MACHINE TRAINS

Machine trains can be complicated jobs for alignment. Job preparation can save a ton of headaches while trying to align multiple gearboxes and spacer shafts.

One step I added only takes about 20 minutes to do but saved probably twice that.

Using a sheave aligning laser (or low tech version being a string), I attached it on a flat surface of the center gearbox and measure the shaft to the laser line, after loosening the entire machine train, we bump the gearboxes and shafts by hand until we are even to the laser.

Flip the laser pointing to the other half of the machine train and repeat. We then move the laser to one end and verify that the entire machine train is straight with a 1/8" end to end over a 15 foot length was done with in 20 minutes. Snug the bolts and begin laser alignment job as normal.

When we then proceeded with our laser alignment we were pleasantly surprised to find that we were in alignment horizontally down the entire length of the machine. Vertical adjustments were all that was needed to finish the job.

Tip provided by Joel Woodthorp of GEORGIA PACIFIC.
 

Cuando haces una alineación, junto con un buen procedimiento y herramientas de alineación, es muy importante ser constante durante la tarea. Siempre obedece todas las regulaciones de seguridad. Siempre gira los ejes en la dirección normal de rotación. Siempre revisa las lecturas repetidamente. Siempre utiliza llave de tuercas, ya que todos los pernos sujetos están siempre igualmente apretados. Esto es especialmente importante cuanto trabajas en pares, donde la tendencia de un técnico es estar en cada lado de la máquina.

Measuring Coupling Backlash with your Laser Shaft Alignment System

This procedure is ONLY possible with laser shaft alignment systems that have a linearized bi-axial (or multi-axial) sensor. This will not be possible with laser systems that have single axis (Y-Axis only) sensors.

Keep in mind that if you desire to see how much torsional play a coupling has (how much it "backlashes"), you should first try to position the laser and sensor as close as possible to the O.D. of the coupling. If the coupling is too small to "skim" across the top of the coupling, place the laser and sensor as close as you can to the shaft (lowest point on the support posts). Obviously, the farther up the components are placed on the support posts, the larger your results will be. If they are "skimming " the top of the coupling, the values will be very close to the actual amount that the coupling halves backlash relative to each other at their O.D. Another alternative (on large couplings) is to instead shoot the beam through one of the coupling bolt holes, provided the hole is close to the rim or O.D. of the coupling. Special magnetic brackets can facilitate this.

Download the procedure on how to measure backlash with a ROTALIGN PRO or ROTALIGN ULTRA laser shaft alignment system

Keep in mind that each coupling has its own characteristics and backlash values that are considered to be "normal". Furthermore, the values seen will change from a misaligned condition to the aligned condition. Elastomeric type (rubber insert type) couplings will be "spongy" and will not have a true backlash stopping point, whereas the shim type coupling will have no backlash at all.

FILE TEMPLATES

In order to save time in the field, some laser alignment tools have the ability to create templates. Templates allow the user to predefine specific parameters of a machine set-up. For example, at a large newspaper printing plant, there are 24 ink pumps. All are identical three-machine trains motor-gearbox-pump, and all have the same target specs. The only difference is the color of the ink they pump. All of the known dimensions and targets are pre-configured into the file. You save it one time as a template and never have to enter the dimensions and targets again. Each time one of these pump sets must be aligned the user opens the pre-defined template, performs the alignment, then saves it as a normal data file.

PIPE STRAIN

When performing an alignment on a new pump installation, check to make sure that pipe stress acting on the pump is within reasonable amounts. To check for this, take a set of zero-reference readings with your laser alignment system, and start the move function, monitoring both the vertical and horizontal planes simultaneously. Slowly unbolt the piping and check to make sure that no more than .002" movement occurs at the shaft. In addition, the retightening can be monitored, to establish the repeatability of the pipe strain. If movement greater than .002" is observed, the piping must be modified to take care of this problem.

