The part is placed between the radiation source and a piece of film. The part will stop some of the radiation. Thicker and denser area will stop more of the radiation. The film darkness (density) will vary with the amount of radiation reaching the film through the test object.These differences in "absorption" can be recorded on film, or electronically.
The energy of the radiation affects its penetrating power. Higher energy radiation can penetrate thicker and denser materials. The radiation energy and/or exposure time must be controlled to properly image the region of interest.
Two of the most commonly used sources of radiation in industrial radiography are x-ray generators and gamma ray sources. Industrial radiography is often subdivided into "X-ray Radiography" or "Gamma Radiography", depending on the source of radiation used.
Gamma rays are similar to X- Rays except that they have much shorter wavelength and differ in their origin. Gamma rays are emitted from the nucleus itself during the process of radioactivity. Gamma rays are produced by a radioisotope. A radioisotope has unstable nuclei that do not have enough binding energy to hold the nucleus together. The spontaneous breakdown of an atomic nucleus resulting in the release of energy and matter is known as radioactive decay.
Most of the radioactive material used in industrial radiography is artificially produced. This is done by subjecting stable material to a source of neutrons in a special nuclear reactor. This process is called activation.
Two most commonly used gamma ray sources in industrial radiography are iridium 192 and cobalt 60.
X - Rays are produced whenever high energy electrons suddenly give up energy. This can be done either by accelerating electrons to a high speed and then stopping them suddenly, or by these high speed electrons striking others and knocking them out of their normal positions. When these dislodged electrons fall back into place they give off X-Rays. X-rays are produced by establishing a very high voltage between two electrodes, called the anode and cathode. To prevent arcing, the anode and cathode are located inside a vacuum tube, which is protected by a metal housing. The cathode contains a small filament much the same as in a light bulb. Current is passed through the filament which heats it. The heat causes electrons to be stripped off. The high voltage causes these "free" electrons to be pulled toward a target material (usually made of tungsten) located in the anode. The electrons impact against the target. This impact causes an energy exchange which causes x-rays to be created.TOP
High-frequency sound waves are sent out at a material to find material changes.A pulse produces an electrical pulse that causes a piezoelectric transducer to send out a sound wave.Reflected waves are transformed back into electrical signals by the transducer and analyzed. Its main applications are in thickness gauging and flaw detection.
Ultrasonic inspections are largely performed by the pulse echo technique in which a single probe is used to both transmit and receive ultrasound. In addition to the fact that access is required from one surface only, further advantages of this technique are that it gives an indication of the type of defect, its size and its exact location within the item being tested. The major disadvantage is that pulse echo inspection is reliant upon the defects having the correct orientation relative to the beam in order to generate a returning signal to the probe and is not therefore considered fail safe. If the sound pulse hits the flaw at an angle other than 90o much of the energy will be reflected away and not return to the probe with the result that the flaw will not show up on the screen.
Through-transmission was used in the early days of UT and is still used in plate and bar production. A probe one side of a component transmits an ultrasonic pulse to a receptor probe on the other side. The absence of a pulse coming to the receiver indicates a defect.TOP
Magnetic Particle Inspection
Magnetic particle inspection (MPI) is a non-destructive testing (NDT) process for detecting surface and slightly subsurface discontinuities in ferroelectric materials such as iron, nickel, cobalt, and some of their alloys. The process puts a magnetic field into the part. The piece can be magnetized by direct or indirect magnetization. Direct magnetization occurs when the electric current is passed through the test object and a magnetic field is formed in the material. Indirect magnetization occurs when no electric current is passed through the test object, but a magnetic field is applied from an outside source. The magnetic lines of force are perpendicular to the direction of the electric current which may be either alternating current (AC) or some form of direct current (DC) (rectified AC).
The presence of a surface or subsurface discontinuity in the material allows the magnetic flux to leak, since air cannot support as much magnetic field per unit volume as metals. Ferrous iron particles are then applied to the part. The particles may be dry or in a wet suspension. If an area of flux leakage is present the particles will be attracted to this area. The particles will build up at the area of leakage and form what is known as an indication. The indication can then be evaluated to determine what it is, what may have caused it, and what action should be taken, if any.TOP
Liquid Particle Testing
Dye penetrant inspection (DPI), also called liquid penetrant inspection (LPI) or penetrant testing (PT), is a widely applied and low-cost inspection method used to locate surface-breaking defects in all non-porous materials (metals, plastics, or ceramics). The penetrant may be applied to all non-ferrous materials and ferrous materials, although for ferrous components magnetic-particle inspection is often used instead for its subsurface detection capability. LPI is used to detect casting, forging and welding surface defects such as hairline cracks, surface porosity, leaks in new products, and fatigue cracks on in-service components.
