whitepaper - alignment

8/14/2019 Whitepaper - Alignment

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ALIGNMENT GRUNDFOS WHITE PAPER | 2

Figure 2. Coupling Insert Damaged byMisalignment

Shaft failure or breakage can occur if the equip-ment is grossly misaligned.

Excessive misalignment can cause the mostdurable and best-designed couplings to wearquickly or even fail. Damage to a couplinginsert can be seen in Figure 2.

Other components with internal clearanceswithin the pump, such as impellers, wear rings,and casings can wear prematurely.

Misalignment may cause the pump and driverto operate with excessive or unusual noise.

Vibration may also be observed due to mis-alignment. However, the vibration data mustbe carefully analyzed before the blame is put

on misalignment. Misalignment may still bepresent but not seen in the vibration data ifforces of the rotating equipment are acting inthe same direction to dynamically balance theunit during operation.

Some failures that are initially attributed tophysical setup misalignment may actually becaused by other mechanical deficiencies. Bentshafts going unnoticed can cause the equipmentto be misaligned.

Deficiencies in the coupling components, suchas a distorted hub, an eccentric hub bore, or

an out-of-square hub bore may also cause theequipment to be misaligned. If the equipment isnot aligned with the consideration of tempera-ture change, the equipment may grow duringoperation and become misaligned.

Although the equipment is typically aligned orthe alignment is checked at the factory prior toshipment, proper final alignment is the responsi-bility of the installer and user of the unit. Thosewith final responsibility cannot allow the flexiblecoupling to compensate for misalignment.

The installing technician or contractor should be

made aware of and understand the specificationand the alignment goals before beginning thework. In addition to understanding the align-ment goals, the installation instructions for thepump, driver, and coupling should be reviewed.


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Figure3.Alignment ToleranceChart

If using hired contractors for alignment, a clausein their contract may be considered that requiresthem to provide initial alignment data, soft footconditions, corrections made to the equipment,runout of the equipment shafts, final alignmentdata, and any moves made on equipment.

The equipment user must establish a specifica-tion for acceptable alignment that will provide aguideline for those installing rotating equipment.A chart, similar to that shown in Figure 3, can bedeveloped to provide alignment guidelines.

The specification must include a dependableand repeatable process that will insure a reli-able installation. The alignment tolerance thatis included in the specification should considerthe shaft operating speed, shaft length, and theseverity of the installed service.

Included within the procedure should be infor-mation on documentation. This documentationshould include, at a minimum, alignment forms

and diagrams of the before and after alignmentdata. This information should be filed with theequipment file for future reference.

An important part of alignment is having theproper training and the proper tools. No mat-ter what method of alignment is used, the dialindicators and lasers do not do the alignment human beings do the alignment.

With proper extensive training and practice, andthe correct tools for the job, equipment align-ment can take less than 60 minutes. Becauseof the criticality of alignment to rotating equip-ment, an organization should not skimp on costsof the necessary tools and training.

ALIGNMENT TERMS

There are a few basic terms used in alignmentthat should be reviewed. The specific terms dis-cussed in this section are important to a success-ful installation.


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ANGULAR MISALIGNMENT

Angular misalignment is the term used when two

shaft centerlines are at an angle to each other, asshown in Figure 4. Angular misalignment canoccur in the horizontal or vertical plane of theshafts. A typical objective is to obtain angularmisalignment to less than 1.

PARALLEL MISALIGNMENT

When the equipment shaft centerlines are paral-lel, but are offset from each other, as shown inFigure 5, it is called parallel misalignment. Thistype of misalignment can also occur in the hori-zontal or vertical plane.

It is important to note that equipment shafts canhave angular and parallel misalignment simulta-neously. Both must be considered for a successfulinstallation.

BOLT BOUND

The term bolt bound is used to describe a con-dition that occurs during the alignment process,where the driver or pump cannot be moved anyfurther. The best method to resolve this problemis to fill-weld the existing bolt hole, redrill in theproper location, and retap. This problem can alsobe resolved by removing the problem equipment

and increasing the diameter of the mountingholes in the feet.

