Handbook Of Shaft Alignment Episode 2 Part 8 doc

Figure16.11 shows the basic setup of the tooling balls on the baseplate and machine cases.Figure 16.12 through Figure 16.14 show the measurements taken by employing thistechnique.A tradi

FIGURE 16.4 Compressor case.

FIGURE 16.5 Thermal image of compressor case

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instruments scan the object for the infrared radiation and amplify the converted electricalsignals from a supercooled photodetector onto a cathode ray tube (CRT), where a photo-graphic image of the object can be recorded.

Figure 16.4 shows a three-stage centrifugal compressor case and Figure 16.5 illustrates thetemperature profile when the compressor is running under full load The white areas showwhere the infrared radiation (heat) is the greatest The hottest areas in the image areapproximately 1358F

Figure 16.6 shows an axial flow compressor with rigid supports at the inlet end andflexible supports at the discharge end Figure 16.7 illustrates the thermal profile of thedischarge end with the compressor running under load (note the hot spot at the oneo’clock position) Figure 16.8 shows a closer view of the flexible support leg The liftingeye is at the left side of the photograph and the flex leg is the black portion just to the right ofthe lifting eye The photograph clearly shows that the support leg stays at ambient temper-atures and does not expand thermally (as originally thought when the machinery wasinstalled)

Although movement of rotating machinery casings does not occur solely fromtemperature changes in the supporting structures and the casings themselves, infraredthermographic studies can assist in understanding the nature of the thermal expansion that

an inclinometer (angle measuring device)

FIGURE 16.6 Axial flow compressors

Tooling balls can be purchased from a tool and die supplier or they can be handmade.Figure 16.9 shows a fabricated tooling ball and Figure 16.10 shows how it was made Figure16.11 shows the basic setup of the tooling balls on the baseplate and machine cases.Figure 16.12 through Figure 16.14 show the measurements taken by employing thistechnique.

A traditional inside micrometer could be used for these measurements but environmentalproblems could occur When capturing the running or hot measurements, any heat radiatingfrom a machine case or even your hands could (and will) increase the temperature of themicrometer itself, changing its length It is not uncommon to measure distances of 20 to 40 in.from tooling ball to tooling ball If you are taking a 30 in measurement and the carbon steelinside micrometer goes from 608F to 1208F, the micrometer length will change by 0.013 in (13mils) Not consistently accurate enough when you are trying to measure +1 mil in positionalchange Figure 16.15 and Figure 16.16 show a custom made set fabricated from invar toconsiderably reduce the inside micrometer thermal expansion error

Tooling balls or similar reference point devices are rigidly attached to the foundation and

to the inboard and outboard ends of each machine case as near as possible to the centerline ofrotation as shown in Figure 16.17 through Figure 16.19 Distances between the tooling balls(and angles if desired) are captured for each tooling ball when the machinery is at rest andthen measured again when the equipment is running and has stabilized thermally Threetooling balls can be set up in a triangular pattern as shown in Figure 16.20 at each bearing oneach machine in the drive train A more accurate method is to set up four tooling balls in afour-sided ‘‘pyramid’’ arrangement at each bearing on each machine in the drive train asillustrated in Figure 16.21

These measurements can then be triangulated mathematically into vertical and lateralcomponents (using the triangular arrangement) or into vertical, lateral, and axial componentdistances (using the four-sided pyramid arrangement) By comparing the coordinates of thetooling ball mounted on each end of all the machine cases from OL2R (or from R2OL)

FIGURE 16.7 Thermal image of compressor end casing

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positional changes can be determined Figure 16.22 shows the mathematics for a triangulartooling ball arrangement and Figure 16.23 for a pyramid arrangement.

Key considerations for capturing good readings:

. Remember that you will probably be dealing with oblique triangular arrangements notright angle triangles (i.e., watch your math)

. Important to have stable positions for the tooling balls

FIGURE 16.8 Thermal image of the support leg

. The tooling ball on the machine case should be located as close as possible to thecenterline of rotation since we are trying to determine where the shafts are going (if thebearing moves, the shaft is sure to move with it).

. Recommend that concave tips be used at both ends of the inside micrometer to ently seat on the round tooling balls when taking measurements

consist-. Keep the inside micrometer away from heat sources to prevent the mike from thermallyexpanding

FIGURE 16.9 Tooling ball fabricated from 0.5 in steel ball and 1.5 in
1.5 in
0.25 in steel plate with

the ball welded to the plate

Standard tooling ball

Round steel ball from ball bearing

1.5" 3 1.5" 3 1/4"

carbon steel plate

“Vee” out a cone with a drill bit in the center

Apply a bead

of epoxy

Tooling balls can be purchased from machine tool suppliers or can be homemade as shown below If standard tooling balls are used, holes must be drilled

in the machine case and baseplate or foundation for installation The homemade design can be attached to machine case and baseplate or foundation with epoxy or dental cement and then removed when the

survey is complete.

