DOUBLE HULLS, OFFICER TRAINING KEY TANKER SAFETY ISSUES

June 18, 1990
About half the tanker oil spills in 1988-89 could have been prevented or minimized if the vessels had been double hulled, contends Tanker Advisory Center Inc. (TAC), New York. The other 50% of spilled oil resulted from the sinking of loaded tankers after an explosion, fire, or in bad weather. There is insufficient information to know whether double hulls would have prevented the sinkings, TAC said. Arthur McKenzie, TAC director, made the comments at the Institute of Marine Engineers London

About half the tanker oil spills in 1988-89 could have been prevented or minimized if the vessels had been double hulled, contends Tanker Advisory Center Inc. (TAC), New York.

The other 50% of spilled oil resulted from the sinking of loaded tankers after an explosion, fire, or in bad weather. There is insufficient information to know whether double hulls would have prevented the sinkings, TAC said.

Arthur McKenzie, TAC director, made the comments at the Institute of Marine Engineers London conference last month.

He supports double hulled vessels on grounds they make tanker operations safer and less polluting,

But, McKenzie added, double hull tanker construction costs would be 25% more than those for single hulls and would raise transportation costs by about 11 %.

At the same conference, Shell International Marine Ltd.'s M.G. Osborne and Lloyd's Register's J.M. Ferguson said response of watch officers to a developing crisis is more important than ship design.

SPILLS PREVENTABLE?

Of the 43 spills from tankers of 10,000 dwt or more in 1988-89, double hulls would have prevented or minimized the effects of 28, TAC said. They would have made no difference on 12 of the spills.

The remaining three tankers, two single hulled and one double bottomed, sank at sea.

There was no evidence about the causes of the three disasters because all 79 crew members involved were lost at sea.

Of the 28 spills that could have been prevented or mitigated, 10 involved ruptures of single skin bottoms through stranding, grounding, or striking bottom.

Nine of those damaged cargo tanks and the 10th damaged cargo and bunker tanks.

Of the 18 tankers that spilled oil through the sides of their hulls, six were fitted with double bottoms.

McKenzie said double hulls can be more effective if scantlings, or dimensions of all structural parts, are increased.

PROPER TRAINING NEEDED?

Even the very best design and construction would not prevent pollution if a severe collision or grounding occurred, Osborne and Ferguson said.

The problem is best resolved by proper training of the bridge team and implementation of a backup decision making process in confined waters, wherein no individual could make a decision jeopardizing the ship without confirmation from another officer.

Osborne and Ferguson said the next generation of tankers will not necessarily be an improvement over the last.

The use of high tensile steel and optimized structural designs to minimize the amount of steel in the hull will require owners or managers to detect early signs of fracture or corrosion.

If those ships also incorporate double bottoms or double hulls, even greater vigilance would be required.

Further, they warned, as the shipbuilding market swings firmly in builders' favor, owners who order new ships will need to exercise great care to ensure that the yard complies with these requirements.

Copyright 1990 Oil & Gas Journal. All Rights Reserved.