SHEAVE ALIGNMENT

When performing a multiple belt - sheave alignment, it is imperative that all the belts and belt grooves are inspected individually for wear. If any of the belts are slipping, then all belts must be replaced at the same time. To achieve an accurate alignment between the pulleys one can use a machinist's straightedge, or place a tightly drawn piece of string, across the faces of the sheaves to see if all four points of contact are made or you can utilize a Laser Pulley Alignment tool. Regardless of which system is used to perform the alignment, it is a good practice to monitor any changes in angularity and / or offset in the sheaves as the hold down bolts of the machine to be moved are being tightened during the belt tensioning procedure, since this will allow the alignment to be maintained true.

VERTICAL ALIGNMENT

Whenever an alignment job is being performed on vertical flange-mounted machines or machines which have their feet mounted to a wall resulting in a vertical shaft orientation, it is recommended to correct angularity first and then proceed to correct any offset that is still present between shaft centerlines.

If instead the offset is corrected first and any angularity is corrected subsequently, there is a good chance you will find yourself making a second offset correction unless you are using one of the better alignment systems which take into account the impact on offset from correcting angularity are utilized in the alignment procedure.

Slipping/Worn Belts

Use a pocket strobe in the field to identify belt related problems on equipment. The pocket strobe can be adjusted to the same frequency/RPM of the equipment. Damaged, worn or slippage in belts can be observed and reported for repair. If a belt has to be replaced, make sure to change the entire belt set and re-align it using a laser belt alignment tool, like the DotLine Laser.

Dealing with Coupling Backlash in Shaft Alignment

In dealing with coupling backlash in shaft alignment, always turn one shaft first to engage the coupling before adjusting the laser beam on your laser alignment tool. This prevents the laser from shifting significantly away from the detector in the beginning of the measurement. Sometimes it is helpful to apply a slight amount of turning force on one shaft to keep the coupling engaged, in the case where both shafts can be easily turned.

Another way to handle backlash is to let gravity work in your favor when taking a measurement. Set up the laser alignment tool at the bottom of the shaft with the coupling backlash taken up. Rotate the shafts during measurement from the bottom to almost the top, but not past the top and then stop the measurement. This will help keep the coupling engaged during measurement.

  ROTALIGN^® ULTRA Trivia

What is wrong with this picture? 

The answer will depend on what laser alignment tool you own.

If you owned a laser alignment system other than a ROTALIGN ULTRA, and relied on the displayed screen to give you the answer, the most logical answer will be:

There is only ONE fix or static foot, you need to have two.

Not anymore. With ROTALIGN ULTRA you can have ONE or NO fix foot and the computer will calculate your “optimum moves”. Carrying an ULTRA to the field is like carrying a ‘paperless graphical assistant’ with you.

The ROTALIGN ULTRA brings to the field with you crucial information that only the graphical experts were able to obtain. You can now ‘graph’ all the different alternatives with the click of a key.  

We should call this feature ‘Bolt Bound Made Easy’ (BBME) what do you think? The smaller your pump the more useful this feature will be for you.

Thanks for your reply.

BOLT-BOUND MADE EASY: OPTIMIZING ALIGNMENT

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 or movable feet in any combination. Such flexibility is imperative when working with machinery on the critical path. Therefore, look for this capability when selecting you laser alignment system.

plumbness

When performing a plumbness check on a vertical shaft machine with a laser-based alignment system, use a familiar reference point to label as 0° or 1200 o’clock, such as a bolt hole or split line. This will make the rest of the point markings easier and also help keep a more consistent history of the plumbness checks. Also try to have your cardinal positions line up with any installed jackscrews as this will make effecting corrective moves later much easier.

Laser Alignment Readings Direction of Rotation

If your laser alignment system allows you to turn the shafts in any direction, always turn in the direction of rotation of operation of the machines. This will prevent undesirable consequences (such as unscrewing pump impellers) and lets the shaft ride in its accustomed wear path within the bearings, resulting in more consistent repeatable readings.

Sloppy Couplings/Backlash

If you have worn couplings, or couplings with a lot of backlash, consider switching to Pass Mode measure mode for uncoupled shafts (if your laser system possesses this feature) to minimize any potential torsional play effect on your readings, even though you are still coupled up and turning the shafts together.

