Aerospace is an industry that has experienced great growth in recent decades. NDT in aerospace has a special driver of its own due to the high levels of human traffic involved; the crash of a civil or military airliner has the ability to cause loss of life reaching catastrophic proportions. Therefore, strict NDT specifications have been set to detect very small cracks and defects in engine turbo discs, blades and airframe structures, in both production and ongoing maintenance.
Digital Radiography (DR) has existed in various forms (for example, CCD and amorphous Silicon imagers) in the security X-ray inspection field for over 20 years and is rapidly replacing the use of film for inspection X-rays in the Security and NDT fields. DR has opened a window of opportunity for the aerospace NDT industry due to several key advantages including excellent image quality, high POD, portability, environmental friendliness and immediate imaging.
DR in Ongoing Aerospace Maintenance
Israel Aircraft Industries’ (IAI) NDT lab provides NDT services for both production and maintenance of aircraft. It uses a digital flat imager in a wide range of maintenance applications: In one case, a nitrogen pressure tank was malfunctioning and exploding during pressure testing. Eight different shots of each tank using an Image Intensifier with a flat-panel, portable DR system revealed tiny cracks 0.05 mm wide and 0.4 mm long in the weld. An attempt was made to use film X-ray but without any success until the DR system was introduced.
A table put together by Mr. David Belo, IAI Radiography Level III Expert at the recent ISR ASNT Section, compares the advantages of DR X-ray as compared to film X-ray. The numbers speak for themselves; significant savings of time and money (annual savings of over $64,000 for a scope of 7,250 images) have been achieved.
DR in the Service of the US Air Force
The US Air Force (USAF) primarily requires NDT inspection for ongoing maintenance purposes, in order to inspect different parts of its aircraft for fatigue, corrosion and ageing (including wing sections, rotors and more). In 2000, the USAF carried out a study comparing DR to film X-ray methods. Due to the fact that deployment for NDT inspection purposes involves moving a vast amount of equipment and aircraft, the USAF sought a cost effective and compact mechanism to perform its NDT maintenance inspections.
It discovered that flat panel, battery-operated digital X-ray systems were in fact cheaper and faster, with a much smaller footprint (space required for shipping) than traditional film equipment (a 65% to 97% reduction).
DR flat-panel based X-ray systems required only 84 minutes for deployment, while film based X-ray equipment required several hours. Thus, DR featured 43% savings in the amount of time required to perform the inspection as compared to the film-based technology. Even more important was the fact that DR based NDT inspections offered a unique battery-operated, portable solution at unparalleled lower prices. According to the USAF, cost assessment showed that economically the Air Force could realize a return on its investment in only 3 months. The conclusion was quite clear – DR meets the needs of Expeditionary Air Force (EAF) technical orders.
These advantages can be observed in practical terms when considering another maintenance case: The rear rotor of an Apache broke off as the aircraft was taxiing on the runway before takeoff. According to procedure, the entire Apache fleet was grounded until each aircraft underwent NDT inspection. Due to the use of a portable DR X-ray system, the entire inspection was conducted in 2 days. If a film-based system had been used for this purpose, the process would have taken at least a week or more. This grounding procedure also applies when a civil aircraft malfunctions. Here, too, a portable DR system can save many man hours of inspection work, thus reducing economic consequences for the airline while ensuring top-rate inspection and preserving ultimate human safety without any compromise.
Just in case you thought drills are the product of 21st century home improvement television programs, maritime archaeologists have proof that bow drills were used as far back as 400 B.C. by the Greek Phocaeans who resided in the western area of modern-day Turkey. (Actually, bow drills are well known even earlier, and were recovered, for example, from the Uluburun Shipwreck dated to the end of the 14th century BCE).
In contrast to the rather mundane uses of modern drills (mainly drilling holes for construction), bow drills were multipurpose – aside from serving for drilling and construction purposes, the bow drill also made fire and was an important tool widely used in wood working, boat building and even dentistry.
