Schematic of the new laser-based Centralign Ultra Expert alignment system, used for precise alignment of internal elements of rotating machines, such as bearing rings,
Bernardo Quintana-Rüedlinger, director of Machinery Service at Prüftechnik, said the efficiency and smooth operation of turbines depends largely on maintaining a short distance between the turbine components and the rotor. “Good alignment of the rotor to the other internal turbine components is therefore extremely important, and turbines should not only be aligned carefully during initial installation, but also with every equipment overhaul.”
The Centralign Ultra Expert meaat surement system is a new-generation product, deriving from the company’s Centralign Ultra system that has been used to align turbine shells to rotors for many years. “This system is a laser-optical measurement method that saves an immense amount of time when compared with conventional methods such as the piano wire technique, theodolite telescopes or the installation of a dummy shaft,” added Quintana-Rüedlinger.
“In addition, it consistently achieves high levels of accuracy.” Centralign Ultra Expert features a precise and stable laser combined with a stationary control sensor designed to automatically correct the value in case of laser drift. A mobile measurement sensor ensures high accuracy and has a resolution of 1 µm, said the company. The laser is designed for precision meaat distances up to 40 m and with upper halves on or off. The system can be used with diameters from 120 mm to 5 m.
“The ease of installation of Centralign Ultra Expert can be easily demonstrated with our experience in the field,” said Nicolas Meunier, sales and application engineer at Prüftechnik Alignment Systems. “That is the case, for example, of one 20 MW steam turbine, whose half-casings had to be aligned with the rotor during scheduled maintenance,” he said.
The turbine housing was opened to remove the rotor, which was then brought to an external company that repaired or replaced the rotor blades as necessary and then balanced the rotor. In parallel, the guide vanes and seals on the turbine were replaced with new ones. After the new and overhauled components were remounted on the turbine, the Prüftechnik Machinery Service Team performed the measurement with Centralign Ultra Expe
A technician from the Prüftechnik Machinery Service Team prepares the installation of the control sensor for Centralign Ultra Expert in a 20 MW steam turbine, after overhaul.
“The laser and the control sensor were mounted and adjusted on the exterior of the turbine. After the adjustment was completed, it was ensured that neither of the two components could move,” explained Meunier. “The laser beam served as the reference line for the subsequent measurement and each individual turbine element was measured.” The team used sensor brackets developed and patented by Prüftechnik, thus the center point of each half-casing was determined. After the measurement points were recorded, two half-casings could be defined as a reference.
“A graphic image showing all horizontal and vertical deviations relative to these references these are generally either the oil deflectors or the bearings was displayed on the Rotalign Ultra computer,” added Meunier. Based on these deviations, the correction values for the different beds of the half-casings could be quickly determined. The mechanics and technicians were immediately able to implement the necessary measures to correct the positioning of the elements.
“Another advantage of Centralign Ultra Expert is in fact that individual segments can be worked on immediately after the first measurement data are received, since there is no wire or dummy shaft to prevent the removal of the half-casings,” said Meunier. In addition, measurement data are immediately available in electronic form and can be analyzed and further processed with the Alignment Center PC software.
Alignment Center is a Windowsbased software platform for all shaft and geometrical alignment applications by Prüftechnik. It is compatible with previous and current Prüftechnik products. For Centralign Ultra, the system offers exclusive turbine-specific features, such as choice of different turbine elements, laser trend monitoring, specific correction methods and customizable color reports.
Source: Diesel and Gas Turbines Magazine