Sandvik Umbilical Tubes: A Look Back at 17 Years in Service

In 1998, tubing made from super duplex stainless steel SAF 2507™ was commissioned for one of the world’s first dynamic umbilicals, located in the harsh Norwegian Sea.

The tubes had to be super robust, reliable and long lasting to survive the challenging conditions of the Åsgard field more than 300 meters below water.

Seventeen years later, the incident free umbilical was replaced as part of a routine inspection, repair and maintenance program for the field. Tests showed the tubes made from SAF 2507™ were as good as the day they were manufactured.

The Background

The Åsgard oil and gas field is 200 km offshore Norway in the Norwegian Sea. Conditions can be rough so, for its new dynamic umbilical, our client needed hydraulic tubing and service lines that were strong enough to withstand corrosion, high pressure, and wear and tear. Thermoplastic hose was ruled out by the client because it just wasn’t strong enough. A sturdy and ultra-reliable ‘fail safe’ solution was needed. Sandvik’s metallurgists recommended super-duplex SAF 2507™ stainless steel.

The Sandvik Solution

With excellent resistance to seawater and marine environments, SAF 2507™ combines high corrosion resistance and mechanical strength, and is particularly well suited for tubes likely to experience high stress and aggressive chloride-rich conditions. Its excellent anti-corrosion, erosion, fatigue and mechanical properties meant it was the perfect choice for the dynamic umbilical’s tubing.

For 17 years the umbilical performed without problems. Then it was decided to replace it as part of routine inspection, repair, and maintenance. After so long, we were curious to know what the tubes were like, so they were returned to Sandvik for integrity testing.

The result

The tubes could have been damaged by a variety of things over their working life in such hostile subsea conditions. Tubing samples were taken from different points on the umbilical and a thorough range of tests was conducted - from visual inspection and chemical analysis to scale electron microscope (SEM) investigations and hydrogen content analysis. Sandvik also compared the mechanical properties of the old tubes with brand new SAF 2507™ tubes.

Despite putting the original samples through the most vigorous tests no signs of corrosion, mechanical degradation or fatigue were found. Burst pressure was well above 25,000psi, more than twice the required design pressure. There were no significant differences in yield, tensile strength or elongation. The visual appearance was excellent.

The test results gave us complete confidence that the tubes were still in good condition and could have withstood another 17 more years of service. They proved the value of SAF 2507™ as a well-established and risk-free solution for use in all the different umbilical functions, including control and chemical injection tubing.

Are you designing the next generation of umbilicals? Are you looking for thinner walls? Greater strength? Better corrosion resistance? Let’s talk possibilities. We are committed to helping you overcome your obstacles. Learn more about our umbilical tubing products for corrosive applications here.