The DERBYSHIRE loss
Derbyshire was launched in late 1975 and entered service in June 1976, as the last ship of the Bridge-class combination carrier, originally named Liverpool Bridge. Liverpool Bridge and English Bridge (later Worcestershire, and Kowloon Bridge respectively) were built by Seabridge for Bibby Line. The ship was laid up 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 what turned out to be the ship’s final voyage, Derbyshire left Quebec Canada, her destination being Kawasaki, though she foundered near Okinawa (Southern Japan). Derbyshire was carrying a cargo of 157,446 tonnes of iron ore.
On 9 September 1980, Derbyshire hove-to in a typhoon named ‘Orchid’ some 230 miles (370 km) from Okinawa, and was overwhelmed by the tropical storm killing all aboard. Derbyshire never issued a distress message. The ship had been following advice from “Ocean Routes”, a commercial weather routing company.
The search for Derbyshire began on 15 September 1980 and was called off six days later when no trace of the vessel was found, and it was declared lost. Six weeks after Derbyshire sank, one of the vessel’s lifeboats was sighted by a Japanese ship.
The Derbyshire‘s sister ship Kowloon Bridge was lost off the coast of the Ireland in 1986, following incidences of deck cracking that were first discovered after an Atlantic crossing. In the wake of this second disaster, a new investigation was sought by relatives of the Derbyshire victims.
In 1994 a deep water search began. In June 1994, the wreck of Derbyshire was found at a depth of 4 kilometres (2.5 mi), spread over 1.3 kilometres (0.81 mi). An additional expedition spent over 40 days photographing and examining the debris field looking for evidence of what sank the ship. Ultimately it was determined that waves crashing over the front of the ship had sheared off the covers of small ventilation pipes near the bow. Over the next two days, seawater had entered through the exposed pipes into the forward section of the ship, causing the bow to slowly ride lower and lower in the water. Eventually, the bow was completely exposed to the full force of the rough waves, which caused the massive hatch on the first cargo hold to buckle inward, allowing hundreds of tons of water to enter in moments. As the ship started to sink, the second, then third hatches also failed, dragging the ship underwater. As the ship sank, the water pressure caused the ship to be twisted and torn apart by implosion/explosion, a feature of double-hulled ships where the compression of air between the hulls causes a secondary explosive decompression.