SHIMS

Shim stock or precut shims are used to raise thedriver during the alignment process. The propershimming of the driver should occur only afterthe installation of the baseplate has beenfinalized and the connection of the piping to thepump is completed.

Typical of the baseplate manufacturers, a mini-mum of 0.125 shim under the driver feet will

allow for proper alignment. Although a mini-mum is recommended, it must be noted that toomany shims may make the installation springy.A stack of the same size of shims, as shown inFigure 6, should have five or fewer shims of thesame size. The precut shims should be sized to fitthe bolt of the equipment feet. The stack should

Figure 4.Angular Misalignment

Figure 5. Parallel Misalignment

also have the thinner pieces of shim sandwichedbetween the thicker pieces.

The use of homemade carbon steel shim is notrecommended. In addition to the possibility ofrusting, the cut carbon steel may have inconsis-tency in its thickness, thereby causing a soft foot.

Precut shim of 304 Stainless Steel material is

available. These precut shims usually have thethickness measured and the exact thickness isetched on the shim. Although the thickness maybe marked on the shim, the thickness should bedouble checked before installation.

Figure 6. Precut 304 StainlessSteel Shim


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To calculate the amount of shim to add to com-pensate for the short foot, the sum of the smallergap values are subtracted from the sum of thelarger gap values.

This amount is divided by two. Use 80% of thequotient as the amount of shim that should beadded under each foot to remove the parallel airgap. The equation can be shown as:

Shimto add underFoot #1andFoot #4

Shim, in the amount of 0.014, should be addedunder Foot #1 and Foot #4. Recheck by followingthe same procedures initially described.

Bent Foot

A bent foot is a type of soft foot that occurs whenthe bottom of foot is not coplanar, meaning thatthe foot slopes from one corner to another. Thebest way to correct bent foot is to remove theequipment and machine the foot, the baseplate,or possibly both.

If the correction must be made in the field, thenthe shims used in alignment must be stepped tocorrect the slope. Depending upon the size of thefoot and the amount of slope in the bent foot,4-6 shims may be stepped to match the slope ofthe foot. Additional modifications to shim mayhave to be made for the proper slope.

If rise of foot is from the outside going in, all ofthe equipment feet must be machined coplanar.This type of bent foot cannot be fixed in thefield. Unless the feet are machined, it will alwaysdeform when tightened.

Squishy Foot

A squishy foot occurs when dirt, grease, paint,rust,or other foreign materials are on the shim,the base, or the equipment foot. The only solutionto squishy foot is to clean the parts and materials.

DIAL INDICATORS

Dial indicators are used to measure the amountof misalignment between the equipment. A dialindicator (Figure 9) can assist in determiningalignment within 0.001. The dial indicatorscome from the manufacturer pre-calibrated, andmust be rechecked on a regular schedule.

Shaft alignment kits are available starting at ap-proximately $600.00. These kits will contain two

Figure 9. Dial Indicator With AlignmentFixture That Clamps to a Shaft


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(2) alignment frames, roller chain, two (2) dial indi-cator assemblies with swivel joints and mountingrods, tubing of varying lengths, instruction manu-als, alignment worksheets, and a sturdy carryingcase with handle. This type of kit will handle thevast majority of shaft alignment situations.

When initially getting ready to use a dial indica-tor, make sure that it works properly and cantravel the full range of the indicator.

Upon installation of the indicators and at thebeginning of the process, note the direction thatthe indicator travels. The indicator should beadjusted to start at zero (0.000).

The indicator needle traveling clockwise is

considered positive, while counterclockwise isconsidered negative travel.

During the alignment process and a full 360sweep, the summation of the left and right sidereadings should equal the summation of the topand bottom readings.

In addition, the indicators should have read thesame reading (0.000) when it reaches the origi-nal position.

BAR SAG

Bar sag is a deflection that occurs in the over-

hung indicator bar due to the bars weight andthe weight of the indicator. Because of the preci-sion that is required for alignment, the bar sagmust be compensated for.

To determine the amount of bar sag, mount theindicator on a pipe in same approach, distance,etc. as it will be mounted on equipment shaft.Next, zero the indicator on top. Then roll the dialindicator 180, so that it is located at the bottom.Read the indicator.

