Checking welds with ultrasound

March 23, 2001, 09:00 CET

Pipeline experts in Statoil have secured approval for ultrasonic inspection of pipe welds. This technique has now been approved by Norwegian and international authorities.

This means that automated ultrasound testing (AUT) satisfies international standards and can be used on board pipelaying vessels. The method has environmental and technical benefits compared to x-ray inspections which were previously carried out.

“We avoid the radiation from x-rays and the emission of chemicals associated in developing x-ray film,” says staff engineer Bjørn Lian in the material and inspection technology unit of Exploration & Production Norway (UPN). He adds that the inspectors no longer have to stay in darkrooms for long periods to read the x-rays.

Among the technical benefits, Mr Lian mentions that only “dangerous faults” are now repaired. With the aid of AUT, a fault that has to be repaired can be determined with complete accuracy. This results in shorter repair time, higher lay rate and lower costs.

AUT was used on four pipelines on the Norwegian continental shelf last summer.

“We achieved a repair rate of 0.8 per cent, whereas the rate for x-ray inspections was between 2.5 and 5 per cent in previous projects,” says Mr Lian.