lesson 03 pdf

8/12/2019 Lesson 03 PDF

1/50

SHAFT ALIGNMENT

AND VIBRATION ANALYSIS

L esson 3 Code: Sabic M 22B 33

LESSON 3R IM AND FACE ALIGNMENT METHOD

A popular method used for years and is still in use today is the rim and face method. Face

Readings obtained as the shafts are rotated and the centerline of the dial indicator stem is

set parallel to the shaft centerline.

Fig. 3-1.

Rim Readings obtained as the shafts are rotated and the centerline of the dial indicatorstem is set to 90 degree angle to the shaft centerline.

Fig. 3-2.

This method produces acceptable results, but is less accurate than the reverse dial

indicator method.

8/12/2019 Lesson 03 PDF

2/50

SHAFT ALIGNMENT


Fig. 3-3.

Fig. 3-4.

1. Parallel run out is measured by readings taken on the outside diameter of the coupling

2. Angular run out is measured by readings taken on the face of the coupling half.

34 Code: Sabic M 22B L esson 3

8/12/2019 Lesson 03 PDF

3/50

SHAFT ALIGNMENT



Fig. 3-5.

Fig. 3-6.

Fig. 3-7.

8/12/2019 Lesson 03 PDF

4/50

SHAFT ALIGNMENT


Find the Total Indicator Run-Out?

Fig. 3-8.

TIR =

TIR =

TIR =

TIR =

3. The support brackets on which the dial gauges are mounted must be rigid and

securely attached to the coupling halves.

4. Zeroing both indicators at top dead center

5. Turn the shaft supporting the gauges through 360 degrees and recording the gauge

reading at 90 intervals. A typical set of readings would appear as follows.

6. The readings taken on the coupling outside diameter or rim represent the parallel run

out in both vertical and horizontal direction.

7. In this case the driving machine has been recorded as 0.275 mm high at the

coupling (remember shaft center line offset is half the total indicator run out).


8/12/2019 Lesson 03 PDF

5/50

SHAFT ALIGNMENT



The run out in the horizontal plane is 0.075 mm. The readings taken on the face of thecoupling show the angular run oul which, in this case, can be seen to be greater in the

vertical plane than the horizontal.

How to check Dial Indicator?

Each time the dial indicator is rotated to the top location it should display a reading of zero.

If it does not then something has moved during the rotation: indicator, bracket, clamping

mechanism, machine. Correct the problem and start over. Face and Rim method produces

acceptable results, but is less accurate than the reverse dial indicator method.

Face and Rim Using Graph:

Measuring misalignment involves taking readings from two dial indicators, the P and A

dial indicators. Before these readings are taken, however, certain distances must be

determined. These distances can be measured with a tape measure. As the distances are

measured, they should be recorded on the data sheet. Although it is difficult to obtain

extremely accurate measurements with a tape measure, it is usually possible to measure

distances to within an eight of an inch. One measurement that should be taken is the

distance between the centerline of the fixed components shaft and the centerline of the A

dial indicators stem (See the following figure).

Fig. 3-9. Distance from Centerline of the Fixed Components Shaft to theCenterline of the A Dial Indicators Stem.

8/12/2019 Lesson 03 PDF

6/50

SHAFT ALIGNMENT


What needs to be determined is the swing diameter of the A dial indicator stem. The

swing diameter is the diameter of the circle through which the A dial indicator travels as

the shafts rotate. The swing diameter is equal to the measurement taken multiplied by 2.

This value should be recorded on the following data sheet in the area labeled D.

Fig. 3-10.

Another tape measurement that should be taken is the distance from the target of the Adial indicator to the centerline of the support bolt for the motor foot that is nearest to the hub

(See the following figure). This foot is generally referred to as the near foot or the inboard

foot. This measurement is easier to take if the dial indicators and the brackets are rotated to

about the 6 oclock position. The value of this measurement is recorded on the data sheet

in the area labeled X.

Fig. 3-11. Distance from the Target of the A Dial indicatorto the Centerline of the Inboard Motor Foot.


