MV Derbyshire, which was first called Liverpool Bridge, was a British ship designed to carry ore, bulk goods, and oil. It was built in 1976 by Swan Hunter and was the last ship in the Bridge-class group of six. The ship was registered in Liverpool and owned by Bibby Line.

MV Derbyshire sank on September 9, 1980, during Typhoon Orchid, south of Japan. All 42 crew members and 2 of their wives died in the disaster. With a size of 91,655 gross register tons, it is the largest British ship ever lost at sea.

History

MV Derbyshire was launched in late 1975 and began service in June 1976 as the last ship of the Bridge-class combination carrier, originally named Liverpool Bridge. It was built by the Seabridge Shipping Ltd. consortium for Bibby Line. The ship was not in use for two of its four years of service life.

In 1978, Liverpool Bridge was renamed Derbyshire, the fourth ship to carry the name in the company's fleet. On 11 July 1980, on its final voyage, Derbyshire departed Sept-Îles, Quebec, Canada, with a destination of Kawasaki, Kanagawa Prefecture, Japan. However, the ship sank near Okinawa, southern Japan. It was carrying 157,446 tonnes of iron ore.

On 9 September 1980, Derbyshire stopped to ride out Typhoon Orchid, about 230 miles (370 km) from Okinawa. The ship was overwhelmed by the storm, resulting in the deaths of all 252 people on board. No emergency call for help was sent. The ship had followed weather routing advice from Ocean Routes, a commercial weather routing company.

The search for Derbyshire began on 15 September 1980 and ended six days later. After no trace of the ship was found, it was declared lost. Six weeks after Derbyshire sank, one of its lifeboats was seen by a Japanese tanker.

Derbyshire’s sister ship, Kowloon Bridge, sank near the coast of Ireland in 1986 after cracks were discovered in its deck following an Atlantic crossing. After this second disaster, Nautilus International, the National Union of Rail, Maritime and Transport Workers, and the International Transport Workers’ Federation helped fund a new investigation requested by relatives of the Derbyshire victims.

Further investigation

In 1994, a deep-water search began. In June of that year, the wreck of the Derbyshire was found at a depth of 4 kilometers (2.5 miles), spread over 1.3 kilometers (0.81 miles). A later exploration spent over 40 days photographing and examining the debris field to find evidence of what caused the ship to sink. It was determined that waves crashing over the ship’s bow had earlier cut off the covers of small ventilation pipes near the front. Over the next two days, seawater entered through these exposed pipes into the front part of the ship, causing the bow to sit lower in the water. Eventually, the bow became vulnerable to the force of rough waves, which caused the massive hatch on the first cargo hold to buckle inward, letting hundreds of tons of water enter quickly. As the ship sank, the second and third hatches also failed, pulling the ship underwater. As the ship sank, increasing water pressure twisted and tore the ship apart through implosion/explosion, a property of double-hulled ships where the compression of air between the hulls causes a secondary explosive decompression.

The formal forensic investigation concluded the ship sank due to structural failure and found the crew not responsible. The report detailed the sequence of events leading to the ship’s failure. Later, in 2001, Douglas Faulkner, a professor of marine architecture and ocean engineering at the University of Glasgow, linked the Derbyshire’s sinking to the science of freak waves, concluding the ship was likely destroyed by a rogue wave.

In 2007, Craig B. Smith, a sailor and author, confirmed earlier findings by Faulkner in 1998. His work showed the Derbyshire was exposed to a water pressure equivalent to 20 meters (66 feet) of seawater (possibly a super rogue wave). The deck cargo hatches on the Derbyshire were identified as the main point of failure when the rogue wave struck the ship. The hatches were designed to handle a water pressure of less than 2 meters (6.6 feet) of water, or 17.1 kilopascals (2.48 psi). However, the typhoon load on the hatches was over ten times the design limit.

Fast-moving waves are now known to create extremely high dynamic pressure. Plunging or breaking waves can cause short, sudden pressure spikes called "Gifle peaks," which may reach pressures of 200 kilopascals (29 psi) or more for milliseconds. This pressure can cause sudden breaking of mild steel. Evidence of this type of failure was found on the Derbyshire. Smith documented scenarios where hydrodynamic pressure of up to 5,650 kilopascals (819 psi) or over 500 metric tonnes per square meter could occur.

Memorials

A bronze plaque was placed on the wrecked ship as a memorial for those who died. On September 21, 1980, the Bibby Line ship Cambridgeshire held a memorial service for the Derbyshire in the location where the ship sank.

The 20th anniversary of the Derbyshire's sinking was celebrated with a memorial service in Liverpool, England. Deputy Prime Minister John Prescott attended the event. He had previously worked as a merchant seaman. Ten years later, another memorial service was held in Liverpool, the Derbyshire's home port, on the 30th anniversary of the ship's loss.

A permanent monument was placed on September 15, 2018, in the garden of the Church of Our Lady and Saint Nicholas in Liverpool.