A wooden bow drill was found on the Ma‘agan Mikhael Shipwreck discovered in 1985 70 m off shore Kibbutz Maagan Mikhael, along Israel’s Mediterranean coast. The ship was excavated, dismantled under water, conserved over a period of seven years and reassembled at the Hecht Museum at the University of Haifa. The artifacts including the bow drill were excavated and retrieved for research in the laboratory on shore. However, from the bow drill only the wood remained, with a hollow and several small wooden cleats that apparently secured a bit; its metal did not survive. Recently, as part of the conservation procedure for this unique item, archaeologists cleaned the drill, including its inner recess, and found minute remains and traces of metal, but its characteristics are not known. The shape of the recess inside the wood could not be traced, nor could we ascertain the shape of the metal bit that did not survive.
Yaacov Kahanov, Head of the Leon Recanati Institute for Maritime Studies, notes that this particular wooden drill is well preserved. “We want to understand how the tool was structured. What kind of metal served as the drill’s bit? What was its shape? How was the carpenter / shipbuilder able to ensure that the bit wouldn’t come loose during usage?”
Using RayzorX Pro digital radiography system, the bow drill was X-rayed from several angles. The detailed, sharp images resulting from averaging and the use of cutting-edge enhancement tools indicated that remnants of metal were still present in the wood although the bit had disappeared. Prof. Kahanov notes: “The X-ray images indicate that there was an iron blade embedded in the wooden bow. The blade obviously corroded, staining the wood and leaving traces of metal behind.”
He adds: “Rayzor Digital Radiography imaging even enables us to see the grooves left by the bowstring. But aside from this, the sharp X-ray images indicate that the blade’s bottom section was square, a shape which artisans apparently realized a century ago optimizes anchoring and stress-resistance. The structure of the tool is brilliant, but we wouldn’t have been aware of this if it weren’t for the advanced digital X-ray equipment used.”
A VIP's office periodically X-rayed with our system reveals a hidden bug in a plant. An automatic subtraction tool in the Xbit software can show these bugs even when the human eye misses them.
Even hard to penetrate objects such as a brick wall can be achieved by using the flat panel systems. This bug was planted in a brick wall at an embassy and was revealed during a random X-ray testing.
An office phone X-rayed periodically for bugs reveals a hidden device. Due to the clarity of the image, no further enhancement was required.
A random shoe check by a personal security team reveals a detonator hidden in the shoe. The image was viewed in negative polarity to better see the fine details.
In the past, the ability to pull out an entire portable X-Ray system from a small bag was considered a fantasy, but today due to developments in technology this dream has finally become a reality. A few years ago a standard portable X-Ray system weighed over 40kg, today our lightest system weighs less than 6kg without compromising on the system’s penetration capability and resolution. These latest technology developments along with the changes in terror doctrine have created a new need for light and compact portable X-Ray systems.
The rise of ISIS in 2013 turned terror into a global threat. The nature of the terror acts became more complex. Until recently, the threat of one bomb in a crowded street or a car bomb was the main concern, but today terror cells carry out combined attacks involving multiple locations, while using several methods. On Milipol eve 2015, a group of terrorists simultaneously executed several attacks throughout Paris forcing the bomb squad to respond immediately to multiple calls at once. As a result, security forces have been required to change their operational model, become more mobile and faster to foil such threats.
This new reality changed the bomb technician requirement of the portable X-Ray system. Innovative technologies have allowed us to adapt to these new needs by reducing the size and weight of the portable X-Ray systems. In the past, the sensor, referred to as the panel, which is responsible for generating the X-Ray image, required a supporting environment of several devices. Our current panels are autonomous with strong battery and wireless capability. These new caricatures have affected the entire system by enabling us to reduce the size of a standard 40kg system and offer new compact 10kg systems packed in a backpack.
The Alpha panel superiority over the FlashX panel is evident in every parameter mentioned. Even though these two panels share the same effective imaging area, the Alpha offers a better working environment for the bomb technician in the field. The panel is not the only means to improve mobility. There are other options, such as a smaller mobile source of radiation and a touchscreen tablet with suitable software to work in harsh environments.
The weight summation of a 2.8kg panel, 1.4kg tablet, 2.2kg X-Ray source and the 0.5kg communication device totals less than 7kg for a large panel system. The weight of a system with the smallest panel can get down to less than 5.7kg. This incredible improvement in size and weight along with the autonomous capabilities of the new systems has resulted in new possibilities and work methods for the bomb technician using our systems.
