Introduction to Vibration

WHAT IS VIBRATION?

• Vibration is the response of a system to an internal or external stimulus causing it tooscillate or pulsate.

OR"A response to some form of excitation".

Why to measure Vibration

• To Detect Machine Condition• To predict vibration fault• To avoid downtime• To Reduce Maintenenace Cost• To Reduce labor cost• To assist in RCA

Types of Maintenance

• Preventive Maintenance• Predictive Maintenance• Shutdown Maintenance• Proactive Maintenence

Vibration has three important parameters

• Frequency• Amplitude• Phase

Frequency

>>F=1/T• Hz• CPM• Orders

Amplitude

• Displacement• Velocity• Acceleration

Scale of Amplitude

Phase

• Phase is a relationshipe between events occuring at different times.

Types of Sensor

• Proximity Sensor• Velocity Transducer/Pickup• Accelerometer

Relationship of Sensors

Types of Mounting

• Hand Held Probe/Pin• Magnet• Stud/ Qucik Mount• Adhesive

Types of Mounting

Orientation for Vibration Measurement

• Horizontal• Vertical• Axial

Identifying Points

Motor & Pump

Vibration Monitoring VS Vibration Analysis

1.Vibration Monitoring2.Vibration Analysis

Vibration Analysis

• Vibration Analysis require data of machine taken through an Analyzer which produces:

Waveform & Spectrum

What is FFT (Fast Fourier Transfomation)

What is Waveform

Spectrum Analysis

• Spectrum (FFT) is the most commonly used plot for Vibration Analysis and Fualt Diagnosis.

• Spectrum is a plot on which frequency is on X-axis and Amplitude is on Y-Axis of the plot.

Most Common Faults

• Imbalance• MisalignmentLooseness

-Structural-Rotating

• Bearing faults• Gear box Faults• Resonance

Unbalance

• High 1X Radial Vibration

• Horizontal to Vertical Phase is 90 Degree

• Vibration is pure 1X high Peak

• Some other problems may confuse with unbalance

Static Imbalance

• The Geometeric Center and Rotational Axis are not co-linear but parallel to each other.

• Heavy Spot is at center of Axis Length but at away from C.G.

Couple Imbalance

• Heavy Spot at the both bearings differs by 180 Degree.

• The wobbling and rocking phenomenon appears at rotor.

• 1X Vibration at both the bearings appear.

Misalignment

• When Geometric Centreline of two coupled shafts are not co-linear along with axis of rotation then it is called Misalignment.

• Angular Misalignment• Off set Misalignment

Angular Misalignment

• Angular Misalignment: This condition exists when Shaft Axis of both the shafts concides at single point. they are no linear and relates to single point making an angle.

• Spectrum Shows 1X, 2X and 3X peaks

Off Set Alignment

• Off Set Misalignment is the type of Misalignment in which Geometric Centerlines of both the machines are parallel to each other.

• Dominant Peak is normally at 2X.

Looseness

Loosness is when their is any machine component is not fixed at its position as per intended purpose.

There are two types of Loosness.

1.Rotating Looseness2.Sturctural Looseness

Structural Looseness

• 1X high Vibration appear in the Spectrum

• Foundation and its Structural Bolts are Loose then this type of Problem exists.

Rotating Looseness

• 1X and its Multiples appear in the Spectrum

• Normally 1X ~ 10X or higher peaks appear in spectrum

• Waveform is almost consistant

Bearing Faults

• FTF• BPFI• BPFO• BSF

Bearing Failure Stages

• Zone A• Zone B• Zone C• Zone D

Gearbox

1.Gear Mesh Frequency2.GM= # of Teeth X RPM3.Side Bands4.Fault Identification