32 Shaft Alignment Tips and Tricks

Efficient operation and longevity of rotating machinery rely heavily on proper shaft alignment. Misalignment can lead to increased wear and tear, decreased efficiency, and even catastrophic failure. However, achieving precise alignment can be challenging without the right knowledge and techniques. In this guide, we will explore essential tips and tricks for effectively aligning shafts, covering key principles, common challenges, and practical solutions to ensure optimal performance and reliability of your machinery. Whether you’re a seasoned maintenance professional or a novice technician, mastering these alignment techniques will help you keep your equipment running smoothly and extend its service life.

These are some Tips and Tricks that have been useful for us when applying Shaft Alignment:

1. Coupling backlash Trick

Sometimes when you take alignment readings the coupling backlash will affect the alignment results. A high amount of backlash will affect the repeatability of the readings. There is a low tech way to eliminate this coupling backlash on most couplings. Wrap duct-tape around the flexible elements of the coupling. After you apply the duct-tape, take alignment readings as normal. This usually works best on a grid coupling. Be sure to wrap the tape tight enough to force both coupling halves to move as one unit. Do not wrap the tape so tight that it masks the misalignment present at the coupling.

2. Soft foot tip

Parallel rocking soft foot is the most common soft foot problem and the easiest to correct. If you have a parallel rocking soft foot there is a procedure that will work most of the time to immediately diagnose and alleviate the problem. Loosen the bolts on the diagonally opposed feet that are exhibiting a high soft foot reading, while keeping the bolts on the other two feet tight. Then measure the deflection on each untightened foot individually as the bolt for that foot is tightened. The defection value displayed for each foot is the amount that each foot is soft. This defection measured is the exact value that each foot should be shimmed. The only time that this quick fix will not work is if the rocking soft foot is being caused by a bent foot or pipe strain. If it does not work, no harm no fail; continue to fix the soft foot using the standard procedure.

3. Vertical Move tip

Many Laser alignment systems now make it possible to view a vertical move in real time. There is absolutely no reason to view a vertical move. After you take your coupling readings, make note of the vertical correction. Don not enter into a live move mode. Simply add or remove the total amount of shim that was displayed in the foot correction. Monitoring a vertical move will only confuse you, because the numbers will jump when the machine is unbolted and jacked up to make a shim correction. The only time that you should monitor a vertical move is when you are moving a very large machine and it is positioned with hydraulic jacks.

4. Horizontal moves

The easiest way to perform a horizontal move is with jacking bolts. If you are currently using a sledge hammer or a 2×4, it is going to take you a lot longer to perform a horizontal move; often overcorrecting back and forth. There is a way to exploit the advantage of horizontal jacking bolts. After you take your alignment readings and get your horizontal corrections, back off the horizontal jacking bolts on the side of the machine that the correction is towards. Then place the exact amount of shim for both the front and back foot correction in between the jacking bolt that you backed off and the machine. Tighten the jacking bolt on the shim, but leave it loose enough to remove the shim. Remove the shim, loosen the hold down bolts, and tighten the jacking bolts on the machine to move it into the corrected position. After the machine hits the jacking bolts on the side of the machine it is corrected towards, tighten the hold down bolts and loosen the jacking bolts. Take alignment readings, the machine should be in the correct horizontal position.

5. Vertical move before horizontal

As long as there is not a gross misalignment condition, you should always perform the vertical correction before a horizontal correction. A horizontal correction will not affect the vertical position of the machine, but a vertical correction will always affect the horizontal position. When a vertical correction is made it is almost impossible to not disturb the horizontal position of the machine. When you make a horizontal correction the vertical position of the machine should remain constant. This will not be the case only if the base plate is severely warped. Therefore, the vertical correction should be performed before the horizontal correction.

6. Horizontal move first if grossly misaligned

The only time that a horizontal move should occur before a vertical correction is if there is gross misalignment. This is because there will most likely be a large horizontal move. When a machine moves along a base plate move than .040”, it will likely change its vertical position. Unless you have a perfectly machined base plate, a large horizontal move will also result in a vertical position change. After the machine is moved enough to alleviate the gross misalignment, then the vertical correction should be completed before the horizontal correction.

