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The problem of evaluating the risk of failure associated with the propagation of a crack in a pipe under pressure has great practical relevance, and it may be tackled with acoustic-emission techniq...

In this paper the detection limit of lack of adhesive defects in GFRP adhesive composite joints was evaluated through a computational simulation model of active pulsed thermography technique. In this study, several simulations were carried out in order to evaluate the influence of the thickness of the collar, heating time and excitation energy on the detection limit of defects. In addition to these analyzes, it was also evaluated the reduction of the thermal contrast of the defects as a function of the thickness of the collar (depth of the defects) and thus it was possible to estimate mathematically the limit value of the thickness of the collar that allows the detection of the defects for each heating time. The results obtained showed that the pulsed thermography technique would be able to detect defects of lack of adhesive that are located up to 8.5 mm deep in this type of composite joint.

We developed a computer simulation model using finite elements for the reproduction of physical phenomena found in active pulsed thermography of GFRP adhesive tubular joints. During the manufacture of the joint, defects such as the lack of adhesive were included in order to evaluate the ability of the active pulsed thermography technique to detect this type of material and joint configuration. The experimental results obtained with the thermographic camera were compared with a numerical approximation obtained through the simulation model developed in this study using the Comsol Multiphysics ® software and, because of their similarity; it was possible to validate the computer simulation model. In both methods assessed in this study, it was only possible to detect the lack of adhesive when the thermographic test was performed from inside the joint, as, on the outer side of the joint, the defects' surfaces are at a depth greater than on the inner side.

This paper presents a numerical-experimental procedure to characterize through-holes with arbitrary shapes present on metallic substrates under composite material sleeves using pulsed laser shearography and dynamic excitation combined to the finite element method. The so-called fitting process consists of matching experimental and numerical results in order to determine the shape and dimensions of the holes under the composite repair, or even quantify defects between layers of the composite laminate. The results show that the technique is capable of characterizing, in the worst case, the geometry of a hole with 83% accuracy and its respective area with a maximum error of approximately 20%. The advantageous results achieved in this research show that the fitting process can be very useful for real applications in the oil and petroleum industry.

Monitorar os equipamentos em tempo real e de fundamental importância em sistemas de producao que apresentam riscos a seguranca e ao meio ambiente. O metodo de Emissao Acustica se destaca entre os ensaios nao destrutivos pela possibilidade de analisar a integridade de equipamentos durante o seu uso. Utilizar redes neurais para analisar os sinais de emissao acustica provenientes de trincas pode ser uma forma de monitorar falhas em equipamentos em tempo real e sem a necessidade da analise de especialistas. A propagacao de trincas pode ser classificada em diversas fases, e e importante parar a producao para reparo antes que a falha no equipamento entre na fase de propagacao instavel. O objetivo deste trabalho e o uso de redes neurais supervisionadas e nao supervisionadas para realizar uma divisao automatica da fase de propagacao de trincas em dutos rigidos de 40 metros e, em seguida, treinar redes neurais supervisionadas para classificar os dados previamente categorizados pela metodologia automatica desenvolvida. Dois conjuntos de dados provenientes de ensaios hidrostaticos diferentes foram utilizados nesta pesquisa. Para um deles, as redes neurais supervisionadas atingiram, em media, aproximadamente 82% de acerto na classificacao das fases de propagacao da trinca para o conjunto de teste e, para o outro, em torno de 90%.

Metallic pipes installed at top side offshore platforms may show corrosion damage. The corrosive process can be external or internal. One of the forms for mitigation consists in installation of composite repair to recompose the structural integrity of the corroded pipe segment. These kinds of repairs are normalized and considered temporary. After the designed time the repairs must be removed. To bypass the inconvenience of repair removing and production losses associated with the replacement of the corroded area, several projects are running to develop methods to ensure the integrity of the repair and the maintenance of the integrity of the piping. This article presents the development of a shearography system for integrity assessment of composite repairs. This system was developed in conjunction with UFSC. Several laboratory tests performed at real piping systems were done to develop: optomechanical and electronic systems, software and procedure to data acquisition. After laboratory tests, several field tests were performed at offshore and onshore situations to defined the final methodology to be used at real situations. Among the tests performed during development can be cited a campaign held in the PRCI. The technology was field proved at Campos Basin platform and shows that shearography inspection could help Integrity Management groups to keep the installation running in a safety conditions. Auxiliary systems derivatives were tested in similar situations in the inspection of structural composite repairs on hulls of FPSO. It was concluded that shearographic inspection is suitable to assessing the integrity of composite repairs on offshore piping. The next step will be hired this type of service in a regular basis.