Coupling Versus Equipment Tolerances in Shaft Alignment

When determining what tolerances to use for shaft alignment, make sure to take into account information provided by both the coupling manufacturer and equipment manufacturer. The coupling manufacturer may state that the coupling can withstand far more misalignment than what the equipment manufacturer suggests for their machines. However, when shafts are not properly aligned, vibration that is sustainable by the coupling will pass directly into the machines' bearings and mechanical seals. These components may not be able to withstand the same forces that the coupling can, and therefore deteriorate or fail prematurely.

DOCUMENTATION

When performing shaft alignments, having a detailed history of the alignment improves communication between those involved with solving and approving the alignment. The best alignment systems automatically record alignment readings and moves in a measurement table. This is ideal for record keeping. Additionally, it is good practice to keep a detailed log of the shim corrections performed. By doing this, each shim correction can be tracked to avoid having stacks of shims installed under each foot (it's recommended to keep no more than 3-4 shims under each foot). If needed, steps can be taken to reverse the shim corrections should the alignment end up going in a direction that was not planned. Murphy's Law If anything can go wrong, it will.

ROUGH ALIGNMENT

When performing shaft alignment, always ensure that the machines are rough aligned first. This ensures that coupling-induced strain is removed to improve the accuracy of the alignment. Shafts that have severe coupling strain may flex, which distorts the true misalignment condition. Use a straightedge, feeler gauges or some other less precise method to position the two machines within some reasonable distance from their desired final aligned location. As a rough rule of thumb for close-coupled machines, rough align to 'nearly eye ball clean', such that the coupling can be made up easily, to avoid much of the above-mentioned 'severe' coupling strain. Straightedge or feeler gauge alignments can be much more precise than this, but time is wasted. The idea is to relieve the shafts of excessive coupling-induced strain to improve the accuracy of alignment corrections.

SAFETY PRIOR TO ALIGNMENT

The number one item that should be taken care of prior to aligning machinery is to ensure that the machines are locked out and tagged accordingly. Isolate machinery from all forms of mechanical and electrical energy. If equipment is accidentally started up while an alignment is being performed, serious injuries can occur. Be sure to close check valves so back pressure from another pump can't make yours start spinning backwards; tie down fan blades so sudden gusts of wind won't cause your shafts to turn or expose you to danger from the blades, etc.

TIGHTEN THOSE BRACKETS!

When using a laser shaft alignment system, always double-check that all brackets and components mounted on the shafts are sufficiently tightened to prevent vibration or just plain gravity from unduly moving them as you rotate the shafts. Also, ensure they are clear of hitting any external obstructions as the shafts are rotated. Also make certain the support posts inserted in the brackets are not only adequately tightened but are burr free. Otherwise, you may be clamping down on a burr rather than the support post itself, and still have mechanical looseness. Any of these factors can affect the measurement accuracy. Performing repeatability checks between alignment readings and corrections is essential in revealing any of these potential pitfalls.

Laser System Lens Cleaning

Always use an optical quality micro-fiber lens cleaning cloth to avoid scratching the polarized coatings of your sensor lens. These are also ideally suited at sucking fingerprints and dust right off the lens surface. Avoid using lint-laden cotton cloths or tissues.

TArgets and Tolerances

When performing shaft (coupling) alignment, very often the terms "Targets" and "Tolerances" are confused or misused.

Target is your desired alignment (cold)…what you are shooting for.
Tolerances are how much you can be off from your Target.

For example
* The Offset Target at the coupling center is ‘0’ mils, and the Offset Tolerance is ± 2.0 mils (for a given RPM), then the Offset will be ‘within tolerance’ when the measured offset value is between plus and minus 2 mils (2.0 < Value < +2.0 mils.)

* The Offset Target at the coupling center is +8 mils (high, by convention), and the Offset Tolerance is ± 2.0 mils (for a given RPM), then the Offset will be ‘within tolerance’ when the measured offset value is between plus 6 and 10 mils ( +6.0 < Value < +10.0 mils.)

