Laser Shaft Alignment with Four Different Measurement Methods
The following was written by our partner Easy-Laser® AB and can also be viewed on their Blog here. Enjoy!
The latest addition to Generation XT, Easy-Laser® XT660 Shaft Alignment tool, gives you access to four different measurement methods for laser shaft alignment – each with its own advantages. Read more to find out how to use them best!
Shaft Alignment Methods
The four shaft alignment measurement methods are 9-12-3, EasyTurn™, Multipoint and Continuous sweep. Here we describe them individually, so that you know when best to use them.
The rotation of the measurement devices around the shaft is similar to that of a clock; positions 9, 12, 3 and 6.
Shaft Alignment Method 1: 9-12-3
The clock method, or 9-12-3 as it is also known, is the origin of all shaft alignment. Anyone who knows how to use analogue dial indicators will recognize this method. A dial gauge is mounted on each shaft, and the measurement values taken at three different points, corresponding to the 9-12-3 positions on a clock, or the angles 0-90-180 of a circle. It is based on geometry (and trigonometry), more specifically circle mathematics. The mathematical assumption is that if we can measure the semicircle, we can then work out what the whole circle will look like, and consequently determine the centre of the circle (rotational centre) for both shafts. These centres can then be compared to each other and we can thus work out how well-aligned the machines are to each other. And with a laser-based measurement system, also obtain direct feedback from the adjustment of the machine in real time.
Shaft Alignment Method 2: EASYTURN
EasyTurn is a unique further development of the shaft alignment 9-12-3 method, with the freedom to choose at which clock position (which angle) you start collecting measurement values. With the help of some mathematics, we can also restrict the total measurement range to 40 degrees full rotation. From a practical point of view, this means that you can use this method where there is limited possibility of rotating the machines, due to the lack of space around the shafts.
This method is the standard setting in most Easy-Laser shaft alignment tools (except XT660, which uses ”Continuous Sweep” as the standard method, see below). Measurement method EasyTurn offers down to 20° between measuring points. Great when machine protection or pipes prevent precise positioning according to the clock method.
Shaft Alignment Method 3: MULTIPOINT
Multipoint is, in turn, a further development of shaft measurement method EasyTurn. Multipoint also means that you can start collecting measurement values from any clock position (angle), and complete collection across as small a rotation as 40 degrees. However, as the name suggests, this method means that values are collected from more than three points.
This is advantageous if taking shaft measurements from larger machines where it is difficult to rotate the shafts. Collect the measurement values across a shorter rotation to increase the mathematical probability of obtaining good measurement values. This method also gives a quality evaluation of the measurement series. The evaluation takes into account shifts in temperature, measurement direction and number of measuring points.
Shaft Alignment Method 4: CONTINUOUS SWEEP
Continuous sweep can be described as Multipoint with automatic, continuous measurement value collection. In practice, this means that you can collect measurement values continuously with the measurement devices in motion i.e., you start measurement value collection (at any clock position/angle) and then rotate the shafts without stopping, in one direction. Continue until you have collected enough measurement values to achieve a good quality calculation (quality evaluation is also performed here just as in Multipoint).
Continuous sweep is best used when it is difficult to stop the machines to register measurement values.
At the end, the shafts’ rotational centre is calculated and presented graphically via images and text. This method is very useful in instances where it is difficult to stop the machines to take stationary measuring points, for example, when aligning large turbines.
We hope you now have a clearer picture of the various measurement methods and when best to use them.