FIGURE 16.10 How to construct a tooling ball

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. During measurements have a reference standard length comparator to insure the meter itself is not thermally expanding or contracting.

micro-. Triangular tooling ball arrangements assume that there will be motion in the horizontaland vertical planes only which may not necessarily be the only directional change that isoccurring (namely axial)

. For best accuracy, use the pyramid arrangement with four tooling balls

. Have two or more people to take measurements and compare notes to insure the readingsare identical (or at least close)

. Capture a set of readings from OL2R conditions and another set of readings from R2OLconditions to determine if there is a consistent pattern of movement

Advantages:

. Relatively inexpensive

. Somewhat easy to set up

Tooling ball arrangements are placed at both ends of both machines The tooling balls attached to the machinery case should be as close to the centerline of rotation as possible.

FIGURE 16.11 Basic tooling ball setup on the machinery

FIGURE 16.12 Measuring between two tooling balls with inside micrometer

. Mathematics somewhat tedious particularly on four-sided pyramid arrangements.. Caution must be taken during running measurements since one end of the inside micro-meter is frequently near a rotating shaft

. If one or more tooling balls disengage from their positions (i.e., it worked out of its hole

or the epoxy gave away), you will probably have to start over

FIGURE 16.13 Measuring a distance with the Acculign invar rods

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Figure 16.24 shows the results of an OL2R survey conducted on a motor-fluid drive-boilerfeed water pump using the inside micrometer-tooling ball method A pyramid tooling ballarrangement was used on this drive system Notice the amount of movement in not only the

up and down and side-to-side directions but also the axial amount of movement Figure 16.25FIGURE 16.14 Measuring the angle with the Acculign inclinometer

FIGURE 16.15 Acculign kit (Courtesy of Acculign, Austin, TX, www.acculign.com With permission.)

FIGURE 16.16 Acculign micrometer in calibration fixture (Courtesy of Acculign, Austin, TX, www.acculign.com With permission.)

Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C016 Final Proof page 488 6.10.2006 12:03am

shows the desired off-line shaft position alignment models for the side and top views for themotor-fluid drive-boiler feed water pump shown in Figure 16.24.

16.8 VERTICAL, LATERAL, AND AXIAL OL2R MOVEMENT

Before we go any farther into these methods, it would be prudent to closely examine the OL2Rdata observed on the motor-fluid drive-boiler feed water pump drive system in Figure 16.24 Payparticular attention to the amount of movement that was observed in the axial direction

As you can see, there was more movement of each machine case axially than there was inthe vertical or lateral (side-to-side) directions On the motor, the outboard end moved 19 milsFIGURE 16.17 Tooling ball setup to measure outboard bearing on motor

FIGURE 16.18 Tooling ball setup to measure inboard bearings on motor and hydraulic clutch

to the west and 35 mils to the east at the inboard end for a total of 54 mils of axial expansion.The fluid drive moved 22 mils to the west on the motor end and 8 mils to the east at the pumpend for a total of 30 mils of axial expansion The pump moved 51 mils to the west on thefluid drive end and 88 mils to the east at the outboard end for a total of 139 mils of axialexpansion (that is over 1=8 in.).

If we bolt and dowel pin the pump to the baseplate in each corner, and the pumpcase expands one eighth on an inch and the baseplate does not expand at all, somethinghas to give Either the foot bolts and dowel pins have to bend or shear, or the pump case has

to distort, or both If the pump distorts, rotating parts inside the pump may begin contactingstationary parts inside the pump damaging the rotor and potentially resulting in a cata-strophic failure

To prevent case distortion from thermal expansion, transverse keys are sometimes used asshown in Figure 16.26 At the coupling end of the pump, a key is placed between the lowerpump casing and the baseplate at a 908 angle to the centerline of rotation The purpose of thiskey is to hold the pump case here and any axial expansion occurs outward from this point.This key is placed near the coupling end to minimize the amount of movement of thatmachine toward the other machine Another key is placed at the outboard end of the machinebut this key is placed between the lower pump casing and the baseplate at a 08 angle to thecenterline of rotation This allows the casing to expand in line with the key but prevents themachine case from moving from side to side Additionally, the inboard bolts are tightened toFIGURE 16.19 Tooling ball setup to measure outboard bearing on pump

Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C016 Final Proof page 490 6.10.2006 12:03am

Inside micrometer–tooling ball OL2R method mathematics

D

E F G e

Angle D is an obtuse angle acute (0
to 90
) obtuse (90
to 180
)

