Non-Rotating

Looseness

1X, 2X, 3X

radial

steady

narrow band

Harmonics can extend to 10 X

Rotating Looseness

(rotors, impellers,

etc.)

1X

radial

varies startup to startup

narrow band

Sometimes 0.5X harmonics also

Centrifugal Pumps

with (V) Vanes

Vane pass = VX

radial

fluctuating vane rate

harmonics of pump

In large pumps strongest amplitude occurs at vane rate.

In smaller pumps strongest amplitudes occur at harmonic of vane rate.

Gear Pumps with (T)

Teeth

tooth mesh = TX

radial

More than one discharge volute (as in multiple rotor pumps) will create harmonics of tooth mesh frequency.

Rotor Rub

0.5X, 1X

radial

steady

narrow band

May excite rotor critical.

Screw Pumps

SX

radial

S = number of screw threads

Cavitation or

Starvation

random

radial

fluctuates

broadband

Random noise sometimes up to 20 kHz