Contents

Area Classification - DefinitionsFire TriangleFlash PointIgnition TemperatureDivisions or zones (gases, vapours and dust)Gas groupsTemperature classification Type of protectionIngress ProtectionType II CoordinationL&TSIEMENSANSI Codes

HAZARDOUS AREA : DEFINATION

The process of identifying the source of hazard (inflammable vapour, dust or fibrous materials), degree of hazard and the extent of area in which the hazard exists can be called area classification.

1. AREA CLASSIFICATIONThe subject comprises of following four major sub-topics:

Divisions or zones (gases, vapors and dust)Gas groupsTemperature classification Type of protection

To an ELECTRICAL ENGINEER, a hazardous area is defined as :a place where concentrations of flammable gases, vapours, or dusts present / occur. Electrical equipment that must be installed in such locations is especially designed and tested to ensure it does not initiate a spark, due to arcing contacts or high surface temperature of equipment which may lead to an explosion.

STRATEGIES in common practice :Minimize the amount of electrical equipment installed in a hazardous area, either by keeping the equipment out of the area altogether or by making the area less hazardous by process improvements or ventilation with clean air. Intrinsic safety equipment and wiring methods; where apparatus is designed with low power levels and low stored energy, so that an arc produced during normal functioning of the equipment or as the result of equipment failure has insufficient energy to initiate ignition of the explosive mixture. Equipment enclosures can be pressurized with clean air or inert gas and designed with various controls to remove power or provide notification in case of supply or pressure loss of such gases. Arc-producing elements of the equipment be isolated from the surrounding atmosphere by encapsulation, immersion in oil, sand, etc. Heat producing elements such as motor winding, electrical heaters, including heat tracing and lighting fixtures are often designed to limit their maximum temperature below the auto ignition temperature of the material involved. Both external and internal temperatures are taken into consideration.

(A) FIRE TRIANGLE

Gas : Available in abundance in refineryAir : available readily in airSource of Ignition is the only factor that can be controlled.

(B) FLASH POINT - A, B, C The flash point of a volatile material is the lowest temperature at which it can vaporize to form an ignitable mixture in air. Measuring a flash point requires an ignition source. At the flash point, the vapour may cease to burn when the source of ignition is removed.

(C) IGNITION TEMPERATURE

The auto-ignition temperature or kindling point of a substance is the lowest temperature at which it will spontaneously ignite in a normal atmosphere without an external source of ignition, such as a flame or spark.

This temperature is required to supply the activation energy needed for combustion.

The temperature at which a chemical will ignite decreases as the pressure increases or oxygen concentration increases. It is usually applied to a combustible fuel mixture

Explosive Limits (based on Minimum Ignition Energy - MIE)

WHY ZONING ?Leak Potential & Presence of Ignition SourcesHazardous properties of hydrocarbonsSafe selection (& optimization) of Electrical Equipment

HOW TO IDENTIFY ZONE-1 AREA

HOW TO IDENTIFY ZONE-1 AREA

HOW TO IDENTIFY ZONE-1 AREA

HOW TO IDENTIFY ZONE-1 AREA

AREA CLASSIFICATION : GRADE OF RELEASE

Grade of ReleaseHazardous explosive mixtureZone 0Continuous Grade ReleaseWhere the release of gas, vapour or volatile liquid is continuous or for long period (more than 1000 hours per year)Zone 1Primary Grade ReleaseWhere the release of gas, vapour or volatile liquid is likely to occur frequently, or if infrequently, will persist for a considerable period of time (between 10 and 1000 hours per year)Zone 2Secondary Grade ReleaseWhere the release of gas, vapour or volatile liquid is likely to occur infrequently, and when occuring is of short duration (less than 10 hours per year)

HOW TO IDENTIFY ZONE-1 AREA

HOW TO IDENTIFY ZONE-1 AREA

GAS GROUP CLASSIFICATIONExplosive gases, vapors and dusts have different chemical properties that affect the likelihood and severity of an explosion. Such properties include flame temperature, minimum ignition energy, upper and lower explosive limits, and molecular weight.

