Gap Voltage and Radial Vibration

R

Thread Starter

RAJESH

We have a 3500 bently nevada system in BFPT for boiler for 700 mw STG. The main pump rotate at 5480 RPM The gap voltage is set at -11V DC for bearing DE end of pump.

Due to setting at -11vdc instead of -10 vdc it will make any difference in radial vibration measurement (dynamic value)? I want to know that it will give erratic reading or not, and if any then how much?
 
S

saudi_contract

no

> Due to setting at -11vdc instead of -10 vdc it will make any difference in radial vibration
> measurement (dynamic value)? I want to know that it will give erratic reading or not, and
> if any then how much?
 
If the setting is say at -13 vdc instead of -10 vdc it will make any difference in radial vibration measurement (dynamic value)? I want to know that it will give erratic reading or not, and if yes or no why?
 
Rajesh,

setting the gap voltage at -11VDC rather than -10VDC will have no effect on the dynamic value for vibration or displacement feedback, unless your gap while running increases by a large amount. The setting of the probe gap voltage at -10VDC allows for the probe to operate in its region of linearity. Take a look at the GE/Bently site for specifics on the probes you are using. Each probe has the ability to measure up to a certain gap with a pure linear curve, if the gap is increased to a certain amount the probe will still produce a reading but the curve begins to become non-linear. I can't quote the gaps for your specific probe since they are all a little different.

But basically having your probe gapped at -11VDC should not cause any erratic readings.

Poor or dirty connections, damaged cables, extension cable connectors not wrapped or grounding out, damaged probes, faulty proximitor modules, and loose or poorly shielding wiring will cause erratic readings in my experience.
 
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