A liquid nitrogen leak aboard Shell’s Shearwater platform in the North Sea caused serious structural damage during a nightshift testing operation, cracking 10mm stainless steel deck plating in three locations and prompting safety warnings and an improvement notice from the UK’s Health and Safety Executive (HSE).
The incident occurred on July 12th during pipework commissioning tests, when operatives were using liquid nitrogen to purge and pressurise new lines.
The release was slow and initially went unnoticed, as cryogenic fluid escaped from valve connectors. Over time, the nitrogen dispersed and exposed a section of the platform to extreme cold, ultimately leading to a structural failure.
Between 2am and 3am, a loud “big bang” was reportedly heard on the platform.
The cause was later attributed to thermal stress fracturing the weather deck. Shortly after 3am, crew discovered a crack along the underside of the weather deck, with the affected stainless steel surface ice cold to the touch.
The fracture forced part of the heavily rusted metal to detach, causing a partial separation of the roof and deck plating.
The stainless steel deck fractured in three separate areas. Debris that included rust flakes and cracked steel fell to the deck below, where liquid nitrogen tanks and cryogenic pump systems were located.
An offshore industry veteran : “I’ve been in this industry over 40 years, and I’ve never seen anything like this happen on a platform. The steel cracked like glass.”
Shell said the incident was immediately reported to the Health and Safety Executive.
Following its investigation, which concluded on August 4th, the HSE stated that the incident could have caused a fatal injury had personnel been present in the impact zone.
An improvement notice issued to Shell reads: “Our investigation has identified underlying causes relating to the adequacy of your existing arrangements and/or adherence to those arrangements such as loss of containment events, suitability of weep and seep bunding, plant integrity checks, response to leaks, contractor management, control of work, monitoring, audit and review.”
Shell has been given until September 30th to comply with the regulator’s recommendations.
Exclusive images obtained by SWD Media shows the damaged section of the platform deck after it was cut out and removed, revealing fracture lines consistent with cryogenic embrittlement.
A Shell spokesperson said: “Shell’s goal of zero harm to people is a priority that drives every decision we make.
“A small amount of liquid nitrogen was released, damaging the deck underneath.
“None of our teams were harmed and we acted quickly to stop the leak and block off the affected area.
“We informed the Health and Safety Executive of the incident immediately and are working with them to implement improvements.”
The Shearwater platform is a Shell-operated, fixed, manned facility in the Central North Sea, located approximately 140 miles east of Aberdeen.
It serves as a key gas processing and export hub for Shell and its joint venture partners.