Installation suggestions and use of dial indicators for centrifugal pump

1. Nonferrous shim packs should be installed under all feet of the pump and driver, particularly

when installing a new pump. The amount should be 0.125 to 0.250 in (3.175 to 6.35 mm) in no more than three pieces to start; for example, one 0.125-in (3.175 mm) and two 0.0625-in (1.59-mm) full shims of stainless steel.

2. Motors have four feet generally, and any “soft foot” should be compensated first. A soft

foot is one that is shorter than the other two or three feet, a condition that puts a twist or strain in the equipment. Simply place a dial indicator stem vertically against the motor foot and release the hold-down bolts sequentially around the unit, recording and retightening at each step. If a 0.002-in (0.050-mm) spring-up occurs on three feet, for example, and 0.006 in (0.152 mm) occurs on the fourth foot, add 0.004 in (0.10 mm) of shim to the fourth foot, eliminating the soft foot.

3. Provide low-sag tooling to reach over the coupling (coupling left in place) for reverse

indicator alignment. A 0.001- to 0.0015-in (0.025- to 0.038-mm) sag is easy to accomplish

on indicator reach bars.

4. Let the indicator indicate on its own bracket or bracket pin, thus preventing any poor

surface condition of shaft or coupling from contributing to poor measurements.

5. Support the dial indicator weight on the motor or pump shaft so it does not contribute

to “reach bar” sag.

6. Do not overlook the fact that many times one can clamp to the shaft behind each coupling

hub and obtain more span and therefore better accuracy.

7. Record all data looking the same way down the unit; that is, top east, bottom, west or

top, north bottom, south or top, right bottom, left. It is suggested that the driver-pump

always be viewed from the driver end.

8. Turn the shafts in the direction they normally turn and approach the 90° points in

a precise manner (do not back up and introduce backlash errors). Turning in the normal

direction is good training because, on gear units, it reduces helix angle lift