To get the most from precision alignment systems, there must be an organizational commitment to excellence, not just a purchase!

Pulp and paper mills are especially challenging places to perform alignment. In the wood yard and paper making areas, there is a wide variety of equipment and mechanical arrangements. The pulp mill and stock preparation areas have so many pumps, they are sometimes wittily referred to as pump mills. Especially in older mills that have been updated, access and space to perform the shaft alignment may be problematical and the machinery bases may be corroded or weak from exposure to water and chemicals.

In every area, but particularly in the pulping and paper machine areas, down time is expensive. Worse, since paper mills essentially always run at maximum capacity, production lost to machinery outages can never be regained. Since alignment is often the last maintenance task performed before startup, the time pressure to finish the alignment or to skip it altogether, is enormous.

Yet, ever increasing environmental and economic demands make any alignment related seal or equipment failures extremely undesirable. So, the pressure mounts on the maintenance department to find better and faster ways to check and correct alignment in order to prevent the machinery failures that inevitably result from poor alignment procedures and practices. As a result, laser shaft alignment systems are accepted as a necessary element of any predictive and preventative maintenance program. However, not every mill uses their laser shaft alignment systems effectively, and not all realize the full benefits that such systems can provide.

Benefits from laser alignment
Numerous articles and papers established the correlation between precision alignment and reduced vibration and wear. One mill using laser shaft alignment systems reported mill-wide average vibration levels dropping by 55 percent on their pumps following a precision alignment program that accounted for thermal growth or cold-to -hot alignment changes.

However, there are coupling manufacturers that claim their coupling eliminates the need for precision alignment. In a paper mill this sales pitch is especially attractive due to the production pressure to quickly finish each outage--that is, skip the alignment--especially unplanned ones. It is true that there are couplings available that mask vibration from misalignment. However, these couplings do not reduce the overall forces on the seals and bearings, nor is there any evidence that these couplings reduce wear. They only hide the symptoms.

For example, one southern paper mill reported area downtime from pump related failures was less than 1 hour in the first 6 months of 1997 compared to over 50 hours for the same period in preceding years. That is over 98 percent reduction in downtime, attributed by the mill to a precision alignment program. What is particularly interesting about this case is that the mill owned laser alignment systems for many years. However, they only started training the mechanics formally in 1995, and only in early 1996 began requiring alignments be completed to precision targets and tolerances. This mill further reports that the cost for pump parts dropped from an average of $28,000 per month in previous years to $7,000 per month for the first seven months of 1997.

Minimize environmental entanglements
Misalignment problems most often take the form of seal wear or failures, bearing wear or failures, broken shafts, and worn or failed couplings. All but the last may result in the pumped fluid leaking into the environment, depending upon pump design. Since precision alignment results in fewer pump failures, one of the sometimes overlooked benefits of good alignment is fewer environmental entanglements.

Ensure lowest energy cost
Several studies are under way to correlate the effects of misalignment on energy consumption. Although published results from various tests indicate from 0 to 20 percent savings, the more scientifically designed procedures produced a much narrower range of savings; 1 to 10 percent, seemingly dependent upon coupling and machine configuration and position of the motor efficiency versus load curve. No one has yet published a broad ranging before-and-after study covering an entire plant or area.

In an interesting development, several thermography venders are showing in their training classes infrared pictures of couplings and inboard bearings before and after alignment. The lower temperatures of the aligned units are strikingly obvious. For the coupling and bearings to run so much cooler, there must be a corresponding reduction in waste heat, and therefore an energy saving. However, it is difficult or impossible to quantify energy savings from thermography, even though the photographs are compelling evidence that the savings exist.

In spite of the early, incomplete, and sometimes anecdotal nature of the evidence, there seems to be little doubt that precision aligned machines use less energy than they would if misaligned. The only question is, how much less? If it is even the lowest estimate of 1 percent, over the course of the life of an alignment, reduced energy costs make up for the added cost of precision alignment many times over.

Modern laser shaft alignment
Precision alignment is more than taking readings and making corrections. It is more than just using the latest laser shaft alignment system. Precision alignment is even more than finishing an alignment with the numbers zeroed. The technical definition is positioning machinery rotating centerlines so that they are collinear, within precision tolerances, at operating conditions. In a broader sense, precision alignment is also a commitment to an ongoing program of excellence in maintenance. What are the elements of a modern precision alignment program?

Training millwrights and mechanics to perform alignment is the cornerstone of any successful alignment program. Look at training as a continuous process, not a one time event. Unused skills suffer atrophy, but even well used skills tend to lose their edge without annual or biannual sharpening. So plan on training right from the beginning.

Who should be trained? Even if not all millwrights are going to perform alignments, all should take at least introductory training to become familiar with the impact of soft foot--that is, machine frame distortion, pipe strain, and other such parameters on machinery alignment and subsequent operating life. Most facilities with good alignment practices discovered handsome paybacks in training mechanical supervisors and vibration technicians.

Another element of a modern precision alignment program is the commitment of the organization. Both management and craft must have an unswerving commitment to aligning every shaft that rotates every time it is disturbed in any way. There must be no such thing as putting it back where it was or good enough. After a shaft has been the subject of maintenance activity, be committed to verifying the alignment and correcting within precision tolerances as required before placing the machine placed back in service.

Precision measuring tools are another element. Today, laser shaft alignment systems are available in various accuracy and performance levels, starting at less than $10,000 and going up to $20,000.

Price is not necessarily an indicator of performance. It is possible to pay laser prices for dial indicator accuracy. Look for systems that have a minimum of 1 micron resolution and that offer NIST traceable certificates. The current generation of systems has small lightweight sensors with fully automatic inclinometers. The built-in inclinometers offer unmatched accuracy and ease of use. The small lightweight sensors fit in tighter places, yet reduce errors in the measurements.

Older generations of equipment required the user to stop the shaft every 45 or 90 degrees to measure. The newer, more accurate systems simply measure continuously while the user turns the shaft as little as 70 degrees or as much as several turns, with or without stopping. The most powerful, sophisticated systems can even measure the misalignment with the shafts completely uncoupled. The laser is simply rotated past the sensor occasionally.

Another element in a modern precision alignment program is having enough laser systems to perform the alignments likely to be required on the busiest day. Some mills own enough laser systems for their day-to-day alignment work and rely on a combination of reserving rental units and using contractors with laser systems for their major outages. This works, but ensure that no alignment goes undone for want of a precision laser system.

When these elements come together, the result can far exceed even the most optimistic projection. It is possible to eliminate misalignment as a root cause of machinery outages. In the words of one maintenance engineer, "We still have some pump failures, but they are no longer due to misalignment."