SELECTION OF ELECTRICAL EQUIPMENT IN HAZARDOUS AREAS/ EXplosion Protection Equipments

SELECTION OF ELECTRICAL EQUIPMENT IN HAZARDOUS AREAS

SELECTION OF ELECTRICAL EQUIPMENT IN HAZARDOUS AREAS
          How to select equipment for various zones?
          Selection Criteria
        Gas Grouping (based on ignition energy)
        Temperature Classification
        Classified Zones
GAS GROUP CLASSIFICATION (based on MESG & MIE)
          Gas group I
        Methane
          Gas group II A
        Ammonia, CO, Propane, Butane, Benzene, Acetone, Methanol
          Gas group II B
        Butadiene, Ethylene, Ethylene Oxide, Diethyl Ether
          Gas group II C
        Hydrogen

GAS GROUP & TEMPERATURE CLASSIFICATION-VARIOUS GASES/VAPOURS (IS 13408 Part I)
 














GAS GROUP & TEMPERATURE CLASSIFICATION-VARIOUS GASES/VAPOURS
Gas                              Representative Gas                                  Ignition Energy
Group                                                                                                                   (mj)
I                                  Methane                                                                          280
II A                               Propane                                                                         260
IIB                               Ethylene                                                                         95
IIC                                Hydrogen                                                                       18
Standards for Methods of Protection as per IS 5571
Equipment
RECOMMENDED PROTECTION METHODS 
ZONE 0
ZONE 1
ZONE 2
Motors
No motors shall be used
Ex  d, Ex p
Ex  d, Ex p, Ex n, Ex e,
Transformers & Capacitors
No transformer & Capacitor shall be used
Ex d
Ex d,
Lighting Fitting
No lighting fitting shall be used
Ex d
Ex d, Ex e, Ex n
Switch Gear & Control Gear
No switch gear & control gear shall be used. When not practiced use type
" i " protection
Ex d
Ex d, Ex o
Generators
No generators shall be used
Ex  d, Ex p
Ex  d, Ex p, Ex e,
Diesel Engines
Unacceptable
     The use of permanently installed diesel engines to be avoided
The use of permanently installed diesel engines to be avoided
Storage batteries
Shall not be used
      Storage batteries shall not be installed in zone 1 areas, except those in portable torches where the enclosures housing the bulb, switch and battery shall be flame proof type.
Ex e

EXPLOSION-PROTECTION METHODS / EQUIPMENT -Popular types
          Flameproof (EX d)
          Increased Safety (Ex e )
          Non-Sparking (Ex n )
          Pressurization (Ex p )
          Intrinsically Safe (Ex i )
          Powder filled Ex ‘q’ type
          Oil immersed Ex ‘o’ type
          •Special Ex  ‘s’ type
 Definition as per IS 2148:
US- Explosion-Proof, UK- Flame-Proof, GERMANY - Pressure-Proof
           A type of protection in which the parts can ignite an explosive atmosphere are to be placed in an enclosure, which can withstand the pressure developed during internal explosion of an explosive mixture, and which prevents the transmission of the explosion to the explosive atmosphere surrounding the enclosure
INTRINSICALLY SAFE EQUIPMENT & CIRCUITS (Ex ‘i’ )

