Piping sYstem, Risk management based on wAll thinning MonItoring and preDiction – PYRAMID

The mass flux and mass transfer coefficient evaluation method through a diffusion-controlled limiting current measurement under flow by using a rotating cylinder electrode has been developed.
The experimental set up for corrosion rate evaluation under controlling the mass transfer coefficient has also been developed.
To clarify the solid particle behavior in a piping flow, a water-circulation loop was fabricated.
Three-dimensional solid-liquid two-phase flow calculations around elbow were conducted with a solid-particle simulation model. Flow drift and separation around the elbow were compared with the experiment described above, and the qualitative agreement was validated.
From these simulations, we defined the position, thickness, and shape of calibrated flaws on elbows and have been machined at INSA.
Online wall thinning EMAT evaluation has been carried out during controlled electrochemical corrosion tests. A good agreement with the profilometer measurements has been found.
Guided waves EMAT measurements have been carried out on non-ferromagnetic pipes in order to validate the CIVA module.
Prototype point focus transducers were fabricated, and it was confirmed that incident beams were successfully focused, observing the sound field experimentally.
Development and validation of simulation tools to support the optimal design of EMAT probes. Specific models of EMAT probes have been introduced in CIVA enabling to simulate the excitation and the propagation of ultrasonic waves into pipes and elbows.
Risk Evaluation: a probabilistic evaluation method of future damage was proposed. The evaluation of the damage progression rate as the degree of belief by Bayesian estimation, the evaluation error of the diagnostic method, and the uncertainty of the progression rate due to uncertain factors are considered. Future thinning is evaluated by a Bayesian estimation using data from EMAT probes.

- Ultrasonic evaluation of the roughness of test samples with different simulated roughnesses.
Based on a method described in the literature, we checked the possibility to evaluate the roughness of a surface from an ultrasonic bulk wave attenuation measurement. These experiments have been carried out on samples on which artificial roughnesses have been simulated by machining a periodic profile of variable pitch and depth.

- Online monitoring of the thickness loss during a controlled electrochemical corrosion experiment.
MATEIS developed a corrosion cell on which we have been able to monitor in situ and in real-time, the thickness loss of carbon steel samples, by time-of-flight measurement of SH bulk waves generated by an EMAT. Good agreement has been found between the ultrasonic estimated values and the once evaluated by profilometry.

- Simulation tools of EMAT excitation in a pipe with the 3D FEM code have been developed by CEA and are under validation thanks to experimental data provided by LVA.

- Simulation of the EMAR technique with CIVA, have shown very encouraging results. The simulation reproduces the experimental procedure (one simulation per frequency composing the investigated spectrum). It has been validated on very simple situations and allows now to account for nonuniform thinning by adding deformation of the test part, for instance

- Modeling of Point Focus EMAT to support probe optimization carried out at Tohoku Univ.
The simulations confirmed the actual focalization of the ultrasonic beam produced by the point focused EMAT developed by IFS.

During the first half of the project, experimental and simulation tools have been developed and validated in simple cases. For corrosion phenomena as well as for ultrasonic waves propagation.
Sixteen elbows, have been machined to simulate actual flaws and are available in France and in Japan for the development of the NDT inspection methods. CIVA simulations will now be used to help the design of new coils and the definition of the optimal network of sensors to be used.
The signal processing of experimental data will also be studied and optimized.
The same code will allow us to estimate the measurement error and then feed the risk management method.