This new generation of compact, smart and lightweight systems is being used for a variety of security applications. The lite backpack has improved the operator’s performance in the field in many aspects, but most importantly in saving lives. What follows are several examples of precisely how the lite backpack is improving the workflow of the user in the field.
Police bomb disposal units must be mobile and agile as a result of recent changes in terror activities. The contemporary trend involves equipping the units with both previous generation systems (in a case) and new generation systems (in small backpacks) to improve their response speed. Consider the terror attack at the Boston Marathon, where there was a high probability of another bomb striking the survivors and the rescuers. In a situation where a bomb has exploded in a public area, the bomb disposal expert can quickly screen suspicious objects and neutralise any additional bombs, to allow safe evacuation of the wounded from the scene.
Army bomb disposal forces mainly deal with roadside charges and booby traps situated in hostile environments. The ability to carry an X-Ray system in a backpack and provide support to the forces conducting a search offers a significant advantage that contributes to the confidence and survival of the military forces. For example, if the detection forces carry a light and easy-to-use X-Ray system during their incursion on foot into a village in Afghanistan, their operational ability will improve. When the force arrives in the village – which is one of the most dangerous and complicated combat fields for military infantry troops – and suspect a roadside charge, the ability to speedily foil the threat by utilising this system to inspect the object will help neutralise dangers much more efficiency.
Bomb disposal experts in marine environments require unique mobility between sea and land or when moving between vessels. They must be able to navigate tight spaces and narrow corridors. Navy bomb disposal experts are required to raid suspicious ships, which they must screen to detect weapons and explosives. Hence, a lightweight system solution assists them in inspecting such places, quickly and safely.
The inspection systems used by special units are mainly for disarming explosive charges in order to enter buildings quickly. Time is vital for these units. The new systems offer optimal mobility with minimal weight and size, leading to high demand and significantly increased use. For example, in a hijack where the kidnappers use multiple explosive charges to improve their negotiation ability, thereby deterring the S.W.A.T team from breaking into the building, a system that is carried on the back can quickly neutralise potential threats and decrease the time required to break into the building and rescue the hostages. In a hostage situation, every second is critical for saving lives and this inspection system can provide a quicker response than ever before.
We have created a unique solution consisting of a lightweight, mobile, quick and easy-to-use system. Our One Platform technology allows the operator to enjoy the current abilities on a customised lightweight system. When choosing and purchasing a new system, it is important to select an appropriate sensor (panel). Selection of the sensor derives from the size of the inspected object. When you select a panel with a large screening area, such as Alpha panel with a 43x35cm screening area, the carrier bag is bigger than the compact bag that’s designed for the SparX (size: 32x25cm). The size of the panel has almost no effect on the weight of the bag; it only influences the bag’s size. Since the difference in weight is negligible, Our main advantage is in the way it operates as an autonomous unit that includes a battery with a nine-hour lifespan and built-in charger. The new smart panel offers a significant reduction to the amount of accompanying equipment, which allows the system to be packed away in a small and easy-to-carry backpack.
Choosing a suitable X-Ray source relates to the type of objects that are usually inspected. A very large selection of X-Ray sources is available on the market and it is crucial to verify the chosen source is suitable for the field conditions (such as resistance to specific weather conditions). We recommend Golden Engineering’s portable battery based X-Ray sources for fieldwork, its systems are fully compatible with most other X-Ray sources in the market. Golden Engineering offers a unique, relatively small, X-Ray source in the shape of the XR150 (with 150kV X-Ray voltage), which fits in a small bag. This can penetrate up to 50mm steel. If the operator usually inspects steel or iron objects, they may consider choosing a larger source, the XRS3 (270kV) with an 80mm penetration ability, which can fit in a small bag, but takes up more room due to its larger size.
The best choice of display is a tablet, which fits easily into a bag and is held in the palm. The tablet should be hardened, so it is suitable for fieldwork, and the screen should work well in direct sunlight. It should also respond to touch with gloved fingers so that the bomb-disposal expert is not required to remove them when acquiring and interpreting an image. We offer the GETAC F110 with an 11.6in screen, which is the ideal size for analysing an X-Ray image in the field. The tablet comes with a convenient handle, has no rivals for operation in direct sunlight and can be used with gloves.
