Based at Sion in the Swiss mountains, HYDRO Exploitation SA is a service provider that specializes in the operation, maintenance and monitoring of electrical installations and hydroelectric facilities. The enterprise employs more than 425 people, with more than 300 civil engineering and electrical engineering professionals based at production and pumping sites from the Rhône glacier to Lake Geneva and the Vaud Jura region of Switzerland.
Currently, HYDRO Exploitation operates facilities that provide approximately 22% of Swiss hydroelectric capacity. Together, these facilities produce nearly 16% of Switzerland’s hydroelectric power. The company’s comprehensive service portfolio embraces all fields of electricity production, from consultancy to repair to the operation of a facility, which includes continuous monitoring and maintenance.
There are over 80 engineers, technicians, project managers and specialists located in Sion who diagnose faults or problems and work independently of suppliers. Multidisciplinary teams composed of specialists in data communications, mechanical, electrical and civil engineering work on preventative and specialized maintenance projects. This work can entail everything from dismantling and reassembling of worn and defective components in production and pumping installations to repair operations for these very powerful machines.
3D Data Analysis of Power Generation Machinery
The HYDRO Exploitation SA workforce possesses a high level of experience in the operation of hydroelectric facilities. They collectively apply their expertise for the restoration, renewal, and optimization of other installations. Inspections are conducted regularly.
The company uses a state-of-the-art portable measurement machine for precision inspection of critical components, points, and surfaces. To measure the geometry of machine shafts—the main rotation axle of a machine—and the injectors, water inlet planes and equipment positions, engineers utilize a Leica Absolute Tracker AT401 from Hexagon Manufacturing Intelligence (North Kingstown, RI), driven by SpatialAnalyzer software developed by New River Kinematics (Williamsburg, VA).
David Rey, a geomatics engineer at the company, works at the center of the civil engineering unit. The use of a laser tracker allows his division to perform highly accurate and remote 3D measurements over long distances, including up to a 160-m radial volume. The ability to acquire 3D coordinate measurements has allowed Rey’s team to improve upon inspection results that were previously available only as vertical data (shaft altitude with a certain accuracy level). The 3D dimensional results provide a much more relevant analysis of the geometry of power generation machinery to support their work with mechanical engineers on the project.
“Due to this tool, HYDRO Exploitation SA has been able to provide its services much more quickly and accurately than it could previously using a conventional method,” said Rey. “With this new measuring technique, the company can fulfill heightened mechanical maintenance requirements and has also been able to win new business.”
Precision Inspection for Critical Maintenance
Electra-Massa SA (Bitsch, Switzerland), is one of the new customers relying on HYDRO Exploitation for a new level of precision inspection. This storage power plant, constructed in 1964 and commissioned in 1969, has a total power of 340 MW. The electrical power generation is provided by three Pelton sets driven by the melt water from the Aletsch glacier via the Gebidem dam, located 750 m above the plant. The 55 cubic meters of water passing through the turbines of the Bitsch plant contain between 10 and 13 kg of sand, which is an hourly mean of nearly 40 tons. As a result, approximately every 10 years the four injectors of the three existing sets are demounted, reconditioned, repaired, and refitted.
Rey and the team take advantage of the portable laser tracker to take a series of different measurements around the injectors. The lightweight system, weighing a total of 8 kg, including the controller, has cable-free operation with WiFi capabilities. Certified to IP54 standards, the AT401’s sealed design protects the unit from dust and other contaminants, so it can effectively measure in even the harshest environments. With the turbine injectors removed, the first step is to use the laser tracker to measure the shape of the outlet orifice and, from that data, check for a possible difference in shape. In theory, this shape should be circular, but according to the local technicians, the component tends to have an oval shape.
Data from the portable laser tracker is used to create graphical representations of the injectors. If the measured shape of an injector is oval compared to the desired circular shape, corrections are required.
Once this measurement has been performed, the maintenance work involves build-up welding and then machining of the outlet orifice, so that it once again has a perfect shape that complies with the part’s mechanical tolerances. Reassembly can start once all four outlet orifices have their shape defects corrected and the injectors have been reconditioned.
“The AT401 from Hexagon Manufacturing Intelligence provides significantly greater quantity and quality of data,” explained Rey. “What’s more, traceability is made easy by the special features of the SpatialAnalyzer software. In fact, each measurement automatically creates a data report.”
One of the most salient features of the laser tracker is its unique PowerLock active vision technology that makes it practical for inspection work in a formidable environment. The operator does not have to worry about “breaking the beam,” as the laser tracker instantly locks onto any moving reflective target as soon as it appears within view of the sensor. This is particularly useful when a co-worker or a component of an assembly impedes the tracker’s line of sight. The technician can focus on the data acquisition work at hand, instead of worrying about the mechanical technicalities of the PCMM.
More Data to Monitor Component Positions
The second measurement stage uses the laser tracker to monitor the position of the injectors relative to the Pelton wheel. This wheel, invented by Lester Allan Pelton in 1879, is a disc equipped with buckets shaped like half nutshells around its perimeter. It transforms the potential energy of the water into the kinetic energy that drives the electricity generator. The point of impact of the water jet must be within a specified tolerance to ensure optimum efficiency and minimum wear on the wheel. This tolerance is directly related to the width of the bucket in question.
The utilization of an AT401 laser tracker has been a turning point for HYDRO Exploitation in terms of the analysis and measurement of mechanical parts as it strives to make plants more efficient. Without the need for AC power, the remote usage of the PCMM is fully realized for the company’s large-scale measurement tasks—its sensor can run continuously without interruption due to what engineers in the field refer to as “hot swappable batteries.” Simply put, this means that tracker operators can switch out the batteries in the field without incurring any downtime. In addition, the laser tracker’s built-in, automatic reading and updating of environmental parameters helps operators avoid inaccurate calculations or wrongly input values.
Electra-Massa is extremely pleased with the quality and reliability of the data presented, forging the development of a long-term collaboration with HYDRO Exploitation. The data acquisition speed of the laser tracker allows the operator to obtain the optimal amount of reliable measurements in a minimal amount of time, saving downtime and money for the client. The mobility and accuracy of the portable measurement system enables Rey’s team to quickly collect rich data, improve traceability, and satisfy requirements set forth by mechanical engineers.
Edited by Joel Martin, Laser Tracker Product Manager
for Hexagon Manufacturing Intelligence.