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Protecting against high waves

November 9, 1999, 08:00 CET

A screen is being installed on Statoil's Norne production ship in the Norwegian Sea to protect against waves washing over the bow and tank deck.

This protective barrier along the tank deck on the starboard side could be supplemented by raising the bows five metres.

Long waves known as "green seas" – masses of water capable of damaging equipment on deck – have washed over the ship sides on two occasions.

When waves 12-13 metres high arrive at long intervals, the ship is trimmed to bring the bows higher out of the water. And it is loaded up to 90 per cent of maximum capacity before discharging in order to lie more easily in such seas.

"These measures bring the bows up high enough to avoid heavy waves breaking over them," explains Hans Eidissen, operations vice president for Norne in the north Norwegian port of Harstad.

In special weather conditions, movement on the exposed tank deck is either restricted or totally prohibited.

Experience with the Norne ship underlay the decision to heighten the bows of the Åsgard A oil production ship now working on this Statoil field further to the south.