For Selection Of Electrical Equipment For Hazardous Areas IS 5572 –Part I Classification of Hazardous Areas for Electrical Installations IS 13408 Part I, II, III Code of Selection, Installation and Maintenance of Electrical Apparatus for Use in Explosive Atmospheres IS 8239 Classification of Maximum Surface Temperature of Electrical Equipment for Use In Explosive Atmospheres IS 6381 Construction and testing of Electrical Apparatus with type of protection ‘e’ IS 2148 Flameproof Enclosures of Electrical Apparatus IS 13346 General Requirements for Electrical Apparatus for Explosive Gas Atmospheres IS 5780 Specification For Intrinsically Safe Electrical Apparatus and Circuits IS 8240 Guide for Electrical Equipment for Explosive Atmospheres IS 2147 Degrees of Protection Provided by Enclosures For Low Voltage Switch Gear & Control Gear IS 4691 Degrees of Protection Provided by Enclosures For Rotating Electrical Machinery IS 8241 Methods of Marking for Identifying Electrical equipment for Explosive Atmospheres IS 8224 Specification for Electric Lighting fitting for Explosive Atmospheres IS 8289 Electrical Equipment with Type of Protection ‘n’ IS 7389 Specification for Pressurized Enclosures IS 2206 (PART I,III)

Specification for Flame proof Electric Light Fixtures

STATUTORY REGULATIONS & APPROVAL REQUIREMENTS Approval / Testing Agencies CMRI (Central Mining Research Institute), Dhanbad, BIHAR CCoE (Chief Controller of Explosives), Nagpur BIS (Bureau Of Indian Standards) DGMS (Director General Mine Safety), Dhanbad, BIHAR DGFASLI (Director General of Factory Advice Service and Labour Instituites), Mumbai

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Summary  Types of Enclosure Protection

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 Enclosure Rating

 IP Protection

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 Certification Code

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 Types of Electrical Equipment Suitable for Use in Potentially Explosive Atmosphere

Useful References Hazardous Area Classification & Selection of Electrical Equipment for Flammable Atmospheres by P.G.Sreejith (www.cholaaxa.com) Flammable Facts MTLFF 03 Explosive Facts By STAHL www.medc.com

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Types of Electrical Equipment Suitable for use in Potentially Explosive Atmospheres Different techniques are used to prevent electrical equipment from igniting explosive atmospheres. There are restrictions on where these different types of equipment can be used as follows :

.

European IEC - Area USA - Area of use Area of use of use Designation Designation Designation Standard Standard Standard Zones 1 & 2 Zones 1 & 2 Class 1 Divisions 1 & 2 EExd Exd UL1203 EN50018 IEC60079-1

Flameproof Enclosure – An enclosure used to house electrical equipment, which when subjected to an internal explosion will not ignite a surrounding explosive atmosphere. Intrinsic Safety – A Zones 0, 1 & 2 technique whereby electrical EExi energy is limited such that any EN50020 sparks or heat generated by electrical equipment is sufficiently low as to not ignite an explosive atmosphere. Increased Safety – This Zones 1 & 2 equipment is so designed as to EExe eliminate sparks and hot EN50019 surfaces capable of igniting an explosive atmosphere. Purged and Pressurised – Zones 1 & 2 Electrical equipment is housed EExp in an enclosure which is initially EN50016 purged to remove any explosive mixture, then pressurised to prevent ingress of the surrounding atmosphere prior to energisation. Encapsulation – A method of Zones 1 & 2 exclusion of the explosive EExm atmosphere by fully EN50028 encapsulating the electrical components in an approved material. Oil Immersion – The Zones 1 & 2 electrical components are EExo immersed in oil, thus excluding EN50015 the explosive atmosphere from any sparks or hot surfaces. Powder Filling – Equipment is Zones 1 & 2 surrounded with a fine powder, EExq such as quartz, which does not EN50017 allow the surrounding atmosphere to come into contact with any sparks or hot surfaces.

Zones 1 & 2 Exi IEC60079-11

Class 1 Divisions 1 & 2 UL913

Zones 1 & 2 Exe IEC60079-7

Zones 1 & 2 Exp IEC60079-2

Class 1 Divisions 1 & 2 NFPA496

Zones 1 & 2 Exm IEC60079-18

Zones 1 & 2 Exo IEC60079-6

Class 1 Division 2 UL698

Zones 1 & 2 Exq IEC60079-5

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Non-sparking – Sparking Zone 2 Zone 2 contacts are sealed against EExn Exn ingress of the surrounding EN50021 IEC60079-15 atmosphere, hot surfaces are eliminated. Special Protection – Zones 0, 1 & 2 Zones 0, 1 & Equipment is certified for use *Exs 2 in a Potentially Explosive Exs Atmosphere but does not conform to a type of protection listed above.

.

* This type of protection is only recognised by National Authorities, not as a European-wide type of protection.

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Selection, Installation and Maintenance of Electrical Equipment Intended for use in Potentially Explosive Atmospheres International and national standards are published giving details of requirements for the safe use of Electrical Equipment in Potentially Explosive Atmospheres as follows : International

. General Recommendations Classification of Hazardous Areas Inspection and Maintenance of Electrical Equipment

U.K.

U.S.A.

EC60079-14

BS5345:Part N.E.C. Chapter 5 1

IEC60079-10

.

