Handbook Of Shaft Alignment Episode 3 Part 1 pdf

Up Side view Scale: Scale: East Top view FIGURE 17.12 Three-element alignment model showing the gear and motor shafts only... Up Side view Scale: Scale: East Top View +90 0 FIGURE 17.14

Gear Pump

10 in.

Up Side view

B

0

Pump Gear output

Motor Gear

10 in.

Up Side view

Scale:

Scale:

East Top view

B

− 110 0

+90 0

Gear Pump

10 in.

Up Side view

Scale:

30 mils

T

B E

10 in.

50 mils

T

B T

B

Pump Gear output

Motor Gear

20 in.

Up Side view

Scale:

Scale:

East Top view

FIGURE 17.12 Three-element alignment model showing the gear and motor shafts only

Motor Gear

20 in.

Up Side view

Scale:

Scale:

East Top view

50 mils

10 in. 100 mils

63 mils down 93 mils down

Pump

120 mils east 220 mils east

FIGURE 17.13 Three-element alignment model showing all three shafts

Figure 17.14 shows the misalignment between the motor and gear shafts in the side and topviews using the line to points reverse indicator modeling technique Figure 17.15 shows themisalignment between the gear and pump shafts in the side and top views It does not matterwhich set of readings is plotted first, the motor to gear or the gear to pump Notice that the

20 in.

Up Side view

Scale:

Scale:

East Top View

+90 0

FIGURE 17.14 Three-element alignment model plotting the motor and gear shafts using the line topoints reverse indicator modeling technique

Motor Gear

20 in.

Up Side view

Scale:

Scale:

East Top view

B

0

Pump Gear output

FIGURE 17.15 Three-element alignment model plotting the gear and pump shafts using the line topoints reverse indicator modeling technique

positions of the shafts in Figure 17.13 are identical to the positions of the shafts in Figure17.15 even though two different methods were used to generate the two graphs.

Again, just as in modeling two-shaft drive systems, all that has been accomplished with thegraph is that the positions of the shafts have been determined At this point, it is imperativethat the restrictions in the up or down and east or west directions be determined at everybolting plane on all three machines and transferred onto the graph Once this has been done,the final desired overlay line can be drawn onto the graph and the movement solutions at all

of the bolting or translation planes can be determined and executed An example of this isillustrated in Figure 17.16 showing the amount of existing shims and the lateral movementrestrictions at each bolting plane Notice that in the side view if you were to name any one ofthe machines as a ‘‘stationary’’ machine, the vertical restriction would have prevented youfrom aligning the drive system; and in the top view if you were to name either the gear or thepump as a stationary machine, the lateral restriction would have prevented you from aligningthe drive system

17.5 MIXING DIFFERENT ALIGNMENT MEASUREMENT METHODS

In some situations, more than one alignment measurement method could be (or may have tobe) employed to measure each set of shafts Figure 17.17 through Figure 17.19 show how youcan use different alignment measurement methods and still model the machinery positions.Two electric motors are coupled together to drive a gearbox and a compressor A laser–detector shaft alignment system was used to measure the alignment between the two motors(Motor A and Motor B) Reverse Indicator readings were taken between Motor B and thegearbox The shaft to coupling spool method was employed between the gear output shaftand the compressor Figure 17.17 shows the dimensions of the four-element drive system, theinformation gathered from the laser–detector shaft alignment system, the reverse indicatormeasurements (before and after sag compensation), the shaft to coupling spool measurements(before and after sag compensation), the amount of existing shims under each bolting plane,and the lateral movement restrictions at each bolting plane You need every piece of infor-mation shown in Figure 17.17 to determine how to correct the misalignment condition thatexists on this drive system

Figure 17.18 shows the side view alignment model of all four shafts and the verticalrestriction boundary The gear shafts were placed on the graph paper centerline and eachshaft was referenced from the gear outward Figure 17.19 shows the top view alignment model

of all four shafts and the lateral restriction envelope Again, the gear was placed on the graphpaper centerline and each shaft was referenced from that point outward Carefully study bothalignment models to determine how the shafts were constructed

Despite the fact that three different alignment measurement methods and tools were used

to determine the relative positions of each set of shafts, the entire drive train can still bemodeled on graph paper As you can see from the shaft positions in the side view, attempting

to call Motor A, Motor B, or the gear as the ‘‘fixed’’ or stationary machine will result in a lot

of headaches and unnecessary work In the top view, attempting to call any of the fourmachines as the fixed or stationary machine will result in unforeseen situations and unneces-sary work It should become obvious why it is recommended that the multiple-element drivetrain alignment laws mentioned above should be adhered to when aligning drive systems ofthis complexity

17.6 MODELING RIGHT-ANGLE DRIVE SYSTEMS

So far, we have examined rotating machinery drive systems that are horizontally mounted,direct in-line machinery But not all drive systems are configured that way Some drive trainsare arranged in an ‘‘L’’ shape, commonly referred to as right-angle drives A right-angled

20 in.

