Reverse Rim Dial Indicator Alignment Overview

7/21/2019 Reverse Rim Dial Indicator Alignment Overview

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Reverse Rim Dial Indicator Alignment

Overview

The reverse rim method is widely acknowledged as the “preferred method” of shaft

alignment.

Figure 3.40 Reversed Rim alignment me

Two rim dial indicators are used to measure the relative position of the movable shaft with

respect to the stationary shaft at two planes along their length

Figure 3.41 The stationary indicator (DIS) measures ofset in a plane along thestationary shat or hub.

Figure 3.

Using two oset readings along with xture setup and machine dimensions the relative

position of the movable shaft is determined by performing calculations or by

graphing!plotting. "ee #.#.$ and #.#.% for detailed reverse dial calculation and graphing

procedures.

Comparison To Rim-Face Dial Method

&hen the rim'face method is used on machines whose shafts have axial end (oat greater

than about ).)*+ mm and especially on machines with plain bearings errors are introduced

into the face reading. "ince the reverse rim method re,uires no face readings measurement

errors that occur when using a rim'face setup due to shaft end (oat are eliminated.



Figure 3.43 Comparison to Rim!ace me

Reverse Rim Fixture Overview

- variety of shaft alignment xtures are available for performing reverse rim alignment.

"election and use of a commercial package designed to accommodate a variety of shaft

diameters is recommended. The xtures should include an assortment of rods to span various

coupling lengths. These packages expedite the precision alignment process. -lso sag values

can be pre'determined for the standard rod assortment.

&hile some xtures are designed to permit reverse rim alignment with the shafts un'coupled

others re,uire that the shafts be coupled during the alignment process.

Figure 3.44 !i"tures# uncoupled shats

any xtures accommodate reverse rim alignment with the indicators mounted either at the

same location along the shaft circumference /as shown above0 or 12) degrees opposite one

another that is in a cross dial arrangement.



Figure 3.46 !i"tures mounted opposite one

Mounting Reverse Rim Fixtures3ixture mounting procedures are obviously dependent on the specic type of hardware being

used. 3or this training you will perform the alignment with the shafts coupled and the

indicators positioned at the same position around the circumference.

To mount the xtures follow these steps4

1. &ith the coupling assembled mount the brackets to the shafts or coupling hubs as

illustrated below.

*. "pan the coupling from each bracket with rods.

#. 5otate the brackets to 1*4)).

6. -ttach the dial indicators with the plungers centered for e,ual positive and negative

travel.

Figure 3.47 $ounting

Fixture Mounting Precautions

5egardless of the specic hardware being used the following precautions should be

observed.

• 7ever attach the xture to the (exible portion of the coupling.



• aximi8e the distance between the dial indicators for the geometry of the machine

being aligned. -s a general rule the plungers should be positioned at least 1)) mm apart.

• 9nsure that xtures are mounted at a position where rotation is possible. :t is

desirable to have #$) degrees of rotation.

• ;efore obtaining alignment measurements determine dial indicator bar sag and

ensure that dial indicator readings are valid and repeatable.

Reverse-Rim dimensions

To accurately determine the position of the movable shaft using reverse rim calculations or

graphing procedures the relative position of the dial indicators and the front and rear feet of

the movable machine must be determined.

These dimensions should be determined using a standard tape measure. 9ach dimension

should be measured to the nearest 1!2” /1'*mm0.

Figure 3.48 ReverseRim dimensions

The “A” Dimension

The “-” dimension is the distance between indicator plungers. The ”-” dimension is measured

parallel to the shafts. This is the most critical dimension and should be measured very

carefully. -s mentioned earlier when setting up xtures for reverse rim alignment care

should be exercised to maximi8e the distance between the indicator plungers based on the

machine geometry and space available.

The “B” Dimension

The “;” <imension is the distance from the movable side indicator to the front foot bolt

center. This dimension is measured parallel to the shafts. 9specially on larger machines it is

sometimes helpful to use a string or straight edge to transfer the position of the movable dial

plunger to the machine base prior to measuring this dimension.

The “C” Dimension

The “=” <imension is the distance between front and rear foot bolt centers. This dimension is

measured parallel to the shaft.



