Hazardous Area Classification

Dattatray K. Nikam Instrument Engineer

Hazardous Area Classification

LET US MAKE OUR REFINERIES SAFER!!!

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


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. iii. Safe selection (& optimisation) of Electrical Equipment.

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 DESRIPTION DEFINITION

Zone 0 Highly Flammable for long period Flammable atmosphere present continuously (Typically 1000 hours / year).

Div 1

Zone 1 Flammable during normal operation

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

Div 2 Zone 2

Most Safer Zone Flammable atmosphere present abnormally (typically as a result of a process fault condition) (Typically less than 10 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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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)

• 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

• 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

• 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 Methane

Propane Ethylene Hydrogen/Accetylene

180 Microjoules 60 Mircojoules 20 Mircojoules

NEC Gas Grouping

Group A Group B Group C Group D

Acetylene Hydrogen Ethylene Propane

20 Mircojoules 20 Mircojoules 60 Mircojoules 180 Mircojoules

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

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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. 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

• 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.

Powder filled Ex ‘q’ type

Oil immersed Ex ‘o’ type

Special Ex ‘s’ type

EX d typical marking: EEx d IIB T5

Ex


- 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

- Enclosures

EX d typical marking: EEx d IIB T5

Round junction box with cable

glands

32 Amp 380v receptable Control station start-stop

Round junction box with cable

glands


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-


JUNCTION BOX

Weatherpro

of seal in Approved

cable

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

INCORRECT

TERMINAL LOCK

Torque in unlocked position


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.


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


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


• INGRESS PROTECTION (IP)

First Digit Second Digit Ingress Protection

(IP) Protection against solid bodies Protection against Liquid

0 No Protection No Protection

1 Objects greater than 50 mm vertically dripped water

2 Objects greater than 12 mm Angled dripped water

3 Objects greater than 2.5 mm sprayed water

4 Objects greater than 1 mm splashes water

5 Dust- Protected water jets

6 Dust- Tight Heavy seas

7 - Effective immersion ( 1 meter )

8 - Indefinite immersion.

NEMA Standards

Type Description

Type 1 General Purpose – Indoor

Type 2 Drip - proof - Indoor

Type 3 Dust - tight, Rain - tight and Sleet (Ice) - resist - Outdoor

Type 3R Rain - proof and Sleet (Ice) - resistant - Outdoor

Type 3S Dust - tight, Rain - tight and Sleet (Ice) - proof-Outdoor

Type 4 Water - tight and Dust - tight - Indoor and Outdoor

Type 4X Water - tight Dust - tight and Corrosion resistant - Indoor and Outdoor

Type 5 - Superseded by Type 12 for control apparatus -

Type 6 Submersible, Water - tight, Dust - tight and Sleet (Ice) - resistant - Indoor and Outdoor

Type 7 Class I, Group A, B, C or D - Indoor Hazardous Locations, Air Break Equipment

Type 8 Class I. Group A, B, C or D - Indoor Hazardous Locations, Oil - immersed

Type 9 Class II, Group E, F or G - Indoor Hazardous Locations, Air Break Equipment

Type 10 Bureau of Mines

Type 11 Corrosion - resistant and Drip - proof Oil - immersed - Indoor Equipment

Type 12 Industrial use, Dust - tight and Drip - tight - Indoor

Type 13 Oil - tight and Dust - tight - Indoor


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


Summary

� Types of Enclosure Protection


� Enclosure Rating

� IP Protection


� Certification Code


� 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


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 -

Area of use

Designation

Standard

IEC - Area

of use

Designation

Standard

USA - Area of use

Designation

Standard

Flameproof Enclosure – An

enclosure used to house

electrical equipment, which

when subjected to an internal

explosion will not ignite a

surrounding explosive

atmosphere.

Zones 1 & 2

EExd

EN50018

Zones 1 & 2

Exd

IEC60079-1

Class 1 Divisions 1 & 2

UL1203

Intrinsic Safety – A

technique whereby electrical

energy is limited such that any

sparks or heat generated by

electrical equipment is

sufficiently low as to not ignite

an explosive atmosphere.

Zones 0, 1 & 2

EExi

EN50020

Zones 1 & 2

Exi

IEC60079-11

Class 1

Divisions 1 & 2

UL913

Increased Safety – This

equipment is so designed as to

eliminate sparks and hot

surfaces capable of igniting an

explosive atmosphere.

Zones 1 & 2

EExe

EN50019

Zones 1 & 2

Exe

IEC60079-7

Purged and Pressurised –

Electrical equipment is housed

in an enclosure which is initially

purged to remove any

explosive mixture, then

pressurised to prevent ingress

of the surrounding atmosphere

prior to energisation.

Zones 1 & 2

EExp

EN50016

Zones 1 & 2

Exp

IEC60079-2

Class 1

Divisions 1 & 2

NFPA496

Encapsulation – A method of

exclusion of the explosive

atmosphere by fully

encapsulating the electrical

components in an approved

material.

Zones 1 & 2

EExm

EN50028

Zones 1 & 2

Exm

IEC60079-18

Oil Immersion – The

electrical components are

immersed in oil, thus excluding

the explosive atmosphere from

any sparks or hot surfaces.

Zones 1 & 2

EExo

EN50015

Zones 1 & 2

Exo

IEC60079-6

Class 1

Division 2

UL698

Powder Filling – Equipment is

surrounded with a fine powder,

such as quartz, which does not

allow the surrounding

atmosphere to come into

contact with any sparks or hot

surfaces.

Zones 1 & 2

EExq

EN50017

Zones 1 & 2

Exq

IEC60079-5


Non-sparking – Sparking

contacts are sealed against

ingress of the surrounding

atmosphere, hot surfaces are

eliminated.

Zone 2

EExn

EN50021

Zone 2

Exn

IEC60079-15

.

Special Protection –

Equipment is certified for use

in a Potentially Explosive

Atmosphere but does not

conform to a type of protection

listed above.

Zones 0, 1 & 2

*Exs

Zones 0, 1 &

2

Exs

* This type of protection is only recognised by National Authorities, not as a

European-wide type of protection.


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 U.K. U.S.A.

General Recommendations EC60079-14

BS5345:Part

1

N.E.C. Chapter

5

Classification of Hazardous Areas IEC60079-10 .

N.E.C. Chapter

5

Inspection and Maintenance of

Electrical Equipment IEC60079-1

Requirements for Flameproof

Enclosures IEC60079-14

BS5345:Part

3

N.E.C. Chapter

5

Requirements for Intrinsically

Safe Equipment IEC60079-14

BS5345:Part

4

N.E.C. Chapter

5

Requirements for Increased

Safety Equipment IEC60079-14

BS5345:Part

6

N.E.C. Chapter

5

Requirements for Purged and

Pressurised Equipment IEC60079-14

BS5345:Part

5

N.E.C. Chapter

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


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).


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.

1 Protected against vertically falling

drops of water.


up to 12mm, e.g. fingers.

2 Protected against water spray up

to 15 degrees from vertical.


up to 2.5mm, e.g. tools.

3 Protected against water spray up to

60 degrees from vertical.


over 1mm, e.g. wires.

4 Protected against water sprays from

all directions.

5 Protected against dusts.

(No harmful deposits).

5 Protected against water jets from

all directions.

6 Totally protected against dust. 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.


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

NEMA 3 is similar to IP 54


NEMA 4x is similar to IP 56


Hazardous Area Classification

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