Handbook Of Shaft Alignment Episode 2 Part 9 pptx

Understand that if you take a set of elevations on scale targets attached to themachinery bearings as shown in Figure 16.46 when the equipment is off-line, then dismantlethe optical inst

16.13 ESTABLISHING REFERENCE PLANES

Since there is a good possibility that the off-line measurements will be taken at a different timethan the running measurements, it is suggested that vertical and lateral reference positions beestablished Understand that if you take a set of elevations on scale targets attached to themachinery bearings as shown in Figure 16.46 when the equipment is off-line, then dismantlethe optical instrument and tripod, and if you go to set the instrument and tripod backup at alater time, the question now becomes ‘‘what was the original elevation of the instrument whenthe first set of vertical measurements were taken?’’

One of the primary considerations when using any method where you are observing points

on a machine case with respect to a remote observation point is to establish stable, ing reference ‘‘planes’’ in the vertical and horizontal directions that enable you to reestablish

nonmov-or ‘‘buck in’’ to that same reference plane fnonmov-or comparison of your off-line and your runningmeasurements This sounds easy but realistically, this is very difficult to accomplish Remem-ber you are trying to measure distances as small as 1 mil (0.001 in.)

1 Set the instrument stand at the

desired sighting location, attach the

alignment scope to the tripod or

instrument stand, and level the

stand using the “rough” circular

bubble level on the tripod (if there

is one on the tripod) Insure that

the stand is steady and away from

heat sources, vibrating floors, and

curious people who may want to

use the scope to see sunspots.

2 Rotate the scope barrel to line up with two of the four leveling screws

and adjust these two leveling screws to roughly center the split

coincidence level bubble in the same tilt plane as the two screws that are

adjusted as shown.

3 Rotate the scope barrel 90
to line up with the other two

leveling screws to completely center the bubble in the circular level as

shown.

4 If the circular level is still not centered, repeat steps 2 and 3.

Adjust these two leveling screws to first adjust the circular level in one direction

and then these two screws for the other direction.

Split coincidence level Circular level

FIGURE 16.44 How to level a tilting level or jig transit, parts 1 through 4

The type of reference plane that you establish is somewhat dependent on the period of timebetween the off-line measurements and the running measurements If you plan on taking theoff-line and running measurements within a 2-h time period, then adhesive-backed targetscould be placed on walls or building columns or any fairly stable object Examples of this areshown in Figure 16.51 through Figure 16.54 If however the time period between off-line andrunning measurements will be over 2 h or perhaps even days later, you should establish amore stable reference position since building walls or structural steel could very well changeshape and position over a long period of time.

For vertical elevation measurements, it is suggested that one of the two methods beemployed One way is to fabricate water-cooled pipe stands and attach adhesive-backedtargets to them as shown in Figure 16.55 It is recommended that at least two referencepoints be established, usually one at each end of the drive train Another way is to use aninvar extension rod contacting a tooling ball, which is rigidly attached to the concretefoundation or baseplate or floor as shown in Figure 16.56

For lateral or axial measurements, adhesive-backed targets can be placed on concretefoundations or floors, or better yet, permanently anchored reference targets imbedded inthe concrete as shown in Figure 16.57

How to level optical tilting levels and jig transits

8 The last step is to rotate the scope barrel

908 to line up with the two remaining

leveling screws yet to be fine adjusted.

Follow the same procedure as outlined in

steps 6 and 7 above When these adjustments

have been completed, the split coincidence

bubble should be coincident when rotating

the scope barrel through the entire 3608

of rotation around its azimuth axis.

5 Once again rotate the scope

to line up with two of the

leveling screws as covered in

step 2 Adjust the tilting screw

to center the split coincidence

level on the side of the scope

barrel as shown.

6 Rotate the scope barrel 180

and note the position of

the two bubble halves Adjust the

two leveling screws in line with

the scope barrel so that the gap

between the two bubble halves is

exactly one half the original gap.

