Handbook Of Shaft Alignment Episode 2 Part 10 pdf

Desired off-line lateral shaft positions FIGURE 16.85 Example of a desired off-line top view lateral shaft position alignment model using themachine case to baseplate or machine case to

16.18.2 DETERMINING THEDESIREDOFF-LINESHAFTPOSITIONSWHEN

USING THEMACHINECASE TOBASEPLATE ORMACHINECASE

TOREMOTEREFERENCEPOINTMETHODS

If you employed one of the following techniques to measure OL2R movement, the data youcollected show how each end of the machinery moved from OL2R conditions (Figure 16.84and Figure 16.85)

Side view

Scale :

Measurement points at or near each bearing

. Calculating machine case thermal expansion using the strain equation

Graph paper similar to what is used for the graphing or modeling techniques covered inChapter 8 can be used to show the desired off-line shaft positions The graph centerline willrepresent the final position of the shafts, which is often referred to as the ‘‘hot operatingposition’’ or running shaft positions If the machinery shafts move from OL2R conditions,lines will be drawn on the graph paper to represent what position they should be in when off-line, so that when they move during operation, they will come in line with each other (i.e., end

up on top of the graph centerline)

Along the graph centerline, mark where the OL2R measurements were taken at the inboardand outboard ends of each piece of machinery Other critical points such as the dial indicator(or laser–detector) reading point locations and foot bolt points can be shown Once thedesired off-line shaft positions are drawn, ‘‘shoot for’’ dial indicator readings can be deter-mined for the shaft positions when off-line

It should become apparent by this time that if you are using dial indicators and bracketsthat have sag and that the shafts should not be in line with each other when off-line, youshould never want to ‘‘spin zeros’’ for the dial indicator readings

Desired off-line lateral shaft positions

FIGURE 16.85 Example of a desired off-line top view (lateral) shaft position alignment model using themachine case to baseplate or machine case to remote reference point methods

16.18.3 DETERMINING THEDESIREDOFF-LINESHAFTPOSITIONSWHENUSING

THEMACHINECASE TOMACHINECASEMETHODS

If you employed one of the following techniques to measure OL2R movement, the data youcollected show how one machine case moved with respect to the other machine case fromOL2R conditions:

Graph paper similar to what is used for the graphing or modeling techniques covered inChapter 8 can be used to show the desired off-line shaft positions The graph centerline willrepresent the final position of the shafts, which is often referred to as the ‘‘hot operatingposition’’ or running shaft positions In these OL2R methods, it is not known how eachmachine moved from OL2R conditions with respect to a fixed point in space (as opposed tothe previously covered methods which do) What is known is how one machine saw theother machine move Therefore, one of the two machine cases or shafts is used as a referenceshaft and its position is placed directly on top of the graph centerline The other machinecase or shaft is then drawn on the graph paper to reflect how it moved with respect to thereference shaft

Along the graph centerline, mark where the OL2R measurements were taken at the inboardand outboard ends of each piece of machinery Other critical points such as the dial indicator(or laser–detector) reading point locations and foot bolt points can be shown Once thedesired off-line shaft positions are drawn, shoot for dial indicator readings can be determinedfor the shaft positions when off-line

If the alignment bar system was used to determine the machinery movement, the desiredoff-line side view (vertical) shaft position alignment model setup might look like Figure 16.86

A little bit of thought is going to have to be put forth to recall how the probes were positionedwhen reading the targets and what decreasing or increasing gaps mean when setting up thechart It is easy to make a mistake here by misinterpreting the movement data, so it is wise tomake sure both the amount of movement and the direction of movement are correct and thatyou have gone over the graph setup at least twice before running out and positioningthe machinery with shoot for readings that are wrong Figure 16.87 shows how the desiredoff-line side view (vertical) shaft position alignment model might look if you used a laser–detector system with custom-fabricated brackets or generic mounting brackets or if you usedthe BRTC system