Reverse Rim Signs

&hen doing a reverse rim measurement it is important to know that dierent set ups aect

the sign of the readings dierently. This eect is caused by the fact that both dial indicators

have the same plus!minus direction and are mounted as the name of the method indicates

in reverse.

The eects of dierent set ups are shown below.

• The set up in gure #.6> doesn?t aect the sign of the dial indicator readings

/hori8ontally and vertically0

Figure 3.49 %o efect on the signs.

• &hen using the set up in gure #.+) and 8eroing at 1*4)) or #4)) the sign of the

movable dial indicator value <: has to be reversed.

• &hen using the same set up as in gure #.+) but instead 8eroing at $4)) or >4)) the

sign of the stationary dial indicator value /<:"0 has to be reversed.



Figure 3.50 &eroing at ' or . Change the si &eroing at * or +. Change the sign o DI

The following measurement procedures describe both situations in the set up shown in 3igure

#.+).

easurement @rocess Averview

The reverse rim dial measurement process consists of the following procedures4

• easuring and documenting as'found misalignment conditions.

• easuring vertical and hori8ontal misalignment conditions.

Abtaining a set of as'found readings is considered optional in some facilities but is highly

recommended here. 3or most alignment tasks it is desirable to obtain and document a

complete set of as'found readings along with the - ; and = dimensions. -s'found readings

are used for a variety of purposes4

• <ocumenting alignment conditions prior to removing e,uipment from service for

repair.

•

<etermining whether or not suspected misalignment is realistic or not.• "upporting and Bustifying actions taken to e,uipment suppliers vendors and

manufacturers.

• aintenance of e,uipment history les.

• ;etter communication between dierent personnel involved with the alignment task.

Abtaining -s'found 5eadings

To obtain a complete set of as'found readings perform the steps below4

1. 5otate the dial indicators to 1*4)).

*. "et both dials to the positive sag value.

#. 5ecord the setting of both dials at 1*4)).



6. 5otate the dial indicators to #4)).

+. <etermine and record the reading on both dials.

$. 5otate the dial indicators to $4)).

%. <etermine and record the reading on both dials.

2. 5otate the dial indicators to >4)).

>. <etermine and record the reading on both dials.

1). 5otate the dials to 1*4)) and ensure that both dials return to their original setting.

To document as'found results use a format similar to that shown below.

Figure 3.51 Documenting as ound readi

easuring Certical isalignment

To measure vertical misalignment perform the following steps4

1. 5otate the dial indicators to 1*4)).

Figure 3.52

*. "et both dial indicators to the positive sag value.

7AT94 3or example if the amount of sag for a xture is determined to be '1) mils /').*+6

mm0 the dial would be set to read D 1) mils /D).*+6 mm0 at the 1*4)) position.



Figure 3.53

#. 5otate both shafts /if possible0 to $4)).

Figure 3.54

6. 5ecord the <:" and <: dial indicator T:5 values.

:nterpreting Certical isalignment <ata

To determine hori8ontal oset from #4)) T:5?s use the following rules

• "tationary "ide Aset E <:" T:5 ! * F reverse the sign /D to '0 or /' to D0

• ovable "ide Aset E <: T:5!*

• =oupling =enterline Aset E /"tationary "ide Aset D ovable "ide Aset0 ! *.

To determine hori8ontal angularity from the two reverse rim osets use the following rule4

• "haft -ngularityE /ovable "ide Aset'"tationary "ide Aset0 /x1)) E mm!1))mm0

- dimension

=onsider the following reverse rim #4)) total indicator readings /T:5?s0.



Figure 3.59 Cloc, readings at o-cloc

1. The "tationary <ial T:5 is D#6 mils /D).2$6 mm0. The stationary side oset is '1%

mils /').6#* mm0 or 1% mils to the left. (Remember, you have to change the sign of

the DIS reading to determine oset (see Section !"!"#$"$

*. The ovable <ial T:5 is D 2 mils /).*)# mm0. The movable side oset is D6 mils

/).1)1 mm0 or 6 mils to the rightt.

#. Certical oset at the coupling centerline is /' 1% D'60 ! * E '$.+ mils //')6#* D

).1)10!* EG).1$+ mm0 or $.+ mils /).1$+ mm0 to the left.

