Oil and Gas

FERRITE TEST

2010-08-11T11:42:00.003+04:00

A. Effects of Ferrite Content. Fully austenitic stainless steel weld deposits have a tendency to develop small fissures even under conditions of minimal restraint. These small fissures tend to be located transverse to the weld fusion line in weld passes and base metal that were reheated to near the melting point of the material by subsequent weld passes. Cracks are clearly injurious defects and cannot be tolerated. On the other hand, the effect of fissures on weldment performance is less clear, since these micro-fissures are quickly blurted by the very tough austenitic matrix. Fissured weld deposits have performed satisfactorily under very severe conditions. However, a tendency to form fissures generally goes hand-in-hand with a tendency for larger cracking, so it is often desirable to avoid fissure-sensitive weld metals.

B. The presence of a small fraction of the magnetic delta ferrite phase in an otherwise austenitic (nonmagnetic) weld deposit has an influence in the prevention of both centerline cracking and fissuring. The amount of delta ferrite in as-welded material is largely controlled by a balance in the weld metal composition between the ferrite-promoting elements (chromium, silicon, molybdenum, and columbium are the most common) and the austenite-promoting elements (nickel, manganese, carbon, and nitrogen are the most common). Excessive delta ferrite, however, can have adverse effects on weld metal properties. The greater the amount of delta ferrite, the lower will be the weld metal ductility and toughness. Delta ferrite is also preferentially attacked in a few corrosive environments, such as urea. In extended exposure to temperatures in the range of 900 to 1700°F (482 to 927°C), ferrite tends to transform in part to a brittle intermetallic compound that severely embrittles the weldment.

C. Portable ferrite indicators are designed for on-site use. Ferrite content of the weld deposit may indicated in percent ferrite and may be bracketed between two values. This provides sufficient control in most applications where minimum ferrite content or a ferrite range is specified.

BP disaster In 60 min (Part I)

2010-07-14T09:15:00.001+04:00

BP disaster In 60 min (Part II)

2010-07-14T09:12:00.002+04:00

HARDENING AND TEMPERING

2010-05-30T00:35:00.016+04:00

HARDENING AND TEMPERING

Heat treatment of steel in a school workshop is normally a two stage process. For example, if a high carbon steel or silver steel screw driver blade has been manufactured, at some point it will have to be ‘’hardened’ to prevent it wearing down when used. On the other hand it will have to be ‘tempered’. This second heating process reduces the hardness a little but toughens the steel. It also significantly reduces the brittleness of the steel so that it does not break easily. The whole process is called ‘hardening and tempering’.

STAGE ONE:

The screw driver blade is heated, slowly at first, warming up the whole blade. Then the heat is concentrated on the area at the end of the blade. This gradually becomes ‘red’ hot.

STAGE TWO:

The screw driver blade is removed quickly from the brazing heart, with blacksmiths tongs and plunged into clean, cold water. Steam boils off from the water as the steel cools rapidly. At this stage the blade is very hard but brittle and will break easily.

STAGE THREE:

The screw driver blade is cleaned with emery cloth and heated again on the brazing hearth. Heat is concentrated at the end of the steel blade. The steel must be watched very carefully as it changes colour quite quickly. A blue line of heat will appear near the end of the blade and it travels towards the tip as the temperature rises along the blade. When the line of blue reaches the tip the brazing torch is turned off. The blue indicates the correct temperature of ‘tempering’.

STAGE FOUR:

The screw driver blade is placed on a steel surface, such as an anvil face. This conducts the heat away and allows slow cooling of the screw driver blade. When cold, the blade should be tough and hard wearing and unlikely to break or snap. This is due to the tempering process.

What is Remnant Life Assessment (RLA)?

