International Experts & Consultants AssociationINTEC

Hazardous (Classified) Locations1910.307

INTRODUCTIONA hazardous location is any location where a potential hazard, either a fire or an explosion can exist due to the presence of flammable, combustible, or ignitable materials.These materials can consist of gases, vapors, liquids, dusts, fibers, etc.

HAZARDOUS LOCATION TYPESClass I Locations:

An area where flammable gases or vapors are or can be present in the air in quantities sufficient to produce explosive or ignitable mixtures. For Example*Petroleum Refineries, Gasoline storage and dispensing areas, Dry cleaning plants, Spray Finishing areas, utility gas plants.

ContinuedClass II Locations:

An area where presence of combustible dust present a fire or explosion hazard. For example:Grain elevators, flour and feed mills, Use or store of magnesium or aluminum powders, producers of plastics, fireworks.

ContinuedClass III Locations:

An area made hazardous due to the presence of easily ignitable fibers or flyings. For example:Textile mills, cotton gins, cotton seed mills, plants that shape or cut wood and create sawdust or flying.

Hazardous Location ConditionsIn addition to the types of hazardous locations, the kind of conditions under which these hazards are present are very important : Normal Conditions, Abnormal Conditions.Division 1:Normal ConditionsDivision 2 :Abnormal Conditions

ContinuedClass I, Class II, and Class III hazardous locations can be either Division 1 or Division 2Good examples of Class I, Division 1 locations: areas near open dome loading facilities or adjacent to relief valves in a petroleum refinery, because the hazardous material would be present during normal plant operations.

ContinuedClosed storage drums containing flammable liquids in an inside storage room would not normally allow hazardous vapors to escape into the atmosphere but, what happens if one of the containers is leaking? You have got a Division 2 Abnormal condition A Class I, Division 2 hazardous location.

Class I, Division 1 & Class I, Division 2

Class II, Division 1 & Class II, Division 2

Class III, Division 1 & Class III Division 2

Nature of Hazardous SubstancesThe gases and vapors of class I locations are broken into four groups : A, B, C, and D. These materials are grouped according to the ignition temperature of the substance, its explosion pressure, and other flammable characteristics.

Group AGroup A is an atmosphere containing acetylene.Equipment with rating up to 536 F (280C) can be utilized.

Group BGroup B is an atmosphere containing hydrogen, or gases or vapors with a hazard equal to hydrogen. Butadiene, and ethylene and propylene oxide are included in this group.

Group CGroup C is an atmosphere containing cyclo-propane, ethyl ether, or ethylene or gases or vapors with hazard equal to these gases.

Group DGroup D is an atmosphere containing acetone, alcohol, benzene, butane, gasoline, propane, natural gases or gases with vapors with a hazard equal to these gases.

Nature of Hazardous SubstancesIn Class II - dust locations we find the hazardous materials in Groups: E, F, G. These groups are classified according to the ignition temperature and the conductivity of the hazardous substance.Conductivity is an important consideration in Class II locations, especially with metal dusts.

Group EGroup E is an atmosphere containing metallic dusts or other dusts with a similar hazard that is equivalent, such as Aluminum and Magnesium dusts.

Group FGroup F is an atmosphere containing Carbon Black, Charcoal Coal, or Coke dusts with 8% or less total volatile material.

Group GGroup G is an atmosphere containing grain dusts, flour , starch, cocoa, and similar types of materials.

ContinueClass III locations are not broken into groups.

Equipment for Hazardous LocationsEquipment for Class I locations:

The equipment used in Class I locations are housed in enclosures designed to contain any explosion that might occur if hazardous vapors were to enter the enclosure and ignite.Also it is designed to cool and vent the products of this explosion.

Equipment for Class II LocationsClass II locations make use of equipment designed to seal out dust. The enclosures are not intended to contain an internal explosion, but rather to eliminate the source of ignition so no explosion can occur within the enclosure.

Equipment for Class III LocationsEquipment used in class III locations need to be designed to prevent fibers and flyings from entering the housing. It also needs to be constructed in such a way as to prevent the escape of sparks or burning materials.It must also operate below the point of combustion.

Types of ProtectionFlameproof Enclosures dIntrinsic Safety iIncreased Safety ePowder/Sand Filled qPressurized Apparatus pOil Immersion oSpecial Protection sEncapsulation mType of protection N N

Flameproof Enclosures dType of protection, for which the parts which can ignite an explosive atmosphere are inside an enclosure which willWithstand the pressure of theExplosion within the enclosure.

Prevent the transmission of theExplosion to an explosiveAtmosphere surrounding theEnclosure.

Intrinsic Safety i Type of protection, for which the energy in the electrical circuit is held so low that sparks, arcs or temperatures capable of causing ignition cannot occur.Includes sub-division into the categories ia & ibIa must not produce any ignition when any combination of two faults is present.Ib must not produce any ignition, in normal operation, when one fault is present.

Increased Safety eType of protection, for which measures are taken to prevent the possibility of non-permissible high temperatures and the formation of sparks or arcs on inner or outer parts of electrical apparatus, on which these do not occur in normal operation, with an increased level of safety.

Powder/Sand Filled qThe electrical apparatus enclosure is filled with powder or sand.An arc occurring in the enclosure does not ignite an explosive atmospheres surrounding the enclosure.

Pressurized Apparatus pPreventing the entry of surrounding atmosphere into the enclosure by holding an ignition-protection gas (air, inert gas) under over-pressure in relation to the surrounding atmosphere

Oil Immersion oElectrical apparatus or parts thereof are made safe by immersion in oil such that potentially explosive atmosphere above the surface of the oil or outside the enclosure will not be ignited.

EEx ib IIB T4E: European StandardsEx ib: Intrinsically safe to category ibII: Certification for use in apparatus group II (in other industries) (I is for mines)B: Explosion classesT4: The ignition temperature of any gas or vapor with which this device will be used is not less than 135 degree C

Division into GroupsProtection from Firedamp and ExplosionGroup I:Contains equipment intended for operation underground in mines endangered by firedamp.

Group II:Contains equipment intended for operation in all explosive gas atmospheres other than those to be found in mines.

Temperature Classes Ignition Groups

Temp. ClassHighest Permissible Surface Temp. in Degree CIgnition Temp of Flammable Substance in Degree CT1450< 450T2300< 300T3200< 200T4135< 135 T5100< 100T685< 85

Explosion Classes

Apparatus group for flameproof enclosure d Limiting Gap WidthMinimum Ignition Current for Intrinsically Safe Circuits iRatio in relation to MethaneA> 0.9 mm> 0.8B> Or = 0.5 to 0.9 mm> Or = 0.45 to 0.8C< 0.5 mm< 0.45

Dust and Water Protection IPThe first number refers to protection against the ingress of solid & the second refers to protection against the ingress of liquids

1st NumberDegree of Protection2nd NumberDegree of Protection 1Protection against large-sized foreign bodies (hands)1Drops of condensed water 2Medium-sized foreign bodies (finger) 2Drops of liquid, with the equipment tilted at any angle up to 15 from the vertical3Protection against the ingress of foreign bodies greater than 2.5 mm thick3Against rain falling at an angle of 60 or less from the vertical4Greater than 1 mm thick4Protection against water splashed from any direction

5Protection against the ingress of dust5Protection against jets of water6Complete protection from the ingress of dust6Protection against water from heavy seas7Protection against immersion in water under stated conditions of pressure and time8Protection against immersion in water under specified pressure for an indefinite period of time.

Area ClassificationOil Water Separator

Floating-Roof Tank

Fixed Roof Tank