Definition as per IS 5780
   A type of protection which a circuit or part of the circuit is intrinsically safe when any spark or thermal effect produced normally is incapable, under prescribed test conditions, of causing ignition of prescribed gas or vapour
INTRINSICALLY SAFE EQUIPMENT & CIRCUITS (Ex ‘i’ )
          Only electrical protective measure (protection technology by way of power limitation), the other protective techniques use mechanical means to prevent ignition from electrical faults (max. 30 volts or 50 mA)
                Ex ‘i’ apparatus is the one which has all the circuits within intrinsically safe
           Ex ‘i’ circuit is the one which has intrinsically safe barriers with Zenner diodes for power limitation
          Minimum IP 20 ingress protection
INTRINSICALLY SAFE EQUIPMENT- Category-   Ex  ib
Ex  ib equipment shall be incapable of causing ignition in normal operation, with a single fault and with the following safety factors:
        1.5 in normal operation and with one fault
        1.0 with one fault, if the equipment contains no unprotected switch contacts in parts likely to be exposed to a potentially explosive atmosphere and the fault is self-revealing
        EX i typical marking: EEx ib IIC T5
INCREASED SAFETY EQUIPMENT (Ex ‘e’)
                Stringiest construction methods to ensure that no sparks, excessive temperature are produced
          Careful terminal design
          Use of good quality insulation material
          Use of special materials to protect the enclosure against impact, ingress of dust & moisture
          Can be used for I, II A, B, C gas groups
          Permitted for us in T1, T2, T3 classes only
          Terminal with minimum IP 54 ingress protection            
          EX d typical marking: EEx e IIA T3
PRESSURIZATION TYPE (Ex ‘p’ )
Definition as per IS 7389
   A type of protection by which the entry of surrounding atmosphere into the enclosure of the electrical apparatus is prevented by  maintaining inside the said enclosure, a protective gas at a higher than that of the surrounding atmosphere
PRESSURIZATION TYPE (Ex ‘p’ ) TYPES
          Dynamic Pressurization (DP) or pressurization by continuos circulation of protective gas (purging)
        DP is a method of maintaining pressure in an enclosure in which after purging the protective gas is passed continuously through the enclosure at a pressure above that of the specified minimum and discharged to the outside atmosphere
        Static Pressurization or pressurization with leakage compensation
-          Air supplied & pressurized continuously from a non-hazardous area to avoid ingress of flammable gases / vapour inside the enclosure
PRESSURIZATION TYPE (Ex ‘p’ )
Pressurized Equipment
          Ingress protection minimum IP 4X
          Over pressure 1.5 times or 0.2 kPa
          Material of construction should be flame retardant, self- extinguishing and should not be affected by protective gas
NON-SPARKING TYPE EQUIPMENT (Ex ‘n’ )
   A type of protection applied to electrical apparatus such that , in normal operation it is not capable of igniting a surrounding atmosphere and a fault capable of causing ignition is not likely to occur
EX n typical marking: EEx n  II T5
NON-SPARKING TYPE EQUIPMENT (Ex ‘n’ )
          Equipment construction in such a way that in normal operation, it is incapable of igniting a surrounding explosive atmosphere and a fault incapable of causing ignition
          Hermetically sealed type
          Restricted breathing type
          Careful design of terminals
-          SUBSTANTIAL COST SAVING
          Applications
        Tools
        Equipment
             POWDER FILLED TYPE EQUIPMENT ( Ex ‘q’)
          Equipment enclosure filled with quartz /sand so that in normal operating condition, any arc occurring within the enclosure of electrical equipment will not ignite the surrounding atmosphere
          No ignition shall be caused either by flame or by excessive temperature of the surfaces of the enclosure
          Enclosure constructional features:
          High mechanical strength
          Ingress protection
          Powder filled
          Insulation of enclosed equipment
        OIL IMMERSED TYPE EQUIPMENT (Ex ‘o’)
          Protection technique in which the equipment or its parts are immersed in oil in such a way that an explosive atmosphere which, may be above the oil or outside the enclosure cannot be ignited.
          Oil used shall be mineral oil confirming to relevant standards
          Constructional features:
         Fully enclosed, leak-proof enclosure
        Oil level indicator
          Transformers, Switch gears, Control gears
         SPECIAL TYPE EQUIPMENT (Ex ‘s’)
          This is a concept that has been adopted to permit the certification of those types of equipment which by their nature, do not comply with the constructional or other requirements specified for equipment with established types of protection but which, nevertheless, can be shown, wherever necessary, by test to be suitable for use in hazardous areas in prescribed zones
          This concept permits flexibility on the part of certifying and assessment authorities in their approach to applications for certification of equipment the use of which would otherwise not permitted in hazardous areas on account of non-compliance with the requirements of standards for established types of protection. This allows flexibility of approach to innovative ideas and new designs, the development of which otherwise be obstructed.
          Examples:
        Factory sealed hand lamps, Encapsulation (Ex ‘m’ type), Gas detection apparatus
Indian Standards for Various Protection Techniques
          IS 5571  Guide For Selection Of Electrical Equipment For Hazardous Areas          
          IS 5572 –Part I    Classification of Hazardous Areas for Electrical Installations      
          IS 13408 Part I, II, III Code of Selection, Installation and Maintenance of Electrical Apparatus for Use in Explosive Atmospheres   
          IS 8239 Classification of Maximum Surface Temperature of Electrical Equipment for Use In Explosive Atmospheres                
          IS 6381  Construction and testing of Electrical Apparatus with type of protection ‘e’       
          IS 2148  Flameproof Enclosures of Electrical Apparatus 
Approval / Testing Agencies
          CMRI (Central Mining Research Institute), Dhanbad, BIHAR
          CCoE (Chief Controller of Explosives), Nagpur
          BIS (Bureau Of Indian Standards)
          DGMS (Director General Mine Safety), Dhanbad, BIHAR
          DGFASLI (Director General of Factory Advice Service and Labour Institutes), Mumbai
Summary of the Gaps:
          No HA classification.
          MCC rooms are existing in Production blocks.
          Utilities buildings are closed to manufacturing areas.
          Street lights are located at adjacent to the manufacturing areas.
          Ordinary AHU panels in manufacturing areas.
Action Plans for Existing plant:
          Form a teams
          Classified the plant area
          Shown the classification in the plant layout as
                Zone 0: Red
                Zone 1: Blue
                Zone 2: Green
          List out the non flame proof equipments in classified area
          Replace with Flame proof equipments
          Pressurize the MCC rooms, wherever necessary
For New Projects:
          Area classification review should be carried out at design stage by Projects team.
          Before finalization, It should be approved by plant EHS and Corp.EHS subsequently.
          Follow the HAC guidelines for all new projects.



No comments:

Post a Comment