In late 1993, Infraspection Institute in New Jersey demonstrated in a carefully controlled study conducted at Miller Brewing Company that misalignment generates heat and wastes energy. This was clearly demonstrated in the comparative infrared signatures obtained on the same machines when running in an aligned and misaligned condition with deferent types of couplings (see Figures 1 and 2.) Precise magnitudes of misalignment were very carefully set with an Optalign® laser system and the results meticulously examined with calibrated thermograms recorded for each case.
Clearly, the energy required to accommodate the increased sliding velocities from misalignment within flexible couplings must come from somewhere, and this wasted energy comes at the direct expense of the efficiency of the rotating machines. While the percentage of savings may not seem very significant, a a plant that reduces energy consumption by 4 percent on an energy bill of $50,000 per month would save $24,000 in just the first year, more than enough to justify the purchase of a higher-end laser shaft alignment system.
In addition, this energy savings comes on top of all the other benefits resulting from better alignment, such as reduced wear and tear on bearings, seals and couplings, and the reduction in unscheduled downtime and repair expenses. The savings from these items (particularly reducing unscheduled downtime) can dwarf those obtained from just the reduction in energy consumption. A classic example of this occurs in a paper -mated loss of production from unscheduled downtime at $1,500 per minute, one critical pump swap-out for a seal replacement lasting one hour would cost the mill $90,000. Better alignment can vastly increase the life of seals and bearings.
Moreover, better aligned machines also result in improved production quality from reduced noise and vibration that can affect manufacturing processes. This is particularly evident in the manufacture of delicate products, or those requiring precise uniformity with exacting tolerances, such as film and optics, and certain delicate types of paper.
The following is a direct quote from Miller Brewing Company staff, cited in the study: "...if you wanted maintenance, less downtime and less cost, there is no other problem you could focus on that would be as beneficial as eliminating shaft misalignment. There is absolutely no other area in machinery maintenance [for] which you will get more 'bang for your buck' in terms of reliability, longevity, productivity and reduced overall maintenance cost than eliminating shaft misalignment."
Figure 1: Falk Grid Coupling - Left: Aligned, Right: Misaligned
Images courtesy of Infraspection Institute
Green Concepts
Figure 2: Dodge Coupling: misaligned
Image courtesy of Infraspection Institute
In Figure 2, we see Infraspection Institute's infrared thermogram from the Miller study for a misaligned Dodge "rubber donut" type coupling. It clearly shows that the energy wasted in overcoming the forces produced by misalignment is significant. It should be noted that some of the heating of the motor on the right can be attributed to the axial force imposed on the bearings by the centripetal forces acting on the coupling, which tend to thin the coupling and pull the shafts inwards.
Effect of an Offset on Power Consumption
Graph 1 - courtesy of J. C. Lambley
The ICI Chemicals study (also known as the Runcorn study) by J. C. Lambley bears out these findings. Lambley carefully contrasted the increase in real power consumption from the two main types of misalignment - offset and angularity - by deliberately and carefully misaligning the 3000 RPM motor driving an NK 32-200 centrifugal pump pumping cold water in a closed loop system. The study was conducted using an Optalign® laser system and two types of couplings, one a pin-type and the other a rubber tire type, similar to the Dodge coupling in Figure 2. Graph 1 illustrates the increase in power consumption with the rubber tire coupling resulting from increasing offset. Graph 2 illustrates the same for increasing angularity.
Soft foot, otherwise better described as machine frame distortion, is another large energy hog. Finding, diagnosing and eliminating soft foot are essential steps in the overall shaft alignment task. Alfred Olsen of SAVO Electronics conducted a study that demonstrated conclusively that the twisting or distortion of a motor frame and the consequent eccentricities in the air gap between rotor and stator produce "hot spots" that result in very significant efficiency and energy losses. His careful study showed that a twisted motor can increase power consumption by as much as 17.4 percent!
A good laser shaft alignment system and training are key ingredients for achieving the green goals of reduced power consumption, downtime and repair expense. The laser alignment system you invest in should offer the capability to diagnose soft foot (not just measure it) and allow for the simultaneous input (when necessary) of both thermal growth data at the machine supports and target specifications at the coupling. Your alignment training program should instill a thorough understanding of soft foot diagnosis and thermal growth targeting. The results of both ingredients will be energy savings that pay for all of it.
Effect of Angular Misalignment on Power Consumption
Graph 2 - courtesy of J. C. Lambley
Sources:
Daintith, E. and Glatt, P., Reduce Costs with Laser Shaft Alignment, Hydrocarbon Processing Magazine, Aug. 1996.
General Motors Corporation and Ludeca, Inc., Precision laser alignment reduces your power bill $$ - Maintenance Study, Ludeca, Inc., Miami, 1993.
Lambley, J. C., Misalignment - Its Effects on Power Consumption, Runcorn, August 1994. Olsen, Alfred, Benefits of Comprehensive Motor Maintenance, Maintenance Technology, Sep. 1996.
Seffrin, James [and] Infraspection Institute, The Miller Study - A Cost-Effective, Pro-Active Method to Find, Prioritize and Correct Coupling Misalignment Using Infrared Thermography and Laser Alignment Technologies, 49 pp., illustr., Burlington, NJ 1994. [An indispensable reference on the topic. -Author]
Alan Luedeking is Vice President of Ludeca, Inc., in Doral, FL. He has 28 years experience in machinery shaft alignment and training and holds an ISO Level I Vibration Analyst Certificate. Besides his work, Alan enjoys spending time with his family and pursuing his interest in numismatics. www.ludeca.com
