200829 Fuel tank overflow

On one of our vessels, the third engineer used the diesel oil (DO) transfer pump to fill up the emergency fire pump diesel oil header tank. Simultaneously, the deck crew was taking fresh water from a shore connection through tank filling pipes located on the poop deck. The small, 100-litre DO tank was fitted with only a small open vent pipe on the poop deck and had neither an overflow nor return line, nor a spill-retaining, save-all tray. The fresh water tanks and the DO header tank overflowed within a few seconds of each other, and although all deck scuppers in the vicinity had been p
lugged, the oil spread quickly and was carried overboard by the running water.

Corrective action
All ships in the company were instructed to blank off the line to similar small-capacity tanks, if connected to the DO transfer piping system.

Editor's note: It is fairly unusual to have a direct connection between a DO transfer pump and a small-capacity tank, such as the one mentioned in this report. Given its volume, the header tank should have been filled only manually, preferably using a hand pump or by siphoning with a small diameter hose, and not by a remotely-located power-operated pump.

Although unlikely with diesel oil under normal conditions, there is a vapour ignition risk especially when manually transferring lower flash point liquids like kerosene and thinners. Static charge can accumulate within the fluid and, during transfer, an incendive spark can occur between the receiving container and the portable container / hose. This must be eliminated by earthing all the components just before the transfer commences.

This incident could have easily been avoided if a proper risk assessment and a 'tool-box' meeting had been conducted.

Past incidents also indicate that risks increase substantially if more than one operation is being conducted on board and there is inadequate planning and coordination between personnel.