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Benefits of Phased Array in Weld Inspection
This free webinar was hosted by Olympus on May 19, 2009. Watch the webinar and review the questions and answers that were part of this presentation.
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On May 19, Olympus hosted the webinar "The Benefits of Phased Array for Weld Inspection". We hope that you found the Phased Array Webinar beneficial and we thank you for attending. During the webinar we received many very good questions related to phased array technology and our portfolio of phased array products ranging from manual testing to fully automated inspections.
Please click here >> to schedule a demonstration of one of our phased array instruments at your facility.
Unfortunately, we were not able to answer all your questions within the time frame of the Question & Answer session. For your convenience, following is a list of our answers:
| Questions | Answers |
| Q: Is Phased Array limited to 1 leg? | A: No, as with all conventional ultrasonic testing. We follow the same rules for set-up and calibration. We can inspect over many legs. |
| Q: It is possible to mount a Tomoscan between Tomoview acquisition to build a system to evaluate and ASTM E1961 cheaper than the PIPE WIZARD | A: Yes, but by the time you include all the mechanics and time on set-ups etc., it is most likely cheaper to just buy a PipeWIZARD. Also, your new system will need approvals; this is "standard" with PipeWIZARD. |
| Q: 1. With all electronics getting cheaper by the day, is there a possibility that phassed array equipment will cost less in the near future? | A: Yes, but we give you no predictions on when and how much. |
| Q: 2. Will phased array systems be able to detect surface defects better in the near future? | A: Phased arrays use the same physics as conventional UT, so they are limited. However, it is easier to generate creeping waves and other interesting wave modes with phased arrays. |
| Q: Is examination to D1.1 Table 6.3 possible? Does the Epoch have the D1.1 feature incorporated with the Phased Array? Or does the Acceptance criteria differ using Phased Array? | A: The EPOCH will provide an Indication Rating from the A-scan but not from the S-scan. The acceptance criteria should be the same for both phased arrays and conventional UT. |
| Q: Does AWS accept the use of phased array yet? | A: Yes, for manual UT. As of today, we don't have an AUT solution, but we are working on it. |
| Q: inspection of welds in pipeline build had the problem of the free distance between of FBE coating is possible to buy a band scanner to SAUT | A: Yes, there are several on the market. |
| Q: Focused Shear Wave: Is this used as a manner of course for flaw evaluation once the flaw location is determined? |
A: Not necessarily as a matter of course. It depends on your procedure. If your detection and sizing procedures uses different set-ups, then the answer is "yes"; if not, the answer is "no".
This assumes that your detection procedure uses unfocused beams, but that again will depend. |
| Q: Which are the code cases regarding this technique? | A: ASME Section V Article 4 Code Cases 2541, 2557, 2558, 2599, 2600. |
| Q: how many scans do we need for each weld for 100% test | A: Depends on the scanning technique, thickness and set-up parameteres. The minimum number of scans is one, using encoded scanning with arrays on both sides and a relatively thin material. For manual scans, the minimum is two (one for each side). |
| Q: Can I use the Epoch 1000i to inspect composite materials with phased array? | A: Yes. You will need the correct array. |
| Q: is there a thickness limitation | A: The thickness limitations are the same as for conventional ultrasonics, i.e. they depend on the material, probe frequency, surface roughness etc. |
| Q: How acurate is phased array in sizing the vertical height of surface breaking flaws. | A: Depends on the sizing technique used. For diffraction-based techniques (TOFD, back diffraction), you may be able to get as accurate as + 1 mm, depending on circumstances |
| Q: We currently use TOF for circumferential welds is this adaptable? | A: Assuming you mean TOFD, it depends on the specifications or codes for the weld. The problem with TOFD is that there are dead zones at the OD and ID, so you will need a supportive NDT technique. |
| Q: Does API 1104 accept use of PA ? | A: Yes. API 1104 does not specify what instrumentation you should use, and API generally accepts phased arrays. |