The operator also needs to choose the communication means according to the combat doctrine. For example, when using a disruptor while handling an object, there is no point wasting space and weight on the wireless system; instead a cable can be fitted into a bag. The opposite is also true: when using a wireless system there is no need to add a cable as it adds extra weight. The Combox integrates the two communication means (wired and wireless) in one device, enabling the operator to switch between these communications means without changing modules.
Moreover, if the reception range is critical, we provide a variety of solutions ranging from several tens of meters (weighing some tens of grams) up to a powerful solution that still comfortably fits into a small bag for one-mile reception.
The bag must be able to protect the equipment from knocks and drops. This valuable system cannot be used without suitable protection. We have a large variety of bags to suit all needs and configurations, from 10kg equipment bags to full equipment weighing 30kg. Furthermore, if the operator already uses specific bags, We can customise them for the requested system configuration, thereby maintaining the purchasing uniformity of that particular unit.
The mobile system relies on software that is responsible for synchronised activation of the system’s components and image processing. Our VEO software provides the optimal solution for the field work scenario. It is user-friendly, offers an intuitive workflow and is the recipient of rave reviews. The software provides graphic touch features fit for working with gloves. The white screen background is suitable for work in the sun and includes unique tools for interpretation of the image at the touch of a button.
Looking to the future, the CBRN area is viewed as a developing threat and requires new technology to counter it. The ability of a terror organisation to set up a dirty bomb in a crowded place has changed the rules of the game. Naturally, the X-Ray solutions and the lightweight backpack systems in particular will become a necessity for EOD teams to handle suspicious objects; especially when neutralising a dirty bomb by employing a disruptor is not an option. With our systems you can do it today.
The Brooklyn Museum in association with D. Giles Ltd., published in 2013 a catalogue called “Soulful Creatures, Animal Mummies in Ancient Egypt” with essays written by curators and preservers Edward Bleiberg, Yekaterna Barbash and Lisa Bruno and a forward by Arnold L. Lehman. The catalog explores the phenomena of animal mummifying (millions were mummified) and the utilisation of modern research techniques in the effort to preserve as well as research and learn about the rare artefacts. The catalog is corresponding to an exhibition by the same name, which is part of an ongoing program at the Brooklyn Museum to share the less familiar or even unknown treasures of the museum’s Egyptian collection with a wider audience. The exhibit and catalog, both published in 2013, are the results of a project that started with the discovery of 30 forgotten animal mummy boxes in the vaults of the museum in 2009.
The catalog and exhibition represent a cross disciplinary method to understanding and preserving the ancient artefacts. The combination of archaeological expertise and Egyptology knowledge along with scientific preserving methods, as well as consulting with medical scientists and other specialists in order to make the most of modern technologies in the inspection and analysis of the artefacts. New insights have been achieved through chemicals analysis, carbon-14 dating, CT scans and digital X-ray inspections. The exhibition puts the rare artefacts on display to the public but also shares the research methods used to study them.
In her article “The Scientific Examination of Animal Mummies, which is included in the above mentioned catalog, Lisa Bruno writes that mummified animals were discovered on a massive scale of millions. Like in a good CIS television drama, the preserver in the museum sets about to reveal the secrets harboured in the animal remains. The objective of a meticulous scientific examination of the animal mummies is to try and tell their story. The story lies in the little and exact details of each specimen. Scientists are looking for the motivation of animal mummifying are trying to use the evidence collected to build ideas and theories about this mysterious practice.
In contrast to early studies of mummies and ancient artifacts (as early as the first expeditions undertaken by Napoleon Bonaparte) the mummies no longer need to be destroyed in order to be researched. Modern nondestructive technologies are available. X-rays were discovered by Wilhelm Conrad Roentgen in 1895 and they were used in a study of artifacts as an imaging tool as early as 1896 (as described in an article by the scientists Carl Georg Walter Koenig). Even portable X-ray is recorded in those early days – in 1896 a British doctor Charles Thurston Holland radiographed a bird mummy on an Egyptian tomb site. In the Brooklyn Museum an X-ray of a dog mummy was taken as early as 1939. Today, with digital radiography and CT scans, the imaging capabilities of the researchers are enhanced tenfold!
