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4. Loosen all holddown bolts except the pivot bolt. Turn the
screw jack until the rear end of the equipment moves against
the indicator by the desired amount.
5. Tighten the holddown bolts and recheck the indicator. If
the reading has changed, loosen the three bolts and re-
adjust. It may be necessary to over or undershoot the de-
sired reading to allow for the effect of bolt tightening.
Correcting Parallel Misalignment
Preparation — Attach the dial indicator to one shaft or cou-
pling hub and place the indicator button on the outside di-
ameter of the other hub. The reach of the dial from one hub
to the other should be parallel to the shafts, and the dial but-
ton shaft should point directly through the center of the shaft
on which it rests. Compress the plunger to about mid-
position and set the dial at zero.
Check the tightness of the dial button and the indicator
linkage by rotating the shaft to which the indicator is at-
tached 360 degrees. The dial should return to zero. Check
for repeatability.
Check for runout by rotating the hub on which the dial
button rests 180 degrees. If the runout exceeds .001 total in-
dicator reading, the hub should be removed and the shaft
checked. Shaft runout must not exceed .001 TIR.
The effect of hub runout can be eliminated by locating a
position on the half coupling where two readings 180 de-
grees apart read zero. Rotate the coupling so that one zero
point is at the top and the other at the bottom when checking
for misalignment in elevation. Place the zero points side to
side in a similar manner when checking for misalignment in
plan.
Measurement — With dial set at zero in the top position,
rotate the shaft to which the indicator is attached 180 de-
grees. If the dial reading is plus, the shaft on which the but-
ton rests is low. If the reading is minus, the shaft on which
the button rests is high.
Never accept a single reading. Look for repeatability. Ro-
tate the shaft several times to see if the reading remains the
same. It is good practice to reverse the procedure and read
from zero at the bottom.
Always rotate the shafts in the same direction when tak-
ing readings. Backlash in the coupling teeth could cause some
differences.
Adjustment — Divide the total indicator reading by two to
obtain the exact amount of shaft offset. As illustrated in
Fig. 42, the indicator will read the total of A plus B but the
required shaft adjustment is only half of this as indicated
by C.
Add or remove identical amounts of shims at all footings
to bring the shaft to the proper elevation. Tighten all the hold-
down bolts and recheck the readings. Parallel alignment must
be within .002 TIR.
To correct parallel misalignment in plan, use a screw jack
and dial indicator as shown in Fig. 42. With a front hold-
down bolt as the pivot, move the rear of the equipment over.
Then, with the rear holddown bolt on the same side acting
as the pivot, move the front end of the equipment over by
the same amount.
FINAL ALIGNMENT — The procedures and tolerance re-
quirements for final alignment are the same as those de-
scribed in the Near Final Alignment section. Final alignment
is performed just prior to grouting and chiller hot check. All
piping, including water and steam, must be completed, but
the water and refrigerant charges need not be in place.
HOT ALIGNMENT CHECK
General — When all chiller components have reached op-
erating temperature (after running near full load for from 4
to 8 hours), a hot alignment check must be made. Hot align-
ment check may be made with couplings assembled or
disassembled.
Disassembled Couplings
1. Shut down chiller.
2. With chiller hot, quickly disassemble couplings.
3. Check angular and parallel alignment in plan and eleva-
tion as described in the Near Final Adjustment section.
Record the indicator readings (see page CL-12) and make
necessary adjustments to bring alignment within .002 in.
TIR and .00033 inches per in. of coupling face traverse
(or in. of indicator swing). Follow procedures described
in the Near Final Alignment section.
4. Reinstall couplings and run chiller until it again reaches
operating temperature.
5. Repeat steps 1 through 4 until alignment remains within
specified tolerances.
Assembled Couplings — If there is room on the shaft be-
tween coupling and component to clamp a sturdy bracket,
the arrangement illustrated in Fig. 43 may be used. The clamps
must have room to rotate with the shaft.
This method is quicker because the couplings do not have
to be disassembled. In addition, eccentricity or coupling face
runout are not problems since both shafts rotate together.
Fig. 41 — Adjusting Angular Misalignment in Plan
74