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Mechanical looseness occurs when there is improper fit between component parts in rotating machinery. This can cause increased vibration and noise. There are two main types of mechanical looseness: 1) rotating looseness between rotating and stationary elements, and 2) structural looseness between a machine and its foundation. Structural looseness specifically increases 1x vibration in the direction of least stiffness, often horizontally. Proper component fits and machine mounting are necessary to prevent mechanical looseness issues.
Powerpoint getmek (v.1)
- 1. MECHANICAL LOOSENESS Gilang Sandy Firdaus (15/385231/TK/43893) Hotjon Junadi Simanullang (15/385235/TK/43897) Jumalin (15/385239/tk/43901) Faris Yoga Andhika (15/385226/TK/43888)
- 2. Mechanical Looseness • An improper fit between component parts. If we consider in rotating machine the looseness causes machine can’t rotating perfectly. So the vibration will be an amplifier that mean produce a loudly sound. • When a component is loose, whatever forces are present will be able to move the affected components much more easily. If there are a little or no forces present, however, vibration may only increase a very small amount.
- 3. 1. Internal assembly looseness : • This category of looseness could be between a bearing liner in its cap, a sleeve or rolling element bearing, or an impeller on a shaft. • It is normally caused by an improper fit between component parts, which will produce many harmonics in the Fast Fourire Transformation (FFT) due to the nonlinear response of the loose parts to the exciting forces from the rotor.
- 4. • Mechanical looseness is often highly directional and may cause noticeably different readings when they are taken at 30° increments in the radial direction all around the bearing housing. • Also note that looseness will often cause sub-harmonic multiples at exactly ½× or _× rpm
- 5. •Structural Looseness Symptoms : High radial vibration harmonics of 1x. •Harmonics can stretch all the way across the spectrum in cases of severe looseness and can even generate half-harmonics in extreme cases (1.5, 2.5, 3.5, etc.).
- 6. 2. Structure Looseness : • This type of looseness is caused by structural looseness or weaknesses in the machine’s feet, baseplate or foundation. It can also be caused by deteriorated grouting, loose hold- down bolts at the base and distortion of the frame or base. • This weakness allows the machine to vibrate more freely in the direction where the weakness is greatest, therefore vibration at turning speed will be elevated.
- 7. • Structural looseness will generate a strong 1X in the direction of greatest weakness – unless there is impacting, in which case there will also be harmonics. To distinguish looseness : • If 1X horizontal more than twice the amplitude of 1X vertical, looseness is suspected. If that amplitude ratio changes when the machine speed is changed the resonance should be suspected.
- 8. 3. Looseness between machine and base-plate : • This problem is associated with loose pillow- block bolts, cracks in the frame structure or thebearing pedestal. • Looses causes higher vibration than normal so it can make the component wear quickly and damaged. Below show the ilustration of looseness between machine and base-plate
- 9. • The FFT of mechanical looseness between machine and baseplate :
- 10. There are two types of mechanical looseness 1. Rotating looseness and non-rotating looseness 2. Structural looseness
- 11. Rotating Looseness and Non-Rotating Looseness • Caused by excessive clearance between rotating and stationary elements of machine • Looseness between two normally stationary parts, such as a foot and a foundation, or a bearing housing and a machine
- 12. Structural Looseness • looseness between a machine and its foundation, will increase the 1x vibration component in the direction of least stiffness • Usually the horizontal direction • Depends on the pshisycal layout of the machine