Hazardous Area

(1)

GUIDE

TO

HAZARDOUS AREA

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Electrical Equipment In

Hazardous Atmospheres

Basic Principles

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Topics Covered

 _{Principles of Explosion Protection}_{Principles of Explosion Protection}  _{Zones of Use}_{Zones of Use}

 _{Gas Groups}_{Gas Groups}

 _{Temperature Classes}_{Temperature Classes}

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Conditions For An Explosion

 _{Three simultaneous conditions are}_{Three simultaneous conditions are}

required and are often shown in the form

of an ignition triangle.

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Ignition or Fire Triangle

 In Order for Combustion (Fire or Explosion) to _{In Order for Combustion (Fire or Explosion) to} Occur, 3 elements must be Present:

Occur, 3 elements must be Present:

– FuelFuel

– Source of IgnitionSource of Ignition – Oxygen or Air Oxygen or Air

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Ignition Triangle

Fuel (Gas, Vapor + Dust + Fibre & Flyings)

+

Oxygen

Ignition Source

+

(Sparks + Hot surface)

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Ignition Triangle

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Primary Explosion Protection

 _{Elimination of Ignition Source, or}_{Elimination of Ignition Source, or} Oxygen

Fuel Ignition Source

Oxygen

Fuel

 _{Elimination of Fuel, or}

(9)

Ignition Source (Energy)

 _Heat_Heat

– Light Fixtures (Lamp / Ballast)_{Light Fixtures (Lamp / Ballast)}

 _{Arcing / Sparking}_{Arcing / Sparking}

– Switches / Relays_{Switches / Relays}

– Plugs and Receptacles_{Plugs and Receptacles}

 _{Potential Source}_{Potential Source}

– Terminals_Terminals – Tools_Tools

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Hazardous Area Zones

 _{Three Zones}_{Three Zones}

– How Likely?_{How Likely?}

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Hazardous Area Zones

0

1

2

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Examples of Zoning

 _{Petrol Station Forecourt}_{Petrol Station Forecourt}

Safe Area

Zone 2 Zone 1

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Examples of Zoning

 _{LPG Tanker}_{LPG Tanker} Zone 0 Zone 1 Zone 2

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Definition of Zones

 _{Zone 0}_{Zone 0}

Zone in which an explosive atmosphere is

continuously present, or present for long

periods.

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Definition of Zones

likely to occur in normal operation.

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Definition of Zones

not likely to occur in normal operation, and if

it occurs it will exist only for a short time.

Sometimes referred to as:

Sometimes referred to as: “The “The remotely Hazardous Area”

remotely Hazardous Area”

(17)

Definition of Zones

Descriptions How Likely? For how long?

Zone 0 Zone 1 Zone 2 Very likely Likely Not Likely > 1000 hrs/year > 10 < 1000 hrs/yr < 10 hrs /year

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Electrical Equipment In

Hazardous Area

 _{Concentrates on the ignition source}_{Concentrates on the ignition source}  _{Different methods employed for}_{Different methods employed for}

prevention

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Principles Involved

 _{Containment of explosion within}_{Containment of explosion within}

apparatus

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Types of Protection and

Explosion Protection Symbol

 _{Containment of Explosion in}_{Containment of Explosion in}

Apparatus

– Flameproof (Ex d)_{Flameproof (Ex d)}

Hazardous Gas, Vapor, Dust etc.

(21)

Methods Of Protection That

“Contain an Explosion”

Housing “Contains” Housing “Contains” Explosion Explosion Metal To Metal Joints

Metal To Metal Joints Extra Care must be Extra Care must be

Taken to prevent Taken to prevent

Corrosion Corrosion

All Bolts Must All Bolts Must

Be Installed Be Installed & & Tightened Tightened Correctly Correctly

(22)

Flame-paths

Flame-path Flame-path

Enclosure Wall

• Joints on covers or openings

are protected by the ‘flame-path’

• Does not prevent explosion occurring

but contains the explosion and prevents ignition of surrounding atmosphere.

