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  How to interpret Acceptance Criteria for Ultrasonic Testing as per AWS D1.1 The Requirements of Ultrasonic Flaw detector equipment as per AWS D1.1 Structural Steel Welding code is given below: Equipment: The ultrasonic equipment’s shall be pulse echo type ‘A’ scan suitable for use with transducers oscillating at frequencies between  1&6 MHz. The equipment shall have valid calibration certificate .The test  equipment shall have a calibrated gain control adjustable in discrete 1 or 2 Db steps over a range of at least 60Db. Probe: Transducers/ search units with following characteristics shall be used.              Angle beam :  70° ,60°,45° (within plus minus 2°).              Crystal Size:   Crystal size shall be square or rectangular in shape and may vary from 5/8 inch to 1 inch (15mm to 25mm) in width and from 5/8 inch to 13/16 inch (15mm...

 Non relevant Ultrasonic Indications can usually be identified as one of the following: Electrical Interference Interference form the transducer (search unit) Interference form the surface of the specimen Interference caused by mode conversion of the sound beam Interference caused by the shape of the specimen Interference caused by material structure Electrical interference can be caused by improper electrical connections of sound energy from the interface between the wedge and test specimen surface. In Immersion Testing, Air bubbles either on the transducer or specimen can cause reduced signal amplitude form the back surface and at times also from the front surface. Surface Interface A small amount of surface wave energy is usually transmitted in all directions around a transducer as shown below. If the transducer is near the edge of a plate, a signal may appear on the CRT.   When inspecting with shear waves, it is possible to detect a surface discontinuity with the small amo...

  Ultrasonic Testing In Ultrasonic Testing we use something called “Ultrasonic Vibrations” we must know two facts about a vibration: A vibration is a back and forth movement. A vibration is energy in motion A depression of a surface from its normal position is called a displacement. Vibrations pass through a solid material as a succession of particle displacements; this can be visualized as shown below: The structure of a material is actually many small particles or groups of atoms. These particles have normal or rest positions and can be displaced from these positions by some force, when the force is removed, the particles will tend to return to their original positions. Energy is transmitted through a solid material by a serious of small material displacements within the material. The transmission of Ultrasonic vibrations through a material is related to the elastic properties of the material. In Ultrasonic Testing a transducer made of Piezo-electric crystals is ...