During the alignment process, this bar sagamount must be included in your alignment

calculations. Instead of zero on the top of the dialindicator, dial in the positive value of the bar sagreading. During the alignment process, the dialindicator should read zero when rolled to bottom.

ALIGNMENT BASICS AND PRELIMINARYCHECKS

There are a number of different tasks to com-plete and check prior to doing the actual align-ment. The preparation for alignment can be asimportant as the alignment itself. Approximately85% of the time spent in aligning equipment iswith preliminary checks, repositioning the equip-ment and post alignment documentation. Thealignment basics and preliminary checks apply toall alignment methods.

To insure accuracy and speed of the alignment,the equipment should be aligned three times.The first time should be during the installation

process (preliminary).Next, the equipment should be final aligned afterit is piped and before the start up of the equip-ment. Finally, the alignment should be checkedwhen the equipment is hot, after running for atime.

Safety of personnel is important during any partof the alignment process. The first step is tolock out and tag all driver controls and isolationvalves. Other safety regulations required at theinstallation site must be followed.

As people are doing the alignment of the critical

equipment, it is imperative to make sure thatthey have the proper training to complete preci-sion alignment.

A properly trained technician in the fundamen-tals of alignment will not only provide a qualityalignment, but also should do it in a timely fash-ion, exceed the recommended standards, and doit right the first time.

The tools used in alignment are also important. Ifusing dial indicators to align, calibrated indica-tors are required with the additional equipmentused to hold the indicators in place. Laser align-

ment kits are typically complete with all thenecessary alignment diagnostic equipment.


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Additional alignment tools include a straight edge,a feeler gauge and a taper gauge. Of course, thenecessary tools to loosen and tighten bolts, cleanparts, and move equipment are also required.

Information about the equipment should also bereviewed before the alignment begins. Thisincludes the recommendations of the manufac-turers, as well as technical information on theequipment that may have been taken previously.

Preliminary checks of the equipment, includingsoft foot, pipe stress, and equipment conditionshould be taken to insure that these would notcause the equipment to become misaligned.

Measurements of the shaft positions should be

taken. The pump and driver shafts should bechecked for runout. The shaft runout should notexceed 0.002 T.I.R. The clearance in bolt holesin equipment feet should be adequate to allowmovement of the equipment.

Pipe stress can have as much or more affectthan soft foot on misalignment. When installingpiping in a system, the piping must start at thepump connections and be erected away from thepump. Pipe stress on a pump can prevent a pumpfrom being properly aligned. This problem can beprevented during the original construction.

A preliminary alignment check should be donebefore grouting to ensure alignment can beobtained. This can be done during fabrication orat the installation site. The equipment feet mustbe free of dirt and scale. Confirm that the drivercan be adjusted by being lowered or moved sideto side. The check must be made with the equip-ment at ambient temperature. The pump mustalso be disconnected from all pipe during thispreliminary alignment check.

The pump and driver must be installed on a goodbaseplate and the proper foundation. Final align-ment should be completed only after the grout-ing has cured during the unit installation. This isto ensure that no changes have occurred duringthe grouting process.

The pump and driver coupling hubs should thenbe installed with the proper gap per the cou-pling manufacturers installation instructions.

Each shaft must turn freely with hubs installedon the shaft. Confirm that the face and outsidediameters of the coupling hubs are square andconcentric with the coupling bores.

Spacer type couplings are aligned with thespacer element removed from the coupling.Gear type couplings are aligned with the samealignment methods, except that the couplingcovers must be moved back out of the way ofthe alignment work.

A preliminary check of the angular measurementof the coupling gap should be made with a feeleror taper gauge, or other tool. In lieu of a feelergauge, a measurement of the distance can betaken between the hubs.

The clearance that is being confirmed is shownin Figure 10. For this preliminary check, do notrotate either shaft. The check should be made at90 intervals in four places, typically at 0, 90,180, and 270. If possible, adjust the alignmentof the equipment until within 0.002 T.I.R. or lessat all four locations.

