202445 Deck tank overloaded

During a company audit it was noticed that the deck tanks used for ammonia storage had been loaded up to 98% at a loading temperature of -22°C. The expected ambient temperature later in the voyage was 20°C.

Deck tanks are high pressure vessels that require strict adherence to the cargo manual. In the case described above, the deck tanks should have been loaded to 89.5% to allow for increased pressure when ambient temperatures increased.

Further inquiries identified that the cargo manuals had the appropriate loading curves, but their usage had not been properly explained to crew. Alternatively, the filling limits can be obtained through the formula as mentioned in IGC code, Par.15.5.1.

Lessons learned

• Be familiar with your cargo manual and don’t hesitate to ask questions.
• Audits are invaluable tools in quality assurance, not exercises in finding fault.