| Q: With all this technology, making it easier for the technician, how will you assist the training centres for giving better training compared to conventional UT training? | A: Good question; training is the limiting factor for a new technology like phased arrays. Olympus supplies our training companies with a lot of material such as animations, videos, Power Points to help them train. However, nothing beats "hands-on" for learning. |
| Q: The DAC Curve or TCG is aplicable to PA technique? | A: Yes, particularly the TCG curves. With a proper TCG calibration and color palette, the operator can simply glance at the screen and see any above-threshold reflections. DAC also works, but requires more work and interpretation than TCG. |
| Q: What does the e in escan stand for?? | A: Electronic scan. This is a fixed angle scan along the array, essentially the same as an old AUT raster scan. There is a definition in the ASME Code Cases. |
| Q: What is a S-scan? | A: Sector scan, sectorial scan, swept angle scan. Unfortunately, a wide variety of terminology was used before anybody tried to standardize it. An S-scan can refer to both the motion of sweeping the beam through a range of angles, and also to the image on the screen. Normally this looks like a pie (for a True Depth S-scan), but there are alternative displays. |
| Q: When registering a PA or TOFD inspection what is the influence in aquisition velocity | A: Very important. If one is travelling too fast along the weld, and not collecting data fast enough, there will be big gaps in the data. This is not allowed by ASME (or other codes). Therefore, the data acquisition rate is a key limiting factor. |
| Q: What is the minimum thickness that can be inspected and the maximum temperature of the material that can be inspected? | A: The minimum thickness depends on the material, probe frequency, surface roughness, and will be the same as for conventional ultrasonics. As for temperature, DNV has approved our pipeline AUT system to 90 degrees C, but normally we would be limited to ~50 C as with standard ultrasonics. |
| Q: what is the minimum defect size that could be detected? | A: The same as conventional ultrasonics using the equivalent transducer - in principle. This will depend on material, frequency, focusing, surface finish etc. However, phased arrays does offer much better imaging than conventional ultrasonics, so the operator may be able to actually find smaller defects by looking at an S- or E-scan. |
| Q: Does VERSION ASME accept the use of phased array yet? | A: Yes. ASME has accepted phased arrays for years as a Computerized Imaging Technology. ASME has also published five Code Cases specifically for phased arrays (2541, 2557, 2558, 2599, 2600). |
| Q: We process ERW pipe at 90 to 150 ft per minute, can PA scan that fast? | A: Yes. Olympus sells pipe mill inspection equipment that works that fast, or faster. However, these tend to be big and expensive systems. |
| Q: How do you know what is the top and what is the bottom on the scan? | A: On OmniScan, you set the plate thickness, and a line called "B0" is the half skip or root of the weld, and the line called "T1" is the full skip or cap. If you have a long range setting, then you may see the "B2" line (one and a half skips), and the "T3" line (two skips). You just need to set the component thickness, and activate the display appropriately. |
| Q: Is passed array for UT what tomography is for RT? | A: Yes and no, from the imaging perspective. Phased arrays does provide a tomographic-type image, but phased array gives a real-time direct image. Tomography is a complex process involving a lot of computer calculations whereas phased array is relatively straightforward. As for the images, phased arrays only show the area scanned, not the full 100% like tomography. |
| Q: I want to know whether phased array is a succesful tool in huge forgings of about 400 to 500mm | A: In principle, yes. You will get much better imaging than with conventional ultrasonics, but you may need a more powerful instrument than the portables for penetration. As for the actual castings, it will depend on the material and geometry. May I suggest that you call your local Olympus agent for a demo. |
| Q: What is BO with relation to saying Top 1? | A: B0 is the root of the weld, or half skip. T1 is the full skip or cap. There is also B2 and T3 for the 1.5 and 2 skips. |
| Q: can you tell me what it means by 2 different index positions | A: Yes. For a long array, it is possible to run two S-scans from the same array simultaneously (and some codes require this). One may come from the start and one for the end of the array, for example. Precise index positions would depend on what your Scan Plan calls for. |
