In the event of failure of the inert gas system, action must be taken immediately to prevent air from being drawn into the tanks.
All cargo and/or ballast pump operations must be stopped and the deck isolating valves for the inert gas system closed. Immediate action must be taken to repair the system.
It is essential that the Company be informed immediately of such a failure together with the reason for failure if known, and of any spares are required to repair the system.
Masters are reminded that national and local regulations may require the failure of an inert gas system to be reported to the harbour authority, terminal operator and to the port and flag state administrations.
In crude carriers, due to the possible presence of pyrophoric iron sulphide deposits, such a failure will require either repair to the system or an external supply of inert gas before discharge or tank cleaning can resume.
In the case of product or chemical carriers where a failure cannot be immediately repaired, discharge or tank cleaning may only be resumed if an external supply of inert gas is provided or the following precautions are taken:-
- Flame screens are checked to ensure they are fitted and in good condition.
- Valves on the vent mast risers are opened.
- No dipping, ullaging, sampling or other equipment is to be introduced into the tank unless essential to the safety of the operation. If it is necessary for such equipment to be introduced into the tank, it is to be carried out only after at least 30 minutes has elapsed since the supply of inert gas to the tank has ceased.
- All metal components of any equipment to be introduced into the tanks must be securely earthed. This restriction is to be applied until a period of 5 hours has elapsed since the supply of inert gas into the tanks has ceased.
- Company permission has been granted.
Points to pounder :
If it becomes necessary, on a product and chemical carrier, to clean tanks while the inert gas system is out of operation, the precautions detailed in the ISGOTT Guide must be observed.
Should a vessel experience a partial failure of the inert gas system during discharge of cargo and the vessel is unable to supply sufficient inert gas to keep the tanks inerted at a positive pressure of at least 100mm water gauge, then the cargo discharge rate must be reduced to a level at which a positive pressure of 100mm water gauge can be maintained.