200884 Fire on VLCC mast riser

A VLCC was loading crude oil from an offshore floating storage and offloading (FSO) terminal. During the operation, the terminal sighted an approaching squall and informed the mooring master and the VLCC crew. Shortly after, the squall descended on the vessels and a flash of lightning resulted in a fire on the mast riser of the loading VLCC.

The VLCC crew responded to the fire in a professional manner. They promptly extinguished it and continued with drenching and boundary cooling for about an hour, after which the FSO terminal gradually reduced the cargo transfer rate.

Root cause / contributory factors
Sudden oncoming squall;
Failure on the part of VLCC crew to detect and respond promptly to the approaching squall by ordering the stoppage of cargo transfer, purging and securing the mast riser in good time.

Lessons learned
When bad weather, especially a thunderstorm or rain squall, is approaching an oil terminal or tanker engaged in loading or unloading, cargo transfer must be stopped promptly and the mast riser should be purged and secured until it is determined that there is no danger from the weather.
The tanker and terminal staff must be fully proficient in dealing with a mast riser fire and should respond as per established safety procedures.
During cargo operations, a positive inert gas pressure must be maintained in the cargo tanks so as to prevent a flame from travelling down the mast riser into the tank.

Editor's note: The following extracts from the International Safety Guide for Oil Tankers and Terminals (ISGOTT) summarises industry expectations:

From 26 Safety Management, 26.1: climatic conditions.
26.1.3 Electrical storms (lightning)
When an electrical storm is anticipated in the vicinity of the tanker or terminal, the following operations must be stopped, whether or not the ship's cargo tanks are inerted:
Handling of volatile petroleum.
Handling of non-volatile petroleum in tanks not free of hydrocarbon vapour.
Ballasting of tanks not free of hydrocarbon vapour.
Purging, tank cleaning or gas freeing after the discharge of volatile petroleum.
All tank openings and vent valves must be closed, including any bypass valves fitted on the tank venting system.

From 26.4 Guidelines for completing the ship/shore safety checklist:
The operations should be suspended and all deck and vent openings closed on the approach of an electrical storm.