SERVICES OVERVIEW
Advanced NDT and Special Applications
The application of the latest technologies to conventional controls, suitable for artefacts and plants with a considerable importance to the customer.
Application fields and limits
There are many application fields for the two techniques; in particular, they are now recognized as valid substitutes for radiographic examination of welds (ASME-API-DNV, etc.), and they have now become standard applications in case of thick vessels. Applications have also been developed on the two techniques to assess the condition of operated equipment. The limits of the two techniques are first of all those inherent to the classic ultrasonic control, so for example the examination surfaces must be regular and clean from anything that may prevent the transfer of the ultrasonic signal and also on hot parts (T>60 ° C) the examination may not be applicable. There are also specific limits for the two techniques that we have reported in detail in the brochure.
Final results
The final results of a TOFD or PA examination are reported in files containing records of the raw data stored during the inspection.
This data can then be processed to be presented in a variety of views. The report will contain not only images but also information about the calibration of the system and the relevant regulations.
EMAT
EMAT is the acronym for electromagnetic acoustic transducer, and therefore indicates a particular type of probe capable of working by exploiting the ultrasonic waves generated in materials thanks to the interaction of this with them through electromagnetic fields. The EMAT probes therefore do not need to have interposed between them and the material under examination of an appropriate means of coupling.
Pros
– No need of laminating agent
– Reduced need of surface preparation
– Possibility to perform measurements up to 700°C with an accuracy of 0.1 mm
– Possibility to perform B-scan and C-scan recordings
– Possibility to perform checks under supports, saddles, supports for corrosion research
Cons
– High cost of the instrumentation (in reference to a thickness gauge UT instrument)
– Impossibility to perform measurements on non-conductive materials
– High probe size (minimum Ø 25 mm)
Final results
The final results of an EMAT examination do not differ significantly from those obtained with a classic ultrasound examination. An instrumental screen occurs in which the detected thickness data is highlighted.
IRIS
Ultrasonic Internal Rotary Inspection System (IRIS) is based on the principle of measuring the thickness of a pipe using longitudinal ultrasonic waves. The IRIS probe consists of a transducer that is placed aligned with the longitudinal axis of the pipe and the ultrasonic beam emitted is incident on a rotating mirror.
Pros
– Possibility of examination of ferromagnetic and not ferromagnetic tubes
– Possibility to detect internal and external defects
– Possibility to detect crateriform erosions and corrosions also under septum and tube plates
Cons
– High cleaning requirement (tube washing at minimum 900 bar)
– Low examination speed
– Unable to detect cracks
– Unable to detect through holes
– High quantity of water required per examination
Final results
The final result with IRIS testing will be a mapping of the tubes with the degree of damage detected and, if necessary, a representation of the signals as a C-scan map.
Pulsed Eddy Current (PEC)
Exploiting the physical principle inherent in the formation of induced currents, some companies have developed a technique that allows the monitoring of corrosion. The physical principle that is exploited can be traced back to the disappearance over time of induced currents in a ferromagnetic material when it has been subjected to an impulsive signal.
Pros
– Ability to perform tests on objects in operation
– Possibility to perform tests on parts immersed in water
– Possibility to perform tests without destroying the object protections
– Very low surface preparation
– Excellent for detecting thinning with large extension surfaces
– High examination speed
Cons
– The data detected by the machine is an average value relative to the area stressed by the probe.
– Does not detect small defects such as craters, pitting, cracks
– High costs of the equipment that today are still covered by royalties and bonuses of use
Final results
The final results of an examination with PEC are slightly different depending on the instrumentation used, in general, however, the instruments return a C-scan type mapping, where the areas with greater reduction in thickness have shades of color tending to red. On some of them is also highlighted the area used for the calibration of the signal. The acquired data are then processed in post process.
Eddy Current Array (ECA)
Eddy Current Array (ECA) technology provides the ability to electronically drive induced currents generated in the metal material using an array of coils all placed within the same probe.