Choosing the correct Averaging Value for rough field conditions

If you are not getting good repeatability in your alignment readings using a continuous sweep measure mode, it may be best to switch to a multipoint mode, where you can take discrete readings at desired rotational positions, and with full control over each. Assuming no mechanical looseness, such lack of repeatability may be due to vibration from surrounding running machinery, or heat waves in the path of the beam, steam, or other causes of air density differences in the path of the beam. Most good laser alignment systems offer the user a detail screen where the actual coordinate values of the beam's position within the sensor can be seen. Look at these coordinate values, and if, while just sitting there, they are changing by more than 0.5 thousandths of an inch (0.0005"), increase the averaging time to a sampling rate of 128 or 256 or about 0.75 to 1.5 seconds per reading, until the coordinate values steady up. You will then find noticeable improvement in your repeatability and accuracy of readings and moves.

Choosing the correct alignment tolerance evaluation

There are several ways of looking at alignment tolerances, including standard versus vector tolerances, as well as sliding velocity tolerances. The most used are standard tolerances, but which are applied differently for short flex versus spacer couplings. The best laser alignment systems will allow you not only to select tolerance types but also coupling types. For standard tolerances, keep in mind that the vast majority of true flexible couplings (such as gear, grid, elastomer element, or diaphragm type) have two separate flex planes. So do all spacer couplings. The difference between short flex and spool piece, spacer, or jackshaft couplings lies in the distance between these flex planes. Any time the distance between flex planes is greater than the diameter of the working flex plane, you are better off calling it a spacer rather than a short flex, from the perspective of achieving satisfactory alignment. Keep this in mind when selecting coupling type, as it will greatly increase the alignability of the machines, and ease your job in the field. For a deeper understanding of the subtleties involved in these issues, it is recommended to attend an in-depth training course in laser alignment.

Diagnosing a Rocking Soft Foot

When taking individual soft foot readings on a four-footed machine, one foot at a time, always with the other three feet tight, if the two highest values appear diagonally opposed to each other, you have "rocking" soft foot situation. There are three potentially correct shimming solutions to this problem, but only one best solution.

Here's how to find it

Loosen both diagonally opposed soft feet, leaving the two not soft feet tight. Feel the shim packs. If one is loose and one is snug, mike the air gap that appears under the loose one and shim that one by the amount of the air gap. If both shim packs are loose, shim both feet, by roughly half the soft foot value you got for each of them individually, or mike the airgaps with both of them loose and shim those amounts individually at each soft foot respectively. There are subtleties involved with this procedure that are best learned in an in-depth training course, but this will already go a long way toward solving these problems. Note If your two largest soft foot values do not appear diagonally opposed, you do not have a rocking problem, and other causes and solutions must be explored, again best learned through specialized training.

Vertical Alignment

Obtaining Positional Repeatability while turning shafts on Vertical Machines

On vertical flange-mounted machines, or those that are foot-mounted to a wall with a vertical shaft orientation, the traditional inclinometer-enabled measure modes will not work, nor will any external gravity operated inclinometers. Thus, in order to obtain repeatability in your rotational positions when turning the shafts, try this wrap a piece of string around the shaft, carefully note the total length of the circumference, then stretch the string out on a flat surface and divide this length into eight equal segments that you will mark out on the string. Now wrap the string back around the shaft again and mark these eight equally spaced positions on the shaft, preferably right where the shaft disappears into the bearing housing or seal, so you can line these marks up with a match-mark on the housing. White-out works nicely, or you can scribe the marks. Alternatively to the string, you can use a pi-tape to mark out your positions. This will give you excellent positional repeatability when rotating the shafts to specific clock positions.

Moving Machines for Alignment

If jackscrews are not available to move a machine laterally, consider using a pair of large carpenter's pipe clamps, tensed against each other and the base. This way you can carefully and precisely control the movement of a machine without having to hit it with it a hammer. However, if hit it you must, then use a shot-loaded, deadblow hammer and never a steel-faced sledge hammer. Again, this will help to protect the machine and you can control the move better while using lighter blows.

Jacking Bolts

If using jacking bolts for your side-to-side corrections, always remember to back off the jack bolts on the opposite side. Remember that once you are done with your side-to-side correction, we recommend to always back off all jackscrews after the alignment is completed and the anchor bolts are tight. If movement is known to occur, it will always be in the path of least resistance, which can be targeted for.

