Guided Wave API

Benefits and Challenges of  Ultrasonic Guided Wave Inspection by Terry M. Webb, BP Refining NDE Specialist Click to edit Master subtitle subtitle style

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Presenter Terry M. Webb, Refining NDE Specialist BP Refining & Marketing Over 25 years of experience in the field of Nondestructive  Testing  Testing in oil refinin refining, g, chem chemical ical plants plants,, nuclea nuclearr power power plants, fossil fuel power plants, and synthetic fuels (coal liquefaction).

job position ClickCurrent to edit Master subtitle style subtitle Provide NDT support to five BP Refineries in the USA and six overseas in the Netherlands, Germany, Spain and Australia. •

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BA Degree from Marshall University in general studies with a major in Nondestructive Testing and minor in Engineering. Certified ASNT NDT Level III in Radiographic Testing, Ultrasonic Testing, Liquid Penetrant Penetrant Testing, Magnetic

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Purpose of Presentation l Educate the inspector and engineer on the

benefits and challenges (pros and cons) of  guided wave pipe inspection. n

Sources l  TWI, “Long “Long Range Range Ultrasonic Ultrasonic Technolog Technologies ies Part Part of  of 

TWI’s Non-De structive Testing Technology Click to editthe Master suNon-Destructive subtitle btitle style Group” broacher downloaded from website, www.twi.co.uk l l

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GUL website, www.guided-ultrasonics.com PetroChem Inspection Inspectio n Services, Inc. 1475 East Sam Houston Parkway South, Suite #100, Pasadena,  Texas  Texas

Contents § § § § § § §

Abstract – Introduction Sensitivity or Detectable Metal Loss General Restrictions Level of Inspection Difficulty GUL System – Challenges and Benefits Teletest System – Challenges and Benefits Conclusion

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Abstract Many inspectors and engineers do not realize there are three main commercial guided wave systems available globally and the differences in those systems  This presentation will discuss two out of the three systems and provide information to help the inspector or engineer decided which guided wave system may be the best for a particular piping inspection situation. The physics or technical details will not be discussed

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Guided Wave Introduction GUL system, Teletest system and MsS (magnetostriction) systems can all be generally described as a ring of guided wave sensors used to generate guided waves in a pipe. §

Guided waves are low frequency sound waves (in tens of kilo hertz sound waves as opposed to mega hertz in conventional ultrasonic testing) generated wrapped Clickby to transducers edit Master subtitle stylearound the pipe circumference. §

The MsS system (not discussed in details in this presentation) by Southwest Research is slightly more complicated. §

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Guided Wave Introduction All three guided wave systems detect pipe wall thickness changes which generate reflective acoustic waves. §

 These sound waves sweep the entire thickness of  the pipe, the pipe acting as a wave guide where the term guided waves originated. Screen response signals are caused by reflections from pipe features like butt welds, pipe tees, supports, clamps, etc.

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Guided Wave Introduction Guided wave system must be considered as a sorting or screening NDT tool instead of a flaw measurement tool. §

Sorting or screening NDT tool will classify pipe in categories of wall loss levels. §

Typically guided waves provide 100% initial pipe wall screening coverage which should not imply 100% full reliable inspection coverage. §

It is impossible to get response from small discontinuities 1% and less of pipe cross-section and longitudinal cracks 3% and less pipe cross-section. §

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Typical GUL Screen Response

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Sensitivity or Detectable Metal Loss Sensitivity or detectable metal wall loss for a crosssectional area should conservatively be expected to be 5%, with perfect conditions down to 2%. §

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Sensitivity or Detectable Metal Loss Guided waves do not measure wall thickness, just changes §

At every change in pipe cross-section thickness a detectable screen indication is noted §

Typical reflectors are pipe bends, circumferential welds, pipe tees, reducers, pipe supports, and of course corrosion §

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General Restrictions of Guided Wave Systems § At each guided wave test, the acoustic performance is situational. Restrictions include but not limited to:

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- Temperature Pipe contents will affect the acoustic waves Surface condition of the pipe Severe corrosion Pipe coatings Soil conditions And many more parameters can affect the final results

General Restrictions of Guided Wave Systems Basically if pipe butt welds can not be resolved on the screen presentation for a length of pipe, the exact inspection distance or how far the acoustic wave has travelled can not be determined. §

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Level of Difficulty Considering Test Conditions §  The following slides detail a guide for best, intermediate and complicated conditions for Guided Wave inspection. §

 The guide takes consideration of many factors for internal pipe product, external surface conditions, and pipe configuration

Note: Pipe flanges stop guided waves; pipe tees severely distort the acoustic sound; area immediately under transducer clamp and short distance on each side of test location not inspected §

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Level of Difficulty Considering Test Conditions Best Conditions § Internal pipe product Gas; vapor §

External pipe surface As new pipe surface, not coated/painted; well bonded coating/paint; mineral wool insulation (only if dry, wet results in attenuation); good condition calcium silicate insulation; and above ground

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Pipe configuration Straight runs of pipe; simple pipe supports (minimal contact); loose bolted pipe supports; no elbows; no smaller diameter pipe branches

Level of Difficulty Considering Test Conditions Intermediate Conditions Internal pipe product §

Low viscosity liquid (minimal acoustic absorbing); medium viscosity liquid (more acoustic absorbing) §

External pipe surface Slight corrosion pitting; thin plastic type coating; wet damaged insulation; underground sandy conditions (better); underground general soils (expect acoustic absorbing); soil-to-air interface

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Pipe configuration Mainly straight runs of pipe Few pipe elbows; reducers; tight encompassing or clamped supports (tight bolted supports); smaller diameter pipe branches (large pipe and small diameter branches, for example 30” diameter