8/12/2019 Lesson 03 PDF

7/50

SHAFT ALIGNMENT



A third tape measurement that should be taken is the distance from the target of the A dial

indicator to the centerline of the support bolt for the motor foot that is farthest from the hub

(See the following figure). This foot is generally referred to as the far foot or the outboard

foot. The value of this measurement is recorded on the data sheet in the area labeled

V.The rim and face method requires that both shafts be rotated at the same time. This

requirement can be made easier if the coupling is partially assembled. For example, with a

grid-type coupling, the grid can be installed to connect the two hubs so that both shafts can

be rotated together. In addition, it is generally preferred that the shafts be rotated in the

direction of normal operation. It is also important to prevent axial shaft movement while the

shafts are rotated. Where anti-friction bearings are used, axial movement is not significant.

However, where sleeve bearings are used, axial movement can result in erroneous dial

indicator readings. To avoid this problem, some mechanics insert a soft pencil eraser

between the hubs. The eraser prevents axial movement without damaging the hubs Taking

dial indicator readings After the required distances have been measured and recorded, the

dial indicator readings can be taken. To measure misalignment in the vertical plane, both

shafts should be rotated so that the brackets are at the 12 oclock position (See the

following figure).

Fig. 3-12. Brackets at 12 Oclock Position.

Marks made on the pump (not shown) can be used to ensure that the brackets are at

exactly 1 2 oclock. Next, the face of each dial indicator is rotated so that a reading of zero

is obtained. Then, both shafts are rotated one complete revolution. The marks on the pump

can be checked to make sure that the brackets are returned to exactly 12 oclock. At this

8/12/2019 Lesson 03 PDF

8/50

SHAFT ALIGNMENT


point in the procedure, the dial indicator readings should both be zero. The purpose of this

step is to make sure that the brackets and the dial indicators are securely fastened. If eitherdial indicator reads anything but zero, it means that something has slipped, and

adjustments are necessary. Next, while the dial indicators are observed, both shafts are

rotated until the brackets are at exactly 6 oclock (See the following figure). In the example,

the P dial indicator read - 1 7 mils, and the A dial indicator read +6 mils.

Fig. 3-13. Dial Indicator Brackets at 6 Oclock.

These first dial indicator readings are recorded on the data sheet. The data sheet has two

circles that are used for the initial dial indicator readings. The circle on the left is labeled P.

It is used for the P dial indicator readings, or parallel misalignment in the following figure,the box at the top has a zero written in to represent the zero reading that was set at 12

oclock. At the bottom is a box for the 6 oclock P dial indicator reading. The small area at

the left of the box is for a plus or minus sign. In Figu re 3-13 , the reading of-17 mils has

been entered in the 6 oclock box.

Fig. 3-14.

The circle on the right of the data sheet is for the A dial indicator readings, or angular

misalignment. In the following figure, the 12 oclock reading of zero and the 6 oclock


8/12/2019 Lesson 03 PDF

9/50

SHAFT ALIGNMENT



reading of +6 mils have been entered.

Fig. 3-15. Initial A Readings: 12 Oclock and 6 Oclock.

Vertical Plan MisalignmentThe dial indicator readings at 12 oclock and 6 oclock can be used to determine parallel

and angular misalignment in the vertical plane. However, to check for accuracy, another set

of readings should be taken and compared with the first set. If the two sets of readings are

the same, then they are probably accurate. If one or more readings do not match, it

indicates that something has slipped. Adjustments should be made, and then the readings

should be checked again. It is extremely important for any measurement taken while

performing a shaft alignment to be repeatable. Without repeatable readings, it is very

difficult to perform an accurate shaft alignment. After vertical plane misalignment

measurements have been taken, graphs or formulas can be used to convert the

measurements into information that specifies exactly which direction and how much to

move the motor in order to correct the misalignment in the vertical plane. Determining

misalignment involves mathematical calculations using signed numbers. The following

section explains how to complete and interpret a graph for vertical plane misalignment and

explain how to describe a general procedure for correcting misalignment in the vertical

plane.