2010-03-22T10:24:00.000+04:00

Life prediction and management of cracked high temperature structures is a matter of great importance for both economical and safe reasons. To implement such a task, many fields such as material science, structure engineering and mechanics science etc. are involved and expertise is generally required. In terms of the methodology of advanced time-dependent fracture mechanics, this paper developed an expert system to realize an appropriate combination of material database, condition database and knowledge database. Many assessment criteria including the multi-defects interaction and combination, invalidation criterion and creep-fatigue interaction are employed in the inference engine of expert system. The over-conservativeness of life prediction from traditional method is reduced reasonably and therefore the accuracy of predicted life is improved. Consequently, the intelligent and expert life management of cracked high temperature structures is realized which provides a powerful tool in practice.

What is Fitness for Service (FFS)?

2010-03-22T10:22:00.000+04:00

Fitness for service assessment is multi-disciplinary engineering analysis of equipment to determine if it is safe and fit for continued service until the end of some desired period of operation (for example, until the next shutdown, until some specific future date, or until the end of its useful life).
Fitness for service assessment may be required, because the equipment may:
• Contain Flaws Such as Locally Thin Areas (LTAs) or Cracks
• Not Meet Current Design Standards
• Operate Under More Severe Conditions than Originally Expected
The main products of fitness for service assessment are (1) decisions to run, alter, repair, monitor, or replace equipment and (2) guidance on equipment inspection intervals.
Fitness for service assessment employs analytical methods, mainly stress analysis, to evaluate flaws such as locally thin areas and cracks as well as damage such as dents, bulges, and distortions.
Fitness for service assessment is multi-disciplinary engineering analysis of equipment to determine if it safe and fit for continued service until the end of some desire

D Scan

2009-12-17T13:22:00.002+04:00

D-scan refers to the image produced when the data collected from an ultrasonic inspection is plotted on an end view of the component. The true definition according to BS EN 1330-4:2000 is the 'Image of the results of an ultrasonic examination showing a cross-section of the test object perpendicular to the scanning surface and perpendicular to the projection of the beam axis on the scanning surface'.

The D-scan view is perpendicular to both the C-scan and the B-scan. However, like the C-scan, the D-scan usually shows ultrasonic data collected through the whole or part of the inspection volume.
The D-scan allows quick discrimination of indications along a weld by presenting their position in depth from the scanning surface. D-scans are often used in the presentation and analysis of TOFD data.

C Scan

2009-12-17T12:48:00.002+04:00

The C-scan presentation provides a plan-type view of the location and size of test specimen features. The plane of the image is parallel to the scan pattern of the transducer. C-scan presentations are produced with an automated data acquisition system, such as a computer controlled immersion scanning system. Typically, a data collection gate is established on the A-scan and the amplitude or the time-of-flight of the signal is recorded at regular intervals as the transducer is scanned over the test piece. The relative signal amplitude or the time-of-flight is displayed as a shade of gray or a color for each of the positions where data was recorded. The C-scan presentation provides an image of the features that reflect and scatter the sound within and on the surfaces of the test piece.
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a two dimensional presentation of data displayed as a top or planar view of a test piece, similar in its graphic perspective to an x-ray image, where color represents the gated signal amplitude or depth at each point in the test piece mapped to its position. Planar images can be generated on flat parts by tracking data to X-Y position, or on cylindrical parts by tracking axial and angular position. For conventional ultrasound, a mechanical scanner with encoders is used to track the transducer's coordinates to the desired index resolution. The images that follow conceptually show C-scans of a reference block made with a conventional immersion scanning system using a focused immersion transducer.
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C-scan from a phased array system is very similar to the one from the conventional probe seen above. With phased array systems however, the probe is typically moved physically along one axis while the beam electronically scans along the other according to the focal law sequence. Signal amplitude or depth data is collected within gated region of interest just as in conventional C-scans. In the case of phased arrays, data is plotted with each focal law progression, using the programmed beam aperture.

