Advanced Nondestructive Testing
XCEL continues to grow a nationwide team of Advanced NDT professionals.
From AUT Corrosion Mapping to Phased Array Ultrasonic Testing (PAUT), Time of Flight Diffraction (TOFD), and beyond, our advanced service lineup includes the most progressive techniques and technology available. These methods are vital for conducting critical examinations and delivering precise results. XCEL recognizes the importance of investing in these state-of-the-art examination techniques to ensure both our company’s and our clients’ ongoing success.
- AUT CORROSION MAPPING
- PHASED ARRAY ULTRASONICS
- TIME OF FLIGHT DIFFRACTION
- DIGITAL RADIOGRAPHY
- REAL-TIME RADIOGRAPHY
- GUIDED WAVE ULTRASONICS
ADVANCED NDT
AUT CORROSION MAPPING
AUT Corrosion Mapping systems utilizing mechanical scanners are employed regularly for equipment condition inspections. Often referred to as AUT Corrosion Mapping, C-Scan or Ultrasonic Corrosion Mapping, this NDT method quickly identifies wall loss and presents a detailed report relative to location, thickness values and area.
Automated Ultrasonic Testing (AUT) Corrosion Mapping plots the opposite surface of pressure vessels, piping, tanks, heat exchangers, and more. This is critical to determine not only the remaining thickness but the topography and area affected. Access to only one side is needed so the underside of a tank floor can be examined from inside the tank, the ID surface of a piping system can be mapped from the outside surface, etc. The systems are capable of acquiring actual wall thickness over large areas of test subjects while the system is on or off-line. AUT Corrosion Mapping is also used for remaining life determinations as prescribed by the facility’s Mechanical Integrity program.
ADVANCED NDT
PHASED ARRAY ULTRASONIC TESTING
Phased Array Ultrasonic Testing (PAUT) is universally capable of assessing almost any damage mechanism where conventional ultrasonic flaw detectors have been used.
Phased Array for weld inspection and crack detection are the most common applications. These tests are done across a wide range of industries including oil and gas, petrochemical plants, power generation and chemical industries, especially for the construction of new piping, pipelines, vessels and structural welded materials. Phased Array can also be effectively used to profile remaining wall thickness in corrosion survey applications when surface condition and part geometry allows.
A Phased Array probe is composed of several small ultrasonic elements which are individually pulsed. By phasing the pulses across the array of elements, the ultrasonic beam can be steered and focused as needed for a particular application. Multiple beams can be generated for a single examination; therefore, a variety of beams can examine the area of interest thoroughly.
Applications for Phased Array Ultrasonic Testing (PAUT)
- Weld evaluation
- Volumetric inspection of forging or casting materials
- Mapping Erosion and corrosion activity
Flaws that Phased Array can detect
- Weld flaws such as lack of fusion, slag inclusions, porosity, surface and/or embedded cracks, and incomplete penetration
- Erosion or corrosion – material loss, pitting, and root erosion
- Discontinuities in forged, rolled or cast materials such as laminations, forging bursts, cold shuts, hot tears and inclusions
- Environmentally or process-induced damage mechanisms such as Microbiologically-Influenced Corrosion (MIC), Hydrogen Induced Cracking (HIC), thermal or cyclic fatigue cracking, caustic cracking and stress corrosion cracking
There are a multitude of phased array benefits due to its universal capability to perform so many inspection tasks. Here are some advantages of Phased Array:
- Information can be displayed in multiple display formats (examples below), which aid in discontinuities/ flaw detection.
- A-Scan displays the amount of received ultrasonic energy as a function of time
- B-Scan displays a profile view (cross-sectional) of a specimen
- C-Scan displays a plan type view of the specimen & discontinuities
- D-Scan displays an end view of the specimen at the current position of the probe
- The data can also be captured and stored for inspector review. This also makes future reference and inspections easier.
- The replayed data can be processed and displayed in various ways using the instrument used to acquire the data or on analysis software that provides additional processing capabilities.
Limitations of Phased Array
- Accessibility to a clean smooth surface
- Material of piece being scanned. Coarse-grained materials and exotic alloys can attenuate Phased Array UT energy the same way it will attenuate conventional UT energy and cause limitations to the inspection.
ADVANCED NDT
TIME OF FLIGHT DIFFRACTION
The Time-of-Flight Diffraction (TOFD) method of ultrasonic testing is an effective and reliable weld testing technique. Due to the use of diffracted signals as opposed to reflected signals it is a valuable complement to PAUT or as a standalone method in certain applications.
The Time of Flight Diffraction (TOFD) method uses a pair of angle-beam L-wave ultrasonic probes that are used in a pitch-catch configuration with the sound beam passing through the area of interest. A transmitter probe emits an ultrasonic pulse which is picked up by the receiver probe on the opposite side. In an undamaged part, the signals picked up by the receiver probe are the result of multiple different wave energies that were generated by the transmitted beam: one that travels along the surface (lateral wave) and another L-wave that reflects off the inside surface (back-wall reflection), and one S-wave that reflects off the inside surface. When a discontinuity such as a crack is present, there is a diffraction of the ultrasonic sound wave from the top and bottom tips of the crack. Using the measured time of flight of the transmitted and diffracted energy responses, the height and depth of the flaw can be calculated.