8/12/2019 Lesson 03 PDF

10/50

SHAFT ALIGNMENT



The information on the data sheet is used to determine the total parallel and angular

misalignment in the vertical plane. As indicated on the data sheet, sag and the thermalgrowth characteristics for the fixed component and the movable component are neglected

in this example. Therefore, thermal growth does not have to be considered when measuring

and correcting misalignment. Determining parallel and angular misalignment in the vertical

plane. The parallel misalignment calculation begins with the value of the P dial indicator

reading at the 6 oclock position. In this example, that value is 13 mils. That value must be

divided by 2. When 13 mils is divided by 2, the results is 6.5 mils, is written in the box

labeled PV. This value represents the parallel misalignment in the vertical plane. The Adial indicator reading at the 6 oclock position represents the angular misalignment. Bar sag

If considered is not a factor for A dial indicator readings. The A dial indicator reading of

+6 mils is entered into the box labeled AV.

The information on the data sheet can be used to create a graph to determine how much

and in what direction the motor should be moved. An advantage of a graph is that it visually

shows the correction that is needed. The first step in creating a graph is to choose a pointof reference, or base point. The base point should be located on the left side of the graph.

As shown in the figure, a straight line is drawn from the base point to the right side of the

graph. This line is called the base line. The horizontal graduations on the graph represent

increments of 1 inch. The vertical graduations represent increments of 1 mil, or .001 inches.

Some information is used to complete the graph. One value needed is the value of D,

which is the swing diameter of the A dial indicator stem. The value of D in this example

is 10 inches. D is plotted on the graph by starting at the base point and moving along the

base line the value of D. In the example (As in the following figure), the move is 10

increments. The point made there is labeled D. The value of X is also needed. This

value is the distance between the target of the A dial indicator and the centerline of the

support bolt for the motors inboard foot. The value of X in this example is 12 inches.

8/12/2019 Lesson 03 PDF

11/50

SHAFT ALIGNMENT



Fig. 3-16. Graph for Plotting Vertical Misalignment.

X is plotted on the graph by moving 12 increments along the base line from point D. Thepoint made there is labeled X

Fig. 3-17. D Plotted on Graph.

8/12/2019 Lesson 03 PDF

12/50

SHAFT ALIGNMENT


Fig. 3-18. X Plotted on Graph.

The value of Y is the distance between the target of the A dial indicator and the

centerline of the support bolt for the motors outboard foot. The value of Y in this example

is 24 inches. Y is plotted on the graph by moving 24 increments along the base line from

point D. The point made there is labeled Y

Fig. 3-19. Y Plotted on Graph.


8/12/2019 Lesson 03 PDF

13/50

SHAFT ALIGNMENT



The value in box AV on the data sheet represents the angular misalignment. Point AV is

plotted on the graph starting at the base point. If the value of AV is positive, movement is

up from the base point the value of AV If AV is negative, movement is down from the

base point the value of AV.

Fig. 3-20. Data Sheet.

In this example, the value of AV is +6 mils. This value is up 6 increments from the base

point. The point made there is labeled AV

Fig. 3-21. AV Plotted on Graph.

8/12/2019 Lesson 03 PDF

14/50

SHAFT ALIGNMENT


Next, starting at point AV, a straight line is drawn to intersect point D. This line, which is

called a reference line, represents the angular misalignment in the vertical plane. The base

line represents the position to which the movable component must be moved in order to

eliminate angular misalignment in the vertical plane.

Fig. 3-22. Graph Showing Angular Misalingmentin the Vertical Plane.

Fig. 3-23.Point XA Plotted on Graph.


8/12/2019 Lesson 03 PDF

15/50

SHAFT ALIGNMENT



The next step is to plot the points on the reference line that represent the motor feet. This is

done by starting at point X on the base line and moving straight down to the reference

line. The point made there is labeled XA. The next point is plotted by starting at point Y

on the base line and again moving straight down to the reference line. The point made

there is labeled YA.

Fig. 3-24. Point YA Plotted on Graph.