7. Machine train alignment

When performing machine train alignment it is important to take measurements at each coupling before performing any moves. This will allow you to see the total picture of the alignment before making any moves. It may be advantageous to move interior machines rather than working from one end of the machine to the other. If you begin the alignment at one end of the machine train and work your way to the other end, there may be an impossible move to make. To avoid this bolt bound condition, view the alignment as a total system. Choose the smallest moves and easiest points to move to be movable and make the other points stationary. Remember, there is no rule that says the same points have to be stationary for horizontal and vertical moves. The easiest way to view the total machine train alignment is to use a laser alignment system that allows you to change stationary points inside of the computer. Then you can play around with the stationary points easily and choose the best possible scenario for your alignment.

8. Clean up

It is very important to clean up before beginning an alignment. The time spent to clean up before the alignment begins will pay dividends throughout the alignment. You should clean all contact surfaces between the base plate and the machine feet. If there are any dirty and rusty shims you should clean them or replace them. You should remove any debris from underneath the machine that may hinder movement. All of this work that you do now will save time when correcting a soft foot and performing the final alignment.

9. One shaft not able to rotate

Occasionally, you will have a situation when one of the shafts is not able to rotate. This alignment should be performed uncoupled. The shaft that is able to rotate should be rotated to the various positions in order to take readings. The shaft that is not able to be rotated should be cleaned as well as possible and any surface deviations should be repaired. Then a bracket can slide along the smoothest surface location of the shaft to take readings in different positions. If you are using a laser-receiver or laser-return beam

System, then the laser should go on the shaft that can rotate. This will minimize the error in the reading due to the surface of the shaft that cannot rotate.

10. Both shafts not able to rotate

When both shafts cannot be rotated you will be at the mercy of the condition of the shafts. Since you will be aligning the center of mass of the shafts rather than the centers of rotation your alignment may not remove an acceptable amount of misalignment from the machine. If you have a flexible coupling then there is no reason to uncouple the machine. Only uncouple the machine if the coupling is rigid. Pick out the smoothest surface on each shaft to mount a bracket. Clean the surface well and repair any damage. Slide each bracket along the shaft and take readings in each measurement location. Take several sets of readings and compare them. Ignore the readings that are on the extremes and average the middle ones.

11. Bent foot

There is a tell-tale sign that the machine has a bent foot. The foot will display a non acceptable reading when it is checked for soft foot. Then loosen the bolt on the foot and take feeler gauge readings at each corner. At least one corner will display a zero value and the foot will seem to ramp up away from the zero value. This foot is bent.

12. Squishy foot

Sometimes a machine will display a high value for soft foot, then when the foot is investigated further with feeler gauges it measures a zero at all corners. This is the ever confusing, notorious squishy foot. This condition is caused by too many shims under the foot. There should never be more than five shims under a foot. When many shims are stacked underneath a foot, small creases in the shim, and dirt will multiply to affect the foot. It may not seem like a lot, but it adds up. Remove the shims and replace them with no more than five shims under the foot.

13. High vibration

Often when there is a high amount of ambient vibration in the area, it will affect your alignment readings. To combat this vibration you will have to take a large amount of readings and average them out. Some laser alignment systems have a feature to increase the averaging. What this feature does is allows to select how many readings that the system will take for each measurement point. The readings are averaged into a mean reading for each point and the coupling conditions are calculated. This method is highly effective as a countermeasure for vibration. Make sure to take at least to sets of readings to check for repeatability.

14. Cardin shaft

There is more than meets the eye when performing a Cardin shaft alignment. First of all some misalignment must exist for the Cardin shaft to function properly. At least one half a degree of angle at each knuckle is needed to lubricate the splines. There can only be misalignment in either the vertical or horizontal direction, not both. The intentional misalignment between the driver and the driven should be pure offset. There should not be any angular misalignment between the output and input shaft. The angle at each knuckle should be the same; this will ensure that there is no angular misalignment present. The maximum angle at each knuckle should be no more than three and one half degrees. If the three and one half degrees is exceeded it will cause an unacceptable axial vibration.

15. Steam

Steam is an arch enemy of a laser alignment system. Assuming that the steam is thin enough to allow the laser beam to travel through, it will affect the beams path and the accuracy of the readings. The only exception to this rule is a return beam system. Since the laser will travel through the steam and back at the speed of light, the readings will be unaffected. For all other laser systems, you must find away to block the steam and stabilize any thermal waves. If you use dial indicators, the steam will not affect your results; but it may burn your hands a little.

