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

19
by Malcolm G. Murray, Jr.
Murray and Gang Tool Works
ALIGNMENT
Definitions
Internal Alignment. This type of alignment refers to machined fits and
precise assembly that ensure that the pump incurs no excessive deviation
from intended tolerances prior to installation on its pedestal and connection
of piping and shaft coupling. Although of obvious importance, this
type of alignment will not be emphasized here. It is covered in numerous
general and specific manufacturers' manuals and shop practice standards.
Further reference to it will be brief, and instructions for its accomplishment
will not be given in this section.
External Alignment. This type of alignment refers to a procedure or condition
that ensures the accuracy with which the centerline of one machine
shaft coincides with the extension of the centerline of an adjacent machine
shaft to which it is to be coupled. For horizontal machine elements,
alignment figures are customarily given in vertical and horizontal planes
along the shaft axis, both necessary for the complete picture. For vertical
machine elements, similar information is given in two convenient planes
perpendicular to each other. Alignment in this chapter will usually refer
to external alignment. Other terms often used are shaft alignment, coupling
alignment, angular, and parallel alignment. See Figure 19-1.
Why Bother With Precise Alignment?
This is a logical and legitimate question. Certainly, if pumps would run
as well with poor alignment as with good alignment, this section of the
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