Assembly in Action: Turbine Rotor Measurements Eliminate Stacking Errors
Using current manufacturing methods, it is virtually impossible to build these massive parts with small enough tolerances so they can be bolted together without inspection. Instead, turbine manufacturers attempt to accurately measure each of the rotors in the assembly. They then match the rotors based on their flatness measurements so that the entire stack will run true. However, the parts’ sizes mean that an enormous number of data points must be collected to have an accurate match. And high production volumes leave little time to perform the necessary measurements. An environment with high vibration and noise adds an additional challenge.
Turbine Metrology’s (Kansas City, MO) Paragon system acquires over 1.2 million samples per second, making it possible to perform all the necessary measurements in a single revolution of the rotor. The company designed its Paragon system so that rotor manufacturers could collect more samples in a single revolution. "The mechanical aspects of the process are difficult. These large and heavy rotors must be centered and rotated accurately enough to prevent their run-out from affecting the measurements," says Neill Fleeman, technical director. "We also needed to eliminate the influence of external seismic and acoustic inputs. Because restacking an assembled rotor can cost upwards of $150,000, these measurements are critical."