PRECAUTIONS TO BE TAKEN IN CARRYING OUT WORK ON EQUIPMENT WHICH ARE LIKELY TO HAVE PYROPHORIC DEPOSITS

PRECAUTIONS TO BE TAKEN IN CARRYING OUT WORK ON EQUIPMENT WHICH ARE LIKELY TO HAVE PYROPHORIC DEPOSITS

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Following precautions shall be taken in carrying out work on equipment which are likely to have pyrophoric deposits:

I        Process lines and other in-line equipment like vessel, columns, pumps, pump strainers, etc shall be purged with inert gas or steam and the inner surface kept wet by use of water sprays (by fog nozzles) or saturate steam before and while opening out for repair, replacement or overhauling. Before opening up for air entry / man entry, chemical solution washing should be used to diffuse pyrophoric iron, if any. ^{Note 1}

ii        Pyrophoric scales and rust particles containing iron sulphide shall be kept isolated from oxygen by blanketing with inert  gas or water until these are removed to a safe area or buried to prevent ignition.

For purging of combustible vapour and removal of pyrophoric deposits from tanks and towers, the following recommended practices shall be observed:

I        The unit shall be purged with saturated steam to wet the interior surface.

ii        A high capacity, flame proof air mover at the top manhole and a large fog nozzle in the neck of the side manhole should be installed.  The air mover should be bonded with the unit.  The fog nozzle  should be turned on without delay and immediately thereafter, the air mover should be turned on.  Fog nozzle shall be continued without interruption until the tank is free of hydrocarbons.

iiii      When the hydrocarbon content is reduced below the LEL then the fog nozzle should be isolated and all loose scales shall be knocked down with high pressure water jest.  The air mover should be stopped after all the scales have been removed.