16.18.4 HOW TODETERMINE THE‘‘SHOOT FOR’’ OFF-LINEDIALINDICATOR

READINGS(ALSOKNOWN AS ‘‘TARGETVALUES’’)

So far in this chapter, we have reviewed a number of methods to determine how machinerywill move from OL2R conditions In addition, we have been able to take these data and plotthe information onto a graph showing where the shafts should be when the equipment is notrunning As you can see, if all of the shafts in the drive system do not move in unison witheach other (i.e., the same amount and in the same direction), the shaft centerlines should not

be collinear when off-line Since the shafts should not be in line with each other when off-line,what should the off-line alignment measurements be to insure the shafts are in the desired off-line positions similar to what is shown in Figure 16.86 through Figure 16.88 What would the

alignment readings be if you were using the reverse indicator method, face–rim, double radial,shaft to coupling spool, or the face–face method?

16.18.4.1 Reverse Indicator Shoot for Dial Indicator Readings

If you will be using the reverse indicator method to align your machinery, apply the followingprocedures to determine what the shoot for readings will be when aligning your machinery tocompensate for OL2R movement:

Side view

Scale:

10 in. 10 mils

Observed amount of proximity probe gap change from OL2R conditions

Vertical probe gap

increased by 12 mils

from OL2R

Desired off-line vertical shaft positions

Vertical probe gap increased by 16 mils from OL2R

Vertical probe gap increased

by 12 mils from OL2R Vertical probe gap increased

by 16 mils from OL2R

Target bar attached

to this machine

Probe bar attached

to this machine Up

FIGURE 16.86 Example of a desired off-line side view (vertical) shaft position alignment model usingthe alignment bars or custom fixtures with proximity probes The desired off-line top view (lateral) shaftposition alignment model is not shown

1 Plot the desired off-line shaft positions of both the driver and driven units Figure 16.89shows a motor and a pump plotted in both the side and top views The amount ofmovement of these shafts are based on the data collected from any of the OL2Rmeasurement techniques explained in this chapter.

2 Based on the chosen scale factor from top to bottom on the chart, measure the A and Bgaps

3 Determine whether the bottom readings taken on each shaft are positive or negative byapplying the following rules Rules to determine the sign (þ) or () of the measurements:

a If the actual centerline of a unit is toward the bottom of the graph with respect to aprojected centerline, the reading will be positive (þ).

Desired off-line vertical shaft positions

Pump defined as the observed or target machine

Laser − detector system observed that the inboard end of the pump raised upwards 20 mils Laser − detector

Laser − detector or prism

Laser − detector system observed that the outboard end of the pump raised upwards 10 mils

Up

FIGURE 16.87 Example of a desired off-line side view (vertical) shaft position alignment model using alaser–detector system with custom-fabricated brackets or special mounting systems The desired off-linetop view (lateral) shaft position alignment model is not shown

b If the actual centerline of a unit is toward the top of the graph with respect to a projectedcenterline, the reading will be negative ().

In other words, try to visualize what is going to happen to the dial indicator stem as ittraverses circumferentially from top to bottom on the shaft of each machine Is it going tomove outward (negative) or inward (positive)? In Figure 16.89, the side view shows thatthe motor centerline appears to be higher from the vantage point of the pump, therefore thedial indicator stem will move outward as it rotates to the bottom of the pump shaft producing

Side view

Scale:

10 in. 10 mils

Observed amount of proximity probe gap change from OL2R conditions

Vertical probe gap

decreased by 4 mils

from OL2R

Desired off-line vertical shaft positions

Vertical probe gap increased by 5 mils from OL2R

Vertical probe gap decreased by

4 mils from OL2R

Vertical probe gap increased

by 5 mils from OL2R Tubing connector

Ball − rod

Ball − rod Prox probes

Up

FIGURE 16.88 Example of a desired off-line side view (vertical) shaft position alignment model using aball–rod–tubing connector system The desired off-line top view (lateral) shaft position alignment model

is not shown

Up Side view

Scale :

