Diving Support Vessel

Reducing Risk of Corrosion Failure on Instrumentation Lines

By selecting Tungum tubing a leading deepwater project company was able to reduce the risk of tube line failure due to saltwater corrosion while also cutting downtime and refit costs.

The Challenge

In 1983 a leading deepwater project company Subsea 7 was building a new diving support vessel – Rockwater 1. On previous vessels they had experienced corrosion problems using stainless steel tubing for the instrumentation lines. Various lines run externally and are exposed to a Salt water environment. As a result of the corrosion and resultant leak points, they had to replace stainless steel tubing multiple times on previous vessels at considerable cost and downtime.

The Tungum Solution

Subsea 7 chose Tungum tubing for its proven history in seawater environments and its resistance to stress and crevice corrosion. The tube possesses a natural protection mechanism whereby, on exposure to salt spray, a very thin oxide coating is generated over the exposed service, no more than two thousandths of an inch thick, when complete. The tube becomes discoloured and it may even have a verdigris coating, but under the oxide layer the tube material is perfect and will remain so for a very long time.

The Result

Subsea 7 installed Tungum for the instrumentation lines and was pleased with the performance of the tubing. Tungum tubing now plays a major role in eliminating downtime of many systems in this vessel as it is highly resistant to seawater and its atmosphere, offering outstanding serviceability, even at intermittent duty in the highly corrosive ‘splash’ zone. The photo on the right was taken in 2010 and shows the tube still in good condition and performing well after 26 years of service! Ultimately Tungum provided 34 years of trouble-free service when Rockwater 1 was decommissioned in 2018.