Portcities Southampton
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Liquids in bulk

The tanker specialises

Like most ships, tankers have become increasingly specialised in recent decades.  Although their basic structure, with a hull subdivided into many tanks, has not changed greatly since the Gluckauf of 1886 (see screen DS5F), today‚Äôs tanker comes in several forms representing enormous advances in size and in sophistication.

Conveying the crude: from tanker to ULCC

The traditional role of the tanker of bringing crude oil from the oilfields to refineries in Europe, USA or Japan has fallen to huge vessels, known first as very-large crude carriers (VLCCs) and then ultra-large crude carriers (ULCCs).  In some cases exceeding 1,000 feet in length, these are some of the biggest structures built by man, and certainly the biggest vehicles.  Larger than even the biggest passenger liners, when laden a ULCC full of crude oil can take up to a mile to stop.  The importance of these ships should not be under-rated.  With economies totally dependant on oil, they have maintained supplies whilst reducing transportation costs to a minimum.

Limits to growth

Until the 1970s, big crude carriers just kept growing in size.  Until the 1960s they were limited to the size that could transit the Suez Canal, as many traded between the Arabian Gulf and Europe.  However, the closure of the canal following the 1967 Arab-Israel War meant that the crude had to go round the Cape, and the Suez size limitation became irrelevant.  Indeed, the only limit seemed to be the depth of water available in major ports.  These ships can only use the deepest ports and channels.  Some do not use conventional ports at all, but load and discharge at artificial platforms built in deep water, like that at Bantry Bay in south west Ireland.

However, the growth of big tankers suddenly stopped, and the average size of new vessels actually declined.  Too many of the big ships had been built, and a recession due to OPEC increasing oil prices in the 1980s left many ships laid up out of use with their owners facing bankruptcy.  There were also concerns about the possibility of these massive tankers causing environmental damage on a huge scale, justifiably so as the grounding of the nearly-new Amoco Cadiz on the coast of Brittany showed.  

Safety concerns have encouraged a trend to build double-hulled tankers, in the belief that the hull having two skins will minimise pollution in the event of an accident.  However, some experts believe this is a waste of money, as the sheer weight of a mammoth tanker and its cargo mean that not even a double hull will be safe if the ship is involved in a serious collision or hits rocks at full speed.  There is a strong case for preventing such accidents, with high standards training, maintenance and supervision to minimise the risk of such accidents.