Where the dial indicator readings will be taken on the motor

shaft with the bracket attached to the pump shaft

A and B indicate the distances between

the two centerlines of rotation where

the readings will be taken when

looking in the side view

C and D indicate the distances

between the two centerlines of rotation where the readings will be taken when looking in the top view

Where the dial indicator readings will be taken on the pump shaft with the bracket attached to the motor shaft

FIGURE 16.89 Example of desired off-line side and top view alignment models of a motor and a pump

to calculate the shoot for reverse indicator measurements

a negative reading From the vantage point of the motor, the dial indicator stem will moveinward as it rotates to the bottom of the pump shaft producing a positive reading.

4 Based on the chosen scale factor from top to bottom on the chart, record the C and Dgaps as shown in Figure 16.89 for the top view Remember, you should always zero yourindicator on the side that is pointing toward the top of your graph paper, in this case, it

is east Apply the same logic explained in step 3 to determine if the reading will bepositive or negative

5 Apply the appropriate gaps at A, B, C, and D into the equations shown in Figure 16.90and solve The shoot for reverse indicator readings solution for the desired off-line shaftpositions in the side and top views for Figure 16.89 is shown in Figure 16.90 assumingthat there is 10 mils of bracket sag

Bottom

0 Top

Bottom

0 Top

Pump

+ 5

0 Top

Bottom

0 Top

16.18.4.2 Face–Rim Shoot for Dial Indicator Readings

Figure 16.91 shows the desired off-line shaft positions of a motor and a pump in both the sideand top views In this particular case, ‘‘front side’’ face readings were taken on the pump shaftand the T-bar overlay was used to model the desired shaft positions Similar to the procedurefor reverse indicator, measure the gaps A, B, FV, and FL Figure 16.92 shows the generalequations needed to solve for the shoot for face–rim readings as well as the specific face–rimshoot for readings you would obtain for the desired off-line shaft positions shown in Figure16.91

16.18.4.3 Double Radial Shoot for Dial Indicator Readings

Figure 16.93 shows the desired off-line shaft positions of a motor and a fan in both the sideand top views Similar to the above procedure for reverse indicator, measure the gaps A, B, C,and D Figure 16.94 shows the general equations needed to solve for the shoot for doubleradial readings as well as the specific double radial shoot for readings you would obtain forthe desired off-line shaft positions shown in Figure 16.93

16.18.4.4 Shaft to Coupling Spool Shoot for Dial Indicator Readings

Figure 16.95 shows the desired off-line shaft positions of a gear and a motor in boththe side and top views Similar to the procedure for reverse indicator, measure the gaps

A, B, C, and D Figure 16.96 shows the general equations needed to solve for the shootfor shaft to coupling spool readings as well as the specific shaft to coupling spoolshoot for readings you would obtain for the desired off-line shaft positions shown in Figure16.95

16.18.4.5 Face–Face Shoot for Dial Indicator Readings

Figure 16.97 shows the desired off-line shaft positions of a motor and a calender roll in boththe side and top views In this particular case, ‘‘front side’’ face readings were taken fromboth the motor to the drive shaft (also known as coupling spool) and from the calender rollshaft to the drive shaft The T-bar overlay was again used to model the desired shaftpositions Similar to the procedure for face–rim, measure the gaps FA, FB, FC, and FD.Figure 16.98 shows the general equations needed to solve for the shoot for face–face readings

as well as the specific face–face shoot for readings you would obtain for the desired off-lineshaft positions shown in Figure 16.97

16.19 ALIGNING SHAFTS FOR RUNNING CONDITIONS (ALSO KNOWN

AS RUNNING ALIGNMENT OR ‘‘HOT OPERATING ALIGNMENT’’)

