Recently I was assigned additional equipment to monitor in an underground mine about 150 miles from my location.

My question concerns the main ventilation fan described below.
1250 Hp
900 RPM
16 blades
108" diameter
2500 lbs Rotor weight
The fan is driven by a 10ft shaft from the motor.
I am told there are Bentley transducers 89129 mounted on the bearing housings with a Bentley monitor 1900/27.

I use an Enpac 2500 analyzer with Emonitor.

My question:
The Bentley monitor reads .107 ips - .126ips on the drive end and .119 ips - .132 ips opposite drive end.
Hooking up the analyzer to the BNC connections provided in the monitor I am reading a 1x of .832 ips on the drive end and 1.015 ips opposite drive end. All other peaks in the plots are less than .015 ips.
Are these excessive? Any suggestions as to where to proceed next?
If the fan goes down the mine soon follows so I cannot inspect anything visually. There does not seem to be excessive vibration on the fan housing (I never leave my yellow handled vibration analyzer behind).
Thanks in advance
Wetmill

I'm not familiar with the Bently transducer or your data collector. I use a CSI 2130. Does the transducer require voltage? Is your data collector providing the proper voltage?

You can't beat the yellow handle vibration analyzer. For those hard to get bearings, I sometimes use the 5' long wooden vibration analyzer with the optional brush attachment.

Clave,

You'll have to find out what the sensitivity of the transducers are. I would bet your sensitivity is off in the Enpac. If one of those vent fans were shaking at 1 ip, you'd know it without the 2500.

I just looked up the 1900/27. The output sensitivity of the buffered outputs is 500mv/in/S. Change your sensitivity for those points and you'll be close to what the monitor is reading.

You'll also have to turn power off (I would assume you have already done this if you got a reading at all. I believe they use digital overall, while you are probably set up on analog overall. If you can find out the band of freqs they are monitoring (low cutoff out to F-max), use digital overall (RSS on Enpac/Odyssey), AND use 500mv/ip, you will match very closely their number. If you just want to see what is out there, then just use the 500 mv/ip and set it up however you like, which is probably what I would do

Dave

This message has been edited. Last edited by: RRS_Dave,