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Soft foot can severely affect the operating condition of a machine, which will undoubtedly shorten its life expectancy. Here are a few simple tips to help avoid soft foot in your machines:

  1. Eliminate rust, dirt and any other contamination from the contact surfaces of the machine feet, shims and frame or foundation.
  2. Never insert more than four shims at a time beneath a single machine foot. More than three shims may cause a spring effect.
  3. Eliminate external forces on the machine such as those from connected piping, conduit, auxiliary supports, etc.
  4. Use high quality, clean and uniform shims when shimming is necessary.

Watch our Shaft Alignment Know-How video on Soft Foot

by Pedro Casanova CRL

Typically,  the need for shaft alignment will be identified from high vibration or thermal data obtained from running equipment, or any time a new installation takes place.
Although there are many methods of measuring misalignment between two shafts, a laser system will help the millwright perform the job accurately and in a timely manner. By definition, shaft alignment means to align two or more rotational centerlines, so that they are colinear at the coupling point under operating conditions.
A laser shaft alignment system should provide the user with an easy user interface. It should allow the user, with a simple rotation of the shafts, to measure the relative misalignment between the rotational centerlines of the shafts.
Laser Alignment
After the misalignment is identified, the laser system should calculate the necessary corrections to bring the machines within the desirable tolerances. The laser system should also help in measuring soft foot on each of the machine feet, by providing an accurate value of the effect the foot has on the bearing alignment within the machine. It should also help to compensate for machine thermal growth or alignment targets provided by the manufacturer or company engineer.
A proper laser shaft alignment system will help reduce labor hours allocated for machine alignment, and provide proper documentation of the work done.

by Adam Stredel CRL

1. Reduced Energy Consumption
Significant power savings can be made through accurate alignment. Precise alignment eliminates reaction forces and reduces energy consumption by up to 10%.

Reduced Energy Consumption
Courtesy of ©ICI PLC

2. Reduced Incidence of Repairs
Mechanical seal repairs decline by up to 65% when precision alignment is carried out on a regular basis.
The rate of repairs declines by up to 30% when precision laser alignment becomes an integral part of the pump repair schedule. Maintenance costs are also reduced through lower parts expense and inventory levels.
Reduced Repairs
Courtesy of ©HOECHST AG Gendorf/Germany

3. Longer Machine Life
Relation between offset and bearing life cycle: The smaller the offset misalignment,  the greater the expected bearing life cycle.
Longer Machine Life
Courtesy of ©The University of Tennessee

by Ana Maria Delgado, CRL

Laser shaft alignment has become ubiquitous these days. And for the most part,  alignments are very similar from one machine train to another. User enters the RPM for tolerance evaluation, enters dimensions of the driver, measures misalignment, and makes corrections. But what happens when an unusual physical configuration exists, as when the foot of the machine is between the flex planes of the coupling? Or the receiver cannot be mounted outboard of the flex planes of such coupling?
Entering a dimension correctly as a negative value can take care of that problem. This will ensure that the corrections at the feet are precise, and the alignment is done properly.

Sample negative dimension with ROTALIGN ULTRA


Does your laser alignment system have this crucial capability? Our ROTALIGN ULTRA laser alignment system does!

by Adam Stredel CRL

In any alignment situation,  one of the most basic principles is rise over run. Think of it as a change in offset over a distance. It is also a way to quantify angles without using degrees. When the laser system measures “angularity”, it expresses it as rise over run, or a change in offset over a distance. This information, along with the dimensions that the user enters are what the system uses to calculate corrections at the feet. That is why it is very important that laser measurements are repeatable and that all dimensions should be accurate to within 1/8 inch. The sensor to coupling dimension is the most critical of these. If the laser measurements are good but the dimensions for the feet are not, any corrections the computer calculates will not work due to the fact that they are “applied” to a different location, not at the actual foot location. If you are making the corrections that the computer says to and your alignment is still off, double check your dimensions.