B scan

2009-12-17T12:41:00.001+04:00

A Single Value B-scan is commonly used with conventional flaw detectors and corrosion thickness gages to plot the depth of reflectors with respect to their linear position. The thickness is plotted as a function of time or position while the transducer is scanned along the part to provide its depth profile. Correlating ultrasonic data with actual transducer position allows a proportional view to be plotted and allows the ability to correlate and track data to specific areas of the part being inspected. This position tracking is typically done through the use of electromechanical devices known as encoders. These encoders are used in fixtures which are either manually scanned or in automated systems that move the transducer by a programmable motor-controlled scanner. In either case the encoder records the location of each data acquisition with respect to a desired user-defined scan pattern and index resolution.

In the case below, the B-scan shows two deep reflectors and one shallower reflector, corresponding to the positions of the side drilled holes in the test block.
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The B-scan presentations is a profile (cross-sectional) view of the test specimen. In the B-scan, the time-of-flight (travel time) of the sound energy is displayed along the vertical axis and the linear position of the transducer is displayed along the horizontal axis. From the B-scan, the depth of the reflector and its approximate linear dimensions in the scan direction can be determined. The B-scan is typically produced by establishing a trigger gate on the A-scan. Whenever the signal intensity is great enough to trigger the gate, a point is produced on the B-scan. The gate is triggered by the sound reflecting from the backwall of the specimen and by smaller reflectors within the material. In the B-scan image above, line A is produced as the transducer is scanned over the reduced thickness portion of the specimen. When the transducer moves to the right of this section, the backwall line BW is produced. When the transducer is over flaws B and C, lines that are similar to the length of the flaws and at similar depths within the material are drawn on the B-scan. It should be noted that a limitation to this display technique is that reflectors may be masked by larger reflectors near the surface.

A Scan

2009-12-17T11:32:00.005+04:00

A scan is an amplitude modulation scan. It gives the information in the form of one dimensional. it is used to detect the presence of flaws in the materials. A-scan ultrasound biometry, commonly referred to as an A-scan

A data presentation method by which intelligence signals from a signal object located are displayed. As generally applied to pulse echo ultrasonics, the horizontal and vertical sweeps are proportional to time or distance and amplitude or magnitude respectively. Thus the location and magnitude of acoustical interface are indicated as to depth below the transducer.

The most basic presentation of ultrasonic waveform data is in the form of an A-scan, or waveform display, in which echo amplitude and transit time are plotted on a simple grid with the vertical axis representing amplitude and the horizontal axis representing time. The example below shows a version with a rectified waveform; unrectified RF displays are also used. The red bar on the screen is a gate that selects a portion of the wave train for analysis, typically measurement of echo amplitude and/or depth.

Isotope

2009-09-26T18:57:00.003+04:00

isotope , in chemistry and physics, one of two or more atoms having the same atomic number but differing in atomic weight and mass number. The concept of isotope was introduced by F. Soddy in explaining aspects of radioactivity; the first stable isotope (of neon) was discovered by J. J. Thomson. The nuclei of isotopes contain identical numbers of protons, equal to the atomic number of the atom, and thus represent the same chemical element, but do not have the same number of neutrons. Thus isotopes of a given element have identical chemical properties but slightly different physical properties and very different half-lives, if they are radioactive (see half-life ). For most elements, both stable and radioactive isotopes are known. Radioactive isotopes of many common elements, such as carbon and phosphorus, are used as tracers in medical, biological, and industrial research. Their radioactive nature makes it possible to follow the substances in their paths through a plant or animal body and through many chemical and mechanical processes; thus a more exact knowledge of the processes under investigation can be obtained. The very slow and regular transmutations of certain radioactive substances, notably carbon-14, make them useful as "nuclear clocks" for dating archaeological and geological samples. By taking advantage of the slight differences in their physical properties, the isotopes may be separated. The mass spectrograph uses the slight difference in mass to separate different isotopes of the same element. Depending on their nuclear properties, the isotopes thus separated have important applications in nuclear energy. For example, the highly fissionable isotope uranium-235 must be separated from the more plentiful isotope uranium-238 before it can be used in a nuclear reactor or atomic bomb .

