Free Webinar: Introduction to Guided Wave Inspection Theory and Technology

Introduction to Guided Wave Inspection Theory and Technology

This webinar includes an introduction to Guided Wave Inspection Theory and Technology. Attendees will learn about the powerful benefits of this solution and its advantages and limitations for pipe inspection as a screening tool and part of an overall NDT program. The basic steps of performing Guided Wave in the field from deploying to reporting will be reviewed for a real perspective of what to expect from the technology and actual data will be reviewed so the viewer can get a basic understanding of the entire Guided Wave process.

Presenter Bio:
Nicholas Bublitz has worked for Olympus Scientific Solutions Americas for 8 years. Having held positions ranging from Technical Support, Sales Management, Technical Support management, and Global Technical Support focusing on phased array, TOFD and automated system technology, he is now involved in many aspects of marketing, business development, product development and technical support across industries. 

Questions & Answers

Q. How do you need to prep the piping if the surface has some corrosion?
A. The pipe usually requires minimum preparation, similar to other Ultrasonics techniques. Loose, scaly material should be wire brushed etc. This is only for where the collar would be placed.

Q. How reliable is this technique to detect ID corrosion in the insulated piping? Would it be able to pinpoint any microbial corrosion of in the pipe? Is there any insulation removal required? What’s the length being scanned?
A. All types of corrosion have potential for detection; it is hard to speculate on reliability without all variables considered. Typically we state 3% CSA detection under ideal conditions. Insulation must be removed where the collar will be placed for any acquisitions. Length varies by specifics; maximum length is 600 ft., 300 ft. bi-directionally.

Q. How do you know which direction the sound came from (positive vs negative direction)? Are the two probe contact points used for measuring timing of received pulse, phase, etc.?
A. The system software is able to determine whether a response is from the forward direction or a rebound from the backwards direction, and uses a green overlay that can be switched on and off to identify those signals. Yes, the sensors measure timing and all receive info and that info is processed.

Q. This issue is on various service water piping, all of these are insulated. We need a rapid, but accurate screening tool to detect the potential corrosion. Based on initial finding the insulation removal and further inspection could be planned.
A. Guided Wave is a rapid screening tool, typical shots are 1-3 minutes, and then areas of concern can have insulation removed for further testing.

Q. Do you have any plans to cover the transducer cable loops to eliminate chance of damage during transport and use?
A. Durability is always a factor. The small cables from the probes go into a larger more robust connection to the unit. We will continually look at product durability improvement. Spares for the small wire are included in the basic kit to avoid downtime if a cable is broken.

Q. Can the system differentiate between internal and external corrosion?
A. No, the system cannot determine if the corrosion is OD or ID, this would be done by follow up with other NDT method including visual, ultrasonics, laser profilometry etc.

Q. Does the system work around elbows or bends?
A. Going around bends and elbows can be unpredictable since it can alter and mode convert the sound. Planning of shots should try to best inspect around these types of features. It is often done past one but going through multiple is usually avoided when possible by shot planning.

Q. How accurate is resolving corrosion under support?
A. Same general sensitivity levels typically (around 3% CSA). Supports typically give a signature so corrosion can be identified as a separate indication.

Q. What is the frequency range?
A. The range is 15-85 KHz. The steps fired are adjustable from 1 KHz to larger steps if desired.

Q. How does it handle changes in pipe diameter?
A. Bands of different sizes are provided in the kit for inspection of the various diameters. If there is a change in the pipe inspected there will be a reflection from it but most of the sound will go through as if there would be a reducer or an expander.

Q. Can we screen metallic coated pipe?
A. A metallic coating, depending on its thickness and the material that is used, will likely have minimal effect as long as it is well-bonded and generally uniform.

Q. What are the temperature limitations for surface temperatures of active pipes?
A. Right now the system is specified to 70c for the pipe, we are aware a higher temperature would be advantageous and are evaluating high temperature software and hardware options.

Q. Is it rain resistant?
A. Yes, the system is IP54.

Q. Is there any way to screen 30 inch diameter pipe?
A. The standard kit covers pipe size up to 24” but this is not a limitation, larger bands will be provided upon request.

Q. How does the external coating, insulation, ground conditions affect the attenuation of the technique? And how does this affect the range at which LRUT or Guided wave can be effectively used?
A. All of these factors will affect attenuation of the signal and possibly range. Reference reflectors like welds and test acquisitions would be able to quantify more accurately.

Q. What are the limitations on wall thickness for the techniques to be used effectively? I assume that the effects of fitting such as Insulation joints would rebound the wave and prevent further inspection downstream?
A. The system has pre-established algorithms for standard pipe schedules and thickness up to 24 inch OD standard pipe. Tests can be done beyond these ranges but are hard to comment on specifics. Joints will usually have a scattering or bending effect and acquisitions should be planned around or tests should be conducted. It is possible to shoot past “features” as typically only a portion of the sound is scattered or attenuated.