DPI is based upon capillary action, where low surface tension fluid penetrates into clean and dry surface-breaking discontinuities. Penetrant may be applied to the test component by dipping, spraying, or brushing. After adequate penetration time has been allowed, the excess penetrant is removed, a developer is applied. The developer helps to draw penetrant out of the flaw where a invisible indication becomes visible to the inspector. Inspection is performed under ultraviolet or white light, depending upon the type of dye used - fluorescent or nonfluorescent (visible).TOP
Time of Flight Diffraction
The TOFD technique was first applied in 1985 at the Harwell Center (UK) in response to insistent requests to size cracks in nuclear reactor welds. The TOFD technique is a fully computerized system able to scan, store, and evaluate indications in terms of height, length, scan, store, and evaluate indications in terms of height, length, and position with a grade of coverage, accuracy and speed not achieved by other ultrasonic techniques. The TOFD technique is based on diffraction of ultrasonic energy from tips of discontinuities, instead of geometrical reflection on the interface of the discontinuities.
This phenomena makes TOFD effective for identifying cracks and lack of fusion located along the vertical axis of the weld (in particular for narrow gap preparation) or with any other orientations, because defect detection is not affected by unfavourable orientation to the primary sound energy angle. unfavourable orientation to the primary sound energy angle. These features have extended the use of TOFD to replace Radiography and complex Ultrasonic inspection by tandem technique wherever planar defects (cracks, lack of fusion) are the main object of examination.
Four different types of waves are involved in the construction of a TOFD image: longitudinal wave generated by the transmitter and partially transformed in spherical wave when the beam crosses the tip of a defect the lateral wave that propagates near the surface between the two transducers .The longitudinal wave reflected by the backwall . The shear waves generated by the mode conversion L/T on the interface of discontinuities.TOP
Phased Array Ultrasonic Testing
Phased array (PA) ultrasonics is an advanced method of ultrasonic testing that has applications in medical imaging and industrial nondestructive testing. Common applications are to examine the heart noninvasively or to find flaws in manufactured materials such as welds. Single-element (non phased array) probes-known technically as monolithic probes-emit a beam in a fixed direction. To test or interrogate a large volume of material, a conventional probe must generally be physically turned or moved to sweep the beam through the area of interest. In contrast the beam from a phased array probe can be moved electronically, without moving the probe, and can be swept through a wide volume of material at high speed. The beam is controllable because a phased array probe is made up of multiple small elements, each of which can be pulsed individually at a computer-calculated timing. The term phased refers to the timing, and the term array refers to the multiple elements. Phased array ultrasonic testing is based on principles of wave physics that also have applications in fields such as optics and electromagnetic antennae.TOP
IRICO has full-fledged facilities and qualified welders for up-gradation of carbon steel, alloy steel and stainless steel castings. Radiographs will be evaluated to the required standards immediately and repairs / up-gradation will be undertaken. Pre heating of casting are done as per the specification using per heating furnaces. If required the casting are send for STRESS RELEVING in the furnance available with us.
IRICO has been already carrying out Radiography and up-gradation work for a few giant organizations like M/s. Bharat Heavy Electricals Limited, M/s AUDCO India Limited, Units at Manapakkam, Kanchipuram and Maraimalainagar, M/s. The KCP Limited, M/s. Peekay Steel Castings Limited, M/s. Sanamar Alloy Castings Limited, Viralimalai, M/s. Aruna Machine Tools Limited etc. to the entire satisfaction of the Inspectors and Clients.
- Peekay Steel Castings Limited - Calicut
- Sanmar Foundries Limited - Viralimalai
- Vee Yes Foundries - Coimbatore
- Super Alloys - Coimbatore
- G.S.Alloy Castings (P) Limited - Vijaywada
- ACC Nihon Castings Limited - Nagpur
- Ultimate Alloys (P) Ltd. - Coimbatore
- Best and Crompton Engineering Limited - Chennai
- Uttarpradesh Steels - Muzaffar Nagar
- Subhadra Alloy Castings - Trichy
- The K C P Limited - Chennai
- Aruna Alloys Steel Limited - Madurai
- Samco Metals and Alloys (P) Limited - Vellore
- Simplex Castings Limited - Raipur
- Sri Padma Balaji Steels (P) Ltd. - Coimbatore
- Auto Shell Castings Ltd. - Coimbatore
Visual inspection is one of the most common and most powerful means of non-destructive testing. Visual testing requires adequate illumination of the test surface and proper eye-sight of the tester. To be most effective visual inspection does however, merit special attention because it requires training (knowledge of product and process, anticipated service conditions, acceptance criteria, record keeping, for example) and it has its own range of equipment and instrumentation. It is also a fact that all defects found by other NDT methods ultimately must be substantiated by visual inspection. VT can be classified as Direct visual testing, Remote visual testing and Translucent visual testing. The most common NDT methods MT and PT are indeed simply scientific ways of enhancing the indication to make it more visible. Often the equipment needed is simple for internal inspection, light lens systems such as bore scopes allow remote surfaces to be examined. More sophisticated devices of this nature using fibre optics permit the introduction of the device into very small access holes and channels. Most of these systems provide for the attachment of a camera to permit permanent recording.
IRICO NDT material testing facility contains light meters, welding gauges, magnifiers, lenses, other measuring instruments and equipments for precise control of surface quality. Our NDT inspectors, engineers and technicians are qualified to NDT Level I, II as per written practice prepared according to ASNT recommended practice SNT-TC-1A and in-house ASNT NDT Level IIIs for providing inspection and consulting services.TOP