A company has been fined £350,000 (€401,535) after the collapse of a storage tank at its Peterhead, UK, premises which left a self-employed worker with life-changing injuries.
The Health and Safety Executive (HSE) investigated the incident, which occurred on 21 June 2023 at Tetra Technologies UK’s offshore supply base. The base handles around 2,000 ship movements per year, supplying North Sea oil and gas installations with deck cargos and quantities of fluids.
Philip Moir, a 62-year-old self-employed rope access technician, was on site conducting surveys of storage tanks when Tank 7 — a bolted steel tank holding approximately 480,776 litres of calcium chloride solution weighing around 700 tonnes — catastrophically ruptured without warning. Moir was almost immediately immersed to chest height in the released fluid. He was subsequently found slumped over the wheel of a nearby cherry picker, which itself, along with a Ford Transit pickup, a small skip and the cherry picker — weighing twelve and a half tonnes — had all been displaced by the force of the escaping fluid. Moir sustained a double fracture of his spine and pelvis, lacerated liver, punctured lung, multiple rib fractures, fractured sternum, a fractured wrist, and extensive chemical burns requiring skin grafts. He has not worked since the incident and is unable to climb ladders or work at height, injuries described as life-changing.
HSE’s investigation, conducted by both regulatory and specialist inspectors, identified that the structural failure occurred around halfway up the tank shell, where the third row of plates split vertically along a bolted seam. Approximately 4.5 mm of the original 5.5 mm steel plate had been lost through corrosion over time, leaving just 1 mm of steel unable to withstand the outward forces of the fluid within. Investigators found that the loss of any protective coating had left the steel surfaces exposed to aggressive coastal air, accelerating external degradation. The density of calcium chloride — more than one third denser than water — further increased the forces applied to the already weakened structure.
The tank was more than 30 years old and the manufacturer’s maintenance manual required six-monthly checks of seams and bolts, and annual external inspections for corrosion. An inspection in 2013 had already identified extensive outer surface corrosion over the lower section of the tank and corrosion at bolted connections, yet no remedial work was carried out on Tank 7. The company was unable to provide evidence of any regular inspection regime being followed in the years that followed.
On the morning of the incident, Tank 7 had been filled to capacity — a step taken to create space at the company’s Aberdeen premises — and failed less than 30 minutes after the final load was pumped in. HSE concluded that the failure of the tank was wholly foreseeable and preventable.
Following the incident, the company removed all bolted tanks from its sites and closed its Peterhead operation, relocating to its Aberdeen premises.
HSE Inspector Mark Carroll comments: ‘This was a completely preventable incident. The corrosion that caused this tank to fail had been identified a decade before it collapsed, yet no remedial action was taken and there is no evidence that the required inspection regime was ever consistently followed. A worker has been left with life-changing injuries as a direct consequence of those failures. Companies have a legal duty to maintain equipment in an efficient state and good repair, and HSE will not hesitate to take action where that duty is not met.’
