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Balancing on CVHE/F Chillers: 

  • Balancing of CVHE chillers:
  • Use either Bentley Probes looking at shaft orbit (mils of movement) or accelerometers measureing the motor vertical or horizontal velocity vibration levels.
  • Idea is to add weight to the balancing nut on the impeller end of the shaft to smooth out the vibration level of the shaft orbit or the velocity level as measured on the motor outboard end of the compressor.
  • Acceptable levels are measured on the motor outboard end in vertical and horizontal radial measurements. The factor spec is .1 in/sec on air without elbow. This is very likely not good enough. My recommendation is to get the air run to less than .05 in/sec velocity pk.
  • To achieve this add balance weight on the nut but only after the chiller has run 8-10 minutes for initial run data. Chiller needs to settle out and be stable before correction weights can be added to balance nut.
  • Install a 20-50 gram weight on balance nut for the trial run. Let the chiller run again for 8-10 minutes to settle out. Watch the initial and trial weight movement during each run.
  • After collecting the initial and trial weight the analyzer should calculate a location and weight amount to balance the chiller. Add that amount at the specified location and run again to find out what the results of that correction weight achieved.
  • Normally only one adjustment to the initial correction weight is required to get levels that are less than .05 in/sec and likely less than that is achieved.
  • I normally collect initial motor outboard vibration data even if I am using the Bentley probes to balance chiller. Then I collect the readings after balance is complete on the motor outboard end.
  • Generate report and maybe install the elbow without o-rings and gasket material to verify that elbow does not increase the vibration levels significantly.
  • Balancing Fans:

    Fan Balancing:

    Using the VB analyzer and the balancing program from the web site Go into the menu mode and select the measurement mode. Then select tach measurement. Collect the phase and amplitude from either the single plane or collect readings from both planes.

    Use these values and put into the balancing program. Note you have the option of using blades or locations and using the 360 degree option.

    Install a trail weight on each of the planes and collect new phase and amplitude readings. Make sure you get a 30% change in the amplitude and or a 30 degree change in the phase data. This will give the program some good data to use in the calculation of good trim weights for the single plane or a 2 plane balance.

    Install the trim weights and see how good the balance is. If the amplitude is still higher than you would like I would only recommend performing one more trim with the new weights and location as perscribed by the balancing program.

    Make sure the amplitude per plane is the higher of the two directions (vertical or horizontal)

    Good Luck!

    Balancing Cooling Towers:

    Cooling Tower Balancing

    Make sure the measurements are collected in both radial directions. I use one direction as inline with the drive shaft and the other direction 90 degrees to this direction. Use the direction that has the higher amplitude. Always double check to see that the final vibration has lowered both directions. I have seen where lowering one direction has raised the other direction. I suspect this tower had more than a balance issue.

    Most of the time I find that the drive shaft where a jack shaft is used to connect the motor to the gearbox also may need to be balanced. Most shafts have 3 to 4 locations for balance weights. Weights can normally be installed on both ends of the shaft coupling. In this case a 2 plane balance would be preferred.

    Always check the shaft alignment before proceeding to balancing the shaft.

    Use the same proceedure as listed in the fan balancing listed to the left.

    Good Luck!


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