The graphing or modeling techniques shown in Chapter 8 illustrated how to align two shaftswith each other to insure they were collinear when off-line If you do not want the shafts to becollinear when they are not running but want them to be in a specific desired off-line position

is similar to what is shown in Figure 16.89 through Figure 16.98

The trick to offset aligning rotating machinery shafts is to shift the position of the shafts towhere they will be when they are running and align the running shaft positions Once theshafts have been shifted to their running positions, the vertical and lateral movement restric-tions can be superimposed onto the model, and the overlay line can then be used to determinethe appropriate vertical and lateral repositioning movements required to put the shafts in thedesired off-line positions

Side view

Scale:

Desired off-line lateral pump shaft position

Desired off-line lateral motor shaft position

FV

B

D

A indicates the distances between the

two centerlines of rotation where the rim reading will be taken when looking

in the side view

Where the dial indicator readings will be taken on the pump shaft

FL

A

D

FV is the face reading taken on diameter D

when looking in the side view

B indicates the distances between the

two centerlines of rotation where the rim reading will be taken when looking

in the top view

FL is the face reading taken on diameter D

when looking in the top view

FIGURE 16.91 Example of desired off-line side and top view alignment models of a motor and a pump

to calculate the shoot for face–rim measurements

Rim sag = 10 mils Face sag = 2 mils

2

(

( ( ( ((

FIGURE 16.92 General equations to calculate the shoot for face–rim measurements and a samplecalculation based on the shaft positions shown in Figure 16.91

Desired off-line lateral fan shaft position

Desired off-line lateral motor shaft position

Where the dial indicator readings will be taken on the fan

shaft at the near indicator location

A and B indicate the distances between

the two centerlines of rotation where

the readings will be taken when

looking in the side view

C and D indicate the distances

between the two centerlines of rotation where the readings will be taken when looking in the top view

Where the dial indicator readings will be taken on the fan shaft at the far indicator location

Figure 16.99 shows the type of information that needs to be gathered on a two elementdrive train before final alignment.

In summary:

OL2R conditions, piping fit up problems, the total shim thickness that exists under themachinery feet, how far can each unit be moved sideways at the feet, what positions theshafts should be in when off-line, and what are the ‘‘shoot for’’ readings

. What positions are the shafts actually in when off-line?

Near sag = 10 mils

((+14) − ( − 21)) + 8

(2 (+14)) + 16

+ ( − 21) (+14) − ( − 21) 2

FIGURE 16.94 General equations to calculate the shoot for double radial measurements and a samplecalculation based on the shaft positions shown in Figure 16.93

Side view

Scale:

Motor Gear

10 in. 10 mils

Desired off-line vertical motor shaft position

Desired off-line vertical gear shaft position

Shaft to coupling spool method

East

Top view

Scale: 10 in. 10 mils

Desired off-line lateral motor shaft position Desired off-line lateral gear shaft position

C and D indicate the distances

between each centerline of rotation where the readings will be taken on the coupling spool when looking in the top view

Motor Gear

Where the dial indicator readings will be taken from the motor shaft to the coupling spool

Coupling flex point Coupling flex point

D

Motor Gear

A and B indicate the distances

between each centerline of rotation where the readings will be taken on the coupling spool when looking in the side view

Figure 16.100 shows the side and top view alignment models for the motor and multistagepump The models show both the actual off-line shaft positions and the running shaftpositions To better clarify the alignment condition, Figure 16.101 shows only the runningshaft positions Superimposed on the side view, the total shim thickness that exists under each

of the bolting planes have been shown and hence we know how far down each shaft could bemoved Superimposed on the top view, the lateral movement restrictions at each of thebolting planes have been shown and so we know how far to the east or west each shaftcould be moved without getting bolt bound Figure 16.101 also shows possible solutions inthe side and top views by superimposing an overlay line Bear in mind that there are otherpossible solutions besides the ones shown

0 Top

Bottom

0 Top

(( − 16) − (+9)) + 5

(2 ( − 16)) + 10

+ (+9) ( − 16) − (+9) 2

0 Top

Bottom

0 Top