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On route from Canada to Japan with a cargo of iron ore and while passing through the South China Seas, the MV Derbyshire ran into a typhoon and sank, going down with all the crew and two officer's wives.
This is an article in Marine Engineering, and in particular maritime disasters, where we will look at the mystery surrounding the sinking of the Bibby Line OBO Carrier MV Derbyshire. We begin with an overview of the vessel.
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Overview of the OBO Carrier MV Derbyshire
The MV Derbyshire was designed to carry ore, bulks, and oil in her cargo holds, and had previously successfully carried all three cargos at different times in her short life.
An image of an OBO carrier is shown below (note the piping for oil loading and discharge):
She left Canada bound for Japan, on what was to be her last voyage, with a cargo of fine iron ore concentrates with two holds (No. 2 and 6) being left empty. This was normal practice when carrying iron ore because of its inherent weight.
She was navigating the South China Seas on the last leg of her voyage when she was overtaken by a typhoon, the name given to gyratory tropical storms in these waters, which are known as cyclones or hurricanes in other parts of the world. These are prevalent in the South China Seas, located in the Pacific Ocean at the end of the hot season proceeding the rainy season. Typhoons have winds up to 75 mph, creating enormous waves of 30 feet high; rogue waves have been recorded at 100 feet.
This was accompanied with wind-blown spray adding to navigation difficulties. All the master can do in this situation is to put the ship's head into the least damaging position, usually with the waves at a slight angle to the bow, and ride out the typhoon.
The image of an oil tanker in the midst of a typhoon in the Seas of Japan is shown below.
(Image from Liverpoolmuseums.org)
So it was in these conditions during "Typhoon Orchid" that the Derbyshire found herself in on or about the 9th or 10th of September 1980 in the South China Seas.
There are a number of reports on the cause of her sinking, but the most recent one blames the cargo air vent system being carried away, allowing the ingress of seawater into the for’d hold. Another theory blames the design of the structure around frame 65.
Whatever the cause of her sinking, she was and is still the largest vessel ever to be lost at sea.
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Design Characteristics of the MV Derbyshire
The MV Derbyshire was originally built and launched as MV Liverpool Bridge in 1976, being renamed in 1978. She was the last of six ships in the Bridge Class, these vessels being specifically designed and built to carry ore, bulk, and oil. They had to be strongly built to withstand the great forces and stresses exerted by the heavy iron ore cargos.
She had nine holds, each separated by a watertight, double-skinned bulkhead. There were two hatch covers per hold, sliding open from the center to the port and stbd sides. These too were of a strong design; unfortunately not robust enough to withstand the huge rogue waves prevalent in South Sea Typhoons.
OBO's were built to increase the ship owner’s profits by being able to carry a variety of cargoes; however these were not a successful design. Two were lost at sea and another suffered an explosion that killed her captain. An inherent fault in her design appears to be the substitution of longitudinal girders by longitudinal bulkheads at frame 65. This was at the location of the transverse watertight bulkhead, separating No. 9 hold from the pump room and slop tanks.
A sketch of the arrangement is shown below.
The Derbyshire particulars were as follows:
- Gross tonnage- 91,665(GT)
- Length – 965 feet
- Beam – 145 feet
- Speed – 15 ½ knots
- Crew compliment – 42
- Construction date – 1976.
- Port of registration – Liverpool.
- Vessel type – Oil/Bulk/Ore Carrier (OBO)
Page 2 examines the investigation into the loss of MV Derbyshire.
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The MV Derbyshire was an OBO carrier, the last of six vessels built to the design of the Bridge Class. Although the design fault at frame 65 was not deemed to be the cause of her sinking; she and all her sister ships had an inherent structural design fault in this area. The MV Derbyshire design fault at frame 65 consisted of the transformation from longitudinal girders to longitudinal bulkheads at the transverse bulkhead at this frame. Here instead of carrying on the longitudinal girders over the pumproom, two longitudinal bulkheads separating the pumproom from the slop tanks were used instead. These were also found to be misaligned adding to the stresses of the loaded vessel promoting serious cracking that weakened the hull structure.
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Investigation into the Sinking of the MV Derbyshire
As there was no evidence of structural failure being the cause of the sinking of the MV Derbyshire, the British Government did not immediately start an investigation.
However, numerous loss scenarios were being espoused by marine experts, and these have been whittled down to the two most likely causes of the sinking:
- Structural failure at frame 65.
- Collapse of the hatch covers.
The structural failure was to be initially investigated through money raised by the Derbyshire Family Association (DFA), a charity set up after the loss of the Derbyshire to clear the crew of being responsible through negligence for her sinking.
Structural Failure at Frame 65
The funds from the DFA were used to pay for investigations into cracks at frame 65 on some of the other Bridge Class OBO carriers.
