Download - Vibration Analysis Predictive Technologies PdM Techniques.

Vibration Analysis

Predictive Technologies

PdM Techniques

Richard HenryVibration and Alignment Specialist

VibrAlign, Inc.

Cardan Shaft Misalignment Identification

Cardan shafts (shafts with universal joints) are often neglected.

Cardan Shaft Alignment

Cardan Shaft Alignment Technical principle

Relative angular velocity


Degree of irregularity


Homokinetic operation is reached by a second cardan joint

Benefits of cardan shaft alignmentVibrations

Vibrations is transfered to gear box and motor

High wrap angle

Benefits of cardan shaft alignment Why is it important?

• Vital part in drives for process machines, breakage of cardan shafts causes down time.

• Badly aligned cardan shafts set limitation in production capacity and product quality.

• Stands for a considerable cost when repair is needed or a breakdown occurs.

• Badly aligned cardan shafts reduces lifetime in gearboxes and motors.

• Break down of a cardan shaft in running condition could be extremly dangerous.

Cardan Shaft Misalignment Typical vibration symptoms

• Unbalance of the drive line (high 1X).

Drive line will not have the same center of rotation as the U-Joints.

• High amplitude 2X and 4X driveline speed.

• Torsional oscilliation

Cardan shaft alignment Measurement principle

Angular error

Cardan shaft alignment Tolerances

No standard, but…

• Angular error within 0.25 mils/in

• Offset within specifications.

Cardan shaft alignment Procedure - Coning

Coning -axis of rotation

Cardan shaft alignmentCase story

Background:

A customer contracted VibrAlign to identify the source of an on-going U-Joint and Gearbox DE Bearing failure problem.

Reasons for the in depth analysis were:


• High vibration level.• Axial bearing had to be changed every 8-10 week.

Cost about $1500 every time.• Reduced production for about 10 hours at a cost about

$1000/hour for each failure.• Necessary to have bearings in stock.• Problem with thermal expansion (high bearing

temps).• No method to perform the alignment.


Vibralign arrived on site and collected initial vibration data. Vibration symptoms indicated severe cardan shaft misalignment.

Using a set of brackets specially designed to measure cardan shaft misalignment, we were able to identify an angular error of approximately 1.5 mils/inch of angularity in both the horizontal and vertical planes.


Vertical angular adjustments were made to the motor by shimming and the motor was repositioned horizontally.

The following spectra and waveforms clearly show an improvement to the operation of this machine.

Gearbox DE Vertical

Gearbox DE Horizontal

Gearbox DE Axial


Results:

• Significant decreasing vibration level.

• The alignment was performed in February -98 and no change of bearing in the gearbox has been done since then.

• Increased production capacity.