| Q: Does ASME accept the change of X-ray for phased array? | A: Very much. They have been using ASME Code Case 2235 for over a decade. ASME has also published five Code Cases specific to phased arrays. |
| Q: did you say that data can be saved and gone back to later for a report or for calibration | A: Generally, yes. For encoded scans, all the data can be saved for auditing, re-analysis and reporting. For manual scans, selective screen shots can be saved. These can be very useful for review, but are not usable for auditing as there is no accurate position data. The calibration can be saved. |
| Q: What are the thickness limitations? Especially on the thin side. | A: The thickness limitations are the same as for conventional UT, so they depend on material, geometry, surface finish, probe frequency etc. |
| Q: Can phase array be used for inspection of longitudinal seam welds? | A: Yes, but the geometry is somewhat more complex than for butt welds, so you may need to use a Focal Law Calculator on TomoView or similar to get the correct set-up. |
| Q: is there a process/proceedure to size defects that are in the base material | A: Probably, but Olympus doesn't write procedures as such. There are many applications where defects have to be sized, and I would suggest you contact a consultant who specializes in sizing for a procedure. |
| Q: Which is preferred for sensitivity calibration - Radius or depth (SDH)? | A: For sensitivity, we prefer SDH, and so do the codes. The radius is mainly used for velocity calibration. |
| Q: How much training is required & how long & who does the traning required for Phased Array. | A: Good question. The actual amount of training required depends primarily on the operator's ability to learn and adapt to the newer technology. However, two weeks minimum is probably the best, depending on the operator's experience. |
| Q: What`s the POD of transverse cracks or lamination ? | A: We cannot quote a POD as it depends on defects, defect sizes, technique, set-up etc. POD studies are expensive and time consuming. However, lamination detection with normal beam arrays should have a very high POD. Transverse defects, without grinding the weld gap, will have a lower POD. If you grind the weld cap, detecting transverse defects should have high POD. |
| Q: What are the code requirements for scan resolution | A: These are defined in ASME Code Cases 2599 and 2600. For thinner materials, on has to circumferentially scan every 1 mm; for thicker, it is higher. For the axial resolution (on a pipe), you need a minimum of 6 dB overlap, which is much the same as for conventional ultrasonics. |
| Q: Encoding capabilities are available in omniscan M and MX and not in the EPOCH unit...is that correct? | A: Not quite. Encoding capabilities are available on the OmniScan MX, but not on the OmniScan M or EPOCH 1000i. |
| Q: How couplant applied and maintained? | A: For manual inspections (OmniScan M and EPOCH 1000i), the same as for conventional UT. For encoded scanning, the couplant is usually pumped water. With the wear pins on encoded wedges, the couplant is pumped down couplant channels and forms a film under the wedge face. Couplant loss is not usually a serious problem. |
| Q: Dear All, is there some specific recommendations for scanning austenitic SS? is there any restriction? | A: There are no specific recommendations as austenitics vary due to different weld grain sizes. However, there is a hierachy of approaches you can try on your welds, starting with the simplest: standard shear wave S-scans; longitudinal wave S-scans; longitudinal wave dual S-scans; customized Transmit-Receive PA (as used in nuclear). |
| Q: Are there any resistance welding applications? | A: If you are referring to ERW welds in pipe mills, the answer is yes. However, these typically require specialized inspection systems. |
| Q: why this method doesnt use scan B ? | A: We can use a B-scan. In fact, an S-scan is just a fancy B-scan using a range of angles. The E-scans that we showed are B-scans; E-scan refers to the beam motion, and a B-scan is a display. |
| Q: how does PA meet AWS requirements for scan patterns A,B,C,D and E? Scan pattern E seems like it must be done manually. | A: AWS D1.1 doesn't have any requirements for A, B, C, D and E-scans. Right now, AWS effectively doesn't accept AUT inspections unless one works through Annex S. All AWS inspections are manual. |
