Centrifugal Pumps Design and Application 2nd ed - Val S. Lobanoff, Robert R. Ross (Butterworth-Heinemann, 1992)

Table 19-3 Continued
Primary Alignment Measurement Methods
Alignment 513
Method Advantages Disadvantages
Face-Face-
Distance (See
Reference 6)
Partial
Projection
Reverse-Indicator
(See Reference
14)
Laser-Optic
(OPTALIGN®)
than face-and-rim
arrangement, for spacer
coupling applications.
Face gap difference can be
derived easily from rim
measurements without the
need for direct
measurement.
Reverse-indicator brackets
are usually variable
geometry type, clamped to
hub rim or shaft, applicable
to a range of machine sizes,
and easy to calibrate for sag
on a horizontal pipe.
Both shafts turn together, so
eccentricity and surface
irregularities do not cause
errors.
Good for long spans.
Applicable mainly to cooling
tower drives, but sometimes
used for pumps with long
coupling spacers. Can also
be used when spacers pass
through a wall or bulkhead,
as on some shipboard
applications. Bracket sag is
usually negligible.
Good for long spans, mainly
cooling tower drives with
metal disk couplings. Avoids
axial float error. More
accurate than
face-face-distance
arrangement if used with
metal disk couplings
provided bracket sag is
accounted for.
Fast.
Accurate.
small, close-coupled
machines.
Less accurate than other dial
indicator methods. May
require precautions to avoid
axial float errors.
Must calibrate and account
for bracket sag. Subject to
diametral tooth clearance
error if used with gear-type
couplings.
Basic equipment.
Will not handle two-element
(table continued on next page)