Cost-effective ultrasonic inspection of large diameter pipelines

To be successful in the ILI business, organization require the right mix of technological capabilities, operational agility and quality standards. The business is fairly competitive, and often technological capabilities are pivotal in the customer proposition of the company. However, the best technologies are not solely required for successful ILI companies. Robustness of the system, operability by the ILI inspector, fitness of the product with commercial route to the market all contribute to a rapid return on investment. Providing a robust, versatile, high-resolution and cost-effective method to inspect large diameter pipelines was recognized as a challenge and opportunity. For that, a Large Diameter Ultrasonic Inspection tool capable of inspecting pipelines of 20 inch to 64 inch with high resolution was developed. The tool is always bi-directional and capable of mitigating 1.5D bends. Gathered data can be reviewed real-time during the inspection. The operating envelope of the tool is such that it can cope with various products in the pipeline, varying from (high salinity) water, crude oil and a multitude of refined products. Despite the fact that product properties (e.g. speed of sound, attenuation, temperature, etc) vary, the tool is designed such that this is not a limiting factor for the operating envelope. The application of advanced ultrasonic beam forming methodologies and signal generation and -processing ensure that the system is versatile and robust for these types of real-life operating conditions. This presentation will provide an overview of the utilization of these technologies, the validation program that has been used to demonstrate tool specifications and the experiences gained at successful projects.

Causes of the field flowline weld joint rust-through damage

The paper presents results of the flowline pipe analysis in order to determine the causes of the butt weld joint rust-through damage (wormhole). Using Baumann sulfur print technique, the presence of iron sulfides scale on the inner pipe surface was studied. Using X-ray diffraction technique, the phase composition of the corrosion products was determined. It was found that chemical composition and mechanical properties of the metal from the studied flowline fragment comply with standard requirements. The resulting hardness values including those in the weld joint zones indicate that the metal has a certain corrosion-cracking resistance. Results of metallographic studies of longitudinal polished samples with full product thickness show that the residues of the weld capping pass remained on the bottom of the corrosion pit in the area of the observed rust-through hole. They have multiple pores up to 3 mm diameter. The corrosion pit surface is covered with iron sulfide layer 1–3 mm thick. The sulfide layer thickness in the area of the corrosion pit is 10+ times higher than on the rest pipe surface; this indicate that the corrosion process progressed faster here. The authors concluded that the cause for the weld joint rust-through damage was the pit corrosion that occurred under the impact of H2S-containing fluids on the lower generating line of the pipeline in the area of the weld startstop, where the weld root side suckback was observed. Probably, there was a flaw in the first weld pass within the corrosion pit area (shrinkage cavity, incomplete fusion, pore, or other), and the accelerated corrosion was the consequence of H2S-containing liquid slug here. This suggests that there was a flaw in the first weld pass within the area of the corrosion pit