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.
Using the VB analyzer
and the balancing program from the web site www.denysshen.com. 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.
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)