The Columbia Encyclopedia, Sixth Edition | 2008 | The Columbia Encyclopedia, Sixth Edition. Copyright 2008 Columbia University Press

Radioactive Isotopes

2009-09-26T17:44:00.003+04:00

radioactive isotope or radioisotope, natural or artificially created isotope of a chemical element having an unstable nucleus that decays, emitting alpha, beta, or gamma rays until stability is reached. The stable end product is a nonradioactive isotope of another element, i.e., radium-226 decays finally to lead-206. Very careful measurements show that many materials contain traces of radioactive isotopes. For a time it was thought that these materials were all members of the actinide series ; however, exacting radiochemical research has demonstrated that certain of the light elements also have naturally occurring isotopes that are radioactive. Since minute traces of radioactive isotopes can be sensitively detected by means of the Geiger counter and other methods, they have various uses in medical therapy, diagnosis, and research. In therapy, they are used to kill or inhibit specific malfunctioning cells. Radioactive phosphorus is used to treat abnormal cell proliferation, e.g., polycythemia (increase in red cells) and leukemia (increase in white cells). Radioactive iodine can be used in the diagnosis of thyroid function and in the treatment of hyperthyroidism. Since the iodine taken into the body concentrates in the thyroid gland, the radioaction can be confined to that organ. In research, radioactive isotopes as tracer agents make it possible to follow the action and reaction of organic and inorganic substances within the body, many of which could not be studied by any other means. They also help to ascertain the effects of radiation on the human organism (see radiation sickness ). In industry, radioactive isotopes are used for a number of purposes, including measuring the thickness of metal or plastic sheets by the amount of radiation they can stop, testing for corrosion or wear, and monitoring various processes.

Oil platform

2009-08-23T02:17:00.002+04:00

An offshore platform, often referred to as an oil platform or an oil rig, is a large structure used to house workers and machinery needed to drill wells in the ocean bed, extract oil and/or natural gas, process the produced fluids, and ship or pipe them to shore. Depending on the circumstances, the platform may be fixed to the ocean floor, may consist of an artificial island, or may float.

Most offshore platforms are located on the continental shelf, though with advances in technology and increasing crude oil prices, drilling and production in deeper waters has become both feasible and economically viable. A typical platform may have around thirty wellheads located on the platform and directional drilling allows reservoirs to be accessed at both different depths and at remote positions up to 5 miles (8 kilometers) from the platform.

Remote subsea wells may also be connected to a platform by flow lines and by umbilical connections; these subsea solutions may consist of single wells or of a manifold centre for multiple wells

SafeRad

2009-08-23T01:36:00.005+04:00

The Small Area For Exposure Radiography allows a number of units to be operated simultaneously in a small area to give very high production rates that can easily keep pace with production. There are no size or configuration limits. SafeRad Radiography systems are consistently helping our clients to meet their production targets and maintain schedules, without any exclusion zones.

The SafeRad Radiography System eliminates the need to evacuate personnel.
GammaBlok is the trademark of our patented radiation attenuation high density plastic.
Selenium-75 radioactive isotopes are used in the SafeRad Radiography Exposure container to give high quality radiographs.
Saferad Ltd also design and manufacture equipment and materials for pipeline radiography safety.

Unlike other companies we don't dilute our efforts on other forms of non-destructive testing equipment. Our equipment is designed by specialists to meet the most demanding requirements of safety and productivity to deliver to you the very best radiography system in the world.

SafeRad Ltd are committed to a programme of continual development to ensure that you have the latest innovative equipment available.

Article from (http://www.saferad.com)

Stopple concept animation

2009-03-08T19:39:00.001+04:00

hot tapping

2009-03-08T19:29:00.000+04:00

Hot tapping, or pressure tapping, is the method of making a connection to existing piping or vessels without the interruption of emptying that section of pipe or vessel. Hot tapping is also the first procedure in line stopping, where a hole saw is used to make an opening in the pipe, so a line plugging head can be inserted.

