October 29, 2014
Setting up OL2R (Offline To Running) and Offset (Cardan) Brackets
By Michael Keohane
OL2R Measurements (Offline To Running) are used to collect very accurate (and actual) Thermal Growth Values and Targets for critical rotating machinery. Offset Measurements (Cardan Shaft) are critical for offset drives to ensure there is no angular misalignment causing lead/lag issues with the drive shafts resulting in production related quality problems.
Both the OL2R and Offset measurements require fixtures that need to be set up in the field. The fixtures establish virtual rotational centerlines that allow these critical, but often overlooked, measurements to be made. OL2R and Offset measurements are done uncoupled and typically at some distance so the initial bracket set up or coning insures that the lasers will stay on the detectors throughout the measurement. The fixtures contain aiming lasers which make set up on the machine in the field extremely easy.
This is the procedure for initial coning of the brackets using the built in aiming lasers. This is done, typically in the shop, prior to the job. Once the brackets have been coned they do not need to be re-coned again except as a check if you are having issues keeping lasers on the detectors. Although Fixturlaser systems have small sensor footprints the detector areas are very large (30mm) so uncoupled measurements over long distances can be easily accomplished using standard measurement techniques. Both OL2R and Offset are measured like uncoupled machines.
Coning is projecting an axis of rotation. When rotated a laser beam will scribe a cone. When the cone is projected in one plane the beam will scribe a circle and its center is the center of rotation in that particular plane. Coning insures that the measuring lasers will stay on the detectors during the measurements.
The coning procedure involves looking at where the laser hits a surface and seeing how big a cone is scribed when the laser is rotated 180 degrees. The lasers can be adjusted to scribe a small cone at distance by adjusting the laser beam ½ way back to its original position in both the X and Y planes.
Fig 1. Fig 2 Fig 3
Figures 1-3 are the initial cone when the laser is rotated 180 degrees.
Fig. 4 Fig. 5
Figure 4 shows adjusting the laser ½ way back both horizontally and vertically using the adjustment screws on the aiming lasers. Figure 5 is the tight cone produced after adjustment.
When the laser is rotated 180 degrees a tight circle is now scribed. Now when the M and S Sensors are mounted on the fixtures they will effectively measure without going off the sensor detectors during the measurement.
Procedure using the Fixturlaser OL2R & Offset Brackets:
The OL2R bracket set up in the shop. Make sure the bracket is tight and doesn’t move. The laser pointer is turned on by turning the pointer. The laser will be adjusted in the x and y planes using the allen head adjustments.
Initial Projection on the wall. In this case at about a distance of 10 feet. Mark the initial position of the laser dot for reference.
Rotate fixture 180 degrees
New position on the wall after 180 degree rotation. The laser dot has moved relative to its initial position.
Adjust ½ way back, using an allen wrench. One adjustment controls the X and the other the Y. Graph paper is used in this example but it isn’t necessary. Watch the laser move as you adjust it.
Laser beam after adjustment. Recheck the cone by rotating the laser 180 degree’s again. It will scribe a tight circle. Fine tune by repeating the procedure if necessary.
Cone each bracket. Once coned the brackets are ready for field use. Use the aiming lasers for easy setup in the field. Simply aim one bracket to the other using the bracket aiming lasers. Once set up with the brackets tight you can turn of the lasers, install the M and S Sensors on the brackets and you are ready to start your measurement.
For Additional information:
Measuring Thermal Growth Targets
Offset Shaft Alignment