Dial Indicator and Laser Shaft Alignment

            Misalignment and unbalance are two major causes of vibration in rotating equipment, vibration that means increase maintenance and reduce machine life. With proper alignment and balancing programs by PdM Solution will reduce in maintenance and operating costs.



    When shaft are misaligned, forces are generated that can produce stresses on the rotating and stationary components. Even couplings do not fail from the stresses produced by gross misalignment, bearing and seals will most certainly fail under these conditions in extreme cases of misalignment, and even the shaft may fracture and break. Of the many methods available to measure shaft alignment, the two most popular are dial indicator alignment and laser alignment.




    The two methods of dial indicator alignment are the rim and face method also the reverse indicator method. The rim and face method will obtain an offset reading on the outside diameter(rim) of the driver coupling hub and an angular reading at the coupling hub face, and will use these readings to mathematically or graphically adjust the driver to the required location for alignment. The reverse indicator method uses the relative measurement of the centerlines of two opposing shafts. This method acquires two indicator reading across the coupling. These readings are used to mathematically or graphically assist in determining the required adjustments and shimming for each foot of the driver or moveable unit.


     If use correctly, dial indicators can be an effective means of shaft alignment. However, the process of taking readings, calculating results, making corrections and repeating the process can be very time consuming.




    Laser alignment offers the potential for much greater accuracy than dial indicator, as well as considerable time savings and several laser systems are available. Some use a single laser and detector configuration, others use a reflected beam approach, and still others use a dual laser configuration that works along the same principle as reverse dial indicator method. A good laser alignment system will have an accuracy of at least 0.0001 in. Laser shaft alignment is one of many proactive and predictive maintenance that PdM Solution performs along with field balancing and vibration analysis.



     A major advantage of laser system is that foot corrections and alignment data at the coupling are provided almost instantaneously. They also will accommodate much longer spans than dial indicators. The major disadvantage is cost but these upfront costs are typically easy to justify through reduced maintenance costs, extended equipment life and shorter downtime.

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