16. Moving the stationary

When presented with a bolt bound condition it may be appropriate to consider moving the stationary machine. They don’t call it stationary for nothing; it is probably heavily piped in or extremely heavy. However, it may be the difference between finishing the alignment in a few hours or a few days. Sometimes you can squeak up to a .010” move out of a stationary machine that will allow the alignment to be within tolerance. It is an option to consider before opening up machine feet or moving bolt holes.

17. Safety

Safety is the first thing to consider before beginning any alignment. The machine that is being aligned should be locked out and tagged out. It is amazing how often this obvious safety procedure is overlooked. The area should be cleared of any foreign objects and cleaned as much as possible. If the alignment is being performed on a pump chain, then the pump that is being aligned should be isolated by closing off any necessary valves. Follow these steps and you will live to align another day.

18. Alignment tolerance

An alignment tolerance is an acceptable window of misalignment. It is impossible to achieve perfection in this world and since this said state of affairs exists, it is necessary to determine an acceptable amount of imperfection. An alignment tolerance is generally obtained from a machine manufacturer, coupling manufacturer, in-house specification, or accepted misalignment based on shaft speed. The alignment tolerance exists to make your life easier; as long as the misalignment is within the tolerance, the machine is aligned. Don’t waste your time trying to align the machines better than within the tolerance, there is no added benefit.

19. Number of shims

No more than five shims should be placed under any machine foot and all effort should be made to limit it to three. Too many shims underneath a machine foot will cause a soft foot condition known as squishy foot. This is when shim variations stack up to cause a sum soft foot effect. Another good rule of thumb is to machine a chalk whenever more than .250” of shim is required underneath a foot. A chalk is a block or metal, preferably stainless steel, usually machined in-house. Follow these shim rules and it will save time and provide for a better alignment.

20. Rotating shafts is important

The only way to obtain centerlines of shaft rotation readings is to rotate the shafts. All surface variations are negated when the shafts are rotated for alignment readings. When you rotate the shafts it provides a pure centerlines of rotation measurement. The ultimate goal of shaft alignment is to align the two centerlines of rotation. There are numerous errors introduced when the readings are taken with the shaft in a static position. Shaft surface deviations will corrupt the values and the center of area of the shafts will be aligned, not the centerlines of rotation.

21. Rigid coupling

A coupled alignment cannot be performed with a rigid coupling. When you take alignment readings while a rigid coupling is coupled, there will be no misalignment displayed. This is because a rigid coupling does not allow for any misalignment to be displayed at the coupling. There are two options to allow the coupling to display misalignment, either loosen the bolts on the coupling to allow the coupling to move freely or perform an uncoupled alignment. If you break the bolts to take readings it will allow you to turn the shafts as one and you can take alignment readings as if it were a coupled flexible coupling. Make sure that the bolts are loose enough to allow the coupling to display all of the misalignment. If this is not possible then you will have to perform an uncoupled alignment. This is accomplished by rotating each shaft to different measurement locations and taking readings. It may take a while to acquire the readings, but they will be highly accurate readings.

22. Take a measurement after each move

It is important to take new set of misalignment readings after each move. Once either a horizontal or vertical move is made the previous set of misalignment readings are no longer valid. The proper move alignment procedure would be to take misalignment readings. Then make a vertical move. Take another set of misalignment readings. Make a horizontal move. Then take a final set of misalignment readings to confirm your move.

23. Turn down a bolt

Turning down a bolt is an efficient and acceptable way to get yourself out of a bolt bound condition; However, There is a right and a wrong way to turn down a bolt. There are a few rules to follow when turning down a bolt. First of all the bolt cannot get turned down more than the minor diameter. Many times this rule is violated and the strength of the bolt is compromised. The filet must remain; this is the radius of material between the head and the shank. You must leave one major diameter worth of thread on the bolt. If you follow these rules and there is still a bolt bound condition then you will have to seek out another remedy.

24. Spacer shaft/jack shaft

A spacer shaft provides for a big advantage when it comes to alignment. The amount of offset that exists between the output and input shaft is divided by the length of the spacer shaft. The lager this spacer length is the smaller the angle that exists between the output and input shaft. This is why you will almost always fin high speed machines coupled with a spacer shaft. When performing an alignment it is perfectly acceptable to take misalignment reading across the entire spacer shaft. If the spacer is too long or the misalignment is too great to measure across the entire spacer length then you can take misalignment readings at each coupling hub. Take a set of alignment readings at each coupling hub then add them together to calculate the net misalignment. Most laser systems make this easy to do right in the computer.

