Tough tubes are built to last

Louise Smyth

Charles Ferreira & Peter Henshaw report on tubing for the power industry of tomorrow

Although we’re still waiting for the final outcome of UNFCCC Paris Agreement, there is no doubt that the world is on a path towards a low-carbon economy.

Key to that transition will be the expansion of power generation technologies that minimise the emission of greenhouse gases.

Of course, there will continue to be a need for a mix of energy sources but it seems hard to escape the conclusion that nuclear and renewables will have to play an increasingly important part in that mix.

To take one example, China plans to build no less than 60 new nuclear power plants over the next decade.

The US-based Superior Tube and the UK- based Fine Tubes, sister companies within Ametek Specialty Metal Products, have a long history of manufacturing precision tubing products for the most demanding power industry applications.

One recent renewable energy project where Fine Tubes put its expertise to good use was at Spain’s Gemasolar power plant. The company developed and manufactured corrosion-resistant heat exchanger tubes for the steam generators as well as the high-performance tubing that makes up the receiver of the Gemasolar central tower.

Real-world case study 

The Gemsolar plant uses unique innovations that make it not only more efficient than other thermoelectric solar plants, but also able to continue producing electricity without sunlight.

Because its central tower receiver and molten salt storage technology enable it to produce electricity for15 hours without the sun (and even 24 hours in summer time), Gemasolar can continue to operate during the night or in cloudy weather. This means that solar energy has become manageable for the first time, and is capable of responding to large-scale commercial demand.

Fine Tubes has been working with the Sener engineering company for several years, developing and producing the corrosion-resistant heat exchanger tubes for the steam generators as well as the high-performance tubing for the central tower – which is capable of absorbing 95% of radiation in the solar spectrum and transmitting this energy to be stored in the molten salt compound in its interior.

“Sener values highly the contribution of Fine Tubes to this project. The service conditions of components required high quality and reliable products – which Fine Tubes has rigorously fulfilled. Other remarkable aspects during the manufacturing process were meeting deadlines, and continuous information transfer, two points where the collaboration with Fine Tubes was crucial and essential for the successful development of the projects,” says Peru Arribalzaga, project manager at Sener.

Because Gemasolar is a first-of-its-kind plant, challenges were present at every project stage. The central receiver is the main component for this type of thermosolar plant and its component parts need to perform reliably in extreme conditions throughout the plant’s lifetime.

Fine Tubes needed to provide extremely robust tubes made from a material with a high resistance to corrosion, thermo- mechanical fatigue and creep to be capable of holding the molten salt. High quality and durability for these tubes is vitally important because the receiver availability is continuous, absorbing an enormous amount of solar energy – the equivalent of more than 1,000 suns.

Sener also required heat exchanger tubing to operate effectively within the steam generator units. Once again, quality and durability were imperative: the units work at very high pressure turning the turbines to generate electrical power for over 27,500 homes per year.

Tailored solutions

There are no ‘off the shelf ’ solutions in a project such as this and Fine Tubes first went to work creating prototype panels. Because the firm was able to exceed the standard definitions required for these component parts, Sener selected it to be the exclusive supplier of tubes for the manufacturing panels of the central receiver. Today, the company has produced over 15km of  high-performance 25mm OD seamless tubing for the system, which holds the 565°C molten salt (nitric salt), housed in the 140m high Gemasolar tower. Made from the corrosion-resistant nickel- chromium alloy, the tubing has superior resistance to very high temperatures and the extreme service conditions.

The company also provided over 300m of 19mm OD heat exchanger tubes manufactured from the same nickel-chromium alloy, but with a thicker wall to withstand the high pressures present within the steam generators.

The plant was officially opened in October 2011. The results achieved in the first year of operation broke all expectations. Since then, its available production hours are increasing rapidly and it is hitting all production goals.

Although nobody can predict exactly how the future of power generation will play out, what case studies such as this demonstrate is that it’s critical the industry’s global supply chain is capable of responding to whatever technological and production demands are placed upon it.

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Charles Ferreira & Peter Henshaw are with Fine Tubes.  

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