In preparation for the exhibition, the Brooklyn Museum conservation laboratory team, led by Kenneth Mozer, were not limited to eye vision only. Lisa Bruno writes that they analysed the animal mummies with tools such as stereomicroscopes, various strengths of electromagnetic radiation, X-rays and Computed tomography (CT). These various imaging tools allowed the researchers to view the rare artefacts in different ways and levels. Imaging tools were also used for analytic methods – such as X-ray diffraction (XRD) and gas chromatography (CG). Other techniques such as Carbon 14 dating, archaeological grounding and historical deduction were used to complete the picture. The combination of different scientific resources is important to such a study. No single discipline can provide comprehensive results when investigating these mysterious objects.
Seeing Inside the Mummies
X-ray is a form of electromagnetic light, which moves in a wave pattern that ranges out of the human eye vision capability. X-rays are short light waves and thus they can be very intensive and powerful, penetrating and passing through most materials and blocked only by denser substances such as metal or bone. In the traditional film X-ray image, dark areas demonstrate very little material (black means nothing but air) whereas white areas are seen where a dense material such as bone has blocked out the X-rays. Various levels of grey demonstrate a range of various material densities. Thus a two dimension image is created depicting a 3-dimensional object.
Today the Brooklyn Museum is at the cutting edge of X-ray technology and owns and uses the RayzorX Pro portable digital radiography system for the nondestructive inspection of its mummy collection with X- rays. The image is generated by the X-ray and is immediately and directly recorded as digital data. Lisa Bruno mentions that this instantaneous imaging is an advantage to the conserving researchers, because the results are immediately available for analysis and any manipulation or repeated imaging can be done on the spot, without repeated transport of rare artefacts. The radiation intensities can be adjusted for the materials present in the specimen that is being examined, thus providing clearer and more articulated images.
Examples of X-ray analysis and techniques are various. Controlled exposure levels can help review the mummy and the materials it is made of in various layers, by exposing the relevant scale (and representing a certain material density) in each different image. For example, an image can concentrate on displaying bones, while the linen wrappings of the mummy are “removed” by controlled over-exposure. Under-exposure can help see the less dense linen of the mummy, this time sacrificing the visibility of bone details. Digital radiography also enables researchers to view the image as a positive reading (meaning bones will be black). This helps researchers in the analysis of the results.
X-ray of mummies can reveal surprising evidence. In Figure 2, the Ibis shaped mummy revealed to contain the bones of snakes. The symbolism or ceremonial value of such a “mixed” item is not clearly understood.
An elaborated Ibis mummy which takes the form of a human body with a carefully wooden carved Ibis head is a wonderful demonstration of external precision and exactness, which is seemingly contrasted by its contents – only a few random bones can be seen in the X-ray image (see Figure 3) instead of the expected careful placement of body parts. However, the careful arrangement of the mummy is clear when one looks at the cross section CT scan of the mummy bundle, in which it is made clear that the bundle is stuffed with feathers.
Mummies that do not contain whole animals were traditionally known as “fake” or “false”. With such a spectacular wrapping, the incomplete contents of the Ibis bundle were a surprise to the researchers. The CT scan revealed the meticulous arrangement of the animal, so that it became clear that even though the contents are not a whole animal, this mummy was costly to make and was of the highest standards and could not possibly be faked. It is now believed that such incomplete mummies were created as a result of lack of resources to meet demand. Another motivation may be that such a high budget mummy was used to preserve the remains of a certain animal, perhaps the incomplete reliquaries of saints and other religious figures.
Mummies that contain only one bone of a large animal are considered also to be representations in a more votive or reliquary sense. An X-ray of a bovine bone fragment is clearly seen in a mummy which is shaped as a miniature bull (see Figure 4).
Modern technologies have enabled conservators to establish new understandings and theories about the motivations leading to the making of animal mummies and the methods used to make them. However it is not to be expected that modern tools will provide all the answers to the mysterious and complex mummifying tradition. Some principles seem to apply widely, but there is an abundance of material variety, creativity and a large time span in which the mummies in the Brooklyn Museum's collection have been constructed. Modern tools enable complex technical data to be collected. Its availability will enable a more comprehensive analysis, using various disciplines for its interpolation. Modern science provides highly suggestive practical evidence and a good basis for theory, as well as new and enhanced results for the better understanding of enigmatic historical objects. But the true answer to the purpose of animal mummies in the larger context of ancient Egypt remains part of the puzzle curators, archaeologists and conservators are trying to solve.
