VCI MAX Data Collector

You may want to post this question in the Mechanical Acoustics/Vibration forum.

I'm not familiar with this data collector, but I'll try to answer the fundamentals of your questions.

1) You need to put trial weights in two separate planes. A 0 weight does nothing for you. The colletor may be able to handle leaving the 1st trial weight in place (plane 1). This can be preferable for time considerations or if the 1st trial weight reduces the vibration amplitudes.

2) I'm not sure. If it won't take a negative for the weight value, just change the weight location by 180 degrees (i.e. -5 ounces @ 45 degrees = 5 ounces @ 225 degrees).

3) I'm not sure what the software is exactly asking. The high spot corresponds to the positon on the rotating memeber represented by the 1X phase angle. If your rotor is operating at a speed well below the 1st balance resonance (critical speed), then the high spot (measured in displacement) should be equal/close to the heavy spot. If you use velocity or acceleration, the relationships between the high/heavy spots changes.

spciesla,
Thank you for the help.
1) I have worked with a vibration vendor who uses CSI equipment. With the CSI equipment he takes his initial reading, installs a trial weight in one plane and looks at the data. If he improves the balance with the trial weight he can skip adding the second trial weight and actually begin using the software to calculate the balance weight and position. If he changes the amplitude and phase but not in the correct direction, he will add the second trial weight and then use the software. Basically it allows him to skip a step if he gets lucky on the first balance weight.
2)Good idea.
3)When you say if I use velocity or acceleration, the relationship between the high spot changes:
A) Does this mean that by using displacement that the heavy spot is at the high spot?
B) Does this mena that if I use acceleration or velocity that the high spot does not equal the heavy spot? If this is the case does this mean that the low spot would be preferrable parameter to select?

Let me try to clarify some things:

1) The number of balance planes needed depends on the physical characteristics of your rotor (mass, stiffness, length, etc.) and operating speed. You should know where the rotor is operating (which mode) before you start balancing. What kind of equipment are you trying to balance? What are the operating speed(s)?

3) When dealing with phase lag (fairly normal convention for vibration measurements) the following relationships hold:

Phase(displacement) = Phase(velocity) + 90 deg = Phase (acceleration) +180 deg

Well below the 1st balance resonance (critical speed), the displacement phase (high spot) is "equal" to the phase of the heavy spot. Using the equation above, the velocity phase is 90 degrees out and the acceleration phase is 180 degrees out.

An excellent reference is:
Machinery Malfunction Diagnosis and Correction by Robert C. Eisenmann (ISBN: 0132409461)

Thank you again for your help.
1) We are balancing a crusher roll. The roll is supported on each side by a spherical roller bearing. The roll itself is approximately 4' in diameter and 5' long. The roll has several elements (teeth). The elements and the crusher roll wear continyously. We always make sure the the roll is built up and the elements are in good condition prior to balancing. The bearings themselves can float. When I say float, I don't mean just in the axial direction as in float and fixed bearings. Rather the pedestal which supports the bearings has a certain amount of vertical and horizontal movement to lessen the impact of extremely large or hard piece of rock. The floating nature of the bearing can make balancing difficult. The roll turns and 412 RPM. I generally place an accelerometer on each bearing in the horizontal position. I have been collecting the data in accerlation to avoid any integration errors. It would not be difficult to collect the data in displacement, I'll just need to filter the integration error out.

VCI is a small company, may be tough to find end users randomly - you should contact their tech support at tech@vibcons.com or phone: (813) 839-2826



Dave G.