6. Hiven an - dimension of 2 inches /*)#.* mm0 the hori8ontal angularity would be /6 G

/'1%0 0!2 E *.$# mils per inch.//).1)1'/').6#*0! *)#.*0 E ).*$# mm !1)) mm

any dierent e,uations may be used for various reverse rim calculations. The information

presented here applies to a reverse rim dial setup such as that shown below. The e,uations

presented are used to calculate the position of the movable machine?s front and rear feetfrom <:" and <: oset values.

=alculations apply to both the vertical and hori8ontal planes of misalignment. Iowever they

are typically applied primarily to the vertical plane. -s presented earlier misalignment in the

hori8ontal plane may be accomplished without calculating or graphing the exact front and

rear feet positions.

Ca%cu%ating the &ront &eet and Rear &eet 'ositions

-s shown earlier and illustrated below the following setup dimensions and oset

designations apply.



Figure 3.60

The position of the movable machine?s front feet is determined using the following e,uation4

Figure 3.61 !ront eet euation

The position of the movable machine?s rear feet is determined using the following e,uation4

Figure 3.62 Rear eet euation.

where4

• E the oset in the plane of the movable indicator.

• " E the oset in the plane of the stationary indicator.

• - E the distance between the stationary and movable dial indicator plungers.

• ; E the distance from the movable dial indicator plunger to the movable machine?s

front feet bolt center.

• =E the distance between the movable machines? front and rear feet bolt centers.

• @ositive results mean the foot is high /vertical0 or to the right /hori8ontal.0

• 7egative results mean the foot is low /vertical0 or to the left /hori8ontal.0

Reverse Rim Ca%cu%ations )am*%es

Sam*%e Data



Hiven the following vertical misalignment data4

• The stationary side oset /"0 is D1* mils /).#)+ mm0 or 1* mils high.

• The movable side oset /0 is D1%.+ mils /).666 mm0 or 1%.+ mils high.

• - E + inches /1*% mm0 ; E % inches /1%%.2 mm0 = E *6 inches /$)>.$ mm0

&ront &oot 'osition Ca%cu%ation

Figure 3.63 The ront eet are /. mils (0.*1 mm) too high2 s

Rear &oot 'osition Ca%cu%ation

&igure !"+ The rear feet are +1.$ mils /1.#1 mm0 too highJ s

Reverse Rim Ca%cu%ations 'recautions

1. 9nsure that osets for the stationary and movable indicators are properly determined

from T:5?s prior to performing calculations.

*. ;e careful 7AT to make mathematical errors when subtracting signed numbers.

#. Abserve parentheses in the e,uations. @erform operations inside parenthesis rst.

6. <o 7AT make human errors substituting real values into the e,uations.

Reverse Rim -ra*hing

-s discussed earlier one way to determine the position of the movable machine?s front and

rear feet from <:" and <: oset values is to perform reverse rim calculations. -nother way

is to construct a scaled graph. - main advantage of graphing methods is that the shaft

centerlines and misalignment conditions are represented visually.

The information presented here applies to a reverse rim dial setup where both dial indicators

are attached at the same location around the circumference.

Hraphing procedures may be applied to both the vertical and hori8ontal planes of

misalignment. Iowever they are typically applied primarily to the vertical plane. -s

presented earlier misalignment in the hori8ontal plane may be accomplished without

calculating or graphing the exact front and rear feet positions.

Setting .* the -ra*h

To construct a scaled reverse rim graph perform the following steps4

1. Abtain graph paper with 1) divisions between bold lines.



*. Turn the graph paper so that the long side is hori8ontal.

#. <raw a hori8ontal line at the center of the page.

• This line represents the stationary shaft center and is drawn across the page midway

down the graph dividing the page. :t is helpful if this line is on top of one of the bold lines.

6. <etermine the hori8ontal plotting scale.

• -lways use the largest scale possible. easure the distance from the stationary

indicator plunger to the centerline of the rear feet of the movable machine. "tandard

graph paper is about *$) mm. The largest hori8ontal scale will be the machine distance

divided by the page width. 7ote your hori8ontal scale.

+. ake a small vertical line on the extreme left of the hori8ontal line.

