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

Table 19-1
Vertical Alignment Movement Methods
Alignment 503
Method Advantages Disadvantages
Integral
Jackscrews,
Threaded into
Machine Feet
Prybar
Portable Jacks
and Wedges
Crane or Hoist
Portable
Alignment
Positioners
No problem locating jacking
surfaces. Inexpensive if
included when the machine
is purchased.
Inexpensive. Readily
available. Can get into
low-clearance locations.
Available in a variety of
types and load ratings, most
fairly inexpensive, with
collapsed heights down to
3 /i6 in.
The obvious solution if
bottom clearance, access, or
load bearing surfaces are
unsuitable for jacking.
In a single device, they give
vertical, precise horizontal
transverse, and precise
horizontal axial movement
capability. Capacities up to
20 tons per pair are
available. Used in groups of
four, the maximum capacity
increases to 40 tons. (For
more details, see References
6, 9, and 14.)
Shims require an extra hole
or slot. Threads sometimes
rust and cause difficulty in
turning the jackscrew. If the
screw breaks, removal of
the remaining fragment may
be difficult. Difficult and
expensive to retrofit after
machine is installed.
Access and clearance are
sometimes a problem,
limiting usefulness and load
capacity.
Safety can be compromised
if the bar slips while
someone is reaching beneath
the machine feet to install or
remove shims.
Sometimes the one needed is
somewhere else, and the one
available is not suitable.
This is not really a
disadvantage for the method,
however, but merely an
indication of poor planning.
Expensive and bulky.
Sometimes have access
problems. Poor small
movement control.
Two inch minimum vertical
clearance required.
More expensive than regular
jacks.
Not usually worth bothering
with for machines smaller
than 500 hp.
(table continued on next page)