● In tankers during loading and discharge Tank vapours can be released and sent clear of the decks through high velocity vent.
● It has a moving orifice , held down by a counter weight to seal around the bottom of a fixed cone.
● Pressure build up in the tanks, as filling proceeds, and it causes moving orifice to lift.
● The small gap between orifice lip and fixed cone gives high velocity to the emitted vapour.
● It is fitted minimum 2 meter above the deck.
● Rate of gas venting should be 30meter/second.
● Each tank should have 1 high velocity vent.
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Requirements of high velocity vent? ( Generally asked by surveyor)