Page 25 - Rotating Machinery Pratical Solutions to Unbalance and Misalignment

Rotating Machinery: Practical Solutions

Figure 1-13. Direction of Vibratory Motion

The first step in the analysis process should be the recording
of all machine information and drawing a sketch of the machine.
In figure 1-14, the basic data for a simple fan are recorded. It
is important to know as many facts about a machine as possible.
In this case, there are eight fan blades, which at 1,725 rpm would
exhibit a first order aerodynamic problem at the blade pass fre-
quency of 8 × 1,725 or 13,800 cycles per minute (cpm).
In analyzing the machine above, the frequency of 1,725 cpm

B D
8 Fan blades
A 25 Ph
1,725 rpm
C

Figure 1-14. A Basic Sketch of a Fan to be Analyzed