Q. Would the tools provide a range by which the CSA has occurred to allow us to priorities the areas to be inspected further? For Example, 5% CSC over 3-6 clock no issue but 5% at 1'oclock would be prioritized. Does the technique provide this?
A. The technique provides clock and position down the length of the pipe and typically a category rating (1, 2, or 3) based on a DAC setup or some other sensitivity level. It does not prioritize these indications beyond category/severity of received signal since each pipe system would have different criteria.

Q. How flexible is the inspection collar for different diameters?
A. A collar is provided for each standard diameter in the range. Depending on the nominal diameter of the band there is some leeway in actual diameter as the bands are flexible in nature and affixed via Velcro. It is the bladder which provided the hold. The combination needs to not only attach to a pipe but do so in a manner that each probe is making good contact.

Q. How does the coating condition affect the technique? Is good surface required if couplant is not being used?
A. The coating type and thickness will have some effect. Coating should be tightly adhered or prepped. Prep is similar to other ultrasonic techniques, remove loose and scaly surface.

Q. Is the system ATEX rated for Hazardous areas?
A. No.

Q. Are there any blank spots like between the probes whereby defects could be missed?
A. The torsional waves are fired for full coverage based on how they propagate. There is the dead zone (typically around 1m) in front and back of the collar that should be noted. Typically a secondary planned shot would be positioned to encompass this area if possible.

Q. Can the pipe be a polymer e.g. polyethylene?
A. Currently this material is not addressed by our software but it may be possible to expand to this and other materials.

Q. If there are 20 foot welds, will they reduce the length of the inspection by attenuation?
A. Welds typically attenuate at a linear rate. A DAC (distance amplitude correction) method based on the welds can adjust for the loss of power in rating defects, i.e. slope of DAC changes as the range gets longer to evaluate defects further away from 0.

Q. How would a side stabbing say 1" off 12" line affect the inspection downstream of the stabbing? Would the waves reform on the other side of the opening?
A. If a side stabbing is like a small branch, which will show up as a non-axisymmetric reflector, the waves will reform after passing the branch. The more structure features one shoots through, the weaker the downstream signal will be and the tougher the data analysis can become, but a 1” branch off a 12” line isn’t that severe of a reflector.

Q. What range of frequencies and test techniques (pulse echo or pitch and catch) do you use to inspect buried pipes and road crossing? Does Olympus provide a special training for these applications?
A. The UltraWave is a pulse echo based system. The frequency range is 15-85 KHz. This is the method used for buried pipe and road crossings. Specific applications would be considered for training.

Q. What about calibration checks or standards?
A. Calibration loops can be built. Many applications are based on sensitivity and DAC on welds if present. Specific codes and standards will dictate. Many oil and other companies require qualification on an internal pipe loop.

Q. What's the difference between magneto restrictive and piezoelectric and their advantages and disadvantages?
A. The magneto restrictive collar needs to be fixed permanently or bonded on the pipe with epoxy in many cases. It generally has only 2 channels, the forward and the reverse, this does not allow detection of flexural modes. There are many different types of Guided Waves including magnetic so it is hard to give a broad definition of all differences in this format.

Q. How can the F-Scan mode can help to separate the defect?
A. The Frequency map lays out the distance travelled versus each frequency to show the total acquisition including indications and geometry reflections. As Guided Wave is a frequency dependent method, some defects may be detected by a range of frequency while invisible to other frequencies. It is easier for the operator to select the most sensitive frequency using this tool that combines all the frequencies in one plot.

Q. Where the collar is placed ...in that area of pipe is the coating required to be removed?
A. It depends on the coating type and thickness, tightly adhered coating that is not excess thickness or attenuative can usually stay in place.

Q. Does the equipment have an integrated GPS?
A. The laptop has a GPS option which can be activated and included into the report as desired.

Q. What is the maximum pipe size which can be tested using UltraWave LRT system?
A. The standard kit covers pipe size up to 24” but this is not a limitation, larger bands will be provided upon request.

Q. What's the maximum work temperature of the collars?
A. Right now the collars are specified to 70c for the pipe, we are aware a higher temperature would be good and are evaluating high temperature software and hardware options.

Q. How many receiving channels does the UltraWave LRT have?
A. 16 channels, operating in pulse echo.

Q. Does a single spacing between the probes on your probe modules permit generation of all the entire frequency range (15 to 85 kHz)?
A. Yes, we have found on our design a single spacing is sufficient for torsional propagation within the desired range, all active focusing etc.

Q. The dead zone seems to be very large according to the A-Scan shown in the webinar (about 4m). Other equipment has a smaller dead zone (about 1m maximum). Why is this?
A. The data shown in the webinar are in feet so 4 feet is approximately 1 meter. Dead zone is frequency and gain dependent as well so will vary a little from each application.