Dead insects in five-year-old air-intake filters and heat from anti-icing panels likely caused an ignition that resulted in a serious fire last year at Equinor’s Hammerfest liquefied natural gas plant in Norway, according to a safety probe report.
Norway's Petroleum Safety Authority (PSA) identified serious breaches of regulations at the LNG plant that resulted in the 28 September fire, which has forced the facility to be taken offline.
Auto-ignition of pre-filters likely cause
The PSA believes it has found the reason why a fire could start in the air-intake filters of a shut-down gas turbine.
Equinor had, as a cost cutting measure, changed is maintenance schedule for air filters from annual replacements to inspection based maintenance, the PSA said.
These filters had not been replaced since 2015 and contained dead insects, which might have reduced the temperature necessary for the filters to self-ignite, the PSA said.
“Technical fire tests and simulation of temperature development in the turbine’s filter housing support the likelihood that the fire broke out because pre-filters in the air intake auto-ignited,” the PSA concluded.
The tests indicate that a biomass build-up — primarily of insects — in the pre-filters may have lowered their auto-ignition temperature.
The control valve for hot-oil supply to the air intake’s anti-icing panels had been opened manually to dissipate excess heat in the hot-oil circuit. This caused the temperature in the filter housing to rise sufficiently to auto-ignite the pre-filters.
The fire caused material damage to the GTG4 air-intake and filter housing and consequential damage from extinguishing work to electrical, instrumentation and mechanical equipment, the PSA found.
The PSA has issued an order for Norwegian state-controlled giant Equinor to devise a plan to correct non-conformities by June this year.
A number of identified non-conformities relate to manning, maintenance, management and control.
PSA to follow Equinor closely
Earlier this month, the PSA raised concerns that Equinor’s low level of manning and frequent use of extended offshore periods for workers is a safety hazard and ordered the company to find a solution to that issue.
PSA director general Anne Myrvold told Upstream that she is concerned over a number of findings related to staffing, maintenance and competence at Equinor, vowing the safety watchdog will follow the company more closely.
“Several of our findings in recent audits have identified similar non-conformities related to manning and maintenance. This will be a focus-area for us,” she said.
Bjorn Asle Teige of Norwegian workers union Safe argued that Equinor has reduced too many positions at Hammerfest LNG, and added that similar problems exists at the operator's offshore installations due to cost cutting since the oil price dropped in 2014.
Another union, Industri Energi (IE), has been highly critical of Equinor’s management of Hammerfest LNG. Leader of IE Frode Alfheim said the PSA’s report identifies several vulnerabilities, which need to be corrected.
“It should be safe to work in Norway’s oil and gas industry,” he said.
IEs representative at the facility, Terje Nilsen, agreed with the PSA’s findings regarding mismanagement and lack of competent personnel.
“It is a complicated facility, which relies on skilled people,” he said.
'Comprehensive programme' - Equinor
An Equinor spokesman told Upstream that the company has already initiated programmes to address these issues.
“We agree with PSA when they see a negative trend concerning manning and competence at our facilities, and we have therefore initiated a comprehensive programme, involving 175 management groups, to identify challenges related to this,” he said, adding that Equinor has already started to implement changes.
When the fire at Hammerfest LNG broke out, the Equinor-operated plant was being ramped up following a shutdown. The turbine had been shut down owing to a fault in an oil filter.
Hammerfest LNG has been shut down since the fire and is due to resume operation on 1 October 2021.