A fire that broke out on a Norwegian offshore FPSO, was caused by a mixture of design errors and faulty operation of the HVAC system.
According to Norwegian investigators, the Petroleum Safety Authority (PSA), the fire broke out on the morning of the 24th March 2015 and originated from the Petrojarl Knarr FPSO’s HVAC system.
Petrojarl Knarr FPSO
The Petrojarl Knarr Floating Production Storage Offloading (FPSO) vessel, is stationed offshore Norway and operated by BG Group.
The FPSO is owned by Teekay, and has been leased to BG Group for an initial 14 years with options to extend. The FPSO is Teekay’s largest to date and was delivered in 2014.
According to the PSA, a power outage had preceded the fire, causing all systems to shutdown. There investigations showed that once power was restored, the fans to the HVAC system were not restarted. However, steam continued to be supplied to the heat exchanger within the system.
The PSA have said that these events cause continual high temperature buildup around the air filter cassette, until they eventually ignited around 8 hours after the initial incident.
The resulting fire occurred in the HVAC system, directly beneath the FPSO’s living quarters. The investigation found that, had it not been for the fire damper vales, smoke could have entered the living quarters.
The fire was eventually extinguished 30 mins after ignition.
The PSA found that a number of breaches and nonconformities during its investigation, covering both technical, mainly design errors and faulty operation, but also relating to the response to the emergency.
On design, the PSA said:
A design error meant that the valve for the steam heating system did not automatically close when the fans stopped. Steam temperature in the HVAC unit was about 100°C.
The filter cassettes used had a maximum design temperature of about 70°C. They collapsed as a result of lengthy exposure to a temperature of roughly 100°C.
On procedures, the PSA said:
The fan system was not restarted after the power failure the day before. Bringing fan systems back on line formed part of the “black start” procedure, but the latter was not followed.
Alarms in the CCR from the HVAC unit were not perceived as critical after the power failure the day before. They were given the lowest priority on the screen.
The system description and restrictions for running the system in manual mode were not clearly explained in the system documentation.
Knowledge about and familiarity with the consequences of operating the system in various operational modes were insufficient, and a lack of clarity prevailed about roles and responsibilities for operating the system.