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

Table 19-3 Continued
Primary Alignment Measurement Methods
Method Advantages Disadvantages
Laser beam has zero sag
even over long spans.
Measurement and
calculating capability are
combined in one system.
Easy to use for basic
alignment problems. Can
also handle certain more
complex problems, but
procedures are more
complex, or extra equipment
is required.
Requires about % in.
exposed shaft for mounting,
but this can be reduced to
9 /i6 in. by using
non-original-equipment
brackets.
Metric and inch systems
both present in same
calculator.
Can be used to measure soft
foot originating from
common causes.
Can be used for progressive
error reduction horizontal
moves similar to the Barton
method used with dial
indicators.
Can be used to accurately
measure sag and its effect
for long spacers and pipes.
or multi-element optimum
move problems without
supplemental calculations.
Supplemental equipment
available at extra cost can
handle such problems. Both
shafts must be turned
together. This requirement
can sometimes be met by
using a roller bracket with
inclinometer on a shaft that
remains stationary.
Subject to error if coupling
backlash cannot be
eliminated during rotation.
Requires careful handling to
avoid damage.
Electrical. Requires periodic
battery replacement, and gas
test for permit to use in
hazardous areas.
Shielding may be required in
the presence of bright
sunlight, steam, or heat
waves.
Expensive.
Recalibration recommended
every two years.
Severe misalignment can
sometimes exceed range of
system, requiring
preliminary alignment by
other means.
For basic equipment,
computer gives numbers and
their orientation on a display
representing the machine
elements but no graphical
shaft centerline relationship
display. The latter is
available in supplemental
equipment at extra cost.
The OPTALIGN* laser-optic alignment system is manufactured by Prueftechnik Dieter
Busch + Partner GmbH & Co., Ismaning, Germany. Represented in the U.S. by Ludeca, Inc.,
Miami, Florida.