Pros
– Larger area can be analyzed in a single probe pass, while maintaining high resolution
– Improved defect detection and sizing with C-scan imaging
– Check complex shapes using custom probes in the part profile to be checked
– Ability to detect defects in tubes arranged longitudinally and transversely to the tube axis (defects such as circumferential cracks could not be detected with conventional technique)
– Possibility to manage the signal to detect defects under septum or under plate
Cons
– Cannot analyze non-conductive materials
– Ferromagnetic tubes cannot be inspected to identify craters or corrosion, only external surface tests
– Always need a calibration tube of the same material to be examined
– High equipment cost
– High and expensive personnel training
– Sample part required
Final results
The final results with ECA tests will be different depending on the particular examined, it will be possible to have for example C-Scan mappings of the defects detected, on which perform the measures related to the extension of the indication detected.
Near Field Array (NFA)
Near Field Array (NFA) technology is derived from NFT technology. The NFA, thanks to ARRAY probes, allows an excellent detectability of crateriform defects and especially of cracks, allowing also a sizing of these, both in extension and in depth.
Pros
– Possibility to dimension small crateriform defects (up to Ø 3 mm)
– Possibility to detect longitudinal and circumferential cracks
– Ease of execution, in fact it is not necessary water or magnets
– Low sensitivity to probe extraction speed
– Easy interpretation of results thanks to C-scan screens
Cons
– No external defects are detectable
– Non-magnetic materials cannot be examined
– Sample tube required
Final results
The final results with NFA testing will be C-Scan mappings of the detected defects, combined with a class evaluation of the tube under test.
Remote Field Testing (RFT)
The RFT technique is used for examination on carbon steel tubes. An RFT probe basically consists of an exciter coil and a detector coil at a certain distance from each other. The probe is passed through the pipe to be inspected. The exciter coil is supplied with a low frequency alternating current (normally sinusoidal).
Pros
– Detection of both internal and external defects
– Detection of defects such as thinning and craters
– No need for couplant or magnetic fields
Cons
– Impossibility to examine finned tubes
– Impossibility to detect small defects with respect to the exciter coil/measuring coil distance
– Impossibility to detect circumferential cracks
– Sample tube required
Final results
The final result with RFT testing will be a mapping of the tubes with the degree of damage detected and, if necessary, a representation of the recorded signals.
Digital radiography
With digital radiography we indicate the digital mode of acquisition from the X-ray image that, unlike the less recent analog technique, allows to exploit software and hardware capable of storing images and their post-acquisition modification.
Pros
– No need for fixing and developing liquids
– Possibility to store the image in digital format
– Possibility of post analysis
– Possibility to evaluate defects in welding and base material
– Possibility to evaluate the residual thickness
Cons
– Limitation related to the size of the part to be examined
– Need for high charge sources
– Operator’s ability to handle the instrumentation
Final results
The final results obtained with digital radiography are files that can be viewed on high-definition screens. These images can be exported with the common means available, but at this point are no longer processable.
Guided wave
Guided ultrasonic waves allow for rapid and complete inspection of long sections of pipeline, exploring the entire circumference of the pipeline and overcoming any changes in direction.
Application fields and limits
Guided waves are mainly applied to the examination of pipes with diameters greater than 3 inches and thicknesses greater than 4 mm. However, there are instruments that can perform examinations on pipes of smaller diameter and thickness without guaranteeing the results obtainable under ideal conditions. On the market there are also instruments that using short-range guided waves can perform an examination of the material under the saddles and supports to verify the state of degradation. The limitations are related to the fact that the signal analyzed by the instrument is related to the cross-section of the tube under analysis, then the indications detected and detectable must have a size related to the cross-section appreciable. Recently commercialized instruments guarantee the detection of indications that produce a reduction of the cross-sectional area of 5% (e.g. uniform or diffuse crateriform corrosion).
Final results
Final results are typically presented in a summary report in which the detected signals are included in the form of wave signals, accompanied by color-scale mapping of the deteriorated areas (C-scan views).
Acoustic emission
Acoustic emission is a passive receptive technique that analyzes the ultrasonic pulses emitted by a defect at the very moment it occurs.
