Vibration can be defined a simply the oscillating motion of a machine or machine component from its position of rest.
What Causes Vibration? These forces may be ones that:
ï Change direction with time, such as forces generated by rotating unbalance
ï Change in amplitude or intensity with time, such as forces generated in an induction motor due to unequal air gap between the motor armature and stator.
ï Friction between rotating and stationary machine components in much the same away that friction from a rosined bow causes a violin string to vibrate. Some of the most common problems that cause vibration include;
ï Misalignment of couplings, bearings an gear
ï Unbalance of rotating components
ï Looseness
Deterioration or rolling-elements bearings
ï Gear Wear
ï Aerodynamic/Hydraulic problems in fans, blowers and pump.

A Vibration Predictive Maintenance Program consists of three logical steps:
DETECTION The first step of the program, detection. Involves measuring and rending vibration levels at marked locations on each piece of equipment on a regularly scheduled basis. The objective is to real significant increases in a machine's' vibration level to warn of developing problems.
ANALYSIS The purpose of vibration analysis-to pinpoint specific equipment problems by revealing their unique vibration characteristics.
CORRECTION If a problem is detected, the obvious next step is to schedule correction.

Ultrasound is defined as a very high frequency sound waves that are not detectable by the human ear. By using special equipment, these sounds can be detected and analyzed.
What can Ultrasound Detect?
BEARING WEAR: ultrasound can be used to detect worn anti-friction bearings. Unlike vibration analysis, it does not have to be as close to the source because sound travels further than vibration.
LEAK DETECTION: It is useful for detection of air-borne noise caused by a leak of either pressure of a vacuum. It can also be used to detect a leak in an open vessel by using a sound generator.
ELECTRICAL PROBLEMS: When electricity escapes in high voltage, it jumps across a gap in the electrical connection. This causes a noise detected by ultrasound.
INTERNAL LEAKS: It is useful to detect internal leaks such as steam traps, valves or from one enclose area to another