Every substance has a differing combination of properties but it is found that they can be ranked into similar ranges, simplifying the selection of equipment for hazardous areas

Maximum Surface Temperature vs Minimum Ignition temperature

The bigger the T-number the lower is the ignition temperature of hazard.TEMPERATURE CLASSIFICATION

INGRESS PROTECTIONINGRESS OF LIQUIDSFIRST CHRACTER OF IP : X (PROTECTION AGAINST SOLIDS) I P - X YThe IP or Ingress Protection, classifies and rates the degree of protection provided against the intrusion of solid objects (including body parts like hands and fingers), dust, accidental contact, and water in mechanical casings and with electrical enclosures

INGRESS PROTECTIONINGRESS OF LIQUIDSSECOND CHRACTER OF IP : Y (PROTECTION AGAINST LIQUIDS)

TYPE OF PROTECTIONINGRESS OF LIQUIDS

Ex CodeNotified Body NameDescriptionLocationUseFlameproofdWill have a CENELEC Hexagon followed by apparatus group and Safety CategoryEquipment is robust can stand an explosion from within, without transmitting the flame to the outsideEquipment has flameproof gaps (max 0.006" propane/ethylene, 0.004" acetylene/hydrogen)Zone 1 if gas group & temp. class correctMotors, lighting, junction boxesIncreased SafetyeWill have a CENELEC Hexagon followed by apparatus group and Safety CategoryEquipment is very robust and components are made to a high qualityZone 2 or Zone 1Motors, lighting, junction boxesOil FilledOWill have a CENELEC Hexagon followed by apparatus group and Safety CategoryEquipment components are completely covered with a layer of oilZone 2 or Zone 1, depending on edition of the standard used.Heavy current equipmentSand/Powder/Quartz FilledqWill have a CENELEC Hexagon followed by apparatus group and Safety CategoryEquipment components are completely covered with a layer of Sand, powder or quartzZone 2Electronics, telephones, chokesEncapsulatedmWill have a CENELEC Hexagon followed by apparatus group and Safety CategoryEquipment components of the equipment are usually encased in a resin type materialZone 1 (Ex mb) or Zone 0 (Ex ma)Electronics (no heat)

TYPE OF PROTECTIONINGRESS OF LIQUIDS

Ex CodeNotified Body NameDescriptionLocationUsePressurized/purgedpWill have a CENELEC Hexagon followed by apparatus group and Safety CategoryEquipment is pressurised with a positive pressure; gas cannot get in for air coming out or equipment is purged with a diluting gas such as air. If air is used, it is ducted in from outside the hazardous area.Zone 1Analysers, motors, control boxes, computersIntrinsically safeiWill have a CENELEC Hexagon followed by apparatus group and Safety CategoryAny arcs or sparks in this equipment has insufficient energy (heat) to ignite a vapourEquipment can be installed in ANY housing provided to IP54 A 'Zener Barrier' or 'opto isol' or 'galvanic' unit may be used to assist with certification.'ia': Zone 0 & 1 'ib': Zone 1Instrumentation, measurement, controlNon sparkingnNow CENELEC recognized; so will have a hexagon followed by apparatus group and Safety CategoryEquipment is non-sparking.Zone 2Motors, lighting, junction boxes, electronic equipment

TYPE 2 COORDINATIONINGRESS OF LIQUIDSType 1: Requires that, under short-circuit conditions, the contactor or starter shall cause no danger to persons or installation and may not be suitable for further service without repair and replacement of parts.

(Damage is allowed, requiring component replacement. Short circuit protective devices interrupt the fault current, but are not required to provide component protection.)Type 2: Requires that, under short-circuit condition; the contactor or starter shall cause no danger to persons or installation and shall be suitable for further use. The risk of contact welding is recognized, in which case the manufacturer shall indicate the measures to be taken as regards the maintenance of the equipment.

(No damage is allowed to either the contactor or overload relay. Light contact welding is permitted, but contacts must be easily separable. No damage protection typically can only be provided by a current limiting device.)

