Australian Transport Safety Bureau (ABTS) has concluded the investigation of a fire incident onboard the world’s first LH2 carrier Suiso Frontier that took place on 25 January 2022 on its maiden voyage.
The ABTS’ investigation has found that the failure of an incorrectly-fitted electrical solenoid valve led to the brief propagation of flame from a liquified hydrogen carrier gas combustion unit’s vent stack
To remind, the Suiso Frontier, built as a prototype ship to assess the technical aspects of transporting liquified hydrogen (LH2) by sea, departed Kobe, Japan on 25 December 2021 with 55 t of LH2 and arrived at the Port of Hastings, Victoria on 20 January 2022 to load additional cargo before returning to Kobe.
After LH2 had been loaded at Hastings on 24 January 2022, the ship was still berthed on the evening of 25 January when the gas control equipment malfunction occurred.
A worker on board the ship observed a yellow gas flame briefly propagate from the gas combustion unit’s vent stack on the ship’s deck. There was no subsequent fire or explosion, and no injuries or damage were reported.
Nevertheless, on 25 February 2022, the Suiso Frontier returned to Kobe in Japan from Hastings, delivering the world’s first cargo of liquefied hydrogen to the country.
Following the incident, ABTS launched an investigation which has now found that the gas combustion unit’s air fan discharge damper actuators – which regulate the flow of air into the unit – were fitted with direct current (DC) electrical solenoid valves, which were incompatible with the 230 V alternating current (AC) supply from the GCU control system.
“During roughly 400 hours of service prior to the occurrence, the solenoid valves were subjected to conditions for which they were not designed”, ATSB Chief Commissioner Angus Mitchell said.
“When one of these solenoid valves failed, the fan discharge damper it was operating closed. Consequently, the temperature of the gas combustion unit increased, eventually resulting in the discharge of flame from the unit’s vent stack.”
In addition to the incorrect solenoid valve being fitted, the ATSB found the gas combustion unit was not equipped to detect the failure of the valve, nor the subsequent closing of the damper.
In response to the incident, the manufacturer of the gas combustion unit, Saacke, fitted limit switches on each air fan discharge damper to monitor the damper position.
In addition, the system’s control logic has been programmed to stop the unit if a fault is detected.
“The ATSB’s investigation highlights the importance of ensuring automated shipboard operating systems are equipped with safety controls to prevent hazardous consequences in the event of a malfunction”, Mitchell concluded.
“The incident also shows the importance of stringent manufacturer quality controls to ensure correct system components are specified and fitted to equipment.”