Pruftechnik Blog

Rotalign

How a leading gas turbine manufacturer keeps thermal growth in check

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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.

Focus on the I-P Interval to maximize reliability

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Learn more about how the I-P Interval can help maximize reliability

Worker viewing graph on manufacturing floor

The Potential Failure (P-F) Curve is a chart used to assess the condition of an asset and its progression toward failure. The X-axis represents the time to failure, and the Y-axis represents resistance to failure. Using the P-F Curve for insight can help you extend the life of your assets and minimize failures.

The P-F Curve originated from a Department of Defense study, which found that managing assets based on their condition was more effective than calendar—or age-based—maintenance.

Every inspection method detects potential failures at a different point. More sensitive tools and more frequent inspections lead to earlier detections of failure, which can have immense benefits for an organization. The value of taking maintenance actions decreases the closer you get to failure. Potential failure, or PF, is when failure can be detected and degradation begins. Functional failure, or FF, is when an asset no longer performs as intended. It does not necessarily mean that the asset is beyond repair.

Most organizations focus their maintenance efforts on the P-F Interval, which includes the time between when potential failure is detected and when an asset reaches functional failure. As organizations move along their reliability journey, they reach a point where they can focus on the I-P Interval instead. Extending this interval means performing maintenance actions to prevent failures before they occur, and should be among the goals of mature organizations.

The P-F Curve starts with asset design and installation. The I-P Interval represents the time between equipment installation and when potential failure begins. Lengthening this timeframe requires precision and planning—ensuring that all components have the correct fit, clearance, alignment, and more. Creating installation standards is one way to eliminate some common recurring failures (such as leaks caused by the use of incorrect or substandard materials). During the I-P Interval, failure can be prevented—not just delayed.

Precision alignment and balancing can improve the lifespan of rotating equipment by reducing the vibration that leads to failures related to bearings, seals, and couplings. When properly aligned, assets experience less unplanned downtime, have a longer lifecycle, and consume less power. This can be accomplished using precision tools and techniques such as laser shaft alignment.

PRUFTECHNIK invented laser shaft alignment in the 1980s. Our newest laser shaft alignment tool, the ROTALIGN touch, takes advantage of today’s technologies to offer sophisticated capabilities that boost ease of use, including:

  • Mobile connectivity
  • Cloud data transfer
  • Software integration

Additionally, an integrated camera enables visual documentation, meaning subsequent alignment jobs are more straightforward.

The ROTALIGN touch makes it easier to transition from focusing on the P-F Interval to the I-P Interval. After all, the goal of reliability is not just to reduce failure, but ultimately to eliminate it. By moving your focus on the P-F Curve back to the I-P Interval, your organization can avoid the most significant number of failures and realize the highest amount of savings.

sensALIGN: the secret sauce in PRUFTECHNIK laser shaft alignment systems

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A worn-out bearing may have many causes. But, in most cases, the source of the problem is misalignment. High resilience from the rotatable shaft may result in bearing damage that affects your machines and leads to production inefficiencies.

sensALIGN

PRUFTECHNIK, the inventor of laser shaft alignment solutions, can uncover the underlying issue. Now a division of Fluke Reliability, it has been diagnosing misalignment for more than 35 years.

In this blog post, we shine the spotlight on one of its latest innovations — and a key feature behind its industry-leading ROTALIGN and OPTALIGN tools.

sensALIGN is the laser and sensor measurement technology that is unique and a differentiator in precision shaft alignment. It is available with both ROTALIGN touch and OPTALIGN touch.

Past measurement practices now obsolete

Let’s see how alignment conditions for rotatable machines were analyzed in the past. Measuring by straightedge and dial gauge was the standard. Even today, some specialists still trust in this ancient technology.

It is not incorrect to use straightedge and dial gauge, but it is time-consuming and requires meticulous and skillful personnel when it comes to getting accurate measuring results.

To accurately measure the angularity of a misaligned machine, it takes at least two measurements on a dial gauge. It is extremely important to put distance between the first measuring point and the second one. The further the distance, the more accurate and precise the measurement.

To measure offset, you repeat the measurement in another clock position different from your first two measurement points. As you can see, this job is time-consuming, and for specialists only.

PRUFTECHNIK has made all this redundant with the sensALIGN laser and sensor technology.

Combining two measurements into one

As we just noted, measuring angularity and offset always takes at least two measurements. The sensALIGN technology does it all with a single measurement.

The single laser beam is shot into the sensor center, where it is focused and minimized by an optical lens. A semipermeable mirror splits the laser beam into two, deflecting one beam onto the front detector and the second onto the rear detector.

This distinctive global technology guarantees that the distance between the first and the second measurement point will always be the same, exact distance. The front detector equals the first dial gauge measurement point, while the rear detector equals the second dial gauge measurement point.

Based on this, the distance between the laser and sensor can be either set down to zero millimeters or up to as much as 10 meters.

The high-performance technology guarantees precision and repeatability.

Now, let’s see and understand how precise PRUFTECHNIK’s sensALIGN detectors are. The resolution of each detector is at 0.001 millimeter; that means 1 micrometer.

And since the detector areas are given in x- and y-axis, sensALIGN can measure shaft angularity and offset in one single shaft rotation.

Live Move and Live Trend features

Additionally, the Live Move feature, which enables aligning the machine shaft with the laser and sensor heads mounted to directly control the alignment process, can be started and terminated in any position.

Another special feature that only PRUFTECHNIK provides is Live Trend, based on the x- and y- split detection areas. The sensALIGN laser and sensor technology can record the thermal growth of the machine while it is running.

ROTALIGN touch is featuring the high-performance sensALIGN 7 laser and sensor heads, including all PRUFTECHNIK intelligent shaft-alignment features such as the advanced multi-coupling measurement and Live Move of up to 6 shaft couplings at a time.

OPTALIGN touch is equipped with the powerful sensALIGN 5 laser and sensor technology. This alignment device is a must-have tool for every maintenance workshop.

OPTALIGN can be easily upgraded with a sensALIGN 7 laser and sensor unit for full access to PRUFTECHNIK intelligent alignment features, including alignment of vertical machines and extended cardan shaft features.

For visuals on how sensALIGN works, please watch this PRUFTECHNIK video.

Learn more about ROTALIGN touch and OPTALIGN touch at PRUFTECHNIK.com.