Further delays for Datteln 4, the continuing curse of T2418 July 2018
Paradoxically, despite the aspirations of its Energiewende, Germany has put more big coal and lignite power plants into operation in recent years than any other European country, the culmination of long-lead-time projects planned over a dozen years ago when no one cared that much about carbon dioxide.
Paradoxically, despite the aspirations of its Energiewende, Germany has put more big coal and lignite power plants into operation in recent years than any other European country, the culmination of long- lead-time projects planned over a dozen years ago when no one cared that much about carbon dioxide.
The last of these to remain in the construction phase – and the only coal fired power station still being built in Western Europe – is Uniper’s 1100 MWe Datteln 4, originally slated for operation in 2011 or thereabouts, which has been delayed for many years in a morass of permitting issues. A big step towards resolution of these was achieved in January 2017 with the issuance by Muenster district court of an emissions control permit, paving the way for completion.
However there is now a new twist in this long running saga: the plant ran into serious stress corrosion cracking problems with the T24 alloy used in its MHPS supplied boiler and is now planning to replace the boiler walls with new walls employing T12 instead, a repair concept developed by MHPS. The repairs will cost about 200 million euros and put back commercial operation to summer 2020. Uniper has booked an impairment of €270 million for Q1 2018 as a result of the further delayed start up.
The issue came to light during commissioning tests in late autumn 2017, during power ramp up. Problems with this alloy have been widespread in recent new build coal projects, but because of the delays it might have been thought that Datteln 4 would have been able to fully apply the lessons from other projects (eg application of special welding procedures and heat treatment) to alleviate the problem.
Uniper has only recently completed its assessment of Datteln 4 and how to deal with it. “We’re talking about 35 000 welds in the boiler pressure pipes that could possibly be damaged,” said Klaus Schaefer in his Q1-18 earnings statement, noting that the damage assessment had been an “unbelievably demanding and time consuming process.”
“We’ve studied a variety of scenarios for repairing the damage as conclusively as possible and for ruling out further damage in the future. In the end, there are two main scenarios. The first scenario is to repair the boiler. This would require us to use special inspection methods to identify all damaged weld seams. This process has not yet been completed. It wouldn’t be possible, however, simply to reweld a weld seam. Instead, the piece of pipe around each damaged weld seam would have to be cut out and replaced. In other words, each defective seam would result in two new seams. Once welded, they would have to be X-rayed, then heat- treated, and finally X-rayed again to check for damage due to heat treatment. A truly Sisyphean task. And even more so because at this point we’re still unable to say definitively how many weld seams are actually damaged. You can imagine how long this could take for the thousands of weld seams that could be affected. The second scenario, which from today’s perspective we believe to make more sense, is to entirely replace the boiler walls.”
He pointed out that 100% of the weld seams had been inspected prior to the initial commissioning phase, but unfortunately, the stress corrosion cracking damage experienced by T24 “only occurs as a result of the interaction of a very specific temperature, pressure, and water chemistry inside the boiler pipes” and thus only happens when the boiler is commissioned.
“All in all, it’s a situation we’re extremely displeased with.”