Fig. 3-25. Point XAP Plotted on Graph.

8/12/2019 Lesson 03 PDF

16/50

SHAFT ALIGNMENT


Information for parallel misalignment in the vertical plane is added using the value of Pv,

on the data sheet. The information is plotted on the graph starting at point X If the value ofPV is positive, movement is pp from point XA. If the value of PV is negative, movement

is down from point XA.The value of PV in this example is 6.5 mils. This value is down 6.5

increments from point XA. The point made there is labeled XAP. This step is then

repeated starting from point VA. Movement is made from point VA down the value of

PV, which is 6.5 increments. The point made there is labeled YAP Next, a dashed line is

drawn to intersect points XAP and YAP. This line represents the combined angular and

parallel misalignment in the vertical plane. Combined Angular and Parallel Misalignment in

the Vertical Plane. The amount that the motor must be moved to correct for both angular

and parallel misalignment in the vertical plane can be determined as follows: First, the

position of the dashed line in relation to the base line must be determined. If the dashed

line is below the base line, as in this example, the motor must be moved up. This is done by

adding shims under the motor feet if the dashed line is above the base line, the motor must

be moved down. This is done by removing shims from under the motor feet.

Fig. 3-26. Point YAP Plotted on Graph.


8/12/2019 Lesson 03 PDF

17/50

SHAFT ALIGNMENT



Fig. 3-27.

Fig. 3-28. Dashed Line/Base Line Relationships.

8/12/2019 Lesson 03 PDF

18/50

SHAFT ALIGNMENT


Second, it is necessary to count the increments between point X, which represents the

inboard feet, and point XAP and between point Y, which represents the outboard feet,

and point YAP. In this example, the distance for the inboard feet is greater than 13.5 mils,

but less than 14 mils. Since it is not generally necessary to use shims less than 1 mil, it is

acceptable to round off numbers. In this example, the value can be rounded off to 14 mils.

The distance for the outboard feet is greater than 20.5 mils but less than 21 mils, so it can

be rounded off to 21 mils. This means that raising the inboard feet 14 mills and the

outboard feet 21 mils will correct for both angular and parallel misalignment in the vertical

plane.

Fig. 3-29. Increment Between Points X and XAP and betweenY and YAP.

Horizontal Misalignment

The graph that is created to show horizontal misalignment is similar to the one shown

earlier for vertical misalignment First, the base point is established and the base line is

drawn. Then, the values of D, X, and V from the data sheet are plotted on the base

line. D had a value of 10 inches. Starting at the base point, this value is plotted by counting

over 10 increments on the base line and placing a point there. X in this example has a

value of 12 inches. Starting at point D and counting over 12 increments plot it. V has a

value of 24 inches. Starting at point D and counting over 24 increments plot it.


8/12/2019 Lesson 03 PDF

19/50

SHAFT ALIGNMENT



The next value plotted is the value of AH from the data sheet, which is the angularmisalignment in the horizontal plane. In this example, All has a value of -5 mils. To plot

point AH, on the graph, the starting point is the base point. If AH is a positive value,

movement is up from the base point the value of AH. If AH is a negative value,

movement is down from the base point the value of AH. Since the value of AH in this

example is -5 mils, movement is down 5 increments from the base point. The point that is

made is labeled AH as indicated in the following figure.

Fig. 3-30. Points D, X, and AH Plotted on Graph.

The next step is to establish the reference line. This is done by drawing a straight line from

point All to intersect point D as indicated in the following figure. The reference line

represents angular misalignment in the horizontal plane.

Fig. 3-31. Reference Line.

8/12/2019 Lesson 03 PDF

20/50

SHAFT ALIGNMENT


The next step is to plot the points that represent the motor feet. This is done by starting at

point X on the base line and moving straight up (or down) to the reference line. The pointmade there is labeled XA. Also, starting at point V on the base line, movement is made

straight up (or down) to the reference line. The point made there is labeled XA. Points

XA and VA for this example as indicated in the following figure.

Fig. 3-32. Points XA and YA Plotted on Reference Line.