Pipelines are subject to a variety of defects such as wall thickness loss, grooves, dents and holes. To restore the pipe integrity, polymeric composite repairs can be used. The inspection of repaired pipes is of fundamental importance, not only to verify the initial integrity, but also to monitor their state over time. Shearography is a laser optical strain measurement technique which compares a strain image in unstressed and stressed conditions to reveal the presence of defects and provides useful information about the interface between the repair and substrate, identifying delamination, interfacial disbond and holes. In this work, two pipes repaired with composites from two different providers were submitted to shearography inspection in order to analyze the repair system integrity. The inspections were performed to verify the presence or absence of detachments between the composite repair and subtracts and/or between the layers of the repair itself. After the procedure, the repairs were removed to compare and confirm the inspection results. Repair A presented some difficulty to be removed, what is in accordance with shearography results that exhibited the presence of only some superficial defects. The pipe surface aspect after composite removal was good, without any type of corrosion. On the other hand, the shearography inspection of repair B indicated lack of adhesion between the steel pipe and the composite repair. The repair removal was very easy, corroborating the inspection results. Also, it was observed that the pipe surface presented metal oxides. Through these inspections it could be noted an excellent correlation between shearography inspection results and the degree of difficulty to remove the repairs. The results from an inspection in an offshore platform are also presented. This inspection showed that shearography is an efficient method to inspect steel pipes repaired with composite materials in field.

The increasing industry demand for specialized materials promotes a breakthrough in material engineering. In this context, composite materials have gained recognition and have been increasingly employed in the most diverse segments of the industry. When applied to equipment with structural requirements, it is fundamentally important to periodically inspect these materials to ensure their integrity and safety. Often inspections are performed in the field, under unstable conditions generated by operational and environmental factors. Shearography is a valuable method of nondestructive testing (NDT) for industrial applications. This optical technique is less sensitive to environmental disturbances when compared to other interferometric techniques. This paper presents a new shearography configuration based on Diffractive Optical Elements (DOE). In the proposed configuration, a diffraction grating is positioned between the camera sensor and the imaging lens. Therefore, a more compact and robust system is obtained. Another advantage of the proposed system is related to phase shifting, which is generated by the lateral movement of the diffraction grating. Thus, phase shifting is relative to the diffraction grating period and not the laser wavelength as in traditional interferometers. This feature makes the system insensitive to variations in laser wavelengths. Since the period of the diffraction grating used is about 60 times greater than the laser wavelength applied, the shearography system using diffraction grating becomes much more robust for external influences compared to other configurations based on the Michelson interferometer. This paper also presents the evaluation of the proposed shearography system as well as prospective steps.

This work presents the development of a special shearography system with radial sensitivity and explores its applicability for detecting adhesion flaws on internal surfaces of joints of composite material pipes. The system uses two conical mirrors to achieve radial sensitivity. A primary 45° conical mirror is responsible for promoting the inspection of the internal surface all way around 360°. A special Michelson-like interferometer is formed replacing one of the plane mirrors by a conical mirror. The image reflected by this conical mirror is shifted away from the image center in a radial way and a radial shear is produced on the images. The concept was developed and tested. Two tubular steel specimens internally coated with composite materials and having known artificial defects were analyzed to test the ability of the system to detect the flaws. The system presented very good results on all inspected specimens. The experimental results obtained in this work are promising and open a new front for inspections of inner surfaces of composite pipes with shearography.

The aim of this study is to evaluate the ability of three nondestructive techniques—ultrasound, thermography and eddy current—for the detection of defects that can occur in metallic substrate with anticorrosive coating and compare the results regarding the advantages and disadvantages of each one of these inspection techniques. For this study, samples were made from a metallic substrate in which a composite anticorrosive coating and two types of defects were introduced: localized corrosion (defects of different geometries and depths inserted into the metallic substrate) and adhesion failure between the coating and the substrate. According to the results, all three techniques showed to be able to detect defects simulating localized corrosion on the substrate. However, the adhesion failure was only effectively detected by thermography and ultrasound and a high correlation between these two techniques was observed.