7 At this point, adjust the tilting screw so there

is no gap in the two bubble halves Rotate the

scope barrel back 180
to its original

position and see if the two bubble halves are

still coincident (i.e., no gap) If they are not

adjust the two leveling screws and the tilting

level screw again as shown and rotate the scope

barrel back 180
until there is no gap

when swinging back and forth through the half

circle The two leveling screws should be snug

but not so tight as to warp the mounting frame.

Key considerations for capturing good readings:

. Provide stable platforms for the optical scale targets

. Establish several (minimum of two, three suggested) vertical, lateral, and axial referencepositions to ‘‘buck’’ back into

. Scale target should be located as close as possible to the bearings since we are trying todetermine where the shafts are going (if the bearing moves, the shaft is sure to move with it)

. Magnetic base holders should be used to hold the scale targets insuring a stable targetposition

. Clamp on circular level bubble sets should be used on the scale target to insure scaletargets are in a pure vertical position

1 Check calibration of the instrument (see Peg Test).

2 Select suitable scale positions at the inboard and outboard ends of each

piece of machinery in the drive train The “platforms” that the scale targets

will be sitting on should be stable and slightly below the centerline of

rotation and usually near the bearings.You can use 2 in 3 2 in pieces of angle

bearing housing.Try to insure that the surface that the scale targets will

sit on is relatively level and flat It is also advisable to install reference

stands at each end of the drive train and affix a “stick-um” crosshair target

to the reference stand.You can make these stands out of 3 in or 4 in pipe, fill

them with a water–glycol or antifreeze solution, insulate the pipe, bolt or

clamp them to the frame or floor, and monitor the water temperature to

insure thermal stability.

3 Set the optical instrument and stand at some remote reference point

away from the drive train where a stable point in space can be established

but close enough to maintain the maximum possible accuracy of the

readings.

4 Accurately level the instrument and take a set of readings at each target

scale mounted on the machinery when it is “off-line” (i.e., not running)

occasionally checking back to the reference targets at each end of the drive

train to insure that you are maintaining the same vertical elevation (i.e.,

shooting through the same horizontal plane).

5 Run the machinery at normal conditions and allow the equipment to

stabilize its position (this can take hours or even days).

6 Check the level accuracy and take a similar set of readings at each target

scale occasionally checking back to the reference targets at each end of the

drive train to insure that you are maintaining the same vertical elevation.

7 Compare the off-line set of readings to the running set of readings to

determine the amount and direction of the movement of each scale.

Optical alignment OL2R procedure for vertical (up and down) measurements

. If possible, try to keep the scale targets in place from OL2R conditions.

. Keep the scale target holding platforms clean

. Move slowly when working around the tilting level or jig transit and stand (if your foot orarm bumped the stand, it is probably not in the level or in the same vertical or horizontalplane any more)

. Readings should be taken at night when equipment is located outdoors to preventthermal instability of the tripod or stand when the sun heats or cools the stand

1 Check calibration of the jig transit (see Peg Test) Two people are

required to do this procedure—the scale target holding person and the

observer.

2 Select suitable scale “anchor” points at the inboard and outboard ends of

each piece of machinery in the drive train The points or “anchors” that the

scale targets (and probably extension rods) will be touching should be stable

and directly above or below the centerline of rotation and usually near or at

the bearings You can have tooling balls firmly affixed to the machine care

or bearing housing as the “anchor” points to hold the scale target against for

reference.

3 Set the jig transit and stand at some position along one side of the drive

train where a stable point in space can be established insuring that

measurements can be taken at each bearing location when the scale target or

extension rod is placed at each “anchor” point at every bearing location.

Orient the optical micrometer on the scope barrel to allow variation in the

position of the vertical crosshair when the micrometer barrel is rotated.