25. Reverse dial indicator spacing

An easy way to avoid math mistakes and make your job easier is to pick convenient distances when setting up the dial indicators. You can’t always do this because you are limited by space, but sometimes you have a few options where you can setup the bracketing. Set up the distance between the dial indicators to be an easily divisible number, like ten. Try to do the same for the distance between the coupling and the dial indicator. The easiest thing to do is force the distance between the coupling and the dial indicator to be half the distance between the two dial indicators.

26. Fixture laser bracketing

The chain brackets for a fixture laser system are counterintuitive when it comes to setting them up. The easiest way to fasten the chain is to put the threaded end on the bracket first. Then bring the stub end of the chain underneath the shaft and place it in its slot. Then tighten the chain bracket. This will save time, if you try to do it the other way it will take a lot longer.

27. Laser system dimensioning

The more accurate the dimensions you enter into your laser system the more accurate your moves will be, but there are two dimensions that matter the most. On a dual beam and return beam system the distance between the two heads or laser and prism is critical. This is the distance used to calculate the shaft angle. If this distance is not correct the whole alignment will be compromised. This is a real advantage of a laser receiver system; the angle calculation distance is a constant value. The other critical distance is the distance to the coupling. The coupling offset is a calculated value based on this distance. If the coupling distance value is not correct, the coupling offset is being exhibited at a false location. All other dimensions should be close, but they do not affect the displayed coupling condition value. It the other dimensions are not correct it will just take you longer to move the machine into alignment.

28. Anti vibration mounts

Anti vibration mounts pose a unique problem during alignment. Since they are made out of rubber the mounts have a certain amount of deflection associated with them for different times in there life span. Especially when the mounts are new they should be set high enough to account for the amount that they will deflect or creep for the first four hundred days. Each mount should be set to the exact same defection before the alignment begins. The mount defection can usually be determined by checking the gap spacing between two points on the mount. If the mounts are not set correctly, the alignment position will change as soon as the machine is in operation.

29. Overhung shaft

There are special considerations when an uncoupled alignment must be performed on an overhung shaft. The weight of the shaft will pull it down and cause it to sit in a different position than it would if it were coupled. This weight must be compensated for, to perform an accurate alignment. The easiest way to do this is to use a load cell to lift the overhung shaft into the position it would be in if it were coupled. You will have to calculate the effective weight of the overhung shaft for the location that you are going to lift it. Then lift the shaft using the load cell till the force on the load cell is the same as the weight you calculated. Then you can take alignment readings. This is very common when performing alignments on propeller shafts.

30. Axial spacing

Axial spacing is critical during some alignments, this only applies to uncoupled alignments where one ore both of the shafts has axial float. This is usually the case for gas turbines and large pumps. If careful attention is not paid to the axial position of the output and input shaft the alignment may not be to within tolerance. You will actually be aligning the shaft for an axial position that the coupling will not be in during operation.

31. Hot alignment check

There are several ways to check for alignment changes due to thermal growth. A hot alignment check is when you take alignment readings on the machine as quickly as possible after you shut it down and then compare the hot readings to the cold readings. There are few problems with this method of detecting thermal growth changes. First of all some of the thermal growth change is not due to thermal growth at all. There is a significant amount of machine movement due to torque. All of this torque movement is gone immediately upon shut down. By the time the machine is shut down, locked and tagged out, and you take alignment readings; at least five minutes has past. A significant amount of thermal expansion will have reversed in this time period. A hot alignment check will only capture a small portion of the alignment change. It is better than doing nothing, but you are not getting the whole picture.

32. Pipe strain hard conduit

Pipe strain doesn’t just come from pipe. Hard conduit can have the same effect on a motor as piping does on a pump. The last two feet of conduit should be flexible; this will make eliminate the chance of pipe strain from conduit. If you still insist on using hard conduit all the way to the motor than make sure that it is installed to the spot it is need on the motor. It should take relatively little fore to position the conduit when affixing it to the motor. If it takes three guys and a come along to attach the conduit chances are you have pipe strain.

Conclusion

Achieving proper shaft alignment is crucial for the efficient and reliable operation of rotating machinery. By following the tips and tricks outlined in this guide, a specialized engineer can minimize wear and tear on equipment, reduce energy consumption, and extend the lifespan of their machinery.

Also, it is important to use the appropriate alignment tools and techniques and to regularly monitor and adjust alignment as needed.

Investing time and effort into proper shaft alignment upfront can lead to significant long-term benefits in terms of performance, reliability, and maintenance costs.