Level of Difficulty Considering Test Conditions Complicated Conditions § Internal pipe product High viscosity liquid (high acoustic absorbing); waxy, paraffin, thick sludge, bottoms type liquid (severe acoustic absorbing); brine product can result in salt out and sound attenuation §

External pipe surface Bitumen or thick plastic coating (high acoustic absorbing); moderate corrosion pitting; concrete casing tightly adhering to pipe; severe general corrosion pitting; underground compacted clay (most severe acoustic absorbing). Factory applied polyurethane coating very attenuating

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Pipe configuration Many elbows; many branches; pipe tees; welded pipe supports

Test Loop for Comparing GUL and Teletest Add text

A permanent test loop was used to compare both GUL and Teletest systems  The same test clamp location was used for both systems and located about midway in the 6” test loop. Each system could easily display the pipe butt welds and the larger defects or machined anomalies placed into the 6” test pipe. 4/30/12

GUL System The guided wave system is based on the piezoelectric array sensors developed by the Imperial College in the United Kingdom §

GUL’s Wavemaker G3 Pipe Screening System uses low frequency guided ultrasonic waves to inspected difficult pipe areas such as road crossings, while in service. §

The G3 model has new advances to enhance focusing capability with reportedly down to 1% sensitivity, GPS, and improved signal amplitude calibration. GUL tightly regulates its training scheme required for all users on GUL equipment §

It has the capability of utilizing longitudinal, torsional, and flexural wave modes §

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GUL System

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GUL System Inflatable Ring with Transducers on Pipe

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GUL Challenges Elbow - Sound loss or distortion § Soil-to-air interface/Road Crossing: 3’ minimum and 8’ ( optimum) of free pipe prior to the ground entrance § Piping tees, flanges can not be inspected. § Couplings, fittings, branches, and corrosion acoustic distortion § Compacted clay deadens the acoustic sound beam. § Maximum temperature generally 150°F § Internal liquid or sludge material will dampen signal § Longitudinal cracks in the pipe will not be detected, unless they exceed 3% cross section using the torsional waves §

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GUL Challenges (continued) Isolated small pin holes can be over looked § Bitumen coating condition, if not brittle and disbanded, limit test to 45’ or less § Specialized Training required. § Verification of Training and Qualification are not standard but closely monitored by GUL § Data Analysis is very operator dependent, software will attempt to analyze but the operator must monitor and correct the software interpretations § Green line on the A-scan was the dead zone of the camp. Each side of the green line was grey line indicating the near field. Teletest did not show near field on their presentation §

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GUL Benefits Rapid scanning of numerous locations in one shift § Limited surface preparation. Painted surfaces good and after local insulation removal (2’ to 3’) hand wire brush cleaning generally satisfactory. Coal tar wrap will require removal and wire brush § Avoidance of general pipe system insulation removal § Long range capabilities (if conditions are right) § 100% of the pipe wall inspected (screened). § Internal and external pipe wall inspection § Inspect insulated pipe § Corrosion Under Insulation (CUI) survey with minimal insulation removal § Inspect inaccessible pipe areas §

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GUL Benefits (continued) Inspect pipe clamps § Inspect underground pipe § Inspect underground pipe at road crossings § Inspect river crossing pipelines § Inspect pipe racks § Inspect concrete encased pipe with restrictions § Sensitive to 3% cross-section change but reliable at 5%. If perfect Best Conditions, 1% sensitivity could be achieved § Set up time and results are faster compared to  Teletest system §

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Typical Screen Response of GUL System Showing the Dead Zone and Near Field

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Teletest System The guided wave system is based on a piezoelectric array sensors clamped around the pipe developed by the Imperial College in the United Kingdom §

The guided wave system is currently part of The Welding Institute (TWI) in the United Kingdom, Long Range Ultrasonic Technology (LRUT) group, and commercially available through Plant Integrity Ltd. (Pi) §

The guided wave system is called the Teletest Focus. §

The Teletest Focus can focus the ultrasound at points around the circumference of the pipe §

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It utilizes longitudinal, torsional, and flexural wave

Teletest System Inflatable Ring with Transducers

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Teletest System with Transducers

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Teletest Challenges Same as GUL Challenges with following changes: § Many more wires to attach to the Teletest clamp than the GUL clamp § Takes a minimum of 15 minutes to download all test parameters from test location on pipe. This does not include evaluation and set up time at that same location § In an 8 hour shift, less test positions can be evaluated compared to the GUL system §

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Teletest Benefits §

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Same as GUL Benefits

Teletest Display of 6” Pipe at PetroChem Test Loop

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Photo of Pitting on Pipe at 11:00 Position

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GUL - Simulated Pitting located at 11:00 Position Simulated pitting located @ 11:00 position.

Simulated pitting located @ 11:00 position.

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Example showing both A-scan and C-scan

C-Scan Display Display showing both A- scan supplemented with C-scan presentation §

C-scan display shows the amplitudes of the reflectors as a function of circumferential position on the pipe and distance from the transducer ring §

This helps in accurately locating the flaws and proper interpretation of the discontinuity §

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Conclusions §  The purpose of this presentation was to provide the benefits and challenges in using ultrasonic guided waves for inspection of piping systems

§  Two of the major guided wave systems used through out the world was discussed to help the inspector or engineer decide which system may be the best for their particular piping situation

This presentation does not endorse any of the major commercial guided wave systems §

Globally the guided wave manufacturers systems are in almost continuous hardware upgrades and software improvements not only for piping but for other plant equipment such as storage tank floors and exchanger tubes §

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