| Q: Can PA probes apply for TOFD inspections? | A: Yes, but typically PA probes working in pulse-echo operate at a lower frequency and lower damping than TOFD probes so the resolution is poorer. Consequently, people typically use dedicated TOFD probes. However, it is still quite possible to use arrays to perform TOFD, and some people do this. |
| Q: We inspect ERW OCTG Casing automatically. 10 years ago Phased array was tried and found to be not adequate for our purposes. | A: Ten years ago, phased array was in its infancy. You may want to revisit PA, and perform a proper evaluation using Scan Plans, and suitable arrays. |
| Q: If our engineering group would like to specify Phased Array as an inspection requirement what standard should they reference or call out? | A: Probably ASME Section V Article 4, Code Cases 2541, 2557, 2558, 2599 and 2600. Also ASTM E-2491. There are no EN or ISO phased array codes yet. |
| Q: Is it possible to scan bimetallic joints or composites? For example mild steel welded with stainless or 12-14% manganese. | A: Yes. Start with the same parameters that you use for conventional UT, develop a technique and Scan Plan - and you should have a good first attempt. You may need to fine-tune afterwards. |
| Q: What is the calibraction Block for API 1104 inspection, in PA technique? | A: Exactly the same as for conventional UT. This is a Zone Discrimination inspection, and uses a very specific type of calibration block. However, with phased arrays, you can use more zones as there is no geographical limitation on the number of probes, as with conventional UT. |
| Q: The webinar demonstrated inspections in the axial direction. May I assume there is no difference in the circumferential direction? | A: Unfortunately, no. Scanning in the circumferential direction will require a somewhat more somewhat more advanced set-up as the curvature of the pipe must be included, as well as a curved wedge. |
| Q: Is there a way to try out and prove a phased array system for our purposes? | A: For sure. Contact your local Olympus rep, and ask them. We can do a Feasibility Study for you, if that is appropriate. |
| Q: can an individual live indication be saved as can happen with normal ut machine? | A: Yes, a screen shot or image can be stored. The problem is that screen shots are not sufficient to allow auditing of the inspection reesults, results, but they can be useful. |
| Q: Will the resolution of the scanned image effect with number of elements | A: Techncially, no since the resolution is defined by the pixel size, range etc. However, changing the number of elements may affect your beam forming, so you may see small differences. |
| Q: Are there basic calibration blocks designed for phased array that meet ASME requirements or do they have to be fabricated for each application? | A: As of today, there is no universal phased array block. However, to calibrate an S-scan, the NAVSEA block is as good as anything. |
Q: can the phased array testing be used in corner joints,or only in areas where all the transducers can be used to shoot it from many different angles. | A: Yes, it is generally better than conventional UT as the imaging gives big advantages. Normally with a complex geometry, we model the beam first, or may even make a mock-up. |
| Q: does phased array require inspectors to aquire additional certification ? | A: Yes, anywhere by North America where they use ISO 9712, EN 473, PCN or CSWIP. In North America, ASNT has not developed a specific PA certification, which can present problems. Right now, we would recommend either a one or two week course, but we haven't managed to get a certification for PA yet. |
| Q: can we start working with manual insp. and them we can ading the ecoding, or the fully autm. | A: Yes and no. The EPOCH is not designed to do AUT. The OmniScan M will only do manual, but you can upgrade the module to an OmniScan MX which will perform AUT. |
| Q: In the circumferential direction, does the diameter play a role the usable refraced angles of inspection? | A: Yes, but it should not be important. With phased arrays, one can adjust the angles to get the correct inspection, and also machine the wedge if needed. It is more important to get the correct set-up. |
| Q: Are you able to Scan a 4" thick plate welded to a 2" thick plate with 3 to 1 transition with automated TOFD? | A: Probably, but you should model it first. You will need at least two TOFD pairs for 4". |
| Q: Can you repeat the list of the ASME code cases for phased array and AUT? | A: ASME Section V Article 4 Code Cases 2541, 2557, 2558, 2599 and 2600. |