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Flame-paths

• Flame paths Must be free from corrosion !!!

• All bolts Must be tightened down correctly !!!

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Increased Safety (Exe) Terminal Box

Flameproof Enclosure (Exd)

Ex de certified

(25)

Cables connected To Exe Terminal block

Enclosure Wall

• Lamp and sparking

devices are contained within flameproof enclosure

• Wiring enters enclosure via

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Types of Protection and Symbol

 _{Avoidance of ignition condition}_{Avoidance of ignition condition}

Hazardous Area

 Increased Safety (Ex e)  Non - Sparking (Ex N, n)

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Increased Safety

 _{Additional Protection Is Given to}_{Additional Protection Is Given to}

Components to Prevent Excessive Components to Prevent Excessive

Temperatures or Arcs and Sparks Temperatures or Arcs and Sparks

Method Of Protection

Ex “e”

_{Ex “e”}

X

_{Terminals Cannot Vibrate Loose, Deform}

Conductors and have Increased Creepage and Clearances

_{Other Factors}

High Temperatures or

(28)

Method Of Protection

Ex “q”

_{Ex “q”}

 _{Powder or Sand Filled}_{Powder or Sand Filled}

– The Enclosure Is Filled With Sand or _{The Enclosure Is Filled With Sand or} Ground Glass

Ground Glass

– Displaces Hazardous Gases_{Displaces Hazardous Gases}

– Isolates Hot or Arcing Components_{Isolates Hot or Arcing Components} – Zone 1 and 2 Applicable_{Zone 1 and 2 Applicable}

X

(29)

Types of Protection and Explosion Protection

Symbol

 _{Prevention of fuel coming into contact}_{Prevention of fuel coming into contact}

with ignition source

- Oil Immersion (Ex o) - Powder Filling (Ex q)

- Encapsulation (Ex m) - Potted capacitors, ballast, etc.

- Oil filled capacitors, windings, etc. - Electronic Ballast, capacitors, etc

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What type of Protection to use?

 _{The hazardous zones are decided by local}_{The hazardous zones are decided by local}

authorities,

authorities, not_not the equipment manufacturer._{the equipment manufacturer.}  _{Different Protection methods are suitable for}_{Different Protection methods are suitable for}

different zones.

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Gas Groups

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Gas Groups

 _{Gas Group II is further sub-divided:-}_{Gas Group II is further}

sub-divided:--

- IIA (Propane)_{IIA (Propane)}

-

- IIB (Ethylene)IIB (Ethylene)

-- IIC (Hydrogen & Acetylene)_{IIC (Hydrogen & Acetylene)} • Qualifying Properties

– Maximum Explosion Pressures

(33)

 Any apparatus (lighting fixture) marked for Gas Any apparatus (lighting fixture) marked for Gas Group II or IIC can be used in

Group II or IIC can be used in ALLALL Gas Group Gas Group area ie. IIA, IIB & IIC

area ie. IIA, IIB & IIC

Gas Groups

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 _{Any apparatus suitable for Gas Group}_{Any apparatus suitable for Gas Group}

IIC can be used where Gas Group IIB or

IIA is required

 _{Any apparatus suitable for Gas Group}_{Any apparatus suitable for Gas Group}

IIA cannot be used where Gas Group IIB

or IIC is required

Gas Groups

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Gas Groups

II A II B II C II A ➜    II B ➜    II C ➜   

Gas Group of the Area/Zone

A pp ar at us G as G ro up

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Temperature Class

(37)

Temperature Class

 _{Gases are also grouped according to}_{Gases are also grouped according to}

temperature above which a gas will

instantly ignite. Called the ‘ignition

temperature’ of the gas.

 _{Apparatus (luminaire) must have a}_{Apparatus (luminaire) must have a}

maximum permissible surface temperature

which is below ignition temperature of gas.