4 Accurately level the instrument, then loosen the vertical sweep axis screw

allowing the scope to tilt up and down Affix several (at least two) adhesive

crosshair targets to the foundation or floor along the full length of the drive

train establishing a vertical reference line or plane Take a set of readings at

each bearing location by holding the scale target or extension rod when

placed at each “anchor” point when the machinery is “off-line” (see “waving

scales”) occasionally checking back to the adhesive crosshair targets attached

to the foundation or floor to insure that you are maintaining the same

horizontal position (i.e., keeping in the same vertical reference plane)

5 Run the machinery at normal conditions and allow the equipment to

stabilize its position (this can take hours or even days).

6 Check the level of accuracy and take a similar set of readings at each bearing

location occasionally checking back to the adhesive crosshair targets

attached to the foundation or floor to insure that you are maintaining the

same horizontal position.

7 Compare the off-line set of readings to the running set of readings to

determine the amount and direction of the movement of each scale target and

. 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.

. Several sets of measurements (minimum of two, three suggested) should be taken for theoff-line measurements and also for the running measurements to verify that the equip-ment is in both a stable off-line and stable running position

angle to the line of sight By

“waving” the scale target toward and away from the observer (jig transit), a precise 908

angle will be obtained when the minimum reading is observed.

90
angle required for accurate reading

FIGURE 16.48 How to take accurate optical horizontal measurements

FIGURE 16.49 Jig transit and scale target on outboard pump bearing for lateral measurement

. Tremendous versatility and range of possible measurement points

. Measuring instruments can usually be placed away from heat sources

. Scale and reference target holding devices usually need to be custom fabricated andcarefully placed to insure long-term stable position

. Instrumentation, targets, and fixturing relatively expensive

16.14 ALIGNMENT BARS WITH PROXIMITY PROBES

This method falls into the category of observing movement of one machine case with respect

to a position on the other machine case This device was invented in the early 1970s by RayDodd while working at Chevron The machinery alignment bar OL2R system is based on theprinciple of the reverse indicator method explained in Chapter 7

Two ‘‘bars’’ are used, a ‘‘probe bar’’ and a ‘‘target bar.’’ The probe bar is attached near theinboard (coupling end) bearing as close as possible to the centerline of rotation on onemachine case The target bar is attached near the inboard (coupling end) bearing as close aspossible to the centerline of rotation on the other machine case The probe bar and target bar

‘‘shadow’’ each other but they do not touch Four proximity probes are attached to the probebar, two vertically oriented probes and two horizontally oriented probes These probe sets aremounted at two locations along the length of the bar, which observe two positions on theFIGURE 16.50 Holding scale target with invar rod extension for lateral measurement

FIGURE 16.51 Adhesive-backed target attached to I-beam.

FIGURE 16.52 Adhesive-backed target attached to I-beam

FIGURE 16.53 Transit with scale target in background.

FIGURE 16.54 Adhesive-backed target attached to wall

target bar The targets could be blocks of steel attached to tubing or they could be the targetbar surface itself as shown in Figure 16.58 and Figure 16.59.

Before starting the drive train when the machinery is off-line and in a stable position, a set

of gap readings are taken on each of the two vertically oriented probes and each of the twohorizontally oriented probes The drive system is then started up and operated under normalrunning conditions until the probe gaps have stabilized Relative machinery casing movementcan be determined by comparing the gaps on each probe before and after the equipment isrunning Strip chart recorders (or similar devices) can be set up to monitor the rate of change

of gap during warm-up and on-line operating conditions and to see when the positions havestabilized (Figure 16.60)

Key considerations for capturing good readings:

. The probe and target bars should be attached to each machine case as close as possible tothe centerlines of rotation to accurately determine shaft motion, not casing expansion orbearing housing warpage (see Figure 16.26)

. Important to have target surfaces at precise 908 angles to the proximity probes

. The bars can be positioned inside or outside the coupling guard or shroud with tions taken to prevent excessive vibration of the bars from coupling windage if mountedinside the guard

precau-. 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

Insulation

FIGURE 16.55 Water-filled pipe reference stand

Floor Reference tooling ball Invar extension rod assembly

FIGURE 16.57 Permanent floor target

Base mounted through bracket to bearing housing of driver machine

Base mounted through bracket to bearing housing of driven machine

Eddy probe driver (1 of 4)