| Q: Can images be viewed on a computer, or must the viewer have the phased array unit | A: The images can be viewed on a computer, provided one has the TomoView software, or if one has the free TomoViewer viewer. However, TomoViewer doesn't allow one to manipulate the data. |
| Q: Do you have a program that will explain your devices in a more detailed fashion? | A: A program, not as such, but we have lots of educational information on www.olympus-ims.com and our ONDT Training Academy Members can give you courses |
| Q: what advances have been made in turbine blade inspections | A: Not sure; the blade or the root? The nuclear industry has developed very advanced techniques for the blade roots. |
| Q: What are the limitation of Phased array technique vis a vis POD | A: We can't give you numbers as nobody has done a phased array POD study yet. Also, it depends if you are looking at manual PA or encoded PA. Encoded PA probably has the best POD, but it will depend on set-up, equipment, defects, procedures etc. |
| Q: does api accept the PA as a insp. process | A: Yes, API inspectors use PA regularly. |
| Q: Are there written standards governing the manufacture, calibration and certification of setup blocks for PA systems? | A: No, since there are no specific PA blocks. However, the standards will presumably apply when somebody finally does develop a PA calibration block or blocks. |
| Q: Is there a simular setup that can be used in other materials like in concrete inspection? maybe with lower frequency elements? | A: Not today. Olympus NDT phased array equipment won't run at the much lower frequencies required by concrete. |
| Q: i would think phased array inspections would be far more superior to any codes or specs. | A: Generally, phased array and AUT inspections find more defects, which is not always popular. However, defect acceptance should be the same with PA or manual UT. |
| Q: i want to do ToFD, PA from both sides with encoder, what solution do you recommend? | A: OmniScan MX is the answer. We have many of these units out in the field doing exactly that. Note that you should also use a scanning jig to hold the probes. |
| Q: where are phased array classes held? | A: All over the world. Check our web site (www.olympus-ims.com) under Trainning to see a list of ONDT Training Companies, schedules, courses, course descriptions, dates, locations, etc. |
| Q: are curved shoes required for pipe diameters less than 20" dia.? | A: Yes, according to code. |
| Q: its possible have assistance of maintenance more close ? | A: Depends where you are located. The answer is probably yes. |
| Q: Can the unit be networked to a computer for flaw recognition? | A: The data can be transferred to a computer for further analysis, usually using TomoView. |
| Q: Is possible to use PAWI in inspection leak corrections with epoxic material of radiators transformer? | A: Our equipment won't do leak detection, so the answer is "no". |
| Q: With a PA S-scan sound beams at different angles are available from almost one index point. With traditional UT, you have different index points. Is there any quantative study showing it is necessary or unnecessary for multiple indexing points? | A: Yes, Try Materials Evaluation August 2008 for an article by Ginzel and Moles to start. If you want more details, it would be easy for you to do your own study. |
| Q: for inspection in stainless steels austenitcos which is the best configuration. Types of wave to use, or multi | A: It depends on the microstructure of your stainless steel weld. If the grains are small, you could probably use regular shera waves; if the grains are large, you will need L-waves, and probably dual arrays. |
| Q: Do you have training facility in Saudi Arabia for AUT? | A: Yes, Jubail Industrial College in Dammam. |
| Q: What is acceptace criteria for AUT accordace with ASME Section VIII and AWS D1.1 | A: Exactly the same as for manual UT. The accept-reject criteria are not set by the inspectors, nor should they be. Changing from manual UT to AUT therefore shouldn't change the accpetance criteria. However, the improved inspection technique (AUT) may produce a higher reject rate to start as AUT will find more than manual UT. |
| Q: What is the diference between a crack and slag inclusion in image? | A: Check the presentation, which will be posted on our web site. The crack will be planar and very directional, while the slag will be smooth, midwall and multi-directional. |
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