The technique is based on the ability of a liquid to be drawn into a “clean” surface-breaking flaw by capillary action. Fluorescent penetrant on surface seeps into the crack.
Emulsifies is applied to the penetrant. Emulsifier mixes with penetrant on the surface, but penetrant in the crack is not emulsified. Emulsifier makes the mixture washable.
Water spray removes the emulsified penetrant. Water removes the surface film as well. Developer draws the penetrant out of the crack.Black light causes the penetrant to glow in dark.
Magnetic particle inspection is a method that can be used to find surface and near surface flaws in ferromagnetic materials such as steel and iron.
The technique uses the principle that magnetic lines of force (flux) will be distorted by the presence of a flaw in a manner that will reveal it’s presence.
The flaw (for example, a crack) is located from the “flux leakage”, following the application of fine iron particles, to the area under examination.
Welder qualifications/Welding Procedure Welder certification is based on specially designed tests to determine a welder’s skill and ability to deposit sound weld metal. The main part of the welder’s test consists of welding one or more test coupons which are then examined using non-destructive and destructive methods. The extent of certification is described by a number of variables, which include the specific welding process, type of deposited metal, thickness, joint design, position, backing, and others. Most often, the test is conducted in accordance with a particular code. Depending on product requirements the test can be administered under the auspices of a national or international organization, such as the American Welding Society (AWS), or American Society of Mechanical Engineers (ASME), but manufacturers may specify their own standards and requirements as well. Most certifications expire after a certain time limit, and have different requirements for renewal or extension of the certification.
The welded sample or coupon is often tested at various stages of fabrication such as for Welding Procedure Qualification Record (WPQR), to qualify Welding Procedure Specification (WPS), to qualify welder as Welder Qualification Record ( WQ or WQR) and to accept the final product in the form of Production Weld test.
X-rays are produced by high voltage x ray machines whereas gamma rays are produced from radioactive isotopes such as Iridium 192 .The x-ray or gamma rays are placed close to the material to be inspected and they pass through the material and are then captured on film.This film is then processed and the image is obtained as a series of gray shades between black and white.The choice of which type of radiation is used (x ray or gamma ) depends on the thickness of the material to be tested. Gamma sources have the advantage of portability which makes
them ideal for use in construction site working.X-rays and gamma rays are very hazardous. Special precautions must be taken when performing radiography.
Ultrasonic inspection uses sound waves of short wavelength and high frequency to detect flaws or measure material thickness. It is used on aircraft, the power stations generating plant, or welds in pressure vessels at an oil refinery or paper mill. Usually pulsed beams
of high frequency ultrasound are used via a hand- held transducer which is placed on the specimen. Any sound from that pulse that returns to the transducer like an echo is shown on a screen which gives the amplitude of the pulse and the time taken to return to the
transducer. Defects anywhere through the specimen thickness reflect the sound, back to the transducer. Flaw size, distance and reflectivity can be interpreted.
