Hazardous Area

GUIDE TO HAZARDOUS AREA

Electrical Equipment In Hazardous Atmospheres Basic Principles

Topics Covered     

Principles of Explosion Protection Zones of Use Gas Groups Temperature Classes Explosion Protection Categories

Conditions For An Explosion  Three simultaneous conditions are required and are often shown in the form of an ignition triangle.

!

Ignition or Fire Triangle  In Order for Combustion (Fire or Explosion) to Occur, 3 elements must be Present: – Fuel – Source of Ignition – Oxygen or Air

Ignition Triangle Oxygen

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

=

+ Ignition Source (Sparks + Hot surface)

Ignition Triangle

Primary Explosion Protection  Elimination of Ignition Source, or Oxygen  Elimination of Fuel, orOxygen  Elimination Oxygen

Fuel

Ignition Source

Ignition Source (Energy)  Heat – Light Fixtures (Lamp / Ballast)

 Arcing / Sparking – Switches / Relays – Plugs and Receptacles

 Potential Source – Terminals – Tools

Hazardous Area Zones  Three Zones – How Likely? – For How Long?

Hazardous Area Zones 2 1 0

Safe Area

Examples of Zoning  Petrol Station Forecourt Safe Area

Zone 2 Zone 1

Examples of Zoning  LPG Tanker

Zone 2 Zone 1

Zone 0

Definition of Zones  Zone 0 Zone in which an explosive atmosphere is continuously present, or present for long periods. How Likely? - very likely

For How Long? > 1000 hrs/yr

Definition of Zones  Zone 1 Zone in which an explosive atmosphere is likely to occur in normal operation. How Likely? - likely

For How Long? >10 hrs < 1000 hrs/yr

Definition of Zones  Zone 2 Zone in which an explosive atmosphere is not likely to occur in normal operation, and if it occurs it will exist only for a short time. Sometimes referred to as: “The remotely Hazardous Area” How Likely? - Unlikely

For How Long? < 10 hrs/yr

Definition of Zones - Occurrence of Gas /Vapor & for How long Descriptions

How Likely?

For how long?

Zone 0

Very likely

> 1000 hrs/year

Zone 1

Likely

> 10 < 1000 hrs/yr

Zone 2

Not Likely

< 10 hrs /year

Electrical Equipment In Hazardous Area  Concentrates on the ignition source  Different methods employed for prevention

Principles Involved  Containment of explosion within apparatus Ex d

Types of Protection and Explosion Protection Symbol  Containment of Explosion in Apparatus – Flameproof (Ex d)

Hazardous Gas, Vapor, Dust etc.

Methods Of Protection That “Contain an Explosion”

All Bolts Must Be Installed &

Metal To Metal Joints Extra Care must be Tightened Taken to prevent Correctly Corrosion Housing “Contains” Explosion

Flame-paths

• Joints on covers or openings • Does not prevent explosion occurring are protected by the but contains the explosion and prevents ‘flame-path’ ignition of surrounding atmosphere. Flame-path Flame-path

Enclosure Wall

Flame-paths

• Flame paths Must be free from corrosion !!! • All bolts Must be tightened down correctly !!! 238 Exd Wellglass

Ex de certified Flameproof and Increased Safety Floodlight

Increased Safety (Exe) Terminal Box

Flameproof Enclosure (Exd)

• Lamp and sparking devices are contained within flameproof enclosure

• Wiring enters enclosure via flameproof barrier gland

Cables connected To Exe Terminal block

Enclosure Wall

Flameproof (Exd) EN50018

Types of Protection and Symbol  Avoidance of ignition condition  Increased Safety (Ex e)  Non - Sparking (Ex N, n)

Hazardous Area

Method Of Protection Ex “e” Increased Safety  Additional Protection Is Given to Components to Prevent Excessive Temperatures or Arcs and Sparks  Terminals Cannot Vibrate Loose, Deform Conductors and have Increased Creepage and Clearances  Other Factors

X

High Temperatures or Sparks

X

Method Of Protection Ex “q” Prevention of fuel coming into contact with ignition source

 Powder or Sand Filled – The Enclosure Is Filled With Sand or Ground Glass – Displaces Hazardous Gases – Isolates Hot or Arcing Components – Zone 1 and 2 Applicable

X

Types of Protection and Explosion Protection Symbol

 Prevention of fuel coming into contact with ignition source - Encapsulation (Ex m) - Potted capacitors, ballast, etc.

- Oil Immersion (Ex o) - Oil filled capacitors, windings, etc. - Powder Filling (Ex q) - Electronic Ballast, capacitors, etc

Hazardous Area

What type of Protection to use?  The hazardous zones are decided by local authorities, not the equipment manufacturer.  Different Protection methods are suitable for different zones.

Gas Groups

Gas Groups  Gas Group II is further sub-divided:- IIA (Propane) - IIB (Ethylene) - IIC (Hydrogen & Acetylene) • Qualifying Properties – Maximum Explosion Pressures – Clearance of Clamped Joints

Gas Groups  Any apparatus (lighting fixture) marked for Gas Group II or IIC can be used in ALL Gas Group area ie. IIA, IIB & IIC

Gas Groups  Any apparatus suitable for Gas Group IIC can be used where Gas Group IIB or IIA is required  Any apparatus suitable for Gas Group IIA cannot be used where Gas Group IIB or IIC is required

Gas Groups Apparatus Gas Group

Gas Group of the Area/Zone

II A

II B

II C

II A ➜







II B ➜







II C ➜







Temperature Class

Temperature Class  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 maximum permissible surface temperature which is below ignition temperature of gas.

