24 / 72
Horizontal End Suction Pump for Chemical Process, ASME B73.1-2001
Installation, Operation, and Maintenance Manual – CPP21
5.2 ALIGNMENT*
In the following pages, alignment procedures are explained with dial indicators. Laser alignment is also possible.
The specific method in laser alignment will depend on the manufacturer’s instructions; however, the basic
principles and rotation of the shafts apply, as in the Reverse Indicator Alignment Method. Therefore, for laser
alignment, you may follow the steps detailed on the next pages, mounting a laser bracket with a measurement
device on each shaft and then proceed with the rotation of the shafts to obtain the readings to determine the
misalignment and correct it.
A. ALIGNMENT OF EQUIPMENT
Correct alignment is mandatory for the successful operation of rotating equipment. A flexible coupling is no
excuse for misalignment. The relationship between shaft centerlines can easily be determined by 1) two step
dial indicator method, 2) reverse indicator alignment, 3) across the disc pack alignment. These can all be solved
by a graphical approach. This procedure will discuss methods 2 and 3. Method 1 is covered in Rexnord's Manual
MT-SS-04-001, "Two Step Dial Indicator Method". Before we get into this alignment procedure, several items
should be considered at this point.
1. Indicator Set-Up
No matter what arrangement you use, indicator sag must be determined. This can easily be determined by
clamping the set-up onto a rigid piece of pipe, rolling the indicator from top to bottom, and reading the
difference. Once the indicator sag set-up has been determined, this number can be algebraically subtracted
from the alignment readings obtain at the bottom. There is no need to be concerned about the side to side
readings as the sag is equal on both sides.
2. Taking Alignment Readings
It is suggested that the dial indicator be zeroed at the top. For convenience, you should mark your coupling at 0°,
90°, 180°, and 270° with a reference mark on the case so that you can be sure to turn the unit exactly 90°. Both
shafts should be turned an equal amount if the coupling is not put together. Now rotate the coupling in 90°
increments recording all readings. It is important to keep your side to side readings straight. A suggestion is to
show compass orientation so that you know which reading to use. After you have made your four position check
and have returned back to the top, it is absolutely necessary that the indicator return to zero where it started. If
it did not, repeat your readings. It is also advisable to check the readings several times to make sure that they
are repeatable.
3. Thermal Growth
If there are thermal growth considerations on the piece of equipment, it is a good idea to get these numbers so
that they can be added to or subtracted from the graphical solution before the equipment move is made, this is
known as “Hot alignment”.
4. Soft Foot
The fact that your equipment could have a soft foot can affect the alignment readings that you obtain. The soft
*
Reprinted with permission of Riddle & Hubbel Company, Distributors of Rexnord Products.
To Next Page
Loading...