Points that represent the motor feet

Information for parallel misalignment in the horizontal plane is added using the value of

PH on the data sheet. This information is plotted on the graph starting at point XA. If the

value of PH is positive, movement is up from point XA. If the value of PH is negative,

movement is down from point XA. In this example, the value of PH is +4 mils. This value

is up 4 increments from point XA The point placed there is labeled XAP his step is thenrepeated, starting from point YA Movement is made up from point YA the value of PH

which is +4 mils. The point there is labeled YAP. Next, a dashed line is drawn to intersect

points XAP and VAP This line represents the combined angular and parallel

misalignment in the horizontal plane. The amount that the motor must be moved in order to

bring the shafts into horizontal alignment can be determined by counting the increments

between points X and XAP, and between points Y and YAP The direction in which the

motor is to be moved is also an important consideration. If the dashed line is below the

base line of the graph. the motor should be moved towards 3 oclock. If the dashed line is

above the graphs base line, the motor should be moved towards 9 oclock.


8/12/2019 Lesson 03 PDF

21/50

SHAFT ALIGNMENT



Fig. 3-33.

Application 1:

Fig. 3-34.

D = 10 Inch

X = 15 Inches

Y = 30 Inches

8/12/2019 Lesson 03 PDF

22/50

SHAFT ALIGNMENT


Fig. 3-35.

Find the amount of raising the inboard feet to correct for parallel misalignment in the vertical

plane. = .

Find the amount of raising the outboard feet to correct for parallel misalignment in the

vertical plane =

Fig. 3-36.

Find the amount that the motor must be moved in order to bring the shafts into horizontal

alignment.


8/12/2019 Lesson 03 PDF

23/50

SHAFT ALIGNMENT



Fig. 3-37.

Application 2:

For the application 1, if the height from foundation to shaft is 30 inches, temperature when

aligned is 100F, operating temperature is 250F, thermal expansion factor is 0.0000063.

Find the effect of thermal growth

Find the amount of raising the inboard feet to correct for parallel misalignment and thermal

growth in the vertical plane = .

Find the amount of raising the outboard feet to correct for parallel misalignment and thermal

growth in the vertical plane = .

8/12/2019 Lesson 03 PDF

24/50

SHAFT ALIGNMENT


Fig. 3-38.

Reverse Dial Indicator Method

1. Plot the measurements A, B, and C on a sheet of graph paper as shown. A suitable

scale is to be selected according to the size of the machine.

Fig. 3-39.


8/12/2019 Lesson 03 PDF

25/50

SHAFT ALIGNMENT



Fig. 4-40.

2. Adjust the zero reading on the indicator at top dead center, and then rotate both

indicators through 180 degrees. Record the total indicator run-out for each indicator

at bottom dead center.

Fig. 3-41.

3. Determine the relative position of the driving machine with respect to the driven

machine by having the TIR (Total Indicator Run out) and determine which machine is

high at each point of measurement. Shift = ( TIR/2).

4. The following chart can be considered to define which shaft is high.

5. Draw a horizontal line on the graph to represent the centerline of the driven shaft.

8/12/2019 Lesson 03 PDF

26/50

SHAFT ALIGNMENT


Fig. 3-42.

Fig. 3-43.

6. Plot the position of the driving machine shaft on the vertical axes of the graph

corresponding to the point of measurement (F and M)

7. Join the two points together, and extrapolate the line back to the position of the

driving machine mountings. The amount of adjustment at both front and rear

mountings required to bring the shaft into line can now be scaled off the graph.


8/12/2019 Lesson 03 PDF

27/50

SHAFT ALIGNMENT



Fig. 3-44.

Fig. 3-45.

8 . Adjust the shim packs under the driving machine mountings accordingly, retighten

the mounting bolts, and recheck the alignment as before. Repeat the process until

the required accuracy achieved.

9. Repeat the whole procedure to obtain alignment in the horizontal plane. This time

the indicators should be set to zero at one side of the coupling and total indicator

run-out read at the other.