O interesse no monitoramento de equipamentos em tempo real é crescente nos dias de hoje, visando a maior segurança de operação dos mesmos. O ensaio de Emissão Acústica vem sendo objeto de desenvolvimentos com o intuito de aplicação em diversos tipos de equipamentos, com destaque na inspeção de dutos rígidos e flexíveis. O presente trabalho apresenta a metodologia e os resultados obtidos de um estudo de aplicação do método de Emissão Acústica para detectar defeitos em propagação em dutos rígidos pressurizados, sendo um trabalho pioneiro nessa área de pesquisa. Para tal, foram confeccionados corpos de prova com defeitos inseridos artificialmente, empregando-se a técnica de ultrassom por Time-of-flight diffraction (TOFD) para acompanhar o crescimento dos defeitos no duto submetido a ensaio hidrostático. Os sinais resultantes foram divididos em classes de Propagação, Propagação Estável e Propagação Instável, e usados como dados de entrada na implementação de classificadores não lineares via Redes Supervisionadas do tipo Retropropagação do Erro. Os resultados atingiram acertos de classificação próximos a 86%, comprovando a eficiência do método para as condições testadas até o presente momento.

Composite pipelines are an attractive solution when traditional materials are not suitable for this purpose, which happens frequently at aggressive environments and also where the structural weight is a limiting factor. This work studies the application of the ultrasonic technique at the detection of defects as lack of adhesive and lack of adhesion, commonly found in adhesive joints of glass fiber reinforced plastic (GFRP) pipelines applied at onshore and offshore facilities. Computational simulations were conducted in CIVA 11© software (beta version) in order to obtain the best possible configuration for the inspections, applying the pulse-echo technique. Experimental results were compared to these simulations and several transducers were tested. An inspection methodology and reference blocks were developed for the calibration of the inspections. Some samples were selected for cutting in order to compare the ultrasonic results and the real condition of the joints. Results show that smaller frequencies are suitable for the inspection of this material and focused probes present more accurate results.

GRP-type composites (Glass-fibre Reinforced Plastics) have been continuously employed in the oil industry in recent years, often on platforms, especially in pipes for water or oil under moderate temperatures. In this case, the pipes are usually connected through adhesive joints and, consequently, the detection of defects in these joints, as areas without adhesive or adhesive failure (disbonding), gains great importance. One-sided inspection on the joint surface (front side) is a challenging task because the material thickness easily exceeds 10 mm that is far beyond the limits of the capacity of thermography applied to GRP inspection, as confirmed by the experience. Detection limits have been evaluated both theoretically and experimentally as a function of outer wall thickness and defect lateral size. The 3D modeling was accomplished by using the ThermoCalc-6L software. The experimental unit consisted of a FLIR SC640 and NEC TH- 9100 IR imagers and some home-made heaters with the power from 1,5 to 30 kW. The results obtained by applying pulsed heating have demonstrated that the inspection efficiency is strongly dependent on the outer wall thickness with a value of about 8 mm being a detection limit.

Acoustic emission testing may be employed as a nondestructive technique to detect flaws in materials and equipment. For pressure vessel construction, the test requires loading by internal pressure in order to open the flaw tips and to generate acoustic emission signals. The present work tries to investigate whether the required pressure level causes flaw propagation, risking vessel integrity. The material employed was a fine grained normalized C-Mn structural steel (ASTM A 516 gr. 60). Fracture mechanics crack tip opening displacement (CTOD) tests were conducted and the acoustic emission probes were placed on the testpieces, which enabled a correlation to be established at any moment between the crack acoustic behaviour and its CTOD value. A relevant result was that intense acoustic activity was detected before the first stable crack extension occurs. On a quantitative basis, it was found that the CTOD value corresponding to the first detectable acoustic emission from the loaded crack tip is lower than the CTOD for the initiation of stable crack propagation. As a final conclusion from this work, it can be said that for this specific steel, acoustic emission testing may be reliably performed at sufficiently low CTOD values, where the risk of fracture may be discarded.