TYPE 2 COORDINATIONL&T STARTERSINGRESS OF LIQUIDS

Motor Rating: 3, 415, 50 HzContactorOverload RelayNominal Backup fuseS - D - FkWIn (A)TypeTypeRange (A)TypeRating (A)0.090.4MNX 9MNX-R30.3 - 0.5HF2FN 32 / FNX 320.120.45MNX 9MNX-R30.3 - 0.5HF2FN 32 / FNX 320.150.57MNX 9MNX-R30.45 - 0.75HF2FN 32 / FNX 320.190.75MNX 9MNX-R30.6 - 1.0HF4FN 32 / FNX 320.250.9MNX 9MNX-R30.6 - 1.0HF4FN 32 / FNX 320.371.2MNX 9MNX-R30.9 - 1.5HF6FN 32 / FNX 320.551.6MNX 9MNX-R31.4 - 2.3HF6FN 32 / FNX 320.752.1MNX 9MNX-R31.4 - 2.3HF8FN 32 / FNX 321.12.7MNX 9MNX-R32.0 - 3.3HF10FN 32 / FNX 321.33MNX 9MNX-R32.0 - 3.3HF10FN 32 / FNX 321.53.5MNX 9MNX-R33 - 5HF16FN 32 / FNX 321.84.8MNX 9MNX-R34.5 - 7.5HF16FN 32 / FNX 322.255MNX 9MNX-R34.5 - 7.5HF16FN 32 / FNX 3236.4MNX 9MNX-R34.5 - 7.5HF20FN 32 / FNX 323.77.9MNX 9MNX-R36 - 10HF20FN 32 / FNX 3248.5MNX 9MNX-R36 - 10HF20FN 32 / FNX 324.59MNX 12MNX-R36 - 10HF25FN 32 / FNX 325.511.2MNX 12MNX-R39 - 15HF32FN 32 / FNX 327.514.8MNX 18MNX-R39 - 15HF32FN 32 / FNX 329.319MNX 25MNX-R314 - 23HF50FN 63 / FNX 631122MNX 25MNX-R314 - 23HF63FN 63 / FNX 631324MNX 32MNX-R320 - 33HF63FN 63 / FNX 631529MNX 32MNX-R320 - 33HF63FN 63 / FNX 6318.635MNX 40MNX-R430 - 50HN, 000*80FN 100 / FNX 100 *22.540MNX 45MNX-R430 - 50HN, 000*80FN 100 / FNX 100 *2647MNX 70MNX-R430 - 50HN, 000*100FN 100 / FNX 100 *3055MNX 70MNX-R445 - 75HN, 000*100FN 100 / FNX 100 *33.560MNX 70MNX-R445 - 75HN, 000*100FN 100 / FNX 100 *3766MNX 80MNX-R445 - 75HN, 00125FN 125 / FNX 1254580MNX 95MNX-R466 - 110HN, 00125FN 125 / FNX 12555100MNX 110MNX-R466 - 110HN, 00 #160FN 160 / FNX 160 #67.5120MNX 140MNX-R590 - 150HN, 0200FN 200 / FNX 20075135MNX 140MNX-R590 - 150HN, 0200FN 200 / FNX 200

TYPE 2 COORDINATIONSIEMENS STARTERSINGRESS OF LIQUIDS

MotorSDFHRC FusesContactorBi-RelayBi-RelayKW/HP 415V,3ph, 50HzI, AmpTypeRatingType 3NA3AmpTypeAmpType ( 50C)Set-Range AmpType ( 60C)Available Set-Range Amp.37/.513KL47323NA380443TF3093UA5000-0K0.8-1.253UA5000-0K0.8-1.17.55/.751.33KL47323NA380443TF3093UA5000-1A1-1.63UA5000-1A1-1.5.75/11.93KL47323NA380163TF3093UA5000-1B1.25-23UA5000-1B1.6-2.31.1/1.52.63KL48323NA380163TF3093UA5000-1D2-3.23UA5000-1D2-31.5/23.73KL49323NA3803103TF3093UA5000-1E2.5-43UA5000-1E2.5-3.72.2/34.83KL50323NA3805163TF3093UA5000-1F3.2-53UA5000-1G4-5.93.7/57.83KL51323NA3807203TF3093UA5000-1H5-83UA5000-1H6.3-9.45.5/7.511.23KL52323NA3810253TF31123UA5000-1K8-12.53UA5000-1K8-11.77.5/10163KL53323NA3812323TF32163UA5200-2A10-163UA5200-2B12.5-18.79.3/12.5193KL54503NA3820503TF44323UA5500-2B12.5-203UA5500-2C16-23.411/1520.83KL55503NA3820503TF44323UA5500-2C16-253UA5500-2C16-23.415/20283KL56633NA3822633TF44323UA5500-2D20-323UA5500-2D20-3018.5/25343KL57633NA3822633TF45383UA5500-2Q25-363UA5500-2R32-37.422/30403KL581003NA3824803TF46453UA5800-2FZ132-503UA5800-2FZ132-4730/40533KL591003NA38301003TF47633UA5800-2TZ140-573UA5800-2PZ150-5937/50653KL601253NA38321253TF477703UA5800-2VZ257-703UA5800-2VZ257-65.545/60783KL611253NA38321253TF49853UA5800-8YZ170-953UA5800-8YZ170-88.955/75963KL622003NA31361603TF501103UA5830-5C85-1053UA5830-5C85-98.275/1001313KL632003NA31402003TF511403UA6230-5A85-1353UA6230-5B115-16890/1251563KL642503NA31442503TF521703UA6230-5B115-1803UA6230-5B115-168110/1501893KL652503NA31442503TF532053UA6230-5C160-2503UA6230-5C160-234132/1802273KL663153NA32523153TF542503UA6230-5C160-2503UA6230-5C160-234160/2152713KL674003NA32604003TF553003UA6230-5D200-3203UA6230-5D200-299200/2703393KL686303NA33655003TF564003UA6230-5E250-4003UA6230-5E250-374250/3353983KL696303NA33655003TF574753UA6830-3F320-5003UA6830-3F320-468