Acute angle

Nearbaseaxial Nearaxial

Near center

Nearbasevertical Nearcenter2deltaxial

Obtuse angle

Obtuse angle

Far end math

Faraxial=((farbaseaxial^2)+(farcenter2deltaxial^2)−(farbasevertical^2))/(2 farbaseaxial)

Farvertical=SQR((farcenter2deltaxial^2)−(faraxial^2))

Near end math

Nearaxial=((nearbaseaxial^2)+(nearcenter2deltaxial^2)−(nearbasevertical^2))/(2 nearbaseaxial)

Far end math

Faraxial=(farbasevertical*cosG)+farbaseaxial

Farvertical=farbasevertical*sinG

Near end math

Nearaxial=(nearbasevertical*cosG)+nearbaseaxial

Nearvertical=nearbasevertical*sinG

*

*

FIGURE 16.22 Triangular tooling ball mathematics

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Near end math

Far end math

Basic equations for oblique triangles

based on the assumption that all of the tooling balls on the base are in the same plane.

D

E

F G

More basic equations for oblique triangles

(the law of cosines)

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pinch the machine case to the baseplate The outboard bolts are sleeved and do not pinch thecase to the baseplate but allow the case to slide preventing distortion from occurring.Not only is the pump case expanding, but so too is the shaft expanding Notice that themachine cases (and probably the shafts) are moving toward each other from OL2R

Foot bolt location Tooling ball location

BRTC location

Inside micrometer–

tooling ball system Ball–rod–tubing connector system

Projected centerline of rotation

of the pump shaft

Actual centerline of rotation of the pump shaftf

Projected centerline of rotation

of the fluid drive shaft

With respect to the pump shaft centerline, the far east bolt set of the fluid drive should be set 5 mils higher than the projected centerline

of rotation of the pump shaft

With respect to the pump shaft centerline, the far east bolt set of the fluid drive should be set 4 mils lower than the projected centerline

of rotation of the pump shaft

With respect to the fluid drive shaft

centerline, the far east bolt set of

the motor should be set 10 mils

higher than the projected centerline

of rotation of the fluid drive shaft

With respect to the fluid drive

shaft centerline, the far east

bolt set of the motor should be

set 11 mils higher than the

projected centerline of rotation

of the fluid drive shaft

10 in.

10 mils

Up Desired off-line side view looking north

Foot bolt location Tooling ball location

BRTC location

Inside micrometer–

Ball–rod–tubing connector system

Projected centerline of rotation

of the pump shaft

Actual centerline of rotation of the pump shaft Projected centerline of rotation

of the fluid drive shaft

With respect to the pump shaft centerline, the far east bolt set of the north of the projected centerline of rotation of the pump shaft

With respect to the pump shaft centerline, the far east bolt set

12 mils to the north of the projected centerline of rotation

of the pump shaft

With respect to the fluid drive shaft centerline, the far east bolt set of the motor should be set 1 mil to the rotation of the fluid drive shaft With respect to the fluid drive

shaft centerline, the far east

bolt set of the motor should be

set 5 mils to the north of the

projected centerline of rotation

of the fluid drive shaft

10 in.

10 mils

North

Desired off-line top view

FIGURE 16.25 Desired off-line shaft position alignment models for the side and top views for themotor-fluid drive-boiler feed water pump drive system

conditions Some flexible coupling designs allow axial movement of the shafts withouttransferring axial forces during the movement (or expansion) On the drive system shown inFigure 16.24, thankfully gear couplings were used between the motor, fluid drive, and pump.

If another type of coupling design was employed that was not forgiving in axial movement,the thrust bearing loads would increase

Based on how the measurements were taken, it is not known in this particular drive system

if each of the machine cases expanded symmetrically Since the measurements were taken ontooling balls located directly under the shafts, the machine cases could have bowed outwardnear the center of the machines as shown in Figure 16.27 If indeed this ‘‘bell-shaped’’distortion occurs, then any OL2R technique that attaches devices near the bearings couldgive a false indication of what is happening to the shafts Later on, we will examine severalmethods where devices are attached near the bearing so that I thought it would be prudent tomention this just as a precautionary note

As mentioned previously in this chapter, I would again like to make it perfectly clear that

we have not collected enough OL2R data on rotating machinery to conclusively state what

Bolt pinching case to pedestal here

Bolt sleeved here to allow

between washer and casing

10–20 mils gap between washer and casing

orientation to centerline

Key at 08

orientation to centerline

Pedestal

Foot

Sleeve Bolt

Pedestal

Washer

FIGURE 16.26 Transverse keys and sleeved bolt to allow for axial expansion

Piotrowski / Shaft Alignment Handbook, Third Edition DK4322_C016 Final Proof page 496 6.10.2006 12:03am