By Eric Elder

When it comes to high-speed machines such as turbines, thermal growth is something that companies almost always must monitor.

A PRÜFTECHNIK services team helped a leading manufacturer of industrial gas turbines for the global power generation market to precisely measure the thermal growth of a turbine unit using the ROTALIGN® touch.

With thousands of units amassing billions of operating hours, this manufacturer understands the importance of precision alignment. That’s why it called upon PRUFTECHNIK, as the global leader in laser shaft alignment, to handle the measurement.

What is thermal growth? It is the expansion of a machine as its temperature increases due to regular operation. Thermal targeting properly aligns the shafts when they heat up to operating temperatures.

Gas turbines produce a large amount of heat and thus are subject to significant amounts of thermal growth. Failure to account for the thermal expansion can result in misaligned shafts that produce unwanted vibrations and damage to bearings. These side effects ultimately reduce the lifetime of a machine and result in machine downtime.

To prevent this, the turbine manufacturer uses the latest technology available to account for thermal growth and to align the shafts of its turbines properly.

Figure 1: An example of a thermal growth trend.

Figure 1: An example of a thermal growth trend.

The gas turbine manufacturer has chosen the PRÜFTECHNIK alignment services and advanced ROTALIGN® series alignment platform to fine-tune its gas turbines for best performance.

ROTALIGN touch features a laser-based system that includes a transmitter and a detector. These are mounted to the gas turbine and the driven machine at a location just above the shafts. Once the devices are stably mounted, the turbine revs up to operational speeds.

As the temperature of the turbine grows, the device logs data that shows the relationship of movement between both the driving and driven machines.

Figure 2: An example of thermal growth results.

Figure 2: An example of thermal growth results.

Data logging is complete once the temperature of the machine has stabilized. The ROTALIGN® series alignment platform is then capable of analyzing the data automatically to determine the horizontal and vertical changes necessary at the mounting locations of the gas turbine, as seen in Figure 2.

These changes allow for the machine to be correctly aligned when it is running at operational temperatures. The gas turbine manufacturer is taking advantage of this technology to gear its turbines for increased reliability and optimal performance. With PRUFTECHNIK products and services, the thermal growth of its machines is in check.


Eric Elder is PRUFTECHNIK Service Manager for the Americas at Fluke Reliability.

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