Up Side view

Scale:

Scale:

East Top view

50 mils

10 in. 100 mils

Pump

Lateral movement restriction points

Baseplate restriction points

FIGURE 17.16 Possible alignment corrective moves after overlaying the boundary conditions

outboard bolts of Motor A to outboard bolts of compressor.

A laser alignment system was used between Motor A and Motor B With Motor A named as the stationary machine, the following moves on Motor B were indicated by the laser:

lower “near” foot 40 mils raise “far” foot 15 mils

gearbox is flexibly coupled to a driver on the input side and to some driven machine on itsoutput side The goal is to align the centerline of rotation of the driver and the input shaft ofthe gear and the driven unit to the output shaft of the gear.

There are two tricks to this modeling method One is to plot the graph in the ‘‘dual scale’’mode similar to the method used for face–rim plotting covered in Chapter 11 The other trick

is to ‘‘fold’’ one of the views of the alignment model where the right angle occurs in the drivesystem

The sample problem shown in Figure 17.20 comprises an electric motor coupled to a speedreducing right-angled gear that drives a roll The reverse indicator was employed between the

82 in.

Face reading diameter = 12 in.

Rim bracket sag = 6 mils

Face bracket sag = 2 mils

+24

− 32

− 56 0

− 28

+46 +33 Field readings

40 + 10

motor and the input shaft of the gear The face–rim method was used to capture the alignmentdata between the motor and the output shaft of the gear.

Figure 17.21 shows the top view of the motor–gear–roll drive system The alignmentplotting techniques in this view are straightforward and follow the modeling principlesexplained in Chapter 10 and Chapter 11

Figure 17.22 shows the side view of the drive system There is a slight ‘‘trick’’ in thisalignment model view however The side view alignment model is split or ‘‘folded’’ as if youwere viewing it from two different directions Figure 17.23 shows how the alignment model isfolded through the center of the right-angled gear (i.e., it is as if you folded the graph paper

FIGURE 17.21 Right-angle drive system top view alignment model

through the center of the right-angle gear through its vertical axis) The left side of the sideview alignment model shows what the position of the motor shaft and input shaft of the gearwould look like if you were looking to the east The right side of the side view alignmentmodel shows what the position of the output shaft of the gear and the roll would look like ifyou were looking to the south Figure 17.24 illustrates how each bolting plane on the right-angled gearbox is identified depending on which direction you are viewing in the side viewalignment model Figure 17.25 shows a possible alignment corrective move in the verticaldirection assuming there were no shims under any of the machinery feet.

Up Side view

0 Motor

T B

0 + 1

−28

+46 + 33 Field readings

T B

0

T B

0 + 4

−22

+52 + 36

Roll

Face reading diameter = 12 ⬙

Rim bracket sag = 6 mils Face bracket sag = 2 mils

+24

−32

−56 0 +8

+27

−26

−53 0

+10

0 S Sag compensated readings

Right-angle bend plane View looking east View looking south

FIGURE 17.22 Right-angle drive system side view alignment model

in

or 20 m ils 10 in

chs

or 20 m il Mo

t or

S ide

Alignment model “fold axis”

South East

Right-angle gear “fold” axis

10 in.

or 20 mils Gear

FIGURE 17.23 (See color insert following page 322.) Right-angle drive system ‘‘folded’’ side viewalignment model

Up Side view

Roll Motor

To determine the corrective moves for this drive system in the top view, a clear ency with the right-angled gear shafts transferred to the transparency will be of assistance indetermining what lateral moves need to be made to correct the misalignment condition asshown in Figure 17.26 In addition, we need to determine the lateral movement restrictions(i.e., the bolt bound conditions) on all three machines in the drive system The gaps betweenthe foot bolts and the holes in the motor and the pillow block bearings in the roll are fairlystraightforward Because the motor will only need to be positioned in the east to westdirection and the roll in the north to south direction, the gaps between the foot bolt and holes

transpar-on the east and west sides and the gaps between the pillow block bearing and bolt holes transpar-onthe north and south sides, respectively, need to be detrmined The gaps in the holes of theight-angled gear however need to be determined in all four directions as the gear may have

to be rotated through its vertical axis Figure 17.27 shows what gaps are needed to bemeasured on the gear feet These restrictions are then transferred to the top view align-ment model The restrictions on the motor and roll can be illustrated as single-planerestriction points, the restrictions on the gear need to be illustrated as ‘‘restriction rings’’

as shown in Figure 17.28 The clear transparency showing the right-angled gear shafts andthe four corner bolts is pitched to insure that the projected centerlines of the input andoutput shafts of the gear fall within the lateral movement boundaries of both the motorand the roll and also within the restriction rings on the gear itself as shown in Figure17.29 Once the transparency is positioned to stay within the lateral movement boundaries

of all three machines, the required moves can then be determined to correct the ment condition

misalign-Up Side view

right angle gear

FIGURE 17.26 Right-angle gear overlay transparency for assistance in the top view alignment model