(38)

What is the Ignition

Temperature

of the Gas/Dust Present?

 T-Rating (Marked on the Fixture)_{T-Rating (Marked on the Fixture)}

It is the Maximum Operating Temperature range of a Luminaire

or Fixture

T-Ratings

 _{Must Be Below the Ignition Temp of the}

Gas / Dust Present

 _{Example: If gas present has ignition temp of}

(39)

Temperature Class

Temperature Class Maximum Surface Temperature

T1 T2 T3 T4 T5 T6 85 ºC 100 ºC 135 ºC 200 ºC 300 ºC 450 ºC

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Ingress Protection

1st Digit Degree of Protection (Dust)

2nd Digit Degree of Protection (Liquids)

0 No protection 0 No protection

1 Large foreign bodies 1 Drops of condensed water 2 Ingress of medium sized

foreign bodies.

2 Liquid falling at angle up to 15 degrees from vertical. 3 Ingress of foreign bodies >

2.5mm dia.

3 Rain falling at angle up to 60 degrees from vertical. 4 Ingress of foreign bodies >

1mm dia.

4 Protection against liquid splashing .

5 Dust sufficient to interfere with operation.

5 Water projected by nozzle from any direction.

6 Complete protection against dust.

6 Conditions on ships decks.

7 7 Immersion in water.

8 8 Indefinite immersion in

water as agreed with customer.

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Explosion Protection Category

Coding

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Explosion Protection Category

Approved to ATEX Directive Group II, Category 2, G=Gas, D=Dust

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Explosion Protection Category

Coding: Ex eqm II T4

“q” = Powder Filling (High Frequency Electronic Ballast) “m” = Encapsulation (Isolating Device)

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Explosion Protection Category

 _{II 2GD Ex eqm II T4}_{II 2GD Ex eqm II T4}

– _{This means that the product has been}_{This means that the product has been}

certified to ATEX Directive Category 2 for certified to ATEX Directive Category 2 for

Gas & Dust application and is suitable Gas & Dust application and is suitable

– for use in zone 1 and zone 2 areas,_{for use in zone 1 and zone 2 areas,}

– for use in Gas groups IIA, IIB or IIC_{for use in Gas groups IIA, IIB or IIC}

– and for gases with ignition temperatures _{and for gases with ignition temperatures}

classified as T4 (less than 135 degC) classified as T4 (less than 135 degC)

(45)

ATEX versus CENELEC (EN)

CENELEC

ATEX

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

(46)

World Standards

(47)

European & IEC

versus

American Standards

vs

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Methods Of Protection That

“Contain an Explosion”

Metal Explosion Proof Enclosure Miniature Explosion Proof Housing

(49)

Types of Protection and

Explosion Protection Symbol

 _{Exclusion of Fuel From Atmosphere}_{Exclusion of Fuel From Atmosphere}

– Pressurization _{Pressurization} Ex pEx p

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• Class I Test Gas

➢ _{Group A Acetylene}

➢ _{Group B Hydrogen or Gases of Equiv. Hazard} ➢ _{Group C Ethylene} ➢ _{Group D Propane}

Nature of Hazardous

Substance

NEC Gas Groups

• Qualifying Properties

–Maximum Explosion Pressures

(51)

NEC Class I Locations

T Codes (

identification numbers)identification numbers)

Identification Number T1 T2 T2A T2B T2C T2D T3 T3A T3B T3C T4 T4A T5 T6 Max. Temp. Degrees C 450 300 280 260 230 215 200 180 165 160 135 120 100 85 Max. Temp. Degrees F 842 572 536 500 446 419 392 356 329 320 275 248 212 185

(52)

Temperature Class

T1 T2 T3 T4 T5 T6 T1 ➜      T2 ➜      T3 ➜      T4 ➜      T5 ➜      T6 ➜     

Temperature Classification of Zone

A pp arat us T em pera tu re C la ss

(53)

