Radiographic test (RT) is a technique used for volumetric flaw detection. Short wavelength electromagnetic radiation such as X-rays penetrate the through thickness of the component and on to photographic films placed on the other side of the component. The film gets exposed to varying levels of radiation depending on the thickness of the penetrated material, and forms the latent images. Discontinuities within the component also affects the amount of radiation received by the film. Exposed films are then processed in dark room and developed radiographic images are viewed on illuminated screen for interpretation.
The most basic form of ultrasonic testing (UT) utilizes a high frequency, high energy cone of sound from a probe to “scan” the interior of a component for volumetric flaws or discontinuities. The sound wave is generated within the probe and transmitted into the component. The sound wave travels within the component and reflects off any internal features, including the walls of the component and any defects within it. As sound travels at a known, fixed speed within a given medium, the operator can predict when should an echo off the component wall be reflected back to the probe. An echo that is detected earlier than expected is therefore a sign of a discontinuity at that location. By moving the probe in a methodical manner across the surface of the component, an operator can not only measure the thickness of the component (Ultrasonic Thickness Gauge Measurement), but also detect any defects within it.
Due to the portable nature of the equipment, and the high accuracy in flaw detection and sizing, UT is often deployed to detect internal discontinuities in welded plate and pipes on site, and for measuring wall thicknesses of in-service pipes, boilers and pressure vessels.
Immersion Ultrasonic Testing is a variation of the standard UT technique. Instead of using a thin layer of oil or water-based gel to aid the transmission of soundwaves from the probe to the component, the soundwave is transmitted either via a jet of water (also known as a squirter) or by immersing the component into a tank of water. Immersion UT is therefore often automated or mechanized, and can carry out rapid, repeatable, and very accurate UT scans to collect data which can be further analyzed. This is unlike the standard, Manual A-Scan method, which does not normally leave a record of the scan.
Some applications for Tank Immersion type Immersion UT include the rapid detection of laminations, determination of Crack Area Ratio after HIC testing, as well as rapid inspection of welded plate coupons. Applications of water jet type Immersion UT include wall thickness measurement of small diameter, thin wall pipes such as those typically used in heat exchangers.
Emission spectrometry is a comparative analytical method in which a small amount of surface material is removed from the specimen. Recent developments in sensors and microelectronics have produced transportable systems that can be used on or adjacent to production lines. In some systems, light from the spark discharge is carried by fiber optics to the sensors, where the wavelengths and intensities of the several spectrum constituents are detected and measured. Photomultipliers are used with diffraction gratings to measure the intensities of preselected analytical lines in the spectrum. The numerical results are displayed in digital form on readouts or printed out in hard copy, or both.
At PTS, we are offering on-site OES tests. Our composition analysis for steel and stainless steel products are accredited to SINGLAS, under test method ASTM E751.
XRF is an acronym for X-ray fluorescence spectroscopy. XRF is a non-destructive analytical technique used to determine the elemental composition of materials. Handheld XRF analyzers work by measuring the fluorescent (or secondary) X-rays emitted from a sample when excited by a primary X-ray source.
Portable hardness test is a means of determining resistance to penetration (hardness) of a specimen and is occasionally employed to obtain a quick approximation of tensile strength. There are 3 types of portable hardness tests available:
All tests under this category are conducted on-site by acquiring portable hardness tester equipment.
Magnetic Particle Test (MT), is an NDT method that utilizes magnetic fields to attract small, ferromagnetic iron fillings towards fine surface breaking discontinuities in order to create a larger or higher contrast visible indication. The technique relies on magnetic fields that are either introduced into the component or generated within the component itself via an electrical current. As such, it can only be used on ferromagnetic or electrically conductive materials. MT is a very effective method of detecting surface cracks in welds, castings and forgings, and often more tolerant of poor surface conditions, making it ideal for inspecting in-service components. For high sensitivity requirements, such as in detecting fine fatigue cracks, the more sensitive Florescent MT technique can be used over the standard colour contrast MT, provided a suitably dark environment can be created on site.
Liquid penetrant test (PT) is used to detect surfacing breaking discontinuities on clean, dry, non-porous materials using dyes. The dye is called the penetrant, and may either be visible or fluorescent, which then has to be conducted under ambient light (visible method) and black light (Fluorescent method) respectively. It is a relative simple technique where the penetrant is applied to the component surface and is allowed to seep into any surface breaking discontinuities, such as cracks, via capillary action. Excess penetrant is removed via cleaning, and a developer is applied, causing the penetrant to resurface, forming a high contrast indication of the discontinuity.
The Feritscope operates by generating an alternating magnetic field in the sample which is proportional to the ferrite content and which the instrument can detect. The instrument, using a non-destructive magnetic method measures the relative permeability of a material in the alternating magnetic field of its probe. This provides a ferrite content reading, which is largely uninfluenced by various extrinsic parameters (lift-off, strain in specimen, curvature of specimen surface, thickness of welded material).
In-situ Metallography refers to the examination of the microstructure of a metallic component on site. It is typically considered a non-destructive method because the area of interest does not need to be extracted for examination in a lab. However, in practice, In-situ Metallography will require the removal of any paint coatings and the application of light grinding followed by etching before examination can be carried out. Examination of the polished and etched surface can then be carried out immediately by using a portable microscope with attached digital camera or alternatively, by making a replica of the microstructure using special resins or plastics followed by examining the replica in a laboratory.
In-situ Metallography can be used to determine the ferrite to austenite ratio in duplex stainless steel, estimate grain size in carbon and stainless steels as well as examining the general macrostructure and microstructure of a component. It has applications in examination of boilers, heat exchangers and reactors during annual shutdown maintenance, check the effects of post weld heat treatment processes on site, and to verify weld microstructure of very large fracture mechanics (CTOD) specimens prior to notching.
Ferroxyl test is used on stainless steel to detect iron contamination, including iron-tool marks, residual-iron salts from pickling solutions, iron dust, iron deposits in welds, embedded iron or iron oxide.
The copper sulfate test is intended to verify the effectiveness of the stainless steel passivation treatment. It can also be used to determine if there is a need for passivation.
The purpose of the copper sulfate test is to determine the presence of free iron which is often transferred onto the surface of a part during fabrication with steel components. The principle of the test is based on an oxidation-reduction reaction which causes the dissolved copper ions to deposit or plate out onto the locations of free iron particles.
Digital Radiography (DR) is a technique used for volumetric flaw detection. X-ray source penetrate through the sample of various density and the X-ray beam attenuated then hits the digital detector.
The attenuated X-ray beam is then digitized and the acquired information is sent to the workstation. Scanning result in digital format provides 65,536 different shades of grey to be analysed, enabling various possibility to detect defects and flaws within the scanned specimen.
Overview of Computed Tomography technique can be found here.
Computed Tomography is a technique whereby thousands of captured X-ray images are superimposed to form a 3D volume reconstruction. This technology features some of the most advanced analysis, without the need of physically destroying the sample/specimen including:
4D CT is an advanced technology which enables analysis of a sample in terms of volumetric 3D data with motion over time.
All 3-Dimensional axis can be sliced to inspect the internal movement of the mechanism being scanned without the need of physically destroying the item.
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