BEARING HEATERS

When using Induction Heaters to heat bearings, make sure that the tops of the vertical post are clean; this will make for better contact of the horizontal crossbar. Applying a thin coat of the Vaseline will also help. This prevents vibration from occurring and possibly false brinelling the work piece being heated.

MISALIGNMENT

When aligning machines, it is usually impossible to achieve absolute perfection; therefore, some misalignment must be accepted, provided this remaining misalignment is small enough that it causes no harm; by definition, this window of permissible misalignment is your alignment tolerance. When leaving misalignment on a machine, ideally you would like to leave the correction at the front feet equal to or less than the correction required at the back feet, with the corrections having the same sign (+ or). Such a result always means the alignment is getting better as you approach the coupling; you always want the centerline of rotation pointing towards the point of power transmission.

Turning Shafts

If you have shafts that are very hard to turn by hand, try using a pipe wrench. This is faster and easier than a strap wrench or chain wrench, since you don't have to loosen and retighten it each time; the pipe wrench simply slides back when you back off. Important glue a couple of strips of virgin rubber to the jaws of your pipe wrench so as not to mar the surfaces of the shaft or coupling as you apply the pipe wrench to turn them. The pipe wrench also has another advantage on shafts that turn very easily, these may need to be held in certain positions while performing certain functions like monitoring moves or checking soft foot. The pipe wrench will serve as a perfect counterbalance to the weight of your brackets and laser components if you position it just right.

REPEATABILITY

All laser systems should be able to take two sets of readings on well-built machines and find agreement at the coupling within 0.5 mils offset and 0.1 mils/inch angularity. It is a good idea to always take two sets of readings immediately after setting up the brackets and compare the coupling results for repeatability. If the readings do not repeat the problem may lie within the machines rather than in the alignment tool itself.

Tolerances & Bolt-Bound

Use Shaft Alignment Tolerances to help solve base- and bolt-bound situations. If, when performing an alignment, a base- 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 the shafts may be misaligned, yet 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 situation. Some laser alignment systems 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 machining or hardware alterations to achieve the alignment.

Tightening Anchor Bolts

Always use a torque wrench when tightening or loosening the hold-down bolts of a machine. Determine the proper torque and abide by it. If space is a problem, you can always use a crowfoot extension adapter on your torque wrench to still get in there. Don't forget to change the setting on your wrench to account for this little extra length! Also, remember to lubricate the threads of your hold-down bolts. White lithium grease or "never-seize" is good, and don't forget to use the torque values for lubricated threads, as opposed to unlubricated ones.

Single-bearing Generator Alignment

When aligning a single-bearing generator with the bearing in the end bell, it is important to align the rotor to the driver while at the same time maintaining the proper air gap clearance between the rotor and stator.

This is not so easy. First, note the exact axial distance from the coupling center to the location where you will measure the air gap clearances between rotor and stator, at the front of the rotor where you have accessibility. Also measure the distance from coupling center to the front feet, to the back feet, and to the bearing in the end bell. Now accurately measure the existing air gaps, in the 12, 3, 6, and 9 o'clock positions and carefully jot them down. (Rotate the rotor, repeat these measurements several times and use the averages.) Now slightly loosen the rigid coupling, allowing a 10 thousandths gap between the faces, but not allowing the rabbet to disengage its seat. Rotate the shafts and measure the misalignment. Now carefully graph the rotor line with respect to the driver centerline from the measured misalignment and plot the position of the stator line with respect to the rotor line based on the measured airgaps, by positioning the stator line one half of the difference in the opposite airgaps toward the larger gap. Mark the positions of the front and rear feet. Now shim and move the front and rear feet of the generator so as to align the stator line with the driver line, by the amounts derived from the graph for the front and rear foot locations. Recheck and confirm that your the alignment is now in tolerance and don't forget to retighten the coupling bolts to the proper torque.