8/12/2019 Lesson 03 PDF

28/50

SHAFT ALIGNMENT


10. When both horizontal and vertical adjustment are complete, a final set of readings at

0, 90, 180 and 270 should be taken, with the indicators zeroed at 0, readings shouldbe recorded

Fig. 3-46. Reverse Indicator Alignment Application.

Fig. 3-47.


8/12/2019 Lesson 03 PDF

29/50

SHAFT ALIGNMENT



Align ment in the Ver tica l Plane :

1. Plot the measurements A, B, and C on a sheet of graph paper as shown. A suitable scale

is to be selected according to the size of the machine.(A=12, B=24, C=48).

Fig. 3-48.

2. Adjust to get the Indicator Reading

I. Reading on Pump

Fig. 3-49.

TIR =-0.02

First Error =-0.01 (-ve)

II. Reading on Motor

Fig. 3-50.

8/12/2019 Lesson 03 PDF

30/50

SHAFT ALIGNMENT


TIR = -0.01

Second Error = 0.005 (+ve)

3. Determine the relative position of the driving machine with respect to the driven

machine. ( -Ve and +Ve) = Case D = All errors below base line

4. Use the following chart

Fig. 3-51.


Fig. 3-52. Driven Shaft Centre-Line Shown on Graph.


8/12/2019 Lesson 03 PDF

31/50

SHAFT ALIGNMENT




corresponding to the point of measurement.

Set the First Error

Fig. 3-53.

Set the Second Error

Fig. 3-54.

8/12/2019 Lesson 03 PDF

32/50

SHAFT ALIGNMENT


7. Join the two points together to establish the reference line, and extrapolate the line

to the position of the driving machine mountings. The amount of adjustment at bothfront and rear mountings required to bring the shaft into line can now be scaled off

the graph.

Fig. 3-55.

8. Adjust the shim packs under the driving machine mountings according to the

corrected values for both foot

Inboard foot correction = 0

Outboard foot correction = 0.01

Retighten the mounting bolts, and recheck the alignment as before.

Repeat the process until the required accuracy achieved.

9. Repeat the whole procedure to obtain alignment in the horizontal plane. This time

the indicators should be set to zero at one side of the coupling and total indicator

run-out read at the other.

10. When both horizontal and vertical adjustment are complete, a final set of readings at

0, 90, 180 and 270 should be taken, with the indicators zeroed at 0, readings should

be recorded.


8/12/2019 Lesson 03 PDF

33/50

SHAFT ALIGNMENT



Fig. 3-56.

8/12/2019 Lesson 03 PDF

34/50

SHAFT ALIGNMENT


Alignment in the Horizontal plane:

1- Plot the measurements A,B, and C on a sheet of graph paper as shown. A suitable

scale is to be selected according to the size of the machine.(A=12, B=12, C=24).

Fig. 3-57.

2- Adiust to get the Indicator reading

I. Readings on pump

Fig. 3-58.


8/12/2019 Lesson 03 PDF

35/50

SHAFT ALIGNMENT



TIR=

First Error = (-ve or + ve)

II Reading on Motor

Fig. 3-59.

TIR=

Second Error= (-ve or +ve)

3. Determine the relative position of the driving machine with respect to the drivenmachine. (-Ve and +Ve) = Case = .. =

4. Use the following chart

Fig. 3-60.

8/12/2019 Lesson 03 PDF

36/50

SHAFT ALIGNMENT



Fig. 3-61.


corresponding to the point of measurement.

Set the first Error

5

Fig. 3-62.


8/12/2019 Lesson 03 PDF

37/50

SHAFT ALIGNMENT



Set the Second Error

Fig. 3-63.

7. Join the two points together to establish the reference line, and extrapolate the lineto the position of the driving machine mountings. The amount of adjustment at both

front and rear mountings required to bring the shaft into line can now be scaled off

the graph.

8. Adjust the shim packs under the driving machine mountings according to the

corrected values for both foot

Inboard foot correction = .

Outboard foot correction = .