ANSI DEVICE NUMBERSINGRESS OF LIQUIDS1 Master Element2 Time Delay Starting or Closing Relay3 Checking or Interlocking Relay4 Master Contactor5 Stopping Device6 Starting Circuit Breaker7 Rate of Change Relay8 Control Power Disconnecting Device9 Reversing Device10 Unit Sequence Switch11 Multi-function Device12 Overspeed Device13 Synchronous-speed Device14 Underspeed Device15 Speed or Frequency, Matching Device16 Data Communications Device17 Shunting or Discharge Switch18 Accelerating or Decelerating Device19 Starting to Running Transition Contactor20 Electrically Operated Valve21 Distance Relay22 Equalizer Circuit Breaker23 Temperature Control Device24 Volts Per Hertz Relay25 Synchronizing or Synchronism-Check Device26 Apparatus Thermal Device27 Undervoltage Relay

28 Flame detector29 Isolating Contactor or Switch30 Annunciator Relay31 Separate Excitation Device32 Directional Power Relay33 Position Switch34 Master Sequence Device35 Brush-Operating or Slip-Ring Short-Circuiting Device36 Polarity or Polarizing Voltage Devices37 Undercurrent or Underpower Relay38 Bearing Protective Device39 Mechanical Condition Monitor40 Field (over/under excitation) Relay41 Field Circuit Breaker42 Running Circuit Breaker43 Manual Transfer or Selector Device44 Unit Sequence Starting Relay45 Abnormal Atmospheric Condition Monitor46 Reverse-phase or Phase-Balance Current Relay47 Phase-Sequence or Phase-Balance Voltage Relay48 Incomplete Sequence Relay49 Machine or Transformer, Thermal Relay50 Instantaneous Overcurrent RelayANSI Standard Device Numbers (ANSI /IEEE Standard C37.2) denote what features a protective device supports (such as a relay or circuit breaker). Device numbers are used to identify the functions of devices shown on a schematic diagram. Function descriptions are given in the standard. List of ANSI device numbers are as follows :

ANSI DEVICE NUMBERSINGRESS OF LIQUIDS84 Operating Mechanism85 Communications, Carrier or Pilot-Wire Relay86 Lockout Relay87 Differential Protective Relay88 Auxiliary Motor or Motor Generator89 Line Switch90 Regulating Device91 Voltage Directional Relay92 Voltage and Power Directional Relay93 Field Changing Contactor94 Tripping or Trip-Free Relay95-100 For specific applications where other numbers are not suitable51 AC Inverse Time Overcurrent Relay52 AC Circuit Breaker53 Exciter or DC Generator Relay54 Turning Gear Engaging Device55 Power Factor Relay56 Field Application Relay57 Short-Circuiting or Grounding Device58 Rectification Failure Relay59 Overvoltage Relay60 Voltage or Current Balance Relay61 Density Switch or Sensor62 Time-Delay Stopping or Opening Relay63 Pressure Switch64 Ground Detector Relay65 Governor66 Notching or Jogging Device67 AC Directional Overcurrent Relay68 Blocking or "Out-of-Step" Relay69 Permissive Control Device70 Rheostat71 Liquid Level Switch72 DC Circuit Breaker73 Load-Resistor Contactor74 Alarm Relay75 Position Changing Mechanism76 DC Overcurrent Relay77 Telemetering Device78 Phase-Angle Measuring Relay79 AC Reclosing Relay80 Flow Switch81 Frequency Relay82 DC Reclosing Relay83 Automatic Selective Control or Transfer Relay