If the rabbet-fit coupling has a tapered engagement, the rotor shaft will drop a bit as you loosen the coupling, affecting the measured vertical angularity. In this case, graph the results and consider that the nonzero vertical offset occasioned by the drop will disappear again once you retighten the coupling. For more detail on both scenarios, you may wish to consult TechNote #1.

The Impact of Washers on Shaft Alignment

Often, maintenance departments invest in good quality Bolts and Nuts (Grade 8), but neglect to do the same with flat washers. The importance of a good washer can not be overstated. If you use a typically thin Grade 2 (or worse) flat washer under the bolt head of the hold-down bolts of your machine, this washer will easily be distorted or warped into the hole in the foot upon tightening the anchor bolt. This is particularly true if the difference in shank diameter of the bolt and hole diameter in the foot is significant. This will often be the case when the hole in the foot has been enlarged to overcome a bolt-bound problem. The result of having "dished" washers is that when the anchor bolts are tightened after completing the alignment, the washers will try to center themselves in the hole in the foot and will pull your machine out of alignment again. This effect is virtually impossible to overcome, resulting in a badly misaligned machine after you just did a good alignment! 

Solution: Always discard warped washers and use high quality flat washers that will not distort or warp into the hole. This will allow the washers to do their job of supporting the bolt head's load on the surface of the foot.

Seal Failures

Often, seal failures are not the cause of an incorrect installation or the wrong seal type for the product being pumped, but a symptom of misalignment. If a seal starts dripping or misting product within days after installation, or suffers a "catastrophic" failure within weeks of being placed in service, the first suspect should not be the seal vendor or the technician installing the seal; misalignment should be considered as a good candidate for the cause of failure. Visualize a typical pump-motor system of bearings, shafts, seal and coupling. The weakest link in the chain is usually the mechanical seal. In the last ten years, seal technology has progressed substantially in both material composition and design (most notably cartridge seals), in compensating for shaft vibration. However, significant misalignment can still overwhelm the ability of a seal to keep both seal faces pressed firmly together or to withstand seal face cracking.

So remember, the next seal failure you encounter, quickly check misalignment with a good laser alignment system to see if the weakest link has failed due to misalignment.

Roll Alignment

When mounting a visual laser roll alignment system on crowned rolls for alignment, mount the laser emitter and reflector units on the top of the rolls and in the center of the crown if possible, to prevent the crown from possibly influencing the perceived vertical angular misalignment. When mounting on straight rolls, mount on the sides of the rolls to prevent sag of the rolls from possibly influencing the perceived vertical angular misalignment. On straight rolls check repeatability by taking readings at one end of the roll and verifying the readings at the other end of the roll. For crowned rolls simply swap the emitter and reflector units.

Roll Alignment

When using a visual laser roll alignment system mounted on the rolls for alignment there are several things to keep in mind. Vertical angle misalignment is corrected by changing the pitch or vertical angle of one roll to match the other. This is usually done by shimming or adjusting with tapered keystock. Key formula Angle = rise / run. Two rolls of the same angular misalignment but different lengths will have different angular corrections. For instance, a 4 foot long roll with an angle of 0.002"/12" will have a correction of 0.008" while a 25 foot long roll with the same angular misalignment will have a correction of 0.050". However, rolls with the same angular misalignment and same lengths but different diameters will require the same angular correction.

Roll Alignment

When attempting to align rolls with roll center separations greater than 10 feet with a visual laser roll alignment system, mount the laser emitter and reflector units on the sides of the rolls closest to each other. This will allow the emitter and reflector units to remain within their ideal separation range of not more than ten feet while the roll centers themselves are further apart. For instance, two 5 foot diameter rolls may have their centers separated by as much as fifteen feet while the laser roll alignment system components are maintained at a separation of not more than ten feet.

Repeatability

All laser systems should be able to take two sets of readings on well-built machines and find agreement at the coupling within 0.5 mils offset and 0.1 mils/inch angularity. It is a good idea to always take two sets of readings immediately after setting up the brackets and compare the coupling results for repeatability. If the readings do not repeat the problem may lie within the machines rather than in the alignment tool itself.