by Ana Maria Delgado, CRL

Use Shaft Alignment Tolerances to help solve base- and bolt-bound situations. If,  when performing an alignment, a base-bound or bolt-bound situation presents itself, take advantage of using the outer limits of your shaft alignment tolerances to help alleviate the situation. It may be possible to optimally position the machine so that the shafts may be misaligned, yet still remain within the required tolerances.
For example, a machine is horizontally bolt-bound at the inboard feet. It is currently well within its angularity tolerance, but just shy of satisfying the offset tolerance. A possible solution to get out of this situation is to try adjusting the offset by moving the back feet and pivoting the machine about the front feet so as to cause the offset to get a bit closer, while still maintaining the angularity tolerance. As long as the angularity remains within tolerance during this move to achieve the offset tolerance, this is a perfectly acceptable solution. Some laser alignment systems even allow you to test the effect of proposed moves without actually making them, thereby allowing you to determine if a proposed move such as the one described above will work, before you actually do the work of trying it.
By evaluating the alignment situation objectively, and planning a move to remain within the tolerance limits of the alignment condition, you can avoid unnecessary moves, machining or hardware alterations to achieve the alignment.

by Pedro Casanova CRL

When you get bolt-bound or base-bound on a critical machine train,  usually one that is very difficult to move,  it is not enough to just be able to fix individual pairs of feet to obtain alternative shimming or moving solutions. You need even more flexibility: the ability to minimize moves across all the feet. The concept of stationary and movable machines is obsolete: All machine feet are movable under given circumstances, so it is essential to be able to find the minimum corrections necessary to align to any conceivable centerline, including fully optimized centerlines, or centerlines optimized among any desired number of fixed and movable feet in any combination. Such flexibility is imperative when working with machinery on the critical path. Therefore, look for this capability when selecting your next laser alignment system.
 

by Pedro Casanova CRL

Machinery Lubrication, September • October 2010
In his book “Machinery Vibration: Alignment”, noted author and expert on precision alignment Victor Wowk illustrates the relationship between misalignment and loss of machine life. Of course, some equipment is more or less tolerant to misalignment depending on bearing type and coupling type. Likewise, the effects of misalignment are magnified as a function of speed.
Read entire article Shaft Alignment has a Bearing on Lubrication Excellence

by Ana Maria Delgado, CRL

Dowel pins in machinery have at least 3 functions. One function is to restrict relative movement and aid in the placement of two mating parts such as seen in bearing housing caps. Another function is to prevent improper orientation of components.  Lastly, dowel pins are used to keep machine components in alignment. Our discussion will investigate this last function. Dowel pins are commonly seen on larger machinery. The dowels are usually placed in machine mounting feet or bearing housings. The intent is to prevent movement between these components and the base plate or foundation, thus keeping the machine train aligned. People rely on the dowel pins to maintain machine alignment and assume that if the dowel pins are in place the machine is aligned. During alignment checks I have never found a doweled machine to meet the tolerances of a precision alignment. I recall one instance where a machine was precision aligned and after the alignment technician left the worksite the maintenance leader insisted on re-installing the dowel pins. Re-installing the dowel pins forced the machine back into a misaligned condition, so the previous efforts and expense were a waste.
How should we approach the alignment of machines held in place with dowel pins? First, we should realize that proper machine mounting bolts when properly torqued are sufficient to hold machinery in place. The dowels should not be required if proper mounting fasteners and proper fastener techniques are used. When installing a machine with pre-existing dowels set the machine in place and re-install the dowels if you like. This will provide a starting point equivalent to a “rough alignment”. Now remove all the dowels except from the machine component that you would designate as the stationary machine, remembering that this dowel may also have to be removed if, for some reason, the alignment process requires that this component needs to be moved. Proceed as with any other machine alignment. The component with the dowel left in place doesn’t really need the dowel and the dowel becomes only a point of reference.
Related article: Alternatives to using dowel pins in machine feet

by Bill Hillman CMRP