Abstract Deep water oil and gas exploitation in Brazil has considerably increased the utilization of flexible pipes in conjunction with floating production systems. Acoustic emission is a nondestructive testing technique that could be used for detection of tensile armour wire rupture, which is a critical failure mode of flexible risers. This paper describes the experimental program implemented including: laboratory results, field experience and the model to define if there is or no armour wire rupture. It was concluded that acoustic emission can be used as a tool to help the integrity assessment of flexible risers using the setup and model developed during this experimental program. Introduction Deep water oil and gas exploitation in Brazil has considerably increased the utilization of flexible pipes in conjunction with floating production systems. Periodic inspections have detected considerable occurrence of damage on the top section of flexible risers which may affect their structural integrity. In order to mitigate the progression of these damages monitoring techniques have been studied and implemented for a continuous flexible riser integrity assessment, apart from the inspection program. Acoustic emission is one of these techniques for detection of tensile armour wire rupture. This paper describes experimental program implemented including: laboratory results, field experience, equation to define if there is an armour wire rupture or not. It was concluded that acoustic emission could be used as a tool to help the integrity assessment of flexible risers. Acoustic emission is a physical phenomenon occurring within materials. The term acoustic emission is used to define the elastic energy released within a material in the form of transient elastic waves. The application of load and/or the presence of a harsh environment produce internal modifications such as crack growth, local plastic deformation and corrosion, and in some cases phase changes. Thus it provides some information about the internal behavior of the materials under consideration. The waves are detected by means of suitable sensors which make it possible to convert the surface movements of the material into an electric signal. These signals are processed by appropriate instrumentation with a view to indicating and locating the acoustic emission sources. Figure 1 shows the schematic principle of the acoustic emission testing. [AFIAP, 2004]

The acoustic emission test has distinguished relevance in non-destructive testing and, therefore, existing research abound at present aiming at the improvement of the reliability of their results. In this work, the methodologies and the results obtained in a study performed are presented to implement pattern classifiers by using artificial neural networks, aiming at the propagation of existing defects in pressurized pipes by means of Acoustic Emission testing (AE). Parameters that are characteristic of AE signals were used as input data for the classifiers. Several tests were performed and the classification performances were in the range of 92% for most of the instances analyzed. Studies of parameter relevance were also performed and showed that only a few of the parameters are actually important for the separation of classes of signals corresponding to No Propagation (NP) of defects and Propagation (P) of defects. The results obtained are pioneering in this type of research and encouraged the present publication.Copyright © 2006 by ASME

During the last years, PETROBRAS has used acoustic emission technique as an inspection tool. In this period, the acoustic emission concept has changed from a revolutionary technique to a global inspection technique with the aim of indicating areas to complementary inspection. In the last years more than 600 acoustic emission tests were done in equipments like pressure vessels, reactors, tanks, spheres, and etc. In 2002, the results of acoustic emission tests and nondestructive tests done on these equipment were collected to build a database in the PETROBRAS environment. Analysis made in this database has shown that exists a clear relationship between acoustic emission and the severity of flaws.Copyright © 2006 by ASME