•

This mark represents the point along the length of the stationary indicator plungerand is labeled4 <:".

$. Using the proper scale make a second vertical line to the right of the rst on the hori8ontal

line.

• This line represents the point along the length of the movable indicator plunger and

is labeled4 <:.

%. ake a third small vertical line representing the point along the length of the front feet of

the movable machine /330.

2. ake the fourth vertical line representing the point along the length of the rear feet of the

movable machine /530.

Upon completion of the steps above the graph will look similar to the one shown below. 3or

this example the - ; and = dimensions all e,ual 1)) mm.

Figure 3.65 Setting up the graph.

'%otting /sets



-fter setting up the graph the next step is to plot the osets in the planes of the dial

indicators on the stationary side /<:"0 and movable side /<:0. To plot the osets perform

the following steps4

1. <etermine the vertical scale.

• The vertical scale is typically 1 hundred of a mm /).)10 per division. :n cases of gross

misalignment where the osets will not t on the page a larger scale such as *'#

hundreds per division is sometimes re,uired.

*. @lot the oset from the stationary side on line <:".

• Use the hori8ontal line representing the stationary shaft centerline as the reference.

-ll points above this hori8ontal line are positive /D0 and all points below the line are

negative /'0.

#. @lot the oset from the movable side on line <:.

:n the example below the <:" oset is G).* mm and the <: oset is G).1 mm.

Figure 3.66 3lotting ofset

Determining 0ovab%e Shaft 'osition

-fter plotting the stationary and movable shaft osets to determine the movable shaft

position perform the following steps4



1. Using a ruler or straightedge draw a line through the two oset points that extends to the

rear feet of the movable machine.

*. =ount the number of s,uares in the plane of the front and rear feet to determine the

position and corrections needed.

:n the example below the front feet of the machine are properly alignedJ no shim changes

are re,uired. The rear feet are positioned ).1 mm too highJ shims need to be removed from

both rear feet.

Figure 3.67 Determining movable shats p

Reversed Rim -ra*hing 'recautions

1. 9nsure that proper hori8ontal and vertical scaling techni,ues are consistently used.

*. -lways double check the position of vertical lines drawn to represent the <:" <: 33 and

53.

#. 9nsure that osets for the stationary and movable indicators are properly determined from

T:5?s prior to plotting points on the graph.

6. 9nsure that positive osets are plotted above the hori8ontal reference line and negative

osets are plotted below the line.



+. &hen interpreting the graph to determine the movable shaft?s front and rear feet positions

in the vertical plane observe the following rules4

• :f the movable shaft is above the hori8ontal stationary shaft reference line the shaft

is too high.

• :f the movable shaft is below the hori8ontal stationary shaft reference line the shaft

is too low.

$. &hen interpreting the graph to determine the movable shaft?s front and rear feet positions

in the hori8ontal plane view the graph the way you view the machine that is standing

behind the movable machine facing the stationary machine. -lso observe the following rules4

• :f the movable shaft is above the hori8ontal stationary shaft reference line the shaft

is positioned to the right.

• :f the movable shaft is below the hori8ontal stationary shaft reference line the shaft

is positioned to the left.Correction 'rocess /vervie1

To correct misalignment involves a number of dierent procedures. The se,uence of steps in

the correction process varies slightly according to the specic alignment conditions of the

machine.

Before Correcting Misalignment

;efore correcting misalignment the following procedures are to be performed4

•

@erform pre'alignment checks and corrections.• "etup the reverse dial xtures.

• =orrect soft foot.

• easure misalignment.

• <etermine alignment tolerances.

• =ompare alignment conditions to specied tolerances.

After Correcting Misalignment

-fter correcting misalignment the following procedures are to be performed.

•

5e'measure alignment conditions.• =ompare alignment conditions to specied tolerances.

• <ocument nal results.

Common Correction Questions

&hen it comes to actually moving the machine that is "AKC:7H the @5A;K9 several

,uestions are often asked4

• <o : start with the vertical or hori8ontalL

• &hat about use of precut shimsL

•

"hould : take a new set of readings after moving vertically or hori8ontallyL• <o : need to use dial indicators to monitor the hori8ontal movesL



• :s it necessary to use tor,uing proceduresL

• <o : move the front feet or the rear feet rstL

9ach of these ,uestions is valid and will be answered in this lesson.