Retighten the mounting bolts, and recheck the alignment as before. Repeat the process

until the required accuracy achieved. When both horizontal and vertical adjustment are

complete, a final set of readings at 0, 90, 180 and 270 should be taken, with the indicators

zeroed at 0, readings should be recorded.

8/12/2019 Lesson 03 PDF

38/50

SHAFT ALIGNMENT


Fig. 3-64.

Fig. 3-65.


8/12/2019 Lesson 03 PDF

39/50

SHAFT ALIGNMENT



Fig. 3-66.

Using Formulas

Rim and Face Alignment - Vertical Plane Misalignment

Instead of graphs, formulas can be used to determine how much to move the motor to

correct for both angular and parallel misalignment in the vertical plane. One formula is for

the inboard feet and the other is for the outboard feet.

Fig. 3-67.

8/12/2019 Lesson 03 PDF

40/50

SHAFT ALIGNMENT


Fig. 3-68.

The formula for the inboard feet is as follows:

Inboard = (X/D x AV) + PV

This formula is used when the thermal growth values for the movable component and the

fixed component are equal. The values for this formula are obtained from the data sheet.

With the values from the example below, the formula reads:

A=D= 6, B=X=12, C=V=24

Inboard = [12/10 x (+6)] + 6.5

Working through the math gives an answer of +13.7 mils, which can be rounded off to +14

mils. When formulas are used, a negative answer indicates that the motor feet must be

moved down to bring the shafts into alignment. A positive answer indicates that the motor

feet must be moved up to bring the shafts into alignment. An answer of +14 mils indicatesthat the inboard feet should be moved up by adding 14 mils of shims.


8/12/2019 Lesson 03 PDF

41/50

SHAFT ALIGNMENT



Fig. 3-69.

The formula for the outboard feet is as follows:

Outboard = (V/D x AV) +PV

Again, this formula is used when the thermal growth values for the movable component and

the fixed component are equal. The values for this formula are also obtained from the data

sheet With the values shown in Figu re F-I , the formula reads:

8/12/2019 Lesson 03 PDF

42/50

SHAFT ALIGNMENT


Outboard = [24/10 x (+6)] + 6.5


mils. This means that the outboard feet must be moved up by adding 21 mils of shims.

Fig. 3-70.

If components have different thermal growth characteristics, the thermal growth values

must be used to determine how much to move the motor to correct for misalignment in the

vertical plane when the components have reached their operating temperatures. In order to

account for the movement that takes place due to thermal growth, the thermal growth valuefor the movable component must be subtracted from the value for the fixed component This

operation can be expressed as the following formula:

Fixed Thermal Growth - Movable Thermal Growth = Combined Thermal Growth

Assuming that the pump has a thermal growth value of-2 mils and the motor has a value of

+2 mils, the formula reads:


8/12/2019 Lesson 03 PDF

43/50

SHAFT ALIGNMENT



-2 mils - (+2 mils) = -4 mils

The combined thermal growth value is added to the formulas used to determine the amount

of movement needed for the inboard and outboard feet to correct for vertical misalignment

The formula for the inboard feet is as follows:

Inboard = [(XID x AV) - PV] + (Combined Thermal Growth) With the values determined

previously, the formula reads:

Inboard = [(12/10 x (+6)) - (-6.5)] + (-4)


mils. An answer of +1 0 mils indicates that the inboard feet should be moved up by adding

10 mils of shims. A negative answer indicates that the motor feet must be moved down.

The formula for the outboard feet, when thermal growth is a factor, is as follows :

Outboard = [(Y/D x AV) - PV] + (Combined Thermal Growth) With the values determined

previously, the formula reads:

Inboard = [(24/10 x (+6))] - (-6.5)1+ (-4)

Working through the math gives an answer of +16.9 mils, which can be rounded off to + 17

mils. This means that the outboard feet must be moved up by adding 17 mils of shims. It is

important to remember that when thermal growth is factored into the formulas and the

motor is moved by the amount indicated by the answers the shafts will be misaligned while

the components are at ambient temperatures. However, the two shafts will be aligned at

operating temperatures.