This design was thought to promote cracking at this bulkhead. After the Kowloon Bridge, a sister ship, broke into three pieces after running aground, one of the breaks was at frame 65. Meanwhile other sister ships were reporting cracks appearing on the deck above frame 65, prompting an examination by the British Board of Trade (BOT).
This concluded that the transition from longitudinal girders to longitudinal bulkheads could have been responsible for the sinking of the Derbyshire. Here misalignment was also evident between the two components, adding to stresses and promoting cracks.
The DFA had by now raised enough money to fund an underwater survey of the Derbyshire wreck. This indeed confirmed that the Derbyshire was in fact in two pieces. The living quarters and engine room aft of the bridge were lying on the seabed a short distance from the rest of the hull.
A further more detailed investigation was once again carried out by the British BOT and confirmed that the wreck was in two pieces.
However, the stern section was found only 600m from the rest of the remains, and as she had descended through 4000m from the surface, it was therefore unlikely that she broke up on the surface, more likely breaking up on the way down. Marine experts in ships sinking therefore deemed that the design at frame 65 was not the cause of the sinking of the MV Derbyshire.
Collapse of the Hatch Covers
This is the most likely scenario cited by a subsequent BOT investigation; a summary is given below.
It was envisaged that as the MV Derbyshire was overtaken by Typhoon Orchid in the South China Seas, and she started to take heavy green water over the fo’c’sle head. These huge waves damaged /detached the boson’s foredeck stores ventilator covers along with the fore peak ballast tank ventilator covers.
This allowed these spaces to quickly fill, with every wave taking the ship down by the head. Subsequent waves dislodged the fore-cargo hold ventilator covers. With these being carried away, the ventilators were open to the sea.
As larger waves crashed over the starboard side of the bow, they dislodged the No. 1 cargo hatch cover and allowed copious amounts of seawater to enter the hold. This ruptured the internal bulkhead, allowing water into the No .2 hold, and this along with further pounding from subsequent waves caused the No. 2 hatch cover to disintegrate. A sketch of the layout and typical wave profile is shown below.
This had a domino effect on the rest of her nine holds' hatch covers, being acerbated as she sunk down by the head, her angle increasing downwards. Eventually as she slipped below the waves, the bridge, accommodation, and engine room broke away from the rest of the hull.
The total time estimated from No.1 hold hatch being breached to the sinking has been estimated as two minutes. This allowed no time for the crew to abandon ship.
It is a mystery, however, that no “Mayday" was picked up- if indeed one was issued. Even when I was at sea in the 1960's, a Mayday was transmitted simply and quickly by the pressing of a button, which also gave the current location of the ship in distress. I like to believe that the Radio Officer got the Mayday away, but atmospherics stopped it being received on mainland China, the many nearby islands, or other ships in the area.
After the non-appearance of the MV Derbyshire at her destination of Kawasaki, where the relief crew waited in vain, a formal search and rescue was carried out by the Japanese Marine Agency. Their ships and aircraft only found oil bubbling up and shining on the surface of the sea, but this was enough to confirm her final resting place, as shown in the sketch below.
1. mpsgov. IMO advice on for’d flooding
2. scitation.aip. Ultimate Limit Assessment of hull.
3. shipstructure. Overview of the MV Derbyshire and the Investigations.
4. IMO. Improvements to design of ore carriers.
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Memorials to MV Derbyshire
Nowhere was the loss of the MV Derbyshire felt more than in her home port of Liverpool. It was from this famous seafaring port that 17 of her crew members were from, never to return to their loved ones and friends.
Medals for the DFA
The Derbyshire Family Association (DFA) was awarded a medal for their contribution to the design changes in future ore carriers to mitigate the high loss of life due to their sinking. Receiving the accolades and medal, the DFA issued a statement expressing the hope that their friends and family had not died in vain.
They also expected that many lives would be saved because of their investigation prompting Marine Vessel Classification Authorities to introduce design codes of practice preventing any similar structural failures leading to loss of ships and crew.
A floral tribute and Service was held on 20th September 1980, aboard the Bibby Line ship Cambridgeshire.
The Cambridgeshire stopped her engines over the last known position of the MV Derbyshire and lowered her Red Ensign to half-mast. At sunrise and front of the ship’s company mustered on the poop, a service of remembrance was held, after which floral tributes were dropped overboard. These floated on the now calm tropical seas over the Derbyshire’s final resting place, a fitting tribute to those who perished in her.
30th Anniversary Memorial Service
30 years later on the 13th September 2010 a memorial service was held in Liverpool’s Parish church, “Our Lady and St Nicholas," in memory and as a continuing tribute to those who died on the MV Derbyshire in September 1980.