Detectable defects
The detectable defects with AE are all those that if stressed by a force (e.g. pressure), in some way can evolve. In particular are well detected:
– Cracks of any orientation
– Delaminations and blisters
– Leaks and/or leakage of gas or liquids
– Active corrosion
– Non-active corrosion with the presence of scales
Non-detectable defects
Not detectable are all those defects that, even if stressed, do not undergo any change over time, for example:
– Slag and porosity
– Crateriform/uniform type corrosion
– Erosions
Final results
The final results are generally presented in a summary report in which are included diagrams depicting the equipment or piping under analysis with attached indications detected during the tests.
Magnetic Flux Leakage (MFL)
The basic concept of magnetic flux leakage control is to detect magnetic field changes in a ferromagnetic material undergoing saturation.
Application fields and limits
The technique of magnetic flux leakage is widely used in the investigation of long pipelines in which large “pigs” are inserted that, driven by the pressure of the fluid they contain, analyze the entire section of the pipe. Another very common application is the investigation of the bottoms of tanks, which are scanned at 100% to identify the corroded metal sheets, both on the walking side and on the opposite side. In both cases, however, the results returned are then to be “completed” with punctual investigations. The most important limitation of the technique is that can not be analyzed non-ferromagnetic materials, also are very important the conditions of cleanliness of the surface and not less of residual magnetization of the same. Also in this case the examination temperatures are those of the environment or slightly higher.
Final results
The final results are presented in the form of a summary report in which the mappings of the parts examined and the parts with defect indications are included. These, at the customer’s discretion, can then be verified and investigated with other CND techniques.
ACFM
ACFM® is an electromagnetic inspection technique that induces an alternating current in the component surface using a variety of probes, including simple pencil scanning probes and multi-field arrays.
More infos
The return signal is converted instantaneously with advanced mathematical techniques using specially created ACFM® software, displayed and stored on a laptop computer. The presence of a discontinuity distorts the primary electromagnetic field and consequently the return signal that, processed by the processor, forms, returning and displaying on the screen, characteristic indications of the type of discontinuity found. The main advantages are:
– Rapid scanning using a portable probe
– Reliable crack detection with accurate sizing (length and depth)
– Reduced cleaning requirements, no need to clean bare metal
– Inspection can be performed on hot surfaces up to temperatures of 650-700° C
Final results
The final result is a signal in the impedance plane from which it is possible to deduce, thanks to appropriate algorithms, length and depth of the detected indications.
APR
Acoustic Pulse Reflectometry (APR) consists on producing a sound signal at one end of the pipe and recording the reflected echoes. The instrument was conceived to carry out non-destructive testing in the aeronautical sector (aircraft hydraulic ducts) and was later adopted also in heavy industry for inspections of heat exchangers and similar systems.
Pros
– Minimal lead time, no sample part required
– Allows to analyze heterogeneous groups of exchangers, different for diameter, thickness and constitutive material
– It can be carried out on manufactures of any material both metallic and plastic
– It is possible to analyze a tube bundle made of different materials (e.g. Al-brass with Cu-Ni or superalloys in a single measurement session)
– The presence of protrusions on the external surface has no influence on the signal and it is therefore possible to analyze finned or ribbed tubes.
– It is possible to examine U-shaped tubes or tubes with any radius of curvature, with internal baffles and grooves, spiral, square or ellipsoidal section, etc..
– Lower costs compared to other techniques
– High speed of test execution
Cons
– Inability to detect defects on the outer surface of tubes
– Min. and max. limits for diameter are ⅜” (9.525 mm) and 4″ (101.6 mm) respectively
– Flushing of the tubes to be inspected is required prior to inspection. The desired degree of cleanliness depends on the purpose of the inspection
Infrared Termography
Infrared thermography is an imaging technique that uses the infrared radiation emitted by bodies to detect the temperature and its variations. Modern thermal imaging cameras allow to visualize temperature differences in the order of a tenth of a degree with very high resolution and the possibility to create accurate thermal maps. Thermography allows to detect the temperature and its variations in objects from a distance. Our company applies thermographic control in industrial, civil, nautical, aerospace and countless other applications.
Pros
– Extended applicability to all production fields
– Rapid intervention and execution
– Immediate and shareable results
– Ability to analyze high-temperature objects from a safe distance
– Ability to analyze large areas in limited time
– Low costs