The preliminary check of the parallel alignmentis next. A straight edge can be used to checkparallel offset as shown in Figure 10. Again, donot rotate either shaft, and check the parallelalignment in four places at 90 intervals. Checkthe alignment on the horizontal axis first, thenthe vertical axis.

During preliminary alignment or final alignment,always recheck alignment after any alteration.Movement in one direction may alter alignmentand modifications made in another direction.

The parallel offset should be rechecked if any ad-justments are made to the angular alignment. Theangular alignment should be rechecked after anyadjustments are made to the parallel alignment.

After the preliminary alignment is completed, the

piping, ductwork, etc. can be attached. Any stressfound at the pipe connections should be removed.The horizontal stress in the piping should berelieved first. This can simply be done byloosening all bolts at the pump flanges andlooking for movement. Make adjustments to pipehangers and supports as necessary.


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Figure 10. Preliminary Alignment Checks

The vertical piping stress should be relieved next.Make any modifications to relieve the horizontalor vertical stresses in stages. The stresses are onlypartially relieved the first time. Additional modi-fications should follow.

The final alignment of the equipment is doneafter the grout is set, the piping is in place, and thebaseplate bolts tightened to the foundation.

Although the coupling installationinstructions mayallow for greater misalignment, the alignmentshould be within 0.004 in all directions, or as re-quired by the manufacturer or user specification.

Methods for final alignment include Rim and

Face, Reverse Dial Indicator, and Laser. The Rimand Face method can be used with the simplestof installations.

It is recommended that the Reverse Dial Indica-tor or Laser Alignment methods be used when

the shaft separation between the equipment isgreater than 50% of the outside diameter inwhich the dial indicators contact the couplinghub rim. A summary of each of these methods isdescribed below.

RIM AND FACE METHOD

The Rim and Face alignment method is typicallyused when it is not possible to rotate both shaftsor if there are space limitations.

A disadvantage of this method is that the dialindicators are running on the surface of thecoupling hub. The hub may have flaws, such assurface defects or eccentricity that may makealignment difficult.

The goal for Rim and Face alignment is 0.002T.I. R. or less when the pump and driver are atoperating temperature.


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This method will obtain an offset reading on theoutside diameter (rim) of the driver coupling huband an angular reading at the coupling hub face,and will use these readings to mathematically orgraphically adjust the driver to the required loca-tion for alignment.

Figure 11 provides a view of the set up of the Rimand Face Method. The indicator bar can also bemounted on the pump shaft if room allows.

Figure 12 shows the dimensions and readingsthat are required for alignment using the Rimand Face Method. Following are definitions usedwith the Rim and Face Method.

Figure 11. Rim and Face Indicator Setup

Figure 12. Rim and Face Method Layout


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DEFINITIONS

IB Inboard (towards pump) driver feet

OB Outboard (away from pump) driverfeet

A The horizontal distance from the rimdial indicator location to the cen-terline of the bolt for the outboarddriver feet

B The horizontal distance from the rimdial indicator location to the center-line of the bolt for the inboard driverfeet

D The diameter of the dial indicator

sweep on the pump coupling hubface

TIR Total Indicator Runout

F The TIR of the pump coupling hubface

R The TIR of the pump coupling hub rim

Two formulas are used in determining themovement required of the driver. Equations 2and 3 define the adjustments needed for theinboard (IB) and outboard (OB) driver locations.These formulas will be used for horizontal

movement, using the horizontal dial indicatorreadings, and for the vertical movement, usingthe vertical dial indicator readings.

F x B RIB Movement = -

D 2

Equation 2. Inboard Driver Movement

F x AROB Movement = -

D 2

Equation3. Outboard Driver Movement

When considering horizontal movement of thedriver, the movement to the left or right is basedon the view from behind the driver, lookingtowards the pump.

RIM AND FACE ALIGNMENT PROCEDURE

Following is the procedure to align equipmentutilizing the Rim and Face Method.

1. Eliminate Soft Foot

a. Determine if a soft foot conditionis present. Follow the procedures toremove the soft foot condition if itexists.