Determining the Sequence of Corrections

=orrecting misalignment involves initial and nal corrections. :nitial corrections are made to

minimi8e the amounts of misalignment and improve the accuracy of alignment

measurements.

@rior to making any moves look at the hori8ontal and vertical positions of the movable

machine. :n general you will start the correction process by making initial corrections in the

plane where the misalignment is worse and then make nal corrections.

0a2ing Corrections If

;oth Certical and Iori8ontal 3ront and 5ear 3eet isalignment is ).+ mm or less

;oth Certical and Iori8ontal 3ront and 5ear 3eet isalignment is greater than ).+ mm

9ither Certical or Iori8ontal 3ront and 5ear 3eet isalignment is greater than ).+ mm

=onsider the following sets of data.

3ront 3eet Certical @osition4 D).* mm5ear 3eet Certical @osition4 D).+ ms

:n this example the hori8ontal misalignment is over twice the vertical misalignment.

Therefore an initial hori8ontal adBustment will be madeJ then nal vertical and hori8ontal

corrections will be made.

0a2ing 3ertica% Corrections

<etermine the vertical position of the movable machine using calculation and!or graphing

techni,ues.



Figure 3.68@ositive values at the feet mean that the movable machine is high therefore you will remove shiadd shims.

3ertica% Correction Ti*s

1. ake shim changes to both front feet and both rear feet as needed.*. -lways check shim thickness with an outside micrometer. @recut shims aren?t always

what they?re markedJ many shim manufacturers designate shims with the “nominal”

thickness.

#. Use consistent and correct tor,uing procedures.

6. -s shim changes are made check for and take precautions to avoid creating soft foot

conditions

4ori5onta% Corrections 'rocess

&hen using the reverse rim method two dierent procedures are commonly used for

hori8ontal corrections4

• <etermining the corrections using calculation or graphing techni,ues and monitoring

movement using dial indicators positioned at the machine feet.

• onitoring movement using dial indicators mounted at the coupling.

To correct hori8ontal misalignment by monitoring movement at the movable machine feet

perform the following steps4

1. easure hori8ontal misalignment using procedures described in #.#.$.+



*. <etermine the hori8ontal position of the movable machine using calculation or graphing

procedures described in #.#% F #.#2.

#. 9nsure that you are standing with the movable machine on your right and the stationary

machine on your left.

• @ositive values at the feet mean that the movable machine is away from youJ

therefore it should be moved towards you.

• 7egative values at the feet mean that the movable machine is towards youJ therefore

it should be moved away from you.

6. @osition dial indicators at the front and rear feet.

+. ove front and rear feet the amounts needed while watching the dial indicators.

Figure 3.69 $onitoring movement using dial indica

To correct hori8ontal misalignment by monitoring using dial indicators mounted at the

coupling perform the following steps4

1. 5otate the dial indicators to >4)) and 8ero them.

*. 5otate shafts to #4)).

#. -dBust the dial indicators to one'half their values.

6. ove the front feet of the movable machine as you watch the movable indicator move to

8ero.

+. ove the rear feet of the movable machine as you watch the stationary indicator move to

8ero.

$. 5epeat steps 6 F + until both dial indicators read 8ero.



Figure 3.70 $onitoring movements using dial indicato

4ori5onta% Correction Ti*s

1. "tart making moves at the feet where the misalignment is greatest.

*. :f not already present install Backbolts wherever possible.

#. ;ring the front and rear feet into alignment togetherJ they?re a team.

6. &hen the feet are within ).)+ mm or so start tor,uing and watch the dial indicators. Use

the proper criss'cross tor,uing se,uence.

After 0a2ing 3ertica% and 4ori5onta% Corrections

After making final vertical and horizontal corrections, you should:

1. Abtain new measurements.

*. =ompare results to specied tolerances.

#. 5epeat corrections until results are within tolerances.

6. Abtain and document a nal set of measurements.

+. 5estore e,uipment in accordance with procedures at your facility.

Reverse Rim Dial Indicator Alignment Overview

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