Equinor investigating welding defects on Castberg FPSO hull
An in-house investigation team from Norway’s Equinor has studied the deviation in quality of welding and inspection of the Johan Castberg production vessel currently under construction at the Sembcorp Marine yard in Singapore.
During the construction of the hull for the Johan Castberg production vessel at Sembcorp Marine in Singapore, Equinor has revealed quality deviations regarding both welding and welding inspection.
In September 2020, Norwegian offshore safety watchdog, the Petroleum Safety Authority Norway (PSA), launched an investigation into challenges related to the completion of the hull and equipment for Equinor’s Johan Castberg FPSO.
In October 2020, Equinor reported that the Johan Castberg project would be delayed by one year, with planned production start in the fourth quarter of 2023.
The main cause of the delay is the Covid-19 pandemic and associated infection control measures introduced at the yards in Singapore, Stord, Verdal and Sandnessjøen.
Other challenges include the progress in Singapore and deviations in welding quality.
Equinor informed on Monday that extensive work is being carried out to quality assure and cross-check welds and repair welding defects, to ensure that the vessel meets applicable safety and integrity requirements before leaving the yard.
“Safety is Equinor’s top priority. We are currently carrying out extensive cross-checking and repair of welds to ensure that the Johan Castberg production vessel meets the safety and integrity requirements. When Johan Castberg comes on stream, there should be no doubt that the vessel is safe”, said Geir Tungesvik, Equinor’s senior vice president for project development.
Equinor noted that the yard is responsible for correcting all deviations in quality and costs related to repair of welding defects are covered by Sembcorp Marine, according to the contract. The cross-checks and improvements are almost completed and are followed up closely by Equinor.
“To ensure learning and avoid similar situations in other projects or at other yards, we have carried out a thorough investigation”, said Tungesvik.
According to Equinor, the investigation team did not find any single event which could have been a direct cause for the welding quality issues, but has pointed out causal factors considered as having had an impact.
These include the fact that the contractor (SCM) failed to provide sufficient competent welders and welding inspectors for execution of the scope and did not sufficiently comply with processes and work routines for execution and follow up of welding and inspection activities.
Furthermore, Equinor has not sufficiently complied with its own work processes and procedures for risk management, construction management, and follow-up at the construction site.
Even if Equinor’s follow-up team found signs of poor quality at an early stage, the extent and degree of seriousness were not understood. Sufficient measures were therefore not implemented.
Finally, Equinor’s follow-up team has not had enough personnel with experience and expertise in welding and welding control and has not utilized the company’s technical expertise in these areas early enough, the Norwegian company said.
“We are preparing a plan with specific actions to follow up the findings and we will share our experience”, said Tungesvik.
The investigation team has studied the causes of the deviations in welding quality in the period from January 2017 to October 2019.
Based on this work, the team recommends Equinor to improve the prequalification process for new suppliers, the practice for follow-up at construction sites, including risk management, and the recruitment process for follow-up teams and team composition.
When Equinor in the summer of 2019 cross-checked Sembcorp’s ultrasonic inspection of welds in the moonpool area of the hull by using its own personnel, it discovered a higher failure rate than reported. It was then decided to cross-check all assembly welds. Unusually high failure rates in fabrication welds were revealed later.
“We have therefore reassessed all structural welds on the hull. This is a very demanding job as the hull has already been built, however, safety comes first. The vessel must meet the requirements incorporated in the plan for development and operation (PDO) and obtain a DNV class certificate before sailing to the field”, said Tungesvik.
A reassessment of all structural welds has been made and extensive cross-checking is being carried out by use of non-destructive testing (NDT), including ultrasound.
“Equinor should have discovered the extent of welding defects earlier, however, the hull is still in dock, allowing us to repair the defects before it is launched”, said Tungesvik.
The hull for the Johan Castberg production vessel is scheduled to be transported to Stord on board the Boka Vanguard heavy-lift vessel in late 2021, however, the Covid-19 pandemic still adds uncertainty to all schedules, Equinor concluded.