We are proud that our X-Ray equipment is being used for such an important project of culture preservation.
From bomb detection through Special Forces to counter surveillance and customs, the security sector is facing ever growing challenges. Throughout the years, radiography has been a common imaging method for inspecting suspicious articles and explosive devices. For a long while, X-ray film was the most common (and practically the only) recording medium. The Digital Age brought about radical changes, and use of Digital Radiography (DR) expanded, while rapidly replacing conventional radiography methods.
Digital Radiography uses X-ray digital detectors instead of traditional film or Phosphor Plates (also known as Computed Radiography or CR). DR yields immediate and superior quality X-ray images at minimum time on target, with minimal radiation levels.
Digital Radiography vs. Film
Much like in a camera, using traditional film in radiography is time consuming and environmentally harmful. Film needs to be chemically developed, and is very limited in terms of image analysis and sharing with others.
Instead of film, DR uses a digital image capture device. Utilizing a wide dynamic range and high resolution, an immediate high quality image is generated. The retrieved image is displayed on a tablet and can be processed, enhanced, shared and digitally stored and accessed, all within a matter of seconds.
These attributes are particularly beneficial for the security industry as they:
Digital Radiography vs. Computed Radiography (CR)
CR makes use of phosphor crystals plates as a recording medium. The X-ray is absorbed and the exposed plate is then scanned with laser. The emitted light captured is converted into a digitized digital image.
Image readout must commence promptly as the amount of energy stored rapidly declines - the recorded image can substantially degrade during processing. Readout process for a single image takes about a minute and requires a dedicated bulky scanner.
With its unique penetration and detection capabilities, DR maximizes speed, safety, quality and overall performance, while making CR pale in comparison:
DR for Pipes Inspection
Digital Radiography or DR is an advancement of traditional Radiography. This technique utilizes DDAs (Digital Detector Arrays) instead of Film or CR (Computed Radiography) in order to create an instant Image. The Radiation reaches the DDA, which has passed through the object, converted by a Scintillator into visible light and then translated into a digital Image. The physics (Angles, Penetration, technique etc.) remain similar and only mild changes are required to make the transition to Digital Radiography.
Why do we inspect Pipes?
Pipes, whether in service, in production or during installation, have a variety of potential problems which can lead to failures. Typical inspections of pipes are performed in order to inspect the welds, measure wall thinning, Corrosion and clogging due residue build-up.
What would I gain by using Portable DR for pipe inspection?
The advantages are enormous in almost every aspect. Starting with the time needed to acquire an image, from setup until the interpretation stage, no need for returning to site for re-shoots, the added safety due to significantly lower dose and exposure time and the fact that consumables no longer take part.
It is no longer necessary to use neither a Dark room nor Chemicals with this technology.
Where are Pipe inspections performed?
Inspections are mainly done at the facilities where the pipes are in service;
In the Oil and Gas Industry we are talking about all the stages of Midstream and Downstream operations, hence starting from the Transportation stage of the Crude Oil (or Gas) up until the final product is produced. Locations could be around Oil wells, in Refineries and in Power generation stations.
Do I need to use special sources of Radiation with DR?
No, all the sources of Radiation (X-ray and Isotopes) which currently exist at your workshop are suitable for use with DR. In fact, with Isotopes you are now able to extend the life cycle since DR requires lower activity (ci) thus replacing them less frequently.
Are there any DR standards for Pipe Radiography?
Yes, the main one being the European ISO 17636-2, and the well known ASME Section V (article 2) which permits the use of DR with mild modifications to the inspection technique.
One of the most problematic parameters to “convert” was Film Density. Due to the fact that with DR there is no equivalent parameter (the closest is Grey levels) other methods had to be developed in order to verify the image quality. Some of these are: SNR (Signal-to-Noise Ratio) and CNR (Contrast-to-Noise Ratio).