Rim and Face Alignment - Horizontal Plane Misalignment

As was done for the vertical plane, two formulas can be used to determine how much to

move the motor to correct for angular and parallel misalignment in the horizontal plane. Oneformula is for the inboard feet and the other is for the outboard feet the formula for the

8/12/2019 Lesson 03 PDF

44/50

SHAFT ALIGNMENT


inboard feet is as follows:

Inboard = (XID x AH) - PH

The values for this formula are obtained for the data sheet. With the values from the

example, the formula reads

Inboard = [1 2/1 0 x (-5) - (+4)

Working through the math gives an answer of -10 mils. When formulas are used, a positiveanswer indicates that the motor must be moved towards 3 oclock. A negative answer

indicates that the motor must be moved towards 9 oclock. In this example, the inboard feet

must be moved 10 mils towards 9 oclock.

Fig. 3-71.


8/12/2019 Lesson 03 PDF

45/50

8/12/2019 Lesson 03 PDF

46/50

SHAFT ALIGNMENT


Fig. 3-72.

12

Inboard = (-9 + 2). 6 2 = 16

= -16 mils

With this formula method, a negative answer indicates that this inboard feet of the motor

should be raised to correct for misalignment in the vertical plane. A positive answerindicates that the inboard fee should be lowered. In this case, the inboard feet of the motor

should bi raised 16 mils to correct for vertical plane misalignment.

The formula for the outboard feet of the motor is as follows:

COutbord =(-MV - FV). + FV

A


8/12/2019 Lesson 03 PDF

47/50

SHAFT ALIGNMENT



Fig. 3-73.

Plugging in the values from the data sheet, the formula reads:

24

Outbord =(-9 +2). 6 2 = - 30

The formula for the outboard feet is similar to the formula for the inboard feet. A negative

answer means that the feet should be raised, and a positive answer means that the

feetshould be lowered. In this example, the outboard feet of the motor should be raised 30

mils to correct for vertical plane misalignment.

8/12/2019 Lesson 03 PDF

48/50

SHAFT ALIGNMENT


Form ula: Reverse Dial Indicator - Hor izonta l Plane Misal ignment

To calculate mathematically how much to move the motor to correct for misalignment in the

horizontal plane, two formulas are used together. One formula is for the inboard feet of the

motor, and the other is for the outboard feet. The formula for the inboard feet is as follows:

Inboard = (Mh - Fh) x B/A + Fh

Fig. 3-74.

The values for this formula are obtained from the data sheet for this example, the formulareads:

Inboard = {+24 - (+20)} x 12/6 + (+20)

= (+4) x (+2) + (+20)

=

(+8)+(+20)=+28 mils


8/12/2019 Lesson 03 PDF

49/50

SHAFT ALIGNMENT



With this formula method, a positive answer indicates that the feet of the motor should be

moved toward the 9 oclock position; a negative answer indicates that the feet should be

moved toward the 3 oclock position. In this example, the inboard feet of the motor should

be moved 28 mils toward the 9 oclock Position.

Fig. 3-75.

The formula for the outboard feet of the motor is as follows:

Outboard = (Mh - Fh) x C/A + Fh

Plugging in the values from the data sheet, the formula reads:

Outboard = {+24 - (+20)} x 24/6 + (+20)

8/12/2019 Lesson 03 PDF

50/50

SHAFT ALIGNMENT


= (+4) x (+4) + (+20)

= (+16)+(+20) = +36 mils

Once again, a positive answer means that the motor feet should be moved toward the 9

oclock position; a negative answer means that the motor feet should be moved toward the

3 oclock position. In this example, then, the outboard feet of the motor should be moved 36

mils toward the 9 oclock position.

Moving the Motor

To correct for misalignment in the horizontal plane, the motor must be moved sideways,

that is, toward the 3 oclock or 9 oclock position. To measure the horizontal movements the

mechanic use continuous-type dial indicators on both an inboard foot and an outboard foot.

(Continuous-type dial indicators give only positive readings.)

lesson 03 pdf

Documents