Bolt-Bound

Being bolt-bound or base-bound means that you cannot move a machine sideways, or lower it when attempting to align it to another machine. This is always a symptom of an improper installation, and the correct solution is to redo the installation so that this problem does not occur. Nevertheless, it is often too late to do this when the problem is discovered, since production wants the machines on line now! So here are a few other solutions, which, while we do not advocate them as substitutes to a correct installation, do serve as good short-term solutions that will get you to the next outage when you can do better.

The first alternative is to perform an "optimal move" of both machines, providing the stationary machine can be moved at all. If it can be, this is by far the best solution.

The second alternative is to enlarge the holes in the machine feet. This must be done within reason, meaning that the increase in hole diameter should never exceed half of the original hole diameter in the foot. This is the permissible limit since most machines (motors in particular) always come from the supplier with small, nominal-sized holes to begin with, the philosophy being that it is always easier to make a small hole bigger than it is to make a big hole smaller! The surface area of most machine feet is usually greater than what is required to support the mass and operating loads of the machine. Therefore, it is acceptable to open up the hole a little, since, if done within the limits mentioned above, it will not affect the structural integrity of the foot nor its load bearing capacity.

The third alternative is to turn down the anchor bolts. Here again, this is also permissible, ONLY provided it's done right! It is very easy to commit one of seven errors that will render the 'Chicago bolt' unsafe. There are other "prohibited" alternatives such as rolling a machine. This should never be done. 

poor repeatability due to Vibration

If you have a lot of vibration from surrounding machinery penetrating your machines as you align them, you may get poor repeatability if taking readings in Sweep mode. The solution is to switch to Multi-point measure mode and pump up the averaging enough to where the readings become rock steady. Your repeatability will likewise improve. This capability should also exist for soft foot readings and for monitoring moves. One system will even give you the standard deviation of your readings for an even better yardstick of the quality.

cleaning before Alignment

Before starting an alignment job, it is imperative to thoroughly clean the area under the feet of your machine to be moved, as part of the process to detect and correct soft foot. However, also be sure to check under the entire machine for loose hardware or debris. For example, a misplaced nut under the motor can cause soft foot distortion problems when lowering the machine for alignment purposes. You could end up "bottoming out" on the nut with the underbelly of the motor. This will not only hinder the alignment but also result in soft foot as you distort the machine frame when tightening the anchor bolts.

Moving a Machine for Alignment

When moving machines for alignment, always use jackscrews. If you don't have them, beating on the machine frame with a steel-face hammer is a lousy idea. First, you run the risk of damaging the bearings, seals and other delicate components in your machines. Secondly, you have little control over the magnitude of your moves. Thirdly, it's unprofessional. If you don't have time to weld or screw on jackscrew assemblies, consider using a couple of carpenter's pipe clamps, tensed against each-other. This makes for a handy portable jackscrew arrangement that is safe, inexpensive and offers you plenty of control. If this is not possible either, and you must hit the machine with a hammer, then at least do so with a plastic-face, shot-loaded deadblow hammer.

V-BELTS

There are four areas of good V-belt maintenance but we will only discuss Alignment in detail:

1. Sheave groove inspection

2. Belt inspection

3. Belt & Sheave alignment
a) Use dial indicator to verify that Total Indicator Runout (TIR) of each shaft end is no greater than 2 mils.
b) Use a dial indicator to eliminate Face Runout of each pulley on its respective shaft. Adjust pulley's bushing mounting screw accordingly. Tolerance 1 mil/inch of pulley diameter
c) Use a string, straightedge or better yet a laser line tool to accurately align the pulleys. This is achieved by:
- Shimming movable machine vertically to eliminate vertical (top to bottom) angularity (twist angle) between pulleys.
- Shifting moveable machine horizontally to eliminate horizontal (side to side) angularity between pulleys
- Shifting moveable machine axially to eliminate axial offset between pulleys.

