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Vibrasindo

provide professional services in the diagnosis and monitoring system with the totality of the machines and realialibility data

Tell-tale Signs of Faults in Mechanical Equipment

 

Misalignment
• High amplitudes at 1X, 2X, and sometimes 3X
• Typically 180 degree (+/- 30) across coupling on shaft:
- Axial for angular
- Radial for parallel
• Cocked bearing - twisting motion:
- 180 degree (+/- 30) top-to-bottom or side-to-side

Unbalance
• High amplitudes at 1X
• Typically 90-degree (+/- 40) from horizontal to vertical
• Phase differences - left and right positions should be stable, otherwise other issues:
- Looseness
- Misalignment
• Other faults need to be corrected before ever starting to correct balance
• Side-to-side phase to determine the unbalance type:
- 0 degrees indicates force (static) unbalance
- 180 degrees indicates couple unbalance

Resonance
• High amplitudes at 1X and other low orders of running speed
• 0 degree phase change on stationary points on machine
• 180 degree phase change indicates parts that are moving in opposite directions at running speed
• Varying machine speed at resonance:
- 180 degree change when moving from below resonance to above resonance
- 90 degree change at resonance
- Slight machine speed change results in large phase shifts

Eccentric Belt Pulley
• High 1X at running speed of pulley
• Phase difference of 0 or 180 degrees on horizontal and vertical readings (versus expected 90)
• Straight line motion in line with belts

Mechanical Looseness
• High amplitudes at multiples of 1X
• Sometimes multiples of 0.5X - E.g: 1.5X, 2.5X, etc.
• Fluctuating phase readings
• Around bearing at 30-degree intervals will be significantly different
• Soft Foot
• High amplitude peak at 1X
• 90 to 180-degree phase shift on machine foot to base
• Difference in phase reading on other feet