The work in progress has been the subject of several communications in scientific meetings and congresses:
1. Piping sYstem, Risk management based on wAll thinning MonItoring and preDiction ; ELyT Workshop 2018, March 6-8, 2018, Satillieu, France
2. Study of the surface roughness measurement by ultrasonic scattering on a carbon steel block ; ELyT Workshop 2018, March 6-8, 2018, Satillieu, France
3. Piping system, risk management based on wall thinning monitoring and prediction - PYRAMID; 4 th ICMST-Tohoku 2018 Japan Society of Maintenology
4. Advanced simulation tools for nondestructive assessment of corrosion affecting steel pipes; 4 th ICMST-Tohoku 2018 Japan Society of Maintenology
5. Corrosion Induced Roughness Characterization by Ultrasonic Attenuation Measurement; 4 th ICMST-Tohoku 2018 Japan Society of Maintenology
6. Thickness Measurement of Uneven Specimen Using Frequency Domain Signal of Pulse Echo by Electromagnetic Acoustic Transducer; 4 th ICMST-Tohoku 2018 Japan Society of Maintenology
7. Piping system, risk management based on wall thinning ; ELyT Workshop 2019, march 10-12 2019, Osaki, Japan
8. Recent advances in PYRAMID project : EMAT experimental results for corrosion characterization ; ELyT Workshop 2019, march 10-12 2019, Osaki, Japan

The PYRAMID project is an International Collaborative Research Project (PRCI), which brings together French public laboratories (MATEIS and LVA at INSA Lyon, and CEA), an International Joint Unit (ELyTMaX), Japanese public laboratories (IFS, and GSE at Tohoku University, GSST at Gunma University), and the Nuclear Technology Research Laboratory at CRIEPI a non profit research foundation, supported by the electrical japanese industries.
PYRAMID project aims to develop new tools and techniques to detect and quantify wall thinning due to Slurry Flow induced Corrosion (SFC) in piping systems. SFC is a special case of Flow Accelerated Corrosion (FAC) in presence of a flow with a high concentration of debris of various kinds (concrete, corrosion, metallic…).
The final goal is to provide a risk management system based on prediction-monitoring of wall thinning due to SFC.
Corrosion modes and rate will be predicted by numerical simulations at any position for actual layouts of piping systems such as elbows. These predictions will be validated by electrochemical experiments under controlled mass transfer coefficient.
Also Ultrasonic Non Destructive Testing (UT) methods will be designed with the help of simulations and their performances will be investigated in corrosion test facilities. The adequate signal processing techniques based on Bayesian approaches will be developed.
UT techniques are widespread in industry because they allow the control in the bulk of the component and help to improve productivity and compliance of products with quality and safety requirements. Among them, Electro-Magnetic Acoustic Transducers (EMAT) allow the generation and sensing of elastic waves in a part without mechanical contact with it; therefore, they can be used at high temperature and in various harsh environments where standard piezoelectric transducers fail. The use of EMAT constitutes a versatile solution adapted to complex cases.
The availability of validated simulation tools to predict the wave field they generate and their sensitivity to an arbitrary wave field is crucial if one wants to benefit of their advantages and limit their drawbacks. Once such tools are developed, they can be efficiently coupled to other tools dedicated to elastic wave propagation and scattering, the complete set of simulation tools allowing the full simulation of non destructive inspections in complex cases.
Elastic Guided Waves (GW) are used in the non-destructive testing of pipes. Numerical study of GW scattering is often computationally expensive because of very short wavelengths compared to the size of the pipe. Furthermore, the number of scattered modes from non-axisymmetric defect (as typical corrosion area, crack…) can be too large for standard finite element method (FE). Accordingly, the simulation platform CIVA deals with models based on a Modal Formalism to simulate non-destructive inspection by GW using the Semi-Analytical Finite Element method (SAFE). Presently, EMAT sources are taken into account in an efficient hybrid SAFE/FE method for computing the scattered modes by an arbitrary complex defect that has been implemented for several years in CIVA NDT simulation platform by CEA.
To increase the method reliability, simulations will help selecting the best technical solution, based on Probability of Detection and flaw characterization performance. Special ultrasonic imaging techniques will also be applied.
This dual approach, which combines simulation and characterization, should make it possible to optimize the inspection process in corroded steel pipes.
From all the data gathered during the project, an industrial risk evaluation of any kind of piping system subject to corrosion will be performed.
The results of the research carried out in the project will be directly applicable to any kind of piping system subject to corrosion that has to be detected, quantified and the subsequent risk evaluated.