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Final Report Summary - INNOPIPES (Innovative nondestructive testing and advanced composite repair of pipelines with volumetric surfaces defects)

Pipeline systems have supreme significance for an effective functioning of industry providing Eastern and Western European markets with energy resources: crude oil, natural gas and liquid petroleum products. Taking into account long life of pipeline networks and situation, when over 20% of large-diameter pipelines are with an exhausted lifetime, an important task at the present time becomes an ensuring of reliability for these transport systems. An intensive study shows that among the main reasons of pipeline accidents are the volumetric surface defects (VSD) arising as a result of corrosion or erosion-corrosion processes and by this way considerably decreasing the pipeline strength. In order to ensure efficient and safe operation of existing pipelines, operating companies routinely inspect the pipes. The methods that are used for this purpose, like “smart pig”, are sufficiently expensive, require, in some cases, significant reconstruction and have an insufficient sensitivity. An application of new composite materials for the repair of damaged pipelines considerably improved situation in the last time. However numerous standards associated with this type of repair are based on simplified approaches and do not take into account the stress-strain state in the damaged areas.

Strategic objective of the project is addressed to the improvement of infrastructure in EU and Third counties by the rising of reliability of existing pipeline systems. Work over this project will serve IRSES main goal achievement – strengthening research partnerships through short period staff exchanges and networking activities between organisations from EU and Third countries.

The scientific and technical objectives are improvement of existing and developing of new methods for detection and repair of VSD based on low-frequency ultrasonic testing with directional waves and advanced composite repair systems to bring efficiency of damaged section up to the level of undamaged pipeline.

To realise the strategic objective in the project period covered from 01.09.2012 to 31.08.2016, 411 of full-time equivalent months have been used for short period staff exchanges and networking activities between organisations from EU and Third countries. Two training events have been carried out in Warsaw, Poland (2013) and Rostov on Don, Russia (2014) where 26 lectures on NDT and advanced composite repair have been presented by ERs from all participating organisations and leading researchers from the host countries. To acquaint the consortium with an experience of ESRs, the round tables for ESRs with their presentations have been organised in the training events. To disseminate the results of project 4 workshops have been carried out in Sozopol, Bulgaria (2014 and 2015), Kaliningrad, Russia (2015) and Gomel, Belarus (2016).

To realise the scientific and technical objectives in the project period covered from 01.09.2012 to 31.08.2016, the following main activities have been executed:

• The mechanism of interaction of low-frequency guided waves with discontinuities and different types of generating and receiving guided ultrasonic waves (piezoelectric, electromagnetic-acoustic, magnetostrictive) have been investigated to define the optimal wave modes for the detection of discontinuities and corrosion damages in long distance pipelines. An effectiveness of the dry acoustic contact technique for a transmission of ultrasonic waves from the ultrasonic antenna array to pipeline material has been studied. The directional properties of ultrasonic antenna array has been analysed according to the number of array elements and the method of its excitation. Recommendations for an application of the long-range ultrasonic testing technology for a pipeline diagnostics have been prepared. Different analytical, numerical and numerical-experimental methods have been developed for an accurate characterisation of damage founded in pipelines by the long-range ultrasonic technique.

• The main types of composite materials used to repair transmission pipelines have been analysed. Perspectives of the materials based on basalt fibres or nitrile rubbers and phenolic resins with different catalysts and additives have been studied for their application in the advanced composite repair systems. Static approach, using a three-point-bending test, and two dynamic methods: impulse excitation and inverse technique based on vibration tests have been developed for an accurate, reliable and effective non-destructive characterisation of elastic, hysteretic and viscoelastic material properties. Micro-indentation, ultrasonic and electrochemical methods, tensile and fatigue tests, simultaneous thermal and dynamic mechanical analyses have been applied to investigate experimentally mechanical, ultrasonic, electrochemical and thermal characteristics of the materials used for a pipeline repair. Analysing the literature, information of pipeline operating companies and experience of project partners, the database structure, containing all the information on the existing composite repair systems, has been developed. New procedure for a determination of the remaining strength factor for pipelines subjected to local metal loss and new design methodology defining the parameters of composite repair has been created.

• Different analytical and numerical models describing a stress-strain state in the linear and elbow pipeline sections, and T-joints with an advanced composite repair have been created. The impact of technological tension on the efficiency of pipelines reinforcement by composite bandages, consolidation effect of the bearing capacity of a transmission pipeline in the contact area with concrete supports along an above ground crossing, and corrosion pits on pipelines and reasons of atmospheric corrosion under stresses have been investigated. An optimisation methodology based on the planning of experiments and response surface technique has been developed for the advanced composite repair systems to considerably decrease the computational efforts. An impact of composite repair geometrical parameters and properties of its constituent materials on the stress-strain state in VSDs has been taken into consideration. The initial data have been prepared for the composite repair industrial approbation.

• To obtain preliminary information for the design of full-scale specimens, additionally to the mechanical tests of materials used for the advanced composite repair, an influence of outer surface quality on the repair effectiveness has been investigated using tensile and shearing adhesion tests. Four full-scale pipe specimens (pipe, pipe with composite bandage, pipe with machined artificial defect, pipe with machined artificial defect and composite bandage) and two full-scale cylindrical vessel specimens strengthened by a composite wrap or without it have been produced for the first and second experimental programs. The methodology for an experimental characterisation of the effectiveness of the developed composite repair of damaged pipe specimen under hydraulic burst test has been developed. Comparative analysis of the test results has demonstrated an effectiveness of the developed repair technology. Appearance and growth of in-service corrosion defects in pipelines at low-cycle modes of loading by the inner pressure have been studied additionally using hydraulic tests of damaged pipes. The experimental results of the first and second test programs have been successfully verified by the corresponding finite element analyses.

The research could be relevant for a wide audience, namely for students and researchers studying and developing effective non-destructive techniques and advanced repair systems as well as for engineers designing and exploiting different pipeline networks.

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