Hot tapping can be performed on pipes carrying natural gas, water, sewage, steam, petroleum products, and chemicals, and on any type of pipe.

INCOTEST

2009-02-01T23:37:00.003+04:00

INCOTEST(an acronym for INsulated COmponent TEST) formerly known as ARCO-TEMP, is a unique corrosion survey method that allows ferrous pipes and vessels to be surveyed through thermal insulation under the following demanding circumstances: without disturbing the insulation or coating

when insulation is aluminium, stainless steel or low alloy steel clad
while plant is in operation
when pipes are hot: up to 500°C (930°F) or cold: down to -100°C (-150°F)
when insulation is wet
when object surface is rough or encrusted
when insulation is irregular or heterogeneous
when insulation is wire mesh reinforced.
Merits
robust, electrically safe but not intrinsically safe
operates over a wide range of climatic conditions
can work up to 8 hours on one battery pack
transducer can be up to 30 metres from the base unit
provides a computed thickness reading within seconds
high reproducibility + or - 0.1mm, hence very suitable for recurrent measurements
measures through any non-conductive and non-magnetic material, eg insulation (with metal skirt either aluminium, stainless steel or low alloy galvanised steel) concrete, fire retarder, up to 100mm thickness and up to 150mm when wall thickness is below 12.7mm
detects and measures average general corrosion or erosion over interrogated area (footprint), depending on insulation thickness
provides instant site report in measuring matrix format.
Technology
INCOTEST monitors the decay of an eddy current pulse within the steel wall. It computes the average thickness of the metal by comparing the transient time ("echo") of certain signal features with similar calibration tests.
The resulting measurement is influenced by a number of factors including variations in metallurgy (magnetic and electrical properties) and temperature. The survey takes 2 to 40 seconds dependent on thickness. The computed wall thickness (can be logged) and validation signal is displayed on the screen, and raw data is stored for later retrieval.

Typical applications
detection of CUI (corrosion under insulation)
detection of FAC (flow accelerated corrosion)
riser pipe wall thickness gauging without removal of marine growth, neoprene or Monel
a proven potential method for non-contact "dry" wall thickness measurements of dirty, coated, rough and/or high temperature objects.

Positive Material Identification (PMI)

2009-01-25T22:46:00.006+04:00

Positive Material Identification (PMI)

The Objective

While engineers push the boundaries of material capacities to their limits in the design, traceability of proper material becomes ever more important. In addition to compatibility issues, several other reasons can exist for material specification including design, corrosion resistance, and compliance to codes and standards such as ASME Boiler and Pressure Vessel Code.

Quality procedures are put in place to document materials as they are received and as they move through the production process, but what happened to those raw materials before they arrived at the receiving dock? Each time raw material changes hands - from the mill to service centers, from processing plants (e.g., pipe, tube and fittings) to subcontractors – the opportunity for error increases, resulting in questionable material quality.

The Solution

With Positive Material Identification (PMI) the alloy composition, and thus, the identity of materials can be determined. If a material certificate is missing or/and you need to be certain about the type of material used, PMI as an NDT method is the best solution. Positive Material Identification is particularly used for high quality metals like stainless steel and high alloy metals.

Magnetic flux leakage (MFL)