Extension cable (1 of 4)

Eddy probe (2 of 4)

Flexible coupling and shaft ends

The target bar can be attached to either the driver or the driven unit

Proximity probe

Proximity probeProximity probe

. Fairly accurate measurements possible with proper setup

. Capable of measuring movement in vertical and horizontal directions

. Can continuously monitor positions of machinery without disturbing sensors or bars

. If the machinery is vibrating excessively when taking the running measurements, theproximity probes average the oscillation effectively to insure accurate distances betweenthe probe tips and the targets

. Can be equipped to measure axial growth if desired

. Somewhat expensive since custom braces and bars have to be fabricated; probes, cables,proximitors, readout devices, and power supplies have to be purchased

16.15 APPLYING LASER–DETECTOR SYSTEMS FOR OL2R MEASUREMENTSLaser–detector systems can also be used to measure OL2R machinery movement in themachine case to machine case measurement category

In a very simple setup, where small amounts of relative movement between machinery cases

is present, a laser (or laser–detector depending on what system you use) could be mounted at

or near the centerline of rotation of one machine near the inboard bearing, and the detector(or prism depending on what system you use) could be mounted at or near the centerline ofrotation of the other machine near its inboard bearing as shown in Figure 16.61 With themachinery off-line, the laser–detector system can be oriented to have the laser strike in the

Probe bar

Target bar

“H”-shaped base to allow for positioning the bar in the up and down direction

“H”-shaped base to allow for positioning the bar in the sideways direction

End view of bars and probes Angle iron

FIGURE 16.59 Fabricated alignment bar design

center of the detector targets The laser–detector system is kept in place on the machine casesand the unit started up and operated until movement stops If movement occurs between themachine cases, the laser will be striking at a different position in the photodetector.

With the plethora of laser shaft alignment systems in existence, it is somewhat amazing tofind out that very few people have tried to use their systems for this purpose The underlying

The probe and target bars can be mounted on either machine case but you have to know what is mounted where.

The distances from the inboard feet to the points where the proximity probes are taking readings on the target bar must be known, as well as the orientation of the horizontal probes.

The gap changes from off-line to running (or vice versa) need to be recorded Remember to capture not only the amount of the gap change but also the direction (increasing gaps means the probe moved away from the target).

Proximity probe alignment bar system Proximity probe alignment bar system

Proximity probe alignment bar system Where is the bracket holding the probes mounted?

compr

Select the mounting location for the bracket that is holding the proximity

probes (i.e., which machine will you attach the prox probe bracket to?).

compr

compr stm turb

Vertical probes Horizontal probes

Vertical probes

Are the horizontal probes

Away

Toward Away

FIGURE 16.60 Alignment bar setup

reluctance seems to originate from the difficulty in mounting the lasers and detectors to themachine cases Since there is such a wide variation in machinery design, custom brackets areusually required to hold the equipment in place similar to those shown in Figure 16.62 andFigure 16.63 These brackets must not only hold the laser and detector in a stable position,but also the laser and detector need to have positional adjustments for centering the beam.Additionally, if laser–detector–prism systems or two single-axis laser–detector units are used,two sets of laser–detector prisms are needed to capture all the required information (verticaloffset, vertical angularity, horizontal offset, and horizontal angularity) With mounts having

a precise 908 rotation feature, one set of such two-axis equipment is sufficient More detail onsuch mounts will be given later

Universal laser–detector mounting brackets can also be purchased as shown in Figure 16.64through Figure 16.67 These brackets have the capacity to rotate the laser–detectors through

a precise 908 arc to capture all of the measurements needed as mentioned previously, thusavoiding the need for two sets of laser–detector equipment

FIGURE 16.61 Basic setup of laser–detector systems used to measure OL2R movement

FIGURE 16.62 Laser–detector–prism systems setup on custom mounts measuring gear and compressorOL2R movement Alignment bar setup also used for comparison