2. Confirm Bar Sag

3. Align Driver from Left to Right

a. Set up the dial indicators as shown inFigure 11.

b. Record measurements A, B and Das shown in Figure 12.

c. Zero the rim and the face dialindicators to 0.000 at the 9 oclockposition of the couplings, as viewedfrom the motor end. Reference the dialindicator diagram in Figure 13.

d. Rotate the indicators on the driver

shaft 180 until they are in the 3 oclockposition.

i. Note the direction of the movementof the needles on the indicators.

ii. Clockwise movement of the needleis considered positive (+).

iii. Counterclockwise movement of theneedle is considered (-).

e. Determine the amount of horizontalmovement of the IB and OB of the driver

i. Make adjustments to the readings

with respect to the Bar Sag.

ii. Utilize Equation 2 and Equation3 to determine the amount ofmovement.


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iii. A positive (+) value of the IBHorizontal

or OBHorizontal

requires the driver to bemoved to the left, as looking toward

the pump from behind the driver.

iv. A negative (-) value of the IBHorizontal

or OBHorizontal

requires the driver tobe moved to the right, as lookingtoward the pump from behind thedriver.

f. Make adjustments to the driver. Tightenall motor bolts using a torque wrench.The same torque on all mounting boltsreduces the influence of deformities inthe motor feet.

4. Align Driver Verticallya. The dial indicators should still be set up

as shown in Figure 11.

b. Zero the rim and the face dialindicators to 0.000 at the 12 oclockposition of the couplings, as viewedfrom the motor end. Reference the dialindicator diagram in Figure 13.

c. Rotate the indicators on the drivershaft 180 until they are in the 6 oclockposition.




d. Determine the amount of verticalmovement of the IB and OB of the driver

i. Make adjustments to the readingswith respect to the Bar Sag.

ii. Utilize Equation 2 and Equation

3 to determine the amount ofmovement.

iii. A positive (+) value of the IBVertical

or OBVertical

requires the driver to beraised, utilizing additional shims asrequired.

iv. A negative (-) value of the IBVertical

or OBVertical

requires the driverto be lowered, by removing the

unnecessary shims as required.

e. Make adjustments to the driver. Tightenall motor bolts using a torque wrench.The same torque on all mounting boltsreduces the influence of deformities inthe motor feet.

5. Recheck the horizontal alignment to insurethat all alignments are acceptable.

6. Document the final readings on analignment form or data sheet, and fileaccordingly.

REVERSE DIAL INDICATOR METHOD

The Reverse Dial Indicator method of alignmentis the most common type of alignment, and isrecommended for most all installations.

The reverse dial indicator method uses therelative measurement of the centerlines of twoopposing shafts. This method acquires twoindicator readings across the coupling.

These readings are used to mathematically orgraphically assist in determining the requiredadjustments and shimming for each foot of the

driver, or moveable unit.

Measurements will be taken in the horizontaland vertical planes of the shafts. The indicatorswill be set up in a similar fashion as shown inFigure 14.

One indicator is mounted on each shaft andmounted 180 opposite each other. Whenreading the indicators, it is important to watchthe direction from zero that the needle travels.

Travel to the right, or greater than zero (0), isconsidered positive (+). Travel of the needle to the

left, or less than zero, is considered negative(-).As graphing is one method in determining thealignment of the equipment in the ReverseDial Indicator method, it is important to haveconsistency between the installation, picturesand the graph paper.


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Horizontal Vertical - If Horizontal change is negative, move LEFT

Moveable Front -0.005 0.011 - If Horizontal change is positive, move RIGHT

- If Vertical change is negative, REMOVE shims

Moveable Back -0.007 0.025 - If Vertical change is positive, ADD shims

Figure 15. Reverse Dial Indicator Alignment Worksheet

REVERSE DIAL INDICATOR ALIGNMENTPROCEDURE

Following is the procedure to align equipmentutilizing the Reverse Dial Indicator Method. Notethat some steps are identical to the Rim and FaceMethod.

1. Eliminate Soft Foot

a. Determine if a soft foot condition ispresent. Follow the procedures to removethe soft foot condition if it exists.

2. Confirm Bar Sag

3. Align Driver from Left to Right (horizontal)

a. Set up the dial indicators as shown inFigure 16.

b. Record measurements A, B and Cas shown in Figure 16.

c. Using graph paper with square grids,utilize the width of a square as 1 inch,and locate the dial indicator locationsand moveable feet on the shaft lineaccordingly.


