Clue to oil-tanker blasts

Press, Volume CXI, Issue 32677, 5 August 1971, Page 13

Clue to oil-tanker blasts

LV.Z. Press Assn.—Copyright) I LONDON, August 4. Scientists in Europe may have solved one of the most puzzling features associated with the boom in oil-tanker building.

In December, 1969, heavy explosions severely damaged three very large crude-oil tankers, the Marpesa, which sank, the Mactra and the King Haakon VII. In all three cases, empty tanks were being cleaned at the time of the explosion. After 18 months research, scientists now believe the villain may be water. When oil products are carried at sea they deposit an oil-wax mixture which may amount to as much as 0.3 per cent

of the cargo—a large volume when tankers of the 200,000ton class, and larger are involved.

Operators have felt that washing is necessary to prevent the sludge layer from growing, which obviously would reduce tanker capacity.

- Today, the International Chamber of Shipping in London issued its second report on the explosions. Their first had discounted the possibility that pyrophoric deposits, such as iron sulphide, had caused the tanker blasts.

Most of the research was carried out in the Netherlands by scientists employed by the Shell Oil Company. In the tank-cleaning process, water is pumped in through nozzles at a velocity of about 130 feet per second, and large amounts of mist andi

droplets are produced when the high-velocity jet hits the tank walls. What the scientists discovered was that the mist produced in the tank during the washing operation is electrically charged. In addition, because of the volume and velocity of the water, there is a large flow .of air, and convection currents are formed between the hot-deck-side of the tank, and the coldsea water-side. The scientists have concluded that during a large part of the cleaning cycle on board ships and even for a long time afterwards, a charged mist can be present inside the tanks leading to electric discharges of up to 40 kilovolts. The chairman of the I.C.S.’s tanker committee, Lord I Geddes, emphasises the im-

portance of the findings, which, he says, are of major importance to tanker-owners throughout the world, regardless of the size of ships they operate. So far, more than £lm has been spent on research into the causes of the explosions. Present research is aimed at establishing whether the electrical discharges can cause ignition. The scientists report says that, because of the many variables involved, it may well be difficult to come to hard-and-fast conclusions regarding the causes of the 1969 explosions.

However, the extension of research into the problem worjd-wide will, the I.C.S. says, give .shipowners the right guidance on action to be taken to avert further casualties. ,