2009-01-18T23:38:00.001+04:00

Magnetic flux leakage (MFL) is a magnetic method of nondestructive testing that is used to detect corrosion and pitting in steel structures, most commonly pipelines and storage tanks. The basic principle is that a powerful magnet is used to magnetize the steel. At areas where there is corrosion or missing metal, the magnetic field "leaks" from the steel. In an MFL tool, a magnetic detector is placed between the poles of the magnet to detect the leakage field. Analysts interpret the chart recording of the leakage field to identify damaged areas and hopefully to estimate the depth of metal loss. This article currently focuses mainly on the pipeline application of MFL, but links to tank floor examination are provided at the end.
MFL principle
As an MFL tool navigates the pipeline a magnetic circuit is created between the pipewall and the tool. Brushes typically act as a transmitter of magnetic flux from the tool into the pipewall, and as the magnets are oriented in opposing directions, a flow of flux is created in an elliptical pattern. High Field MFL tools saturate the pipewall with magnetic flux until the pipewall can no longer hold any more flux. The remaining flux leaks out of the pipewall and strategically placed tri-axial Hall effect sensor heads can accurately measure the three dimensional vector of the leakage field.
Given the fact that magnetic flux leakage is a vector quantity and that a hall sensor can only measure in one direction, three sensors must be oriented within a sensor head to accurately measure the axial, radial and circumferential components of an MFL signal. The axial component of the vector signal is measured by a sensor mounted orthogonal to the axis of the pipe, and the radial sensor is mounted to measure the strength of the flux that leaks out of the pipe. The circumferential component of the vector signal can be measured by mounting a sensor perpendicular to this field. Earlier MFL tools recorded only the axial component but high-resolution tools typically measure all three components. To determine if metal loss is occurring on the internal or external surface of a pipe, a separate eddy current sensor is utilized to indicate wall surface location of the anomaly. The unit of measure when sensing an MFL signal is the gauss or the tesla and generally speaking, the larger the change in the detected magnetic field, the larger the anomaly.

Phased Array (PA)

2009-01-14T23:38:00.004+04:00

Phased Array (PA) ultrasonics is an advanced method of ultrasonic testing that has applications in medical imaging and industrial nondestructive testing, originally pioneered by Albert Macovski of Stanford University.[1] In medicine a common application of phased array is the imaging of the heart (images of the fetus in the womb are usually made by curvilinear array, a multi-element probe that does not actually phase the signals). When applied to steel the PA image shows a slice that may reveal defects hidden inside a structure or weld.

Principle of operation

The PA probe consists of many small ultrasonic elements, each of which can be pulsed individually. By varying the timing, for instance by pulsing the elements one by one in sequence along a row, a pattern of interference is set up that results in a beam at a set angle. In other words, the beam can be steered electronically. The beam is swept like a search-light through the tissue or object being examined, and the data from multiple beams are put together to make a visual image showing a slice through the object.

Time Of Flight Diffraction (TOFD)

2009-01-14T23:31:00.003+04:00

The Time Of Flight Diffraction (TOFD) is a Advanced NDT method developed in the 70's by AEA. AEA Sonomatic specializes in this method.
This method differs from traditional pulse echo technique in that it monitors diffracted signals at the edges of defects which are directly related to the true position and size of the defect, as opposed to the reflection on defects according to a reference reflector.
The TOFD technique uses two probes in a transmitter-receiver arrangement. When sound is introduced into the material via the transmitter the defect will oscillate. Each defect edge works as a source point of ultrasound signals. These very weak signals are called diffracted waves and their appearance does not relate to the orientation of flat or spherical defects. These diffracted signals are received via the receiver probe. The diffracted signals are evaluated with the Microplus-Systems to clear gray scale B-scan or D-scan images (transversal- or longitudinal projection of the object being tested).
The amplitude of the signal is not displayed , but the position of the signals on the time scale are. Thus it is possible to determine the defect location exactly - length, and defect height.
Therefore the Probability of Detection (POD) increases greatly (up to 90 % !) for flat or spherical defects when compared to traditional techniques.
By use of today's advanced computer techniques it is possible to evaluate signals very rapidly. That makes it possible to perform scans with a speed of hundreds of millimeters per second. In practice speed is limited only by the mechanic.
Applications for TOFD
The main TOFD applications are:
o In-service defect monitoring.
o Defect detection, documentation and evaluation during the production.
The dead zone under the outside surface has always been a limitation of TOFD. Defects close to the surface could not be detected (surface breaking cracks are detectable).. AEA Sonomatic succeeded in reducing this zone to 2 mm! For that reason TOFD can be applied down to 6 mm wall thickness. On the upper end it is usual to inspect up to 350 mm wall thickness.
Advantages of TOFD

