Page 101 - Rotating Machinery Pratical Solutions to Unbalance and Misalignment

A Single Plane Balancing Technique
Chapter
Chapter
Chapter
Chapter
Chapter
A Single Plane
A Single Plane
A Single Plane
A Single Plane
A Single Plane
Balancing Technique
Balancing Technique
Balancing Technique
Balancing Technique
Balancing Technique

INTRODUCTION

here is a simple balancing technique that is very useful in
balancing cooling tower fans and fin fan coolers. This is the
T T T T T four-circle method and will be discussed in some detail. The
basic advantage of this method is that it does not require a vibra-
tion analyzer that has a strobe light, or other methods of measur-
ing phase angle. This method requires only amplitude
measurements.
The main disadvantage of this method is that it requires start-
ing and stopping the fan several times. However, it does work
very well on these relatively slow-speed rotating elements.

GRAPHICAL SOLUTION

First, the amplitude of the vibration at 1 × rpm is measured
and recorded. A circle with a radius equal to the measured ampli-
tude is then drawn. Note that any convenient scale can be used for
laying out the graphics, i.e., 5 mils equals 1/4 inch.
As an example, a cooling tower fan has three blades and
operates at 330 rpm. An initial vibration was taken and the ampli-
tude of vibration in the radial direction was recorded as 46 mils at
330 cpm. The vibration pickup was attached to the gear box and
will remain attached at the same point throughout the balancing
process.