In a nutshell, ASME Section V states: qualification of the digital radiographic system requires a demonstration of the image quality indicator (IQI). The demonstration of the IQI requirements shall be considered satisfactory evidence of compliance with the procedure. In other words, no changes need to be applied to the technique.
The ISO 17636-2 requires, in addition to the Wire type IQI, a Duplex Wire IQI in order to measure the Basic Spatial Resolution (BSR). The Standard also requires measurements of the SNR (Signal-to-Noise Ratio) and CNR (Contrast-to-Noise Ratio) both of which are included in our software.
What is a Duplex wire IQI?
Duplex wire IQI is used to evaluate and measure the BSR (Basic Spatial Resolution) or total Image Un-sharpness in a Digital image. The IQI consists of 13 tungsten wire pairs housed in rigid plastic. The wires are exactly spaced to correspond to the diameter of each pair. The level of un-sharpness is indicated by the number of wire pairs which can be seen. As un-sharpness increases, the wires merge to form a single image and the spacing cannot be identified. Measurement is not evaluated visually; it is evaluated mathematically using a Line Profile tool. By pulling the Line Profile Tool over the wires, a plot is formed of distance vs. grey levels (or DDR).
Duplex Wire IQI
Normally, a 20% dip is required in order to determine that the wire is “seen”. Then, after determining that the wire is “seen”, we go to a conversion table and “translate” the wire number into an un-sharpness value. This number determines the DDA’s effective resolution.
Would the fact that Digital Panels are rigid affect the image quality?
Being rigid has absolutely no effect on Image quality however, it does have an effect on the number of shots for medium size Pipes. For small bore pipes we need to take two shots just as with Film. In large diameters, the curvature of the pipes does not cause significant effect on the un-sharpness (Ug) in the Image therefore the number of shots remain the same. Moreover, Digital Radiography standards such as ISO 17636-2 state the same number of shots as with Film.
Just as with conventional Radiography, Pipes are inspected for three main purposes:
Pipe inspections using a DR system
As opposed to conventional Film Radiography, with DR we are able to utilize a safer alternative to Isotopes (for thin walled Pipes) which is a Pulsed X-ray source. This is mainly due to the dose sensitivity of the Detectors which require a lower dose / energy compared to conventional Film Radiography. However, using an X-ray source for wall thickness measurements requires applying a slightly different methodology due to the differences between the Spectrum of an X-ray source and the Spectrum of an Isotope. Using an Isotope requires only one exposure in order to visualize the inner wall while not “burning” the outer wall; using an X-ray source requires taking two shots at two different exposures (low exposure and high exposure) since it is not possible to visualize the inner wall without “burning” the outer wall. In other words, with an X-ray source we will take a low exposure “shot”, in order to see the outer wall, and a high exposure “shot”, in order to see the inner wall. These two images are then combined, processed and presented as one easy-to-interpret image.
The DWT (Double Wall thickness) Technique
The DWT technique is complementary to the Tangential technique. When having thick walled pipes it becomes difficult to perform wall thickness measurements due to the very large cross section which needs to be penetrated. The DWT technique requires penetrating only twice the wall (front and back) thus allowing using lower Energies or lower exposure times.
With this technique we actually convert grey levels into material thickness (mm or inch) as opposed to counting the number of pixels in the Tangential Technique.
When using DWT we must know or calculate the absorption coefficient (µ) which is specific for each material as a function of the energy (kV). This is less complicated than it seems since the software will do the calculation for us (with a little bit of our help).
With the Automatic measurement tool the technician can easily perform high accuracy measurements with one or two screen taps. A line profile is stretched
over the defect or pipe and with a simple tap, the software will automatically detect the edges of the crack or, the end & start of the wall thus providing the user with a measurement.
Automatic Wall thickness and defects measurements
Some DR standards require having the capability to make Image statistics, usually in a region of Interest (ROI) and not on the entire Image. The main parameters being measured are the SNR (Signal to Noise Ratio) and CNR (Contrast to Noise Ratio). SNR is parameter which indicates the level of Noise in the image which in turn, determines the sensitivity or minimum defect size which can be identified in the current setup. CNR is a measure of image quality based on the contrast vs. noise, rather than on the raw signal.