PUSTER VALLEY: NEW CHAPTER IN HYDROPOWER

Autor: Roland Gruber , 21.05.2013

As it did in the past, textile manufacturer Moessmer of Bruneck is committed to the use of hydropower. As the oldest industrial operation in the Puster Valley, the firm’s tradition-steeped history goes back more than 100 years.

Over the last few months the current facilities were subjected to a comprehensive modernisation process, fitting them with the latest technical equipment. Thanks to a newly granted permit, the existing solution with two machines from the early 1980s was able to be updated to a GHE-PIT turbine solution with considerably higher output. The conversion on the premises of the textile factory turned out to be a complex challenge both for the planners and the construction engineers. In the end, they were able to keep within schedule. As a result, clean electricity has been generated on the Moessmer textile factory grounds since the end of last year.

They count designer fashion labels such as Prada, Armani, Dolce & Gabbana or Louis Vuitton among their clientele. Superior quality, produced with sustainable manufacturing processes that reflect a successful symbiosis of tradition and modern style, has long been the hallmark of fabrics by Moessmer, one of the very few textile manufacturers in the Alps that still covers the entire production process from wool to top-quality fabric. Production has been up and running in Bruneck since 1894, making the factory the Puster Valley’s very first industrial operation – and a highly successful one to boot, as Moessmer was already appointed supplier to the Austrian imperial court by the turn of the century. The brand quickly took root and was destined for further success, despite the turmoil of the two world wars, turbulent market developments and changes in ownership. What remained was the backbone of the firm’s manufacturing power: the hydropower, which the owners still rely on as they did back then. “The reason why the factory was established here in Bruneck in the 1890s can be found in Rienz. They used the force of the moving waters to drive the mechanical equipment by means of transmissions. Years later, in 1923, the first power station was built, which provided around 220 kW,” says Dr Josef Zingerle, Head of Controlling at Moessmer. The start of the factory’s independent electricity generation was a milestone in the firm’s history, as Zingerle explains. “In the early 1980s the power station was completely refurbished. They installed two Kaplan turbines, which were still in operation until June last year.” What was to follow was a new chapter in the history of hydropower generation at Moessmer.

PROBLEMS WITH HIGHER WATER VOLUMES
In 2010 the permit for the Moessmer power station expired, and to get the much needed extension called for swift action. The idea was to come up with a new concept in order to be able to accommodate new, future requirements as well as the changed basic conditions. These concern primarily the operation of the “Bruneck” upstream plant, which was constructed back in the late 1950s. Says Zingerle, “Until 2002 or 2033, the water was usually available to our turbines around the clock. But from then on, the operator adjusted the production to the economic electricity rates at the Energy Exchange. This means that the motive water began arriving at irregular peaks. On the one hand, our turbines were not designed to handle the higher water volumes, which means that quite a bit of the water remained unused. On the other hand, the two machine units were unable to react quickly to the constant changes. If you consider that at low levels the water often wasn’t available for more than three or four hours at a time, while the turbines took about thirty or forty minutes to synchronise for parallel grid operation, you can imagine that the whole operation wasn’t always running very efficiently at all.”

ONE GHE-PIT TURBINE TO REPLACE TWO KAPLAN ONES
In practice, this means that the design flow rate of previously 18,300 l/s would have to be adjusted to that of the upstream plant, which was 22,000 l/s. Besides, it was also necessary to find the machine solution that would provide the best outcome in terms of technology, economy and ecology. After intensive deliberations and research on various possible arrangements on the part of the owner and contracted planning office Studio G of Bruneck, the final decision came out in favour of a Kaplan-Pit turbine, which owes its name to the term for a shaft with an open top. Its excellent controllability and superior efficiency, combined with its low space requirements, were the most convincing arguments that sealed the decision in favour of this machine version. Where to obtain such a machine was decided rather quickly when the contract was put up for tender early last year. It was decided to award the contract for the electromechanical equipment to Upper Austrian hydropower engineering specialist GHE (Global Hydro Energy), which also enjoys an excellent reputation as an expert in Kaplan-Pit turbines. “We had had excellent collaboration experience with GHE in the past, so we were confident that they were up for it. Where quality was concerned we really had a lot of confidence. On the other hand, however, it was also extremely important for us to have a partner that would be able to deliver just in time – and demonstrate handshake qualities at the same time. In both respects, GHE has fully lived up to our expectations,” as Studio G’s panning team confirms.

HIGH-SPEED CONSTRUCTION PROJECT
Especially the time schedule represented a central criterion for getting the new power plant up and running. After all – as in many other Italian hydropower construction projects that year – the main goal in terms of time was to complete the entire modification and reactivation before the year was out. It was a tough challenge, considering that the plans called for particularly sensitive constructional measures – and that while the textile manufacturing operation had to be kept running. Once the new permit was obtained (this one will be valid until 2040), the earth was broken and the project kicked off in late June last year. The old machine units were dismantled, the old power house was knocked down, and preparations for the actual civil engineering work were begun. The contracted building firms saw themselves up against a very tight schedule from the very start. After all, the existing facilities had two machine units installed, which had required the construction of two separate tailraces, which were around 170 m apart. “Due to the difference in altitude between the tailraces the overall efficiency of the facility was not quite optimal, especially since the larger ones of the two machines – the one whose tailrace was further upstream – also had a lower gross head. So the obvious thing to do was to use the lower tailrace for the newly installed turbine,”explain the planners of Studio G. “In effect, this means that the higher one of the existing tailraces had to be brought down, while the lower one had to be expanded and adapted to the 22 m3/sec water flow.”

