Measuring Vibration for Axial Shafts

Ask the manufacturers of the probe then.

There are two basic approaches.

In the first approach you float the rotor from the active to the inactive shoe and using an dial indicator you determine the total float. From there you center the rotor in the float and zero the monitor. Alarms and shutdowns are then set basis the float. For example if the total float was 10 mils, the rotor would be centered in the float and the monitor zeroed. Alerts would be set at about 10 mils active and 10 mils inactive, indicating that the rotor had moved 5 mils into the bearing. Danger might be set at 15 mils active and 15 mils inactive. that would indicate that the rotor had moved 10 mils into the bearing.

In the second approach you do the same thing, but instead of setting the rotor in the middle of the float and zeroing the monitor, you set the rotor hard against the active thrust bearing and zero the monitor. Using the logic from above, in this case the active alarm would be at 5 mils, and the active danger would be at 10 mils. However the inactive alarm would be at 15 mils (the 10 mil float plus 5 mils) and the inactive danger would be set at 20 mils (the 10 mil float plus 10 mils into the bearing).

That is an overview of the process, if you have specific questions feel free to ask. If this is a process you are unfamiliar with I would recommend getting a technician from your monitoring company out to set the monitor for you.

Oh an by the way, while the probe does measure both vibration and position, in the axial direction the measurment is position. In the radial direction the probes are used to measure vibration.

hi

thanks for your kind information. I would like to know one more thing that how can we calculate exact gap voltage to be set if we are fixing the proble at the center of the float.

And the other thing is we have an Ingersoll Rand made over hanging Instrument air compressor. We are unable to move the rotor in both side i mean both active and inactive shoes sides,In that case how we will set our axial vibration probe.

Please give me advise

Regards

Pramod

Once you have mechanically located the rotor in the center of the float, you then want to set the probe to the middle of its range. For a Bently probe with a -24 VDC supply this is typically -10 VDC, but you need to consult the probe calibration curve to determine what the middle of the range is exactly, or conduct a calibration if you have the capability.

If you can get the rotor on the active shoe of the IR machine, I would just zero the monitor there. The service manual should be able to tell you the cold float clearance and you could just use that to set the alarms.

Thanks for the information

Regards

Pramod