Leak of oil-based mud

What happened?

There was a spillage of oil-based mud from a vessel alongside. The leak occurred when a vessel was preparing to transfer oil-based mud to the shore base. Just prior to transfer starting, the shore base team was about to conduct a pressure test to ensure there was no leakage on their hose. The pressure test was carried out with the objective of maintaining 5 (five) bars pressure at manifold using a dry-break fluid connection. Unfortunately, during the test, about 20-25 litres of the mud came out of the tank ventilation.

The officer on duty immediately instructed the crew on deck to contain the spillage to avoid the mud going overboard. The vessel reported the occurrence to the DPA.

What went right

Before starting the job, the crew and the shore base team conducted a toolbox meeting. After that, the crew prepared to close all valves that needed to be closed and also placed scupper plugs on deck to avoid any spill overboard.

What went wrong

• Before starting the pressure test no-one ensured the valve seals were well-maintained and in good condition;
• During the pressure test, 5 (five) bars pressure could not be maintained, which indicated internal leakage;
• The officer on duty was informed about the overflow by the shore base lifting crew, not by the AB on duty;

What was the cause

The valve seal was damaged, causing the valve’s failure to be fully closed even when the valve’s handle was in a full closed position. The oil-based mud cargo had mixed with certain chemicals remaining at the valve seat leaving the valve surface and seal deteriorated.

Actions taken

• Replaced the damaged valve;
• Arranged regular monthly cleaning on manifold valve;
• Ensured that after carrying out loading/discharge cargo, all lines were blown out to ensure there is no residual chemicals or mud at line and manifold.

Members may wish to refer to:

• Low pressure mud hose parted (2011)
• MSF: water based mud spill on deck
• MSF: Tank corrosion