QMT Features: March 2014
No problem with heavy parts
Software solves the problem of measuring massive components to hundredths of a millimetre

Andritz Hydro is a leading global supplier of integrated systems for hydro-electric power generation. At its production site in Ravensburg it produces the massive Francis turbine wheels that generate the power. Three Francis turbines just under eight meters in diameter and weighing 200 tonnes supplied by Andritz for the Guri II project in Venezuela were the largest turbines ever built in Europe.  But despite their monumental proportions, the turbines are precision components and have to be accurate to a few hundredths of a millimetre.

Generating up to 800 megawatts, a single Francis turbine is truly a beast. Fabricated from cast components, a Francis turbine weighs in at 200 tons and measures nearly 26 feet in diameter. The power that this beast generates is impressive— around the same amount of power as an average-sized nuclear power plant. Yet despite its size, the efficiency of the turbine is entirely dependent on the accuracy of the blades and their geometry. Quality control is crucial. At 120 revolutions per minute, a slight deviation from the correct dimensions can have devastating effects.

Quality control of a 200-ton part poses a unique set of challenges. For starters, their physical size makes the task of taking of measurements extremely difficult, and without the proper equipment, practically impossible.
At the heart of Andritz’s answer to meeting this measurement challenge is the use of is Polyworks Inspector metrology software provided by Duwe-3D.

The challenge is access

Yener Korkmaz, director of test and measurement at Andritz Hydro Ravensburg, who is responsible for quality assurance, inspection and incoming goods, explains: “Taking the measurements themselves, such as target points, alignment, analysis, etc., doesn’t pose a challenge, our key challenge really lies in accessing the part, since space is often limited and we physically cannot move to a better position.”

Because the components are neither freestanding on a measurement table, nor are they accessible from all sides, Mr Korkmaz and his team used to have to measure the massive parts where they were being fabricated among all the other components and tools. What’s more, measurements taken using gauges were simply not precise because they varied according to the gauge material.

The solution for Andritz Hydro was 3D metrology. Since many of the measurement points on a turbine are partially hidden and access is limited, it decided that a tactile measuring device was the best choice. This was a practical answer too as there were not many points that needed measuring on each turbine. Andritz chose to do this with a FaroArm, Faro laser tracker and the PolyWorks Inspector software and, equipped with this solution, the size and weight of a part were no longer a problem.

Andritz Hydro had actually changed its alignment software to PolyWorks three years previously. The the main reason being that although the alignment features of the previous software met the requirements, in terms of analysis and export data, PolyWorks offered several advantages.

Hans-Peter Klimm, foreman in the measurement and testing department at Ravensburg, appreciates the flexibility and scope that PolyWorks provides. As he explains: “Most software solutions offer specific functions and if these functions don’t give the desired result, then it‘s game over. In PolyWorks, we can use different paths to reach a goal. We use the many export and import options and the various interfaces, and this allows us to find creative solutions for specific problems.”

Internal customers

Mr Korkmaz added that every department within the organization is treated as a customer, each with different data-processing requirements, and PolyWorks can be used seamlessly for all of these.
The 3D measurement solution has met the challenge of dealing with these enormous components, but measuring them is still far from routine work. This is due in large part to the fact that the turbines are not standard products, each one is unique and made to the customer’s requirements. Each turbine is a separate project, so the measurement requirements are always different.

Because of the size of the part and access problems, the measurement arm or the tracker has to frequently be relocated. The PolyWorks software makes this a lot simpler as all that is required is to put in details of the new location in the coordinate system. Once that has been done, the orientation of the measurement data and the various positions in the coordinate system are managed in the PolyWorks software. What’s more, the tracker and the arm can be combined into one measurement, increasing flexibility and range.

When a location is changed, the arm also takes its reference from the coordinate system of the tracker. PolyWorks automatically registers the arm in the tracker’s coordinate system, without the need for additional reference points.

For hard-to-reach test points, such as areas deep inside a wheel or a shaft, the PolyWorks/Talisman Apple mobile phone app comes into play.

Mr Korkmaz says: “PolyWorks/Talisman is a very useful tool for us. If operator is in a position where they can’t access the computer and there are no colleagues around it comes to the rescue.”
It can trigger measurements remotely and retrieve project data, so the technician doing the measurement can immediately validate the data and make any corrections if required.

Two hours, one man
Since many of the parts that need to be measured are very big, it is not uncommon for Andritz Hydro’s customers to build access structures around them. While these structures let them examine the part in its entirety, there is a big drawback in that space is very limited. That meant that simply measuring these parts in front of the customer with a big gauge was sometimes impossible or, at best, led to errors.  

The mobility offered by the 3D metrology solution makes it possible to carry out quality control at the customer’s site, directly at the locations where it is to be mounted – it can even support the installation of the turbines in the power plant. Working in areas where space is limited is no longer a problem.

It used to take two technicians up to 1½ days to measure a 100-ton blade, and a significant amount of that time was spent getting the measuring equipment in place and working around the space limitations. Now the job can be completed in 2 hours—with a single technician.

The reliability of the current 3D metrology measurement solution has led to further applications at Andritz. It is also being used in mechanical fabrication to set up components in the right alignment. Before making the root weld seam, Andritz checks that the parts are correctly set up using PolyWorks and the Faro laser tracker.
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