SPECIAL CIVIL ENGINEERING MEETS JET GROUTING
The expansion pushed the planners and construction specialists to their very limits, Due to the static conditions and restricted space conditions, the cross-section of the tailrace could be expanded only by lowering, but not by widening. To ensure a properly safe extension of the outer walls down to the required depth, the team decided to use a method known as “jet grouting” – a special engineering method that allows for setting up underground concrete structures by means of a high-pressure injection technique. During the procedure, an injection pipe is inserted into the ground. Once the proper depth is reached, a mineral compound is squirted in at extremely high pressures of up to 600 bar, which binds to the soil to form a solid concrete body. The rotating motion when the pipe is lifted out creates a concrete cylinder. Placed next to each other, these can be used to form regular underground walls without the need to dig up the soil. There are many advantages to this construction method: for one thing, it allows for the use of small machines, which can work even under very restricted spatial conditions; what is more, the ‘jet stream method’, as it is also known, has both a static and sealing function, which was particularly important for the Moessmer hydropower project. As a result, not only could the side walls be stabilised with a solid foundation, but the construction pit could be sealed more densely as well. Especially the latter was of critical importance for the subsequent construction of the new power house. “By the time we could start building the power house, we were 11 m below ground-water level. Here, again, we used jet grouting to create a sealed construction pit. It all worked very well,” recall the Studio G engineers. The base plate for the tailrace was also constructed by jet grouting. The concrete base, which is now situated around 4 m lower, was therefore prepared underground, with the soil above it being removed only later on.

INNOVATION IN HYDRO-STEEL ENGINEERING
The next construction steps required the intake channel to be adjusted top the new conditions along a 28 m stretch. This was done by gradually reducing its cross-section as it approaches the turbine. One question arose in connection with the design of the power house: due to the lower elevation of the installation site for the new machine, the engineers dispensed with the usual roof construction. Instead, the Studio G engineers planned a concrete ceiling just above the edge of the terrain. For mounting and maintenance purposes, a 6 m x 4 m, double slidable steel cover was placed onto the insert opening, which can be shifted very easily by hand. This solution was implemented by South Tyrolean steelwork engineering specialist Wild Metal, which had been awarded the contract for all steel construction and hydraulic steelwork engineering for the project. Their task gave the steelwork engineers from Ratschings the opportunity to prove yet again their reputation for being extremely inventive and resourceful. Numerous designs were constructed in three dimensions by Wild’s in-house construction department and quickly issued to the manufacturing department and partner firms. Highlights of their engineering ingenuity include the turbine pit, which is 8.5 m long and 3.6 m wide, as well as the reinforcing ring, which measures 4 m in diameter and whose contact surface with the guide vane assembly was engineered to an extreme level of precision. For the sluice gate at the intake, which has a width of 8.2 m and height of 3 m, the hydraulic cylinders were arranged so that they hardly reach above the sluice body. The downstream gate was anchored so deeply that the corresponding 10 m frame also remains almost fully hidden. A pressure-tight, cylindrical access shaft with hydraulically optimised bottom (also by Wild) was inserted into the suction pipe. The construction was complemented by some made-to-measure covers, as well as the railing and access ladders for the pit and turbine shaft, and the creatively designed spiral staircase, which provides access to the central level. An indoor crane – a special construction by Wild Metal – allows for controlling the guide vane system, which measures 3.6 m in diameter, in a space with only 4.7 m head clearance. The space between the twin crane car and ceiling is only 5 cm.

UNBUREAUCRATIC SUPPORT
Technically, the lowering of the tailrace and the construction of the power house posed the greatest challenges for everyone involved – especially since the entire project had to be completed within a few short months. With the actual starting shot to the project being fired in late June of last year, the engineers could begin with the installation of the machine in late autumn – exactly as planned. This alone is reason enough for the engineers of Studio G to commend the contracted firms and the owner for their commitment: “Both representatives of the owner, Dr Niedermair and Dr Zingerle, were often at the construction site, and they contributed very actively to the project. We also commend the contracted firms for keeping the schedule the way they did, and for their competent way of handling the project.” A rather important issue for the construction part of the project arose in connection with the intake. The plans called for the newly build power plant contributing to the electricity grid of the Bruneck Public Utilities. That raised the question of whether it would be possible to get the grid hookup up and running within such a short time. “We were very happy to see that the Public Utilities people were very helpful and unbureaucratic. As a result, we were able to start up operations right on time,” say the Studio G engineers.

