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Horizontal End Suction Pump for Chemical Process, ASME B73.1-2001
Installation, Operation, and Maintenance Manual – CPP21
Figure 5.8 Indicator sag in across the disc pack alignment analysis example.
With the indicator bracket attached to the pump hub, reading out the center member a convenient distance, (in
this example 8 inches [203.2 mm] was used) rotate the unit in 90° increments and take readings.
Bottom reading is then corrected for indicator sag. The indicator sag in the example was determined to be -
0.004 inch (-0.102 mm). The -0.004 inch (-0.102 mm) was subtracted from -0.025 inch (-0.635 mm) indicator
reading to give an actual of -0.020 inch (-0.508 mm) reading.
As this is a TIR (Total Indicator Reading) it is two times the actual center member center line location relative to
the pump shaft extension or -0.020 inch (-0.508 mm) / 2 inches (50.8 mm) = -0.010 inch (0.254 mm). (What we
are trying to do here is to determine the angle the center member makes with respect to the pump shaft.)
A plus reading at the bottom indicates that the center member tips down as it extends away from the pump.
Using a scale of one small division on the graph equals 0.001 inch (0.0254 mm); plot the 0.010 inch (0.254 mm)
as shown in the example.
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