N.E.C. Chapter 5

IEC60079-1

Requirements for Flameproof Enclosures

IEC60079-14

BS5345:Part N.E.C. Chapter 3 5

Requirements for Intrinsically Safe Equipment

IEC60079-14

BS5345:Part N.E.C. Chapter 4 5

Requirements for Increased Safety Equipment

IEC60079-14

BS5345:Part N.E.C. Chapter 6 5

Requirements for Purged and Pressurised Equipment

IEC60079-14

BS5345:Part N.E.C. Chapter 5 5

Requirements for Non-Sparking Equipment

IEC60079-14

BS5345:Part 7

Requirements for Equipment with Special Protection

IEC60079-14

BS5345:Part 8

.

MEDC advise that all Explosion-proof electrical equipment is maintained, by suitably trained personnel, in accordance with the Manufacturers' recommendations. Any spare parts used should be purchased from the original Manufacturer and repairs should be carried out by the Manufacturer or under his supervision, in order that the item remains in conformance with the certification documents.

The Certification Process All Electrical Equipment, intended for use in a Potentially Explosive Atmosphere, should be certified as suitable for such use. The methods of obtaining certification differ in detail, see below, between each certifying body or group of bodies (e.g. CENELEC). Basically this process consists of supplying a representative sample of the equipment along with a set of drawings to a recognised test/certification body e.g. BASEEFA who in turn test the equipment against a recognised Standard e.g. EN50018 and issue a Certificate. The user of the equipment can then refer to this Certificate to enable him to safely put the item into service in a zone appropriate to the Certification. European Practice – after 1st July 2003 After the above date the ATEX Directive comes into force throughout the EEC. This becomes a mandatory requirement for all equipment intended for use in a hazardous area. The fundamental difference between current practice and ATEX certification is that ATEX addresses the essential

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safety requirements for hazardous area equipment and uses Standards as part of the method of conforming to these. Amongst other documentation required by certifying authorities will be Technical Manuals in order that the user is informed of installation methods etc. ALL EQUIPMENT, BOTH ELECTRICAL AND MECHANICAL, INTENDED TO BE PUT INTO SERVICE WITHIN THE EEC AFTER 1ST July 2003, WILL HAVE TO HAVE BEEN CERTIFIED IN ACCORDANCE WITH THE ATEX DIRECTIVE. In practice this means re-certification of all currently certified electrical equipment. MEDC have started this process and all relevant equipment will be covered by the implementation date of 1st July 2003. It should be noted also that MECHANICAL equipment is covered by the ATEX Directive so for the first time items such as gearboxes will have to carry ATEX certification. The equipment coding will be as the current practice plus an additional code as follows: ExII2G i.e. Ex – Explosion proof in accordance with ATEX. II – Group II surface industries. 2 – category 2 equipment (suitable .....for use in Zone 1) note:

Category 1 is suitable for Zone 0. Category 3 is suitable for Zone 2.

G – suitable for atmospheres containing gas ( D is suitable for atmospheres containing dusts). Equipment will be CE marked when certified to ATEX. European Practice – Current – until 30th June 2003 The method is basically as above. In addition all electrical equipment intended for use in the European Economic Community (EEC) must comply with Electromagnetic Compatibility regulations (EMC) and manufacturers must issue, on request, an EC Declaration of Conformity in accordance with the EMC regulations. When certified, an item of equipment and its' certificate, carry a code e.g. EExdIIBT4. This can be broken down as follows: E – European certificate in accordance with harmonised standards Ex – Explosion-proof electrical equipment d – flameproof enclosure type of protection II – Group II surface industries B – gas group B T4 – temperature class T4 (135 degrees centigrade surface temperature).

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North American Practice Sample equipment and supporting documentation are submitted to the appropriate authority e.g. .U.L., F.M., C.S.A. The equipment is tested in accordance with relevant standards for explosion protection and also for general electrical requirements e.g. light fittings. After successful testing a listing is issued allowing the manufacturer to place the product on the market. The product is marked with the certification details such as the gas groups A,B,C,D the area of use e.g. Class 1 Division 1

World-wide Certification Most countries outside Europe or North America use the IEC Standards as a basis for their own national standards. The Russian Federation certifies equipment to GOST standards, these closely follow CENELEC practice. There is a scheme in place which will when fully adopted allow for internationally recognised certification to become a reality, this is the IEC EX SCHEME. This uses the IEC standards and IEC recognised test and certification bodies to issue mutually recognised test reports and certificates. The scheme is in its infancy and its level of success cannot yet be measured.

Ingress Protection 2 digits are used to denote the level of ingress protection that a piece of apparatus enjoys :– (The first digit denotes the level of protection against solid objects and the second against liquids)

.

.

Solids

.

Liquids

0 No protection.

0 No protection.

1 Protected against solid objects up to 50mm, e.g. hands. 2 Protected against solid objects up to 12mm, e.g. fingers. 3 Protected against solid objects up to 2.5mm, e.g. tools. 4 Protected against solid objects over 1mm, e.g. wires. 5 Protected against dusts. (No harmful deposits). 6 Totally protected against dust.

1 Protected against vertically falling drops of water. 2 Protected against water spray up to 15 degrees from vertical. 3 Protected against water spray up to 60 degrees from vertical. 4 Protected against water sprays from all directions. 5 Protected against water jets from all directions. 6 Protected against strong water jets from all directions, e.g. Offshore.

.

7 Protected against immersion between 15cm and 1m in depth. 8 Protected against long immersion under pressure.

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North American practice is to use NEMA standards to describe ingress protection, i.e.: NEMA NEMA NEMA NEMA

3 is similar to IP 54 4 is similar to IP 55 4x is similar to IP 56 6 is similar to IP 67

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