Ultrasonic thickness structural health monitoring photoelastic visualization and measurement accuracy for internal pipe corrosion

Abstract

Oil refinery production of fuels is becoming more challenging as a result of the changing world supply of crude oil towards properties of higher density, higher sulfur concentration, and higher acidity. One such production challenge is an increased risk of naphthenic acid corrosion that can result in various surface degradation profiles of uniform corrosion, non-uniform corrosion, and localized pitting in piping systems at temperatures between 150°C and 400°C. The irregular internal surface topology and high external surface temperature leads to a challenging in-service monitoring application for accurate pipe wall thickness measurements. Improved measurement technology is needed to continuously profile the local minimum thickness points of a non-uniformly corroding surface. The measurement accuracy and precision must be sufficient to provide a better understanding of the integrity risk associated with refining crude oils of higher acid concentration. This paper discusses potential technologies for measuring localized internal corrosion in high temperature steel piping and describes the approach under investigation to apply flexible ultrasonic thinfilm piezoelectric transducer arrays fabricated by the sol-gel manufacturing process. Next, the elastic wave beam profile of a sol-gel transducer is characterized via photoelastic visualization. Finally, the variables that impact measurement accuracy and precision are discussed and a maximum likelihood statistical method is presented and demonstrated to quantify the measurement accuracy and precision of various time-of-flight thickness calculation methods in an ideal environment. The statistical method results in confidence values analogous to the a90 and a90/95terminology used in Probability-of-Detection (POD) assessments. RightsCopyright 2015 Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. ABSTRACTOil refinery production of fuels is becoming more challenging as a result of the changing world supply of crude oil towards properties of higher density, higher sulfur concentration, and higher acidity. One such production challenge is an increased risk of naphthenic acid corrosion that can result in various surface degradation profiles of uniform corrosion, non-uniform corrosion, and localized pitting in piping systems at temperatures between 150°C and 400°C. The irregular internal surface topology and high external surface temperature leads to a challenging in-service monitoring application for accurate pipe wall thickness measurements. Improved measurement technology is needed to continuously profile the local minimum thickness points of a non-uniformly corroding surface. The measurement accuracy and precision must be sufficient to provide a better understanding of the integrity risk associated with refining crude o...

Structural health monitoring of offshore wind turbines: A review through the Statistical Pattern Recognition Paradigm

“…This approach was reviewed by [38] and [39]. Another example is presented in [40], where different techniques for corrosion monitoring are introduced and the application of flexible ultrasonic thin-film piezoelectric transducer arrays is described. Lastly, [41] suggests a methodology to enhance the reliability of SHM for flexible risers, which are widely used in offshore oil exploration facilities and are essentially composite structures consisting of several metal armours and polymeric layers.…”

Structural health monitoring ultrasonic thickness measurement accuracy and reliability of various time-of-flight calculation methods

“…2 and previously described [19,22]. The gain for each sensor was individually adjusted to maximize the first back-wall reflection amplitude without saturation.…”

“…8 [17]. The industry recognized a 90 confidence value can be determined as the cumulative distribution point from the maximum likelihoodμ andσ model, while the a 90/95 confidence value can be determined with the Delta method to establish Wald confidence intervals [18]; alternatively, the a 90/95 confidence value can be determined using a simulation method to construct a set of distribution models with the μ and σ parameters from the relative likelihood confidence region perimeter [19].…”

Ultrasonic thickness structural health monitoring of steel pipe for internal corrosion

“…A confidence region of the most likely µ and σ parameters corresponding to the relative likelihood values greater than α as derived from a χ 2 distribution with two degrees of freedom is shown in Equation 8.14 [Meeker and Escobar (1998)]. The industry recognized a 90 confidence value can be determined as the cumulative distribution point from the maximum likelihoodμ andσ model, while the a 90/95 confidence value can be determined with the Delta method to establish Wald confidence intervals [Annis (2009)]; alternatively, the a 90/95 confidence value can be determined using a simulation method similar to Monte Carlo to construct a set of distribution models with the µ and σ parameters from the relative likelihood confidence region perimeter [Eason et al (2015b[Eason et al ( , 2016a].…”

“…Photoelastic beam profile construction of a proprietary 7.5 MHz thick-film sol-gel transducer for: a) maximum spatial amplitude, b) minimum spatial amplitude, c) final frame image, d) normalized maximum amplitude, e) normalized minimum amplitude, f) filtered normalized minimum amplitude, and g) filtered smoothed normalized minimum amplitude, and h) isosurface plot. Figure previously published[Eason et al (2015b)]. 3.3.2.2 Sol-Gel TransducerWhen applying Equation 3.1 to the proprietary 7.5 MHz thick-film sol-gel transducer with D = 4.0 mm, f = 7.5 MHz, and c = 5840 m/s, the resulting near-field length is 5.0 mm.The same elastodynamic simulation parameters from the manual contact transducer are used except with a single element 4 mm × 4 mm rectangular contact transducer with flat focus and a Gaussian frequency spectrum centered at 7.5 MHz with 100% bandwidth at -6 dB.The calculated near-field length of 5.0 mm from Equation 3.1 and CIVA model results are shown inFigure 3.7 with a comparison to the corresponding photoelastic beam profile image fromFigure 3.2g.…”