User's Manual

Table Of Contents
7. Repeat these steps for all measurement points at each speed, if you set up more
than one speed.
8.
Press Next Step.
An X appears next to the Reference Run measurement on the Acquire Data Select
Measurement screen.
Watch Dog checks to validate reference run data
After you acquire the last reference run reading, the Watch Dog application checks the
data for any potential problems using the criteria below. If a problem exists, a message
displays.
You can view the Watch Dog information without selecting the reference run. From the
Balance main menu, press ALT > F10 Watch Dog Checks.
1xRPM is less than 50 percent of total energy
This check is available in both the Basic and Advanced Balance modes. The only vibration
frequency that is significantly reduced by the balance procedure is at 1xRPM, rotational
frequency. If less than half of the vibration energy is at 1xRPM, the Balance program
displays a message. The analyzer lists the points causing this alert with the percentage of
energy at the rotational frequency.
You may want to acquire a frequency signature at the points to determine the other
frequencies and consider other possible causes. Emerson recommends you use the same
vibration units (acceleration, velocity, or displacement). Changing units can dramatically
change the apparent distribution of energy. For example, displacement emphasizes the
lower frequencies and acceleration emphasizes the higher frequencies.
Vibration is direction sensitive
Note
This is available only in Advanced Balance mode.
Two common conditions cause vibration magnitude at the rotational frequency to be
significantly different at various radial positions in the same measurement plane:
The structure may be highly constrained in one direction, but very flexible in
another. Some vertical pumps have this condition when braced in only one
direction.
A resonance near rotational frequency at the axis with the higher magnitude.
The first condition may cause the second. Resonance is the greater concern because the
equipment may be difficult to balance or to keep balanced.
Three severity levels indicate the condition of a measurement point:
Ratio Status
Greater than 3:1 but less than 8:1 Moderate
Balance
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DRAFT