East North South West

FIGURE 17.27 Lateral movement restrictions on the gear in all four directions are needed

17.7 FINAL COMMENTS ON ALIGNING MULTIPLE-ELEMENT

DRIVE TRAINS

Multiple-element drive trains can get extremely complex if you do not keep your wits aboutyou when aligning the machinery Some drive systems can consist of up to 20 or moreelements in ‘‘L’’ shapes, ‘‘U’’ shapes, ‘‘S’’ shapes, or other ridiculously complex arrangements.Regardless of how many pieces of machinery are in the drive train or how the shaft-to-shaftmeasurements were taken, the positions of all the machinery can be accurately illustrated on

West

Lateral movement restriction points on motor and roll Lateral movement restriction points on right-angle gear

FIGURE 17.28 Top view alignment model showing the boundary conditions

an alignment model as shown in this chapter Once the movement restrictions are posed onto the alignment model to visualize your boundary conditions, usually by movingmore than one element, an effective alignment solution can be attained.

superim-REFERENCE

Piotrowski, J., Aligning multiple-element drive trains and right-angle drives,’’ P=PM Technology, 5(2),1992

18 Aligning V-Belt Drives

Up to this point, the machinery discussed in this book has been directly driven by flexible orrigid couplings, but there are alternative power transmission schemes that are frequently used

in industry known as belt drives Examples of belt drive machinery can be seen in Figure 18.1through Figure 18.4

18.1 BELT DRIVE SYSTEMS—ADVANTAGES AND DISADVANTAGES

There are several advantages and disadvantages of belt drive equipment:

Advantages

space

changing the diameter of the sheaves to adjust the speed is fairly inexpensive

Disadvantages

wear and eventually begin to slip over time

a short period of time

and reduced belt life

draw the sheave onto the bushing incorrectly inducing an excessive radial or face runoutcondition

18.2 V-BELT STANDARDS INFORMATION

Standard cross-sectional and length dimensions have been established for V-belts as shown

in Figure 18.5 and Figure 18.6 Figure 18.7 shows how to calculate the required length of

a V-belt

591

FIGURE 18.1 Belt driven fan.

FIGURE 18.2 Belt driven fan

18.3 SHEAVE INFORMATION

Standard information on sheaves is shown in Figure 18.8

18.4 V-BELT RECOMMENDATIONS AND RULES OF THUMB

Here are some guidelines for successful, long-term belt operation:

ft=min and above 5000 ft=min

the sum of the sheave diameters nor should it be less than the largest sheave diameter

(refer to belt tensioning guidelines and procedures)

approxi-mately 10 mils=in.)

FIGURE 18.3 Belt driven fan

. Worn sheaves may shorten belt life by 50%.

18.5 SHEAVE AND BELT WEAR

Sheave and belt wear indicator should be used to determine if these components are wornexcessively These Go=No go gauges are typically made out of plastic and can be obtainedfrom your power transmission supplier Figure 18.9 shows what to look for when using thegauges

FIGURE 18.4 Belt driven dredge

18.6 ADJUSTING BELT TENSION

Possibly the most critical requirement for successful belt installation and belt life is toestablish the correct belt tension It is often the most difficult to do and subject to a greatdeal of speculation and guesswork There are two general guidelines that are followed One

FIGURE 18.5 V-belt cross section standard dimensions

Typical V-belt design

Typical VX-belt design

Belt length is measured on the outside diameter

of the belt

Belt length is measured on the inside diameter of the belt

FIGURE 18.6 V-belt length measurements for V- and VX-type belts

using a belt tensioning gauge as shown in Figure 18.10 and the other without one as shown inFigure 18.11 As mentioned previously, if you have installed new belts, it is recommended thatyou check and if necessary, adjust the belt tension after 24–48 h of operation since the beltswill stretch slightly after their initial use.

Usually one of the machines has an adjustment for tensioning the belts Adjust the position of this machine

so that it is in the center of its shaft separation travel

FIGURE 18.7 How to determine the correct length of a belt

Groove angle The groove angle can vary on standard

Usually stamped here

FIGURE 18.8 Sheave nomenclature and dimensions