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Hazardous area
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- 2. BASIC CONCEPT FIRE TRIANGLE CLASSIFICATIONOF HAZARDOUS AREA MIC PROTECTION METHODS
- 3. HAZARDOUS AREA :- “AREA WHICH CONTAINS EXPLOSIVE AIR , GAS MIXTURE OR EXPECTED TO BE PRESENT IN A QUANTITY SUCH AS A REQUIRE SPECIAL PRECAUTION , CONSTRUCTION & USED OF ELECTRICAL APARATUS”
- 4. In the 1700's,certain gases or the lack of oxygen were detected with various hit and miss types of detection. The candles on miners caps, or if carried by the miner, would either go out from the lack of oxygen or the flame would get larger with a different coloring of the flame if certain gases were in the area. Of course, in some instances these open flames caused fires or explosions. By 1815, the Davy's Safety Lamp came into use in the mines. This certainly changed the way for miners to check for certain gases. They took these canaries in small cages with them down the coal mines where they worked. The canaries were the miners alarm signal to show them when the coal-gas levels got too high. The canary stopped singing and was most likely to be laid feet up on the bottom of the cage, poisoned by the mine gas.
- 5. FLAMMABLE MATERIAL :- CONTAIN FLAMMABLE GAS , VAPOURS , DUST etc Eg- GASOLINE, PROPANE, HEXANE, AMMONIA etc
- 6. Hazardous atmosphere isan atmosphere that may expose a worker to the risk of death or incapacitation, or prevent a worker from getting out of the confined space because of an injury or critical illness. Such an atmosphere can be explosive, flammable, poisonous, corrosive, oxidizing, irritating, oxygen deficient, toxic, or otherwise harmful which can result in death, illness ..
- 7. IGNITION ENERGY :- Aspecific mixture of fuel and oxidant that yields the most rapid combustion at a specific measured quantity. FLASH POINT :- The flash point of a volatile material is the lowest temperature at which it can vaporize to form an ignitable mixture in air.
- 8. Gas Representative Gas Ignition Energy Group (mj) I Methane 280 II A Propane 260 IIB Ethylene 95 IIC Hydrogen 18
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- 10. Why Area Classification??? HAC is a method of analyzing and classifying the environment where explosive gas atmospheres may occur to allow the proper selection of electrical apparatus to be installed in that environment.
- 11. 1.The flammable materialsthat may be present; 2. The physical properties and characteristics of each of the flammable materials; 3. The source of potential releases and how they can form explosive atmospheres; 4. Prevailing operating temperatures and pressures; 5. Presence, degree and availability of ventilation (forced and natural); 6. Dispersion of released vapours to below flammable limits; 7. The probability of each release scenario.
- 12. Zone 0: Anarea in which an explosive gas atmosphere is present continuously or for long periods; Zone 1: An area in which an explosive gas atmosphere is likely to occur in normal operation; Zone 2: An area in which an explosive gas atmosphere is not likely to occur in normal operation and, if it occurs, will only exist for a short time.
- 13. ZONE EXPLOSION LIMIT ZONE 0 > 1000 h/year ZONE 1 more than 10 but less than 1000 h/yr ZONE 2 less than 10
- 14. PRIMARY DESIGNATION THREE CLASSES LISTEDWITH ROMAN NUMERAL NOMEMCLATURE
- 15. FLAMMABLE GASSES & VAPOURS. PRESENTDURING NORMAL OPERATION. POSSIBLY PRESENT DURING BREAKDOWN CONDITION. Eg.- PROPANE,GASOLINE, HEXANE, AMMONIA etc.
- 16. COMBUSTABLE DUST. COULD BEPRESENT DURING BREAKDOWN. Eg.- CORN,WHEAT,SOYABEAN DUST,FLOUR,DUST FROM WOODS & PLASTICS etc.
- 17. EASILY IGNITABLE FIBERS& MATERIAL that PRODUCES FLAMMABLE FLYING. COULD BE PRESENT WHERE MATERIAL HANDELED,MANUFACTURED OR USED. Eg.- WHERE RAW COTTON IS STORED.
- 18. SECONDARY DESIGNATION TWO DIVISIONS LISTEDWITH NUMERIC NOMEMCLATURE
- 19. IGNITABLE CONCENTRATION OF FLAMMABLEGASSES & VAPORS. POSSIBLY PRESENT DURING BREAKDOWN & FAULTY CONDITION. Eg.- WHERE DELIVERY TRUCKS ARE UNLOADED.
- 20. CONTAIN DUST OFELECTRICALLY CONDUCTIVE NATURE. MECHANICAL FAILURE OR ABNORMAL OPEARATION MIGHT PRODUCE IGNITABLE OR EXPLOSIVE MIXTURE. Eg.- AREAS OF OPEN CONVEYORS,OPEN TOP BINS, DUST OF MAGNESSIUM OR ALLUMINIUM.
- 21. WHERE FLAMMABLE GASSES HANDELEDBUT NORMALLY ENCLOSED. ACCEDENTIAL RUPTURE OR BREAKDOWN. Eg- ROOMS NEAR TO CLASS I DIVISION 1 AREAS.
- 22. AREAS NEAR ELECTRICAL EQUIPMENT. Eg-AREAS ARROUND CLOSED CONVEYOR; AREAS AROUND ENCLOSED PROCESS EQUIPMENT.
- 23. SECONDARY DESIGNATION SEVERAL GROUPS LISTEDWITH ALPHABETIC NOMENCLATURE MATERIALS ARE GROPED BY ONES WITH SIMILAR CHARECTIRISTICS
- 24. CLASS I HAS4 GROUPS ie A,B,C,D VARIABLE FALAMMABLE GASSES ARE ARRANGED BY SIMILAR CHARACTIREISTICS - IGNITION TEMPERATURE -SAFE CLEARANCE DISTANCE
- 25. CLASS II HAS2 GROUPS ie E,F VARIABLE COMBUSTABLE DUSTS ARE ARRANGED BY SIMILAR CHARACTIREISTICS - IGNITION TEMPERATURE -HOW TIGHT EQUIPMENT SEALS NEED TO PREVENT DUST ENTERING IN EQUIPMENT
- 26. COMBUSTABLE DUST SUCHAS FLOUR ,GRAIN,WOOD,PLASTICS PRIMARY CONCERN OF GRAIN ELEVATORS
- 27. The maximum clearancebetween two parallel metal surfaces that has been found, under specified test conditions, to prevent an explosion in a test chamber from being propagated to a secondary chamber containing the same gas or vapor at the same concentration.
- 28. T Class Max. Surface Temperature (Deg. C) T1 450 T2 300 T3 200 T4 135 T5 100 T6 85
- 29. S No Name of the Minimum Flash point Iignition Flammable limit chemical Ignition Deg. Cen. temperature LEL UEL Current (Deg C) (MIC) mA 1 Methane 85 - 595 5% 15% 2 Ammonia - - 630 105 mg/l 200 mg/l 3 Ethylene 45 - 425 2.7% 34% 4 Propane 70 - 470 2% 9.5% 5 Acetylene 24 - 305 1.5 % 100%
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