Types of Explosion Protection for Electrical Equipments

           Different construction techniques used for electrical equipments working in marine hazardous areas to prevent explosion. Explosion protection equipments are identified by the symbol Ex followed by the letter indicating the type of protection
Flameproof enclosure (Exd)
      > It is gas tight and will withstand without damage an explosion of the flammable gas within it thus prevents transmission of flame.
      >These are used where the spark or arcing occurs during normal operation. Starters, wound induction motors, commutator motors are equipped with this enclosure

Intrinsic safety (Exi)
      > These circuits produce neither spark nor any thermal effect. This is done by limiting the circuit conditions less than 30 V and 50 mA

Increased safety (Exe)
      >These circuits are built by the elimination of open sparking such as switch contacts or commutators

Non-sparking (Exn)
       >A new British classification derived from the German Exe

Powder filled (Exq)
       >Quartz sand is filled

Oil immersed (Exo)
       >This involves placing equipments in oil filled tanks to prevent gas from reaching any arcs that may be produced

Pressurisation (Exp)
        >Air or inert gas is supplied to the equipment slightly above atmospheric pressure to prevent entry of the flammable gas. Used for pump room lighting

Special protection (Exs)
        >Precautions taken to prevent explosion which are not specifically covered by the previous designations

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