The VOC management plan is to ensure that the operation of a tanker, to which regulation 15 of MARPOL Annex VI applies, prevents or minimizes VOC emissions to the extent possible.
Methods and systems for the control of VOC during transit are
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Best Practices/Design
- Manual pressure relief procedures (tank pressure control);
- P/V valve condition and maintenance;
- Condition of gaskets for hatches and piping;
- Inert gas topping up procedures;
- Partially filled tanks;
- Loading sequence and rate; and
- COW procedures.
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Vapour Pressure Release Control Valve (VOCON ) peocedure:
This procedure requires the monitoring and the recording of the pressure drop during a release of gas from the cargo tank vapour system. This can be undertaken with the use of the Inert Gas pressure gauge in the cargo control room or, as available, located on the Inert Gas pipeline on deck.
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The VOCON operational procedure
- Before opening the mast riser, note the pressure in the Inert Gas pipeline system.
- Open the pressure release valve and record/monitor the pressure within the Inert Gas pipeline at regular short intervals (every 30 seconds for a mast riser release).
- Plot the pressure drop profile. This can be achieved either manually or by use of the Inert Gas Oxygen and Pressure Recorder in the Cargo Control Room but an increase in the Recorder paper feed rate will be required to achieve definition of the plot.
- When the rate of pressure drop becomes constant (after the initial rapid pressure drop) then the gas release should be stopped and the valve closed.
- Monitor the Tank Gas Pressure after completion of the controlled release in order to check the final pressure obtained within the Vapour/Inert Gas system.
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