This ultrasonic UT testing method is commonly performed on welds, weld overlay cladding, piping, pressure vessels, storage tanks, and structural steel. Fabricated vessels and piping can be thoroughly examined for fabrication flaws with Time of Flight Diffraction. Sizing of cracks and welding flaws can be done precisely using the TOFD UT testing method. Time of Flight Diffraction is also effective at measuring the remaining wall of a welded joint that has been damaged by preferential corrosion or root erosion.
Applications for Time of Flight Diffraction
- Detecting cracking and sizing cracks as well as other planar defects, e.g. lack of fusion
- In-service defect monitoring and detecting manufacturing defects
- Weld examination – for pressure vessels, piping and storage tanks and spheres; in-service and new construction examinations
- Flaw growth monitoring and discrimination of defects between weld overlay, clad and base metal
- Measuring wall loss at welded joints damaged by preferential corrosion/root erosion
Time of Flight Diffraction UT Testing Advantages
- Very fast and effective scanning welded joints (new construction and in service)
- Position and size data for every flaw can be compared for repeat scans of the same areas to track flaw growth or corrosion rates
- Can also be used for in-service defects, such as cracking, corrosion, erosion, etc.
- Measuring wall loss at welded joints is typically more effective with TOFD than with angle-beam pulse-echo methods
Limitations of Time of Flight Diffraction
- Weld must be accessible from both sides
- Gathers and displays information in a way that requires experience to interpret
- Not always code accepted as a stand-alone inspection technique
ADVANCED NDT
DIGITAL RADIOGRAPHY AND COMPUTED RADIOGRAPHY
DR and CR are both radiographic techniques that produce a digital image of the subject that can be post-processed to optimize the image for viewing. The wide dynamic range allows greater flexibility than conventional film in many cases. The elimination of chemicals and film, as well as reduced exposure and image processing time makes CR or DR a wise choice for many applications.
Digital Radiography (DR) systems using digital detector arrays (DDAs) are a logical progression of the radiographic technique. With typically even shorter exposure times than CR and practically real time results, DR is an excellent choice for many applications.
Two of the biggest advantages of Digital Radiography:
- Very short exposure times required to capture an image on the DDA, again saving time and exposure to radiation
- The image processing is practically instant, allowing adjustments to be made with minimal impact
Computed Radiography (CR) uses photostimulable phosphor plates (PSPs) in place of film to capture the image. The exposed PSPs are then scanned and the captured data is converted into a digital image file. The software allows for certain post-imaging processing to take place to optimize the image.
Two of the biggest advantages of Computed Radiography:
- Digital images can be saved on an optical disc or other secure storage media eliminating the need to store boxes or envelopes of film that can degrade over time
- Viewing software allows for measurement and other tools to improve image evaluation
ADVANCED NDT
REAL-TIME RADIOGRAPHY
Real Time Radiography using a C-arm arrangement is a valuable tool used to screen insulated piping for CUI.
Real time radiography (RTR) for corrosion investigation is an excellent screening tool designed to detect Corrosion Under Insulation (CUI). The low-energy Xray source and hand-held detector provide instant imagery of the surface profile of piping under insulation. When corrosion is detected, further investigation can be planned and performed based on the information provided. Due to the speed, small footprint, and the ability to provide focused information, RTR can provide substantial cost savings to our clients by preventing unneeded insulation removal. Small two-man RTR crews can access suspected (CUI) areas of facilities quickly and efficiently, allowing clients plenty of time to develop further prove-up inspection and equipment repair.
ADVANCED NDT
GUIDED WAVE ULTRASONIC TESTING
Guided Wave Ultrasonic Testing is an excellent screening tool to investigate corrosion of insulated, buried or similarly inaccessible pipe/piping.
Guided Wave Ultrasonic Testing (GWUT) has quickly become a preferred method for screening large piping segments, insulated piping, or inaccessible/difficult to access piping. GWUT is an effective screening tool for detecting anomalies in piping that can then be followed up by a quantitative means of NDT to determine the severity. Under the right conditions, GWUT can be used to screen many feet of piping for internal/external corrosion in just a matter of minutes from a single access point. It can also be used to locate girth welds on insulated piping circuits should those welds need to be accessed for any type of inspection. Primary applications are insulated piping, buried piping, and pipeline road crossings.
Technology based on Results.
- Automated Ultrasonic Corrosion Mapping
- Phased Array Ultrasonic Testing (PAUT)
- Time of Flight Diffraction (TOFD)
- Real Time Radiography (RTR)
- Guided Wave Ultrasonic Testing (GWUT)
- Digital Radiography (DR)
- Computed Radiography (CR)
- Eddy Current Testing (ECT)
Why choose XCEL?
- Multiple ASNT Level III technicians
- Qualified technicians with numerous Advanced NDT certifications
- Versatility and cross-utilization across service lines
- Advanced solutions for problems common to the oil and gas sector
- Our ASNT Level III instructors hold certifications in RT, PT, MT, VT, LT, UT, ET
