ULTRASONIC THICKNESS GAUGES & FLAW DETECTOR

1] Ultrasonic Thickness Gauge :

All ultrasonic thickness gauges must be calibrated to the velocity of sound of the material that they are measuring. Coatings such as paint, epoxy and bitumen have a velocity of sound which is around 1/3 of that of steel. Traditional Single Echo Technology measures the time taken for a single back wall echo to pass through the material under test as well as surface coating, giving an apparent material thickness measurement. With Multiple Echo, readings are taken by measuring the time delay between any three consecutive back wall echo’s which means that the coating thickness is completely ignored. Times of T2 and T3 are equal to the time that is takes to just travel through the metal. Only by looking at 3 Echo’s measurements can be automatically verified ( where T2=T3)

2] Ultrasonic Flaw Detector :

Of all the applications of industrial ultrasonic testing, flaw detection is the oldest and the most common. It governs the propagation of sound waves through solid materials used to detect hidden cracks, voids, porosity, and other internal discontinuities in metals, composites, plastics, and ceramics. High frequency sound waves reflect from flaws in predictable ways, producing distinctive echo patterns that can be displayed and recorded by detection instruments. Ultrasonic testing is completely Non destructive and safe, and it is a well established test method in many basic manufacturing, process, and service industries, especially in applications involving welds and structural metals.

3] Ultrasonic Transducers :

A transducer is a device that converts energy from one form to another form. Ultrasonic transducers convert electrical energy into high frequency sound energy and vice versa.

Transducers typically used for ultrasonic flaw detection utilizes an active element made up of piezoelectric ceramic, composite, or polymer. When this element is excited by a high voltage electrical pulse, it vibrates across a specific spectrum of frequencies and generates a burst of sound waves. When it is vibrated by an incoming sound wave, it generates an electrical pulse.

A coupling gel is used normally between the transducer and the test piece since sound energy at ultrasonic frequencies does not travel efficiently through gasses.

Types of ultrasonic transducers commonly used in flaw detection applications:
1. Contact Transducers
2. Angle Beam Transducers
3. Delay Line Transducers
4. Immersion Transducers
5. Dual Element Transducers