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Figure 16. Reverse Dial Indicator Setup

d. Zero the rim and the face dialindicators to 0.000 at the 9 oclockposition of the couplings, as viewedfrom the motor end. Reference the dialindicator diagram in Figure 15.

e. Rotate the indicators on the drivershaft 180 until they are in the 3 oclockposition.



iii. Counterclockwise movement of the

needle is considered (-).

f. Determine the amount of horizontalmovement of the IB and OB of the driver.

i. Utilizing the Reverse Dial Indicatorgraph, mark the points that are half

the indicator readings under theirpositions. A vertical square shouldbe considered 0.001.

ii. Draw a line connecting these twopoints, and extending to a pointbelow or above the moveable feetpositions.

iii. The graph will show how much thefeet will be required to move, basedon a vertical square being considered0.001.

iv. The graphed points below the shaftposition (+) will require the feet to

be moved to the right.v. The graphed points above the shaft

position (-) will require the feet to bemoved to the left.


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g. Make adjustments to the driver. Tightenall motor bolts using a torque wrench.The same torque on all mounting boltsreduces the influence of deformities inthe motor feet.

4. Align Driver Vertically

a. The dial indicators should still be set upas shown in Figure 16.

b. Zero the rim and the face dialindicators to 0.000 at the 12 oclockposition of the couplings, as viewedfrom the motor end. Reference the dialindicator diagram in Figure 15.

c. Rotate the indicators on the driver

shaft 180 until they are in the 6 oclockposition.




d. Determine the amount of verticalmovement of the IB and OB of thedriver. Note that Equations 4, 5, and 6

are used in calculating the slope and therequired shim removal or addition. Thesteps are similar to those for horizontalmovement.

i. Utilizing the Reverse Dial Indicatorgraph, mark the points that are halfthe indicator readings under theirpositions. A vertical square shouldbe considered 0.001.

ii. Draw a line connecting these twopoints, and extending to a pointbelow or above the moveable feet

positions.iii. The graph will show how much the

feet will be required to move, basedon the a vertical square beingconsidered 0.001.

iv. The graphed points below the shaftposition (+) will require shim to beadded.

v. The graphed points above the shaftposition (-) will require shim to beremoved.

e. Make adjustments to the driver. Tightenall motor bolts using a torque wrench.The same torque on all mounting boltsreduces the influence of deformities inthe motor feet.

5. Recheck the horizontal alignment to insurethat all alignments are acceptable.

6. Document the final readings on an

alignment form or data sheet, and fileaccordingly.

LASER ALIGNMENT METHOD

The laser alignment method is considered aprecision-based performance technique thatprovides a faster, more accurate way to alignequipment.

It is ideal for alignment of equipment over longdistances, and it is less prone for user error. Becauseof the range of technology between variousmanufacturers, the steps for laser alignment are

not discussed in detail in this article.

The laser alignment equipment consists of atransducer system. Figure 17 provides a view of a

Figure 17. Setup of Laser Alignment Equipment


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laser alignment system installed on a pump andelectric motor. The system contains a laser diodeand position sensor on one mounting bracket.

The diode emits a pulsating, non-hazardous, laserbeam that is directed at the opposite bracket. Theopposite bracket contains a prism that redirectsthe laser beam back to the position sensor. Likeother shaft alignment techniques,the shafts are rotated to determine the verticaland horizontal readings for angular and parallelmisalignment.

The shaft positions and readings are automaticallyprovided to a small computer. The computer thencalculates the relative movement required at thefeet of the moveable machine. Figure 18 provides aview of the diagnostic computer.

A major advantage of the use of laser alignmentis the precise measurement of misalignment.Laser alignment can detect misalignment to0.00004. In addition, with the use of laseralignment, bar sag concerns are eliminated.

However, there are drawbacks and limitationsto the laser alignment method. Laser alignmentequipment typically costs more than $10,000.Service companies or those companies withmany pumps or large pumps are the primarybuyers of laser alignment equipment.