What is the Ignition Temperature of the Gas/Dust T-Ratings Present?  T-Rating (Marked on the Fixture) It is the Maximum Operating Temperature range of a Luminaire or Fixture

 Must Be Below the Ignition Temp of the Gas / Dust Present  Example: If gas present has ignition temp of 215o C, then T- Rating requirement is T3 (200o C).

Temperature Class Temperature Class

Maximum Surface Temperature

T1

450 ºC

T2

300 ºC

T3

200 ºC

T4

135 ºC

T5

100 ºC

T6

85 ºC

Ingress Protection 1st Digit 0 1 2 3 4 5 6 7 8

Degree of Protection (Dust) No protection Large foreign bodies Ingress of medium sized foreign bodies. Ingress of foreign bodies > 2.5mm dia. Ingress of foreign bodies > 1mm dia. Dust sufficient to interfere with operation. Complete protection against dust.

2nd Digit 0 1 2 3 4 5 6 7 8

Degree of Protection (Liquids) No protection Drops of condensed water Liquid falling at angle up to 15 degrees from vertical. Rain falling at angle up to 60 degrees from vertical. Protection against liquid splashing . Water projected by nozzle from any direction. Conditions on ships decks. Immersion in water. Indefinite immersion in water as agreed with customer.

Explosion Protection Category Coding

Explosion Protection Category ■

II 2GD Ex eqm II T4

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

Explosion Protection Category Coding: Ex eqm II T4

“e” = Increased Safety (Primary Protection Method)

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

Explosion Protection Category  II 2GD Ex eqm II T4 – This means that the product has been certified to ATEX Directive Category 2 for Gas & Dust application and is suitable – for use in zone 1 and zone 2 areas, – for use in Gas groups IIA, IIB or IIC – and for gases with ignition temperatures classified as T4 (less than 135 degC)

ATEX versus CENELEC (EN)

CENELEC

ATEX

Zone 0

Category 1

Zone 1

Category 2

Zone 2

Category 3

World Standards

European & IEC versus

American Standards vs

Methods Of Protection That “Contain an Explosion”

Miniature Explosion Proof Housing

Metal Explosion Proof Enclosure

Types of Protection and Explosion Protection Symbol  Exclusion of Fuel From Atmosphere – Pressurization

Hazardous Area

Ex p

Nature of Hazardous Substance NEC Gas Groups • Class I

Test Gas

➢ Group A

Acetylene

➢ Group B

Hydrogen or Gases of Equiv. Hazard

➢ Group C

Ethylene

➢ Group D

Propane

• Qualifying Properties –Maximum Explosion Pressures –Clearance of Clamped Joints

NEC Class I Locations T Codes (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

Temperature Class Apparatus Temperature Class

Temperature Classification of Zone

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

T2      

T3      

T4      

T5      

T6      

Temperature Class  T6 apparatus is suitable for use in a T5, T4, etc. to T1 areas  T2 apparatus is suitable for use in T2 and T1 areas only

Primary Explosion Protection  Elimination of Fuel

Oxygen

Fuel

Ignition Source

Primary Explosion Protection  Elimination of Oxygen Oxygen

Fuel

Ignition Source

What is the Classification of the Hazardous Location?  Class - Type of Fuel Potentially Present – Class I - Gases, Vapors – Class II - Ignitable Dusts – Class III - Fibers & Flyings

(Gases or Vapors) Applications Petrochemical Refineries Steel Mills Chemical Plants Oil & Gas (Production)  Sewage Treatment     

 Tank Farm  Fuel Service  Aircraft Hangers  Paint Spray  Power Plants

Class II (Ignitable Dusts) Applications  Pharmaceutical  Mines  Grain Silos  Coal Fired Power Plants  Food Processing (Flour, Cocoa, etc.)  Fertilizer Plants  Metal Grinding  Pulp & Paper

Class III (Fibers & Flyings) Applications  Textile Mills  Rope Manufacturing  Lumber & Saw Mills  Cotton Gins  Cotton Seed Mills  Flax Processing Plants

Occurrence of Hazard  Division 1 / Zone 0 and 1 – Hazardous Substance Present Under Normal Conditions. Open System Using Flammable Liquid to Manufacture End Product

 Division 2 / Zone 2 – Hazardous Substance Present Only Under Abnormal Conditions. Closed System Storage Tanks

Principles Involved  Limitation of energy in system to safe level

Types of Protection and Explosion Protection Symbol  Energy Limitation – Intrinsic Safety

Ex i

Ex i - Intrinsic Safety (EN 50020)  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 intrinsic circuit from non protected circuits  This includes the occurrence of:– ia – ib

-

2 fault conditions 1 fault condition

Potentially Explosive Atmosphere  An area in which there can be a flammable gas, liquid or vapour present at some point in time.

Hazardous Areas  An area containing a potentially explosive atmosphere, which, if ignited, could give rise to damage to property or injury to persons.