SLOW RUNNER WITH CONVINCING QUALITIES
Full of suspense, the owner and planners awaited the premiere ‘performance’ of the new turbine, which was lowered by 3.1 m to protect it against cavitations. The Pit-Kaplan turbine has several benefits for this type of application. Apart from its modest space requirements, it provides higher full-load efficiency in arrangements with a low head than vertical Kaplan turbines. Also, this type of turbine is usually highly reliable. Besides all that, it also provides easy access for maintenance, repair and inspection purposes. To top it off, the fast, efficient control of this turbine makes it the ideal choice for applications like the Moessmer project. All these quality features are packed into the Pit-Kaplan turbines by GHE. Hundreds of reference facilities all over the world testify to their popularity. Compared to the previously installed turbines, the new one is a real ‘slow runner’, whose rotor moves at a very moderate 190 rpm. A spur wheel gearing transmits the rotational speed to 750 rpm. This arrangement was well calculated: after all, the intermediary gearing reduces the efficiency loss to only around 1 per cent. This is a record number – and a great argument in favour of the spur wheel gearings by Eisenbeiss, which are specifically designed for Pit-Kaplan turbines. At 750 rpm, the turbine drives the generator (manufactured by Hitzinger), which is designed for a rated output of 1,500 kVA. The turbine’s capacity at a net head of 6.70 m and maximum design flow rate of 22 m3/sec is 1,353 kW – a value that can hardly be achieved during the winter season, when the water levels are low.

QUICK REATCION TO CHANGING WATER VOLUMES
More significant, however, is the rated medium output as referenced to a medium design flow rate of 11 m3/sec. Under these conditions, the two old turbines generated around 308 kW and 324 kW, respectively. By comparison, the rated medium output of the new turbine is now 832 kW. This sharp increase has several reasons: “One reason, of course, lies in the fact that the tailrace of the larger of the two machines was further upstream, which means it had a lower gross head. The new turbine now has the gross head of the lower one of the two machines. Another reason can be found in the excellent hydraulic design of the GHE turbine, which achieves very high efficiency levels to start with. However, there is another factor that comes into play where the overall efficiency of the facility is concerned: the new machine offers very good control qualities, reacts quickly to changing water volumes, and synchronises within a very short time for parallel grid operation. This process, which used to take between thirty and forty minutes, now usually takes less than sixty seconds. With frequently changing water volumes, this is a key criterium,” say the planners of Studio G. The turbine control assembly was also provided by GHE. It is based on the highly proven, custom configurable HEROS control unit, which offers a characteristically high level of operating convenience.

ADAPTATION OF THE INTAKE CONSTRUCTION
The start of regular operation of the facilities went ahead on schedule last December. Since then, the power station has been working reliably, its high efficiency rates confirming to the operator that they made the right decision – even if the machine has been running mostly on partial load, due to the seasonal water conditions. “After the necessary adjustments, the new machine unit is now living up to all our expectations. What helped shape our decision to go with GHE was the assurance of a guaranteed service over the next years. We will soon see how the output will change during the water melting season. The overall annual production depends essentially on the prouction of the upstream station,” explains Dr. Zingerle. Even if the heart of the facility is already pumping at a healthy beat, the overall project “Moessmer Power Station” is not quite finished yet. The to-do list still has a few as yet unfinished items on it, including the renewal and adaptation of the intake construction, which is situated around 250 m above the power station. The main objective there is to implement the ecological regulations and high-water safety standards, Studio G will once again play a leading role in making it all happen.

PERFECT SYNERGY BETWEEN TRADITION AND NEW TECHNOLOGY
The managers of the renowned textile manufacturer can consider their reconstruction project a true success – and with good reason: as planned, the reconstruction work, which involved clearing some complex administrative hurdles, was completed in record time. It was only around six months that the factory had to make do without its own hydro-powered electricity supply. Now, the path has been cleared towards a reliable, efficient operation until the current permit expires, i.e. 2040. As 120 years ago, when the first water usage permit was granted for the manufacturing location in Bruneck, hydropower is still a part of the Moessmer operations that no one would want to do without. And what would fit the mission of the Puster Valley’s oldest industrial enterprise better than hydropower – the epitome of traditional and modernity in perfect unity. Just like the textile factory itself.   

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Moessmer - traditional manufacturing operation

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Textile manufacturer Moessmer is the oldest traditional manufacturing operation in the South Tyrolean Puster Valley. Today, like back then, the firm is committed to the utilisation of hydropower.

Engine and generator

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To protect it against cavitations, the new machine unit has been lowered in elevation by 3.1 m.

Turbine with high efficiency

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The turbine by GHE is designed for a flow capacity of 22 m3/sec. Its main characteristics are a high efficiency and excellent controllability.

Schematic graphic

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Schematic graphic of the machine installation site. (graphic: GHE)

The indoor crane

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The indoor crane, which was specially constructed by Wild, allows for lifting the 3.6 m guide vane assembly in a restricted space with only 4.7 m head clearance.

The Fine-screen trash rack

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Only the fine-screen trash rack was kept; the sluice gate was completely remanufactured by Wild Metal. There are no guiding rods for the gate sticking up in the air. (photo credits: Wild)

Perfect performance

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Efficiency performance of the Eisenbeiss spur wheel gearings depending on the load of the turbine. (graphic: Eisenbeiss)

Technical characteristics