4. Belt tensioning

SHIMS

Shims should be clean, and of corrosion and crush resistant material. Most commercial pre-cut shim manufacturers supply four sizes of shims in thirteen standard thicknesses as follows Sizes A, B, C, and D, each in thicknesses .001", .002", .003", .004", .005", .010", .015", .020", .025", .050", .075", .100", and .125". For cheap shims always check these for actual thickness with a micrometer; better quality shims usually only need to be checked for thicknesses of 0.050" and above, since these are usually nominal and are subject to standard material variations. The shims should be free from burrs, bumps, nicks, and dents of any kind. Size numbers or trademarks should be etched into the shim, not printed or stamped. Typically, Size A is a 2" x 2" shim used for machines from a quarter to fifteen H.P. Size B is 3" x 3" and is good for machines up to 60 H.P. Size C is 4" x 4" and is for machines 50 to 200 H.P., and Size D goes up to 1,000 H.P. The best shim makers also supply sizes G and H for very large machines. For most situations, use the smallest commercial shim that will fit around the hold-down bolt without binding. The smaller the shim, the more accurate the alignment corrections will be. Even the smallest Size A Stainless Steel 304 shim will support enormous equipment loads. Rule of thumb Use no more than three shims under any foot if possible, four maximum. With all thirteen standard thicknesses in hand, you will never need more than three shims to make up any desired thickness from 0.001" to 0.150". When inserting the shims under the machine feet, NEVER let your fingers get under the feet, and insert them until you feel them hit the anchor bolt. Then, withdraw them slightly. This way, you know you won't get the slot of the shim caught in the threads of the bolt.

Learn more about our SS 304 Precut Shims

installing new equipment

When installing new equipment, it is a good idea to add a 1/8" shim pack beneath the equipment (e.g., pump and motor) to ensure room for downward movement.

INDUCTION HEATING

When using an induction heater:

1) Make sure the surfaces of the vertical posts are clean.

2) Improve the contact between the vertical post and the crossbar by applying a light coat of Vaseline to the contact surface of the vertical post.

3) The temperature probe should always be placed on or as close as possible to the inner race or ID of the workpiece being heated.

4) For the most efficient heating, always use the largest possible crossbar that will fit through the ID of the work piece being heated. (Stacking of multiple crossbars is permissible.)

5) It is not a requirement that the workpiece must touch the crossbar(s). Just so long as the bar goes through the bore someplace.

6) Most important of all is that the workpiece being heated always be automatically demagnetized. Any induction heater that does not do this COSTS you money instead of saving it.

FLANGE SHIMMING

If you have a vertical flange-mounted motor and need to shim it to get rid of angularity, you have five choices. You can do all positive shimming, all negative, half-positive & half-negative, zero-plus and zero-minus shimming. How to decide which?

If your pump impeller hangs from the thrust bearing in the motor and you do not want to change the pump shaft's axial position, you must do half positive/half negative shimming. This makes your pivot point the shaft centerline itself, so you have no z-axis effect from shimming. This also minimizes the amount of shimming needed. If this is not the case, then choose all positive shimming if you have no shims between the flanges to begin with. If you have plenty of shims already there, you can do all negative shimming. If the bolt circle diameter is the same as flange diameter, or you have some shims there to start with, choose the 0+ solution, which means all positive shimming but forcing one bolt location to be zero (no correction). The 0- solution is similar but in the negative direction. Only the Rotalign Pro offers you all five solutions to choose from at will.

Tip If you are using Optalign Plus or SmartAlign, enter a flange diameter equal to bolt circle diameter to force a zero-plus solution, or, enter flange diameter equals zero to force a half positive/half negative solution. Otherwise enter the flange diameter normally and you will have an all positive solution.

SHAFT ROTATION

When rotating shafts to take alignment readings, always rotate the shafts in the direction of operation of the machines. Going the other way could, in the worst case, unscrew the impeller off the pump shaft! Also, turning the opposite way could cause a shaft to try and "climb up" a worn bearing differently than it does in operation, the wear pattern in the machine's bearings having been occasioned by the normal rotation. Always turn your shafts in the SAME direction when taking readings. If you have a sloppy coupling that allows significant backlash, and you overshoot your desired position a bit, always come back a bit too far and then turn forward again, to take up the unwanted rotational play in the same direction for each desired position. Of course, if you take readings with Rotalign Pro or Optalign Plus, in Sweep Mode, backlash is no problem.

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