• TOFD defect detection does not depend on the defect orientation, in contrast to the pulse echo technique .
• In contrast to the radiography method, planar defects and cracks, which are not perpendicular to the measured surface can be detected .
• Defect height can be exactly determined.
• Higher POD improves risk reduction and calculation.
• The evacuation of areas because of radiation is not necessary. That means less interruption in the production process less during pre-service or in-service inspections and fewer logistical problems for the manufacturer.
• The inspection results are immediately available, as is a permanent record and a permanent print as longitudinal or transversal projection of the weld is available.
• When Engineering Critical Assessment (ECA) is applied, only the relevant defect has to be cut, thereby preventing needless repairs which could harm the integrity of the weld.
• Because of the high test speed the costs are less than those for radiography for wall thickness above 25 mm.
• The inspection can be performed above 200° C.
• Since the Microplus-System is easy to transport, it is possible to perform test on all feasibly accessible areas.
• TOFD saves costs, if applied during construction, since it is possible to distinguish pre-service and in-service defects. That means the unit can stay longer in production, and is safe.

Hardness Testing (HT)

2009-01-14T23:23:00.002+04:00

HT: The hardness of steel is generally determined by testing its resistance to deformation. A number of methods are employed including Brinell, Vickers and Rockwell. The steel to be tested is indented by a hardened steel ball or diamond under a given load and the size of the impression is then measured. For steel there is an empirical relationship between hardness and tensile strength and the hardness number is often used as a guide to the tensile strength, e.g. 229 Brinell = 772N/mm2 (50 tons/sq.in).

Radiographic testing (RT)

2009-01-14T23:21:00.004+04:00

RT: A source of ionising radiation positioned at on one side of item to be inspected, and a photographic film placed in close proximity to the other side. The radiation is partly absorbed during transmission and differences in material thickness or absorption qualities are recorded on the film giving a full-size image showing internal detail. The higher the Material density more radiation absorbtion will occur.
Processed films are called radiographs, Industrial radiography requires X-rays or gamma rays to reveal hidden flaws in solid objects. X-ray radiography is generated electrically by means of a high voltage X-ray tube. Gamma rays are produced by the natural disintegration of nuclei in a radioactive isotope. Common types being Iridium 192 and Cobalt 60. Radiography's main benefits are that it provides a non-destructive method of detecting hidden flaws in materials and fabrications and provides a permanent record. Radiography is particularly good at detecting volumetric flaws such as voids, gas pores and solid inclusions, It is also good at determining the nature and dimensions (length and width) of flaws - however it cannot be used to measure through-thickness of defects.

Eddy Current (ECT)

2009-01-14T23:16:00.002+04:00

EC: Eddy Current can be used in two different manners, Firstly for finding surface and subsurface flaws, and Secondly for determining different metallurgical characteristics. Eddy current is based on the principle of measuring changes in the impedance of an electromagnetic coil as it is scanned over a surface of conductive material.
An alternating current in the coil produces a magnetic field that is induced in the material. To counter the coil's primary magnetic field, eddy currents are produced in the material. Eddy currents produce a secondary magnetic field H'B to oppose the coil's primary magnetic field HB. When the coil is scanned over a discontinuity, the secondary magnetic field is distorted, thereby changing the loading on the coil. Changes in coil loading directly affect the coil impedance, these changes are signified on the trace as a (possible) flaw

Penetrate testing (PT)

2009-01-14T23:13:00.004+04:00

PT: This method involves applying a visible or fluorescent dye to the surface. After application by immersion or spray the dye enters any discontinuities via capillary action. The component is wiped dry and any subsequent seepage from fissures is detected by drawing the liquid out into a white absorbent coating applied after drying off (See Diagrams Below). This method is suitable for any non ferrous components or material that is non absorbent. Typical applications are forged, cast or welded products.