The environment in which the laser alignmentequipment is used is also a limitation. Theatmospheric temperature must be between32 and 131 Fahrenheit for the use of laseralignment. The environment must also be free ofsteam, dust, or air currents.

These detractors will prevent the reading of thelaser beam properly. However, it is possible touse a plastic pipe to shield the beam from thesteam, dust, or air currents.

FINAL CHECKS AND WORK CLOSEOUT

After the equipment has been aligned, someadditional tasks and checks should be performed.

Make sure that each shaft turns freely with thecoupling hubs installed.

Figure 18. Laser Alignment Diagnostic Equipment

The safety equipment should be removed andthe equipment energized.

The driver should be bumped to check forproper rotation.

Reinstall the safety precautions and completethe assembly of the coupling per theinstallation instructions.

Rotate the coupled shafts to ensure they turnfreely.

Install the coupling guards per OSHA orapplicable requirements.

The safety equipment should be removed andthe equipment energized.

Once the pump is ready to operate, the pumpand piping that has been drained should befilled. As the pump and the system piping isfilled, observe for any piping distortion due toimproperly supported piping. Poorly supportedpiping may cause misalignment.

After the piping is installed, the pump unit isoperated under normal conditions and isthoroughly warm, stop the pump unit to recheckalignment while it is warm. This also ensuresthatthere is no additional pipe strain.


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reviewed. This should always be done prior to theassembly or reassembly of the driver on the pump.

As a rule of thumb, the process industry recom-mends that the shaft runout and the concentricityof the mounting fit should be within 0.002 totalindicator runout (T.I.R.) per foot of rabbet fit diam-eter of the motor mount. In addition, the mount-ing face must be perpendicular to the shaft within0.002 T.I.R. per foot of rabbet fit diameter.

The driver shaft runout should not exceed 0.002T.I.R. or 0.001 T.I.R. per inch of shaft diameter,whichever is greater. For a solid shaft motor, theshaft end float must not exceed 0.010 T.I.R., and0.005 T.I.R. is recommended if the pump has amechanical seal.

These requirements may be more stringent thanthe National Electrical Manufacturers Association(NEMA) [1], but they are essential for solid shaftdrivers and 2-pole motor speeds. Typical NEMAtolerances are acceptable for deep well turbinesand 4-pole rpm or lower speeds.

Some manufacturers and models do not usea rabbet fit between the pump and driver, butalign the driver shaft to the pump stuffing box.This practice is also acceptable to use if therabbet fit is not concentric with the shaft.

When final aligning vertical pumps, the drivershould be within 0.0005 per inch of stuffing boxbore for pumps with mechanical seals, and 0.001per inch of stuffing box bore for packed pumps.

For large motors, the use of jacking bolts may berequired to move the motor.

ALIGN EQUIPMENT TRAINS

There are occasions when more than twopieces of equipment are installed in a trainfor a service. An example would be a pump,gear reducer, and a driver. The alignment of a

train can become more demanding due to anadditional variable.

It is important to understand the equipmentinvolved. As previously mentioned, theinstallation and operation manuals for all of

the equipment in the train should be reviewed.A consistent procedure should be developed toprovide a sequence of alignment that will beused for each time the equipment is aligned.

A guideline used in the industry is the fixing ofthe middle piece of equipment, usually the gear-box, and move the other equipment in otherwords, start in the middle and move outward.Rough readings should be taken to insure noneof the equipment would be bolt bound.

If the equipment is bolt bound, the position ofall equipment should be graphed to determineoptimum position. This technique is acceptableif piping has not already been installed. Ifthe piping is already installed and fixed, thenadditional care should be taken to insure thatpipe stress is not put on the pump.

REFERENCES

1. National Electrical Manufacturers Association(NEMA), 1300 North 17th Street, Suite 1847,

Rosslyn, VA 22209; http://www.nema.org.

ACKNOWLEDGEMENTS

Figures 2, 6, 7,9, 17, and 18:Diagnostic Solutions, LLC.
http://www.nema.org/http://www.nema.org/http://www.nema.org/http://www.nema.org/http://www.nema.org/http://www.nema.org/

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