Temperature Class

 _{T6 apparatus is suitable for use in a T5, T4,}_{T6 apparatus is suitable for use in a T5, T4,}

etc. to T1 areas

 _{T2 apparatus is suitable for use in T2 and}_{T2 apparatus is suitable for use in T2 and}

T1 areas only

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Primary Explosion Protection

 _{Elimination of Fuel}_{Elimination of Fuel}

Oxygen

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Primary Explosion Protection

 _{Elimination of Oxygen}_{Elimination of Oxygen} Oxygen

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What is the Classification

of the Hazardous

Location?

 Class - Type of Fuel Potentially Present_{Class - Type of Fuel Potentially Present}

– Class I Class I - Gases, Vapors- Gases, Vapors – Class II - Ignitable DustsClass II - Ignitable Dusts – Class III - Fibers & FlyingsClass III - Fibers & Flyings

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(Gases or Vapors)

 PetrochemicalPetrochemical  RefineriesRefineries

 Steel MillsSteel Mills

 Chemical PlantsChemical Plants  Oil & GasOil & Gas

(Production)

 Sewage Sewage Treatment

Treatment

 _{Tank Farm}_{Tank Farm}  _{Fuel Service}_{Fuel Service}  _Aircraft_Aircraft

Hangers

 _{Paint Spray}_{Paint Spray}  _{Power Plants}_{Power Plants}

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Class II (Ignitable Dusts)

 PharmaceuticalPharmaceutical  Mines Mines

 Grain SilosGrain Silos

 Coal Fired Power PlantsCoal Fired Power Plants

 Food Processing (Flour, Cocoa, etc.)Food Processing (Flour, Cocoa, etc.)  Fertilizer PlantsFertilizer Plants

 Metal GrindingMetal Grinding  Pulp & PaperPulp & Paper

(59)

Class III (Fibers & Flyings)

 Textile MillsTextile Mills

 Rope Manufacturing_{Rope Manufacturing}  Lumber & Saw Mills_{Lumber & Saw Mills}  Cotton GinsCotton Gins

 Cotton Seed Mills_{Cotton Seed Mills}

 Flax Processing Plants_{Flax Processing Plants}

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Occurrence of Hazard

 Division 1 / Zone 0 and 1Division 1 / Zone 0 and 1

– Hazardous Substance Present Under Normal Conditions.Hazardous Substance Present Under Normal Conditions.

Open SystemOpen System

Using Flammable Liquid to Manufacture End ProductUsing Flammable Liquid to Manufacture End Product

 Division 2 / Zone 2Division 2 / Zone 2

– Hazardous Substance Present Only Under Abnormal Conditions.Hazardous Substance Present Only Under Abnormal Conditions.

Closed SystemClosed System Storage TanksStorage Tanks

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Principles Involved

 _{Limitation of energy in system to safe}_{Limitation of energy in system to safe}

level

(62)

Types of Protection and

Explosion Protection Symbol

 _{Energy Limitation}_{Energy Limitation}

(63)

Ex i - Intrinsic Safety (EN 50020)

 _{Circuit is controlled to reduce potential spark}_{Circuit is controlled to reduce potential spark}

energy to below that which would ignite any

flammable gas present.

 _{Zenner barriers are used to isolate the}_{Zenner barriers are used to isolate the}

intrinsic circuit from non protected circuits

 _{This includes the occurrence of:-}_{This includes the occurrence}

of:-– iaia -- 2 fault conditions2 fault conditions – ibib -- 1 fault condition1 fault condition

(64)

Potentially Explosive Atmosphere

 _{An area in which there can be a flammable}_{An area in which there can be a flammable}

gas, liquid or vapour present at some point

in time.

(65)

Hazardous Areas

 _{An area containing a potentially explosive}_{An area containing a potentially explosive}

atmosphere, which, if ignited, could give rise

to damage to property or injury to persons.