After months of accelerated reliability testing, CPNL Engineering has announced the successful completion of dynamic tests with its articulated pipes at the University of Exeter, as part of the EU-funded MARINET research programme. CPNL applied for this programme in 2013 and was granted a period of 60 days. A total of four different test scenarios of 25,000 axial load cycles ranging from mild (10kN axial load with head stock movement varying from -7°C to 7°C) to extreme (up to 80kN with head stock movement varying between -28°C and 28°C). A 3D scan will subsequently provide the exact measures of wear compared to a 3D scan made prior to the test in September.
"Now the time has arrived to put these results into context," said CPNL Engineering director Ton Tuk. "Although, our core business is to design and supply cable protection systems, we have to consider that these systems needs to be retrofitted to existing installations and/or incorporated into new projects with investor confidence. Therefore, we kindly request organisations to step in – on a voluntary basis – to provide wave and tidal/current interaction data to validate the test results, so we can make a joint step towards an independent outcome to be presented in January 2015 in a scientific journal."
The study is related to the growing concern for power cable failures. One of the known causes, inadequate mechanical protection for the given installation and environmental load conditions remained relatively under-exposed in the last years. Above indicated interactions cause external abrasion and mechanical wear as well as cycling bending, eventually resulting in premature cable failures.
"Cable protection systems should protect cables. A contribution to cable failure is, from our point of view, unacceptable. That is why testing is so important. For now, our articulated pipes have proven to be more flexible and robust in static tests and during installation in several offshore wind farms . The recorded installation time with our CPS is 12 hours per cable," Marloes Tuk, business development, added. "An unbiased validation of the operational lifetime in the right context is what we seek. More is more here. The more data we have, the more reliable the outcome will be."
The University of Exeter performed axial load regimes, consisting of 25.000 cycles per sample of articulated pipes, aimed to replicate the field load conditions by combining cyclic bending motions with oscillating tensile forces, which is equivalent to operational lifetimes in the order of 30 years.