As the facilities which raise oil and gas from the seabed for processing on the surface, risers are key components in the offshore petroleum industry.
The flexible type brings up about 50 per cent of Norwegian petroleum production.
Risers on fixed installations are made of steel. But floating units, such as production ships or semi-submersible platforms, must rely on flexible tubes.
The latter are manufactured from several layers of polymer materials to provide a tight seal, and incorporate steel reinforcement to provide the necessary strength.
They are heavy, expensive and fall into a completely different technological league than conventional rigid risers.
“These are complex products, with many possible failure modes,” explains PSA principal engineer Trond Sundby.
“They make heavy demands on monitoring, design calculations and inspection.”
But the requirements in Norway’s regulations are absolute – flexible piping systems must have the same high level of safety as steel ones.
“The industry must work purposefully to develop methods and tools for condition monitoring of flexible risers,” says Mr Sundby. “New technology is crucial for preventing undesirable incidents in this area.”