The company has achieved a world first in creating transducers that can carry out reliable ultrasonic testing at 4,000 meters below sea level, the depth at which the Prestige lies on the seabed. The transducers, along with the other equipment, have been operating under a demanding workload in extreme conditions. Their operation has been entirely successful and the whole recovery project is due to be completed by the end of summer.
The Prestige was carrying around 70,000 tonnes of oil when it sank off the north-west coast of Spain. An estimated 13,800 tonnes remain in the hull. The recovery operation – described as ‘environmental science’s moon shot’ by one journalist - is designed to prevent any further damage to the environment. The underwater engineering and operations company Sonsub, which specialises in underwater work, is the main contractor to Repsol YPF, which was appointed by the Spanish Government to design, develop and manage the recovery project.
Working from their survey ship, the Polar Prince, positioned above the wreckage, Sonsub sent down remotely operated vehicles (ROVs), initially to carry out ultrasonic scans of the Prestige’s deck, and later to drill through and position valves. In the next phase of the operation, the valves were opened to release the oil, which rises upwards and is captured in 300-ton shuttle tanks in the same manner that a hot air balloon captures hot air.
It is only recently that ROVs have been able to operate at such depths and Sonsub upgraded models specifically for this purpose. It commissioned Phoenix to design probes which could be mounted on the robots and operate in the same exacting conditions. John Turner, special projects manager at Phoenix’s Warrington headquarters, said: “Ultrasonic testing is a crucial part of the recovery operation as it reveals the best places to drill. The ship’s deck was strengthened by metal beams running along the underside. These have to be located by ultrasonic sensors since the valves have to be sited carefully between them.”
Inspection results can be analysed in real time as data is fed back through the umbilical cord which links the robot to the ship above. At the same time, a video camera on the front of the ROV feeds back live views of the whole operation. John Turner added: “The biggest problem in creating transducers was to design ones that could withstand the tremendous pressure which, at 4,000m underwater, is equivalent to 400 bar or 6,000 lb per square inch. We believe it is the first time ever that ultrasonic transducers have successfully operated at this depth. The devices had to be proven to operate at 500 bar, and we know that the concept is good for 650 bar or more.”
The work was carried out by Phoenix’s technical support team. For further information on the technical support service and how it can assist in your project contact Phoenix on +44 (0)1925 826000.