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO O parque industrial nos países em desenvolvimento necessita, cada vez mais, se adaptar a uma nova filosofia de serviço em que equipamentos considerados como seguros são aqueles que podem ser inspecionadas de forma confiável. Neste contexto, ensaios não destrutivos (END) são valiosas ferramentas usadas no controle de qualidade, manutenção de componentes e, principalmente, na avaliação da integridade estrutural de tais equipamentos. Este trabalho teve como objetivo avaliar a eficiência de diferentes técnicas de END (radiação penetrante, partículas magnéticas e ultrassom) na detecção de descontinuidades simuladas em amostras de material metálico e de compósito. Os resultados experimentais mostraram que os ensaios com raios X, dentre todas as técnicas adotadas na inspeção da amostra metálica, apresentou a maior eficiência na detecção das diferentes geometrias de descontinuidades. Entretanto, nenhuma das técnicas de END possibilitou a detecção de descontinuidades na amostra do material compósito. The industrial park in developing countries need, increasingly, to adapt to a new service philosophy in which equipments considered as safe are those that can be inspected in a reliable way. In this context, non-destructive testing (NDT) are valuable tools used in quality control, maintenance of components and especially in assessing the structural integrity of such equipment. This study aimed to evaluate the efficiency of different NDT techniques (penetrating radiation, ultrasound and magnetic particles) in the detection of simulated discontinuities in samples of metallic and composite materials. The experimental results showed that the X-ray, considering all techniques adopted in the inspection of the metallic sample, showed the highest efficiency in the detection of different geometries of discontinuities. However, anynone of NDT techniques allowed the detection of discontinuities in the sample of the composite material.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO Um dos principais mecanismos de falha em risers flexíveis é o rompimento de arames da armadura de tração. A experiência tem mostrado que esta classe de dano tende a surgir primariamente na parte emersa do riser, próximo à sua terminação. A ruptura dos arames ocorre de forma progressiva, podendo ser causada por diferentes processos, tais como corrosão pelo ingresso de fluido no espaço anular entre capa e armadura, desgaste excessivo associado com o contato e atrito entre arames adjacentes ou entre as diferentes camadas metálicas da armadura, ou mesmo a presença de níveis elevados de tensões produzidas pelos carregamentos mecânicos aos quais o riser é submetido durante a operação. O deterioramento progressivo pode dar origem a defeitos localizados que agem como concentradores de tensão e levam o arame à ruptura através de um processo de fadiga. O duto flexível é capaz de manter-se em operação mesmo com alguns dos arames de suas armaduras rompidos, porém uma sequencia de rupturas pode levar à ocorrência de vazamentos ou mesmo a falhas catastróficas. O monitoramento contínuo em tempo real é uma das principais alternativas para evitar que o dano progressivo nas armaduras do riser resulte em acidentes com severas consequências econômicas e ambientais. As técnicas de monitoramento da integridade de risers flexíveis podem ser classificadas como diretas, onde é possível identificar diretamente a existência de um dano/falha, ou indiretas, em que o sistema de sensoriamento registra indicações secundárias, possivelmente consequência da falha. Esta dissertação relata o desenvolvimento de um sistema de monitoramento baseado em vibrações. Trata-se de uma técnica indireta baseada em eventos, onde no momento da ruptura do arame um sinal de vibração, distinto tanto na frequência quanto na amplitude, é detectado por acelerômetros instalados na capa polimérica externa do riser. No trabalho, são apresentados resultados de quatro ensaios em escala real que demonstraram a viabilidade do sistema para um primeiro teste de campo. Estratégias de instrumentação dos dutos e as variações dos sinais detectados são apresentadas e discutidas. Os resultados mostraram que a resposta vibratória do sinal de ruptura apresenta características específicas, garantindo uma boa confiabilidade na detecção. Porém, em se tratando de uma técnica indireta, verifica-se que quando dois sistemas de monitoramento de naturezas complementares são empregados em conjunto, as probabilidades de detecção dos eventos de rupturas aumentam significativamente. The main failure in flexible risers is the disruption of the wires from the tensile armor layer. Experience has shown that this class of damage occurs primarily near to the top riser connector. The breaking of the wires occurs gradually and may be caused by different processes as corrosion by inflow of fluid in the annular space, excessive wear associated with the contact and friction between adjacent wires or between different riser layers. The progressive deterioration can lead to localized defects that act as stress concentrators and may break the wire from the tensile armor layer through a fatigue process. The flexible pipe is able to remain in operation even with some broken wires, but a sequence of ruptures can conduce to a catastrophic failure. Real time continuous monitoring is one of the main alternatives to prevent progressive wire damage results in an accident with severe economic and environmental consequences. This thesis describes the development of a monitoring system based on vibrations. This is an indirect technique based on events, where in the moment of the wire break, one vibration signal is registered. This signal can be distinguished both in frequency and amplitude and detected by accelerometers installed on the polymeric outer layer of the riser. We present results of four tests in real scale that demonstrated the viability of the system for an initial field test. Instrumentation strategies in riser and the variations of the signals detected are presented and discussed. The results showed that the vibrational signal has specific characteristics ensuring good detection reliability.