MSF: Grub screws and perished valves – trouble with methanol transfer

What happened?

The Marine Safety Forum (MSF) has published Safety Alert 20-06 relating to problems with methanol transfer caused by problems with grub screws and perished valves. A vessel was advised by an installation of a discrepancy in the quantity of methanol received compared to what was expected.

Investigation revealed that these discrepancies whereby a quantity of methanol was unaccounted for, had been occurring for years. Unknown to the crew, during the transfer of methanol to the installations, a quantity of the methanol was also being discharged to sea via the system flushing line. This was possible as a spool piece was incorrectly left in place and two valves either side of the spool piece were passing fluid.

What were the causes? What went wrong?

One rubber valve was found to be perished and the other Teflon valve was found with signs of corrosion. On closer inspection it was found that a grub screw, for limiting the movement of the gears was too far in and was restricting the range of movement. This resulted in the Teflon valve not closing fully and had been that way most likely from newbuild.

The MSF’s member identified the following root causes:

• Insufficient knowledge of the methanol cargo system;
• Insufficient Planned maintenance;
• Insufficient transfer procedures in place;
• Poor communication.

Actions and recommendations

• Proper and recorded confirmation from the receiving installation that they have received the correct quantity of cargo;
• Review cargo systems or any appropriate liquid transfer systems to ensure that any set-up designed to avoid discharge to sea is correctly in place;
• Update planned maintenance system.

Members may wish to refer to

• “The Carriage of Methanol in Bulk Onboard Offshore Vessels” recently published in conjunction with Oil Companies International Marine Forum: https://www.marinesafetyforum.org/guideline/the-carriage-of-methanol-in-bulk-onboard-offshore-vessels/
• High Potential dropped object near-miss: antenna fell to deck [immediate cause: two grub screws were found to have come loose.]
• Failure Of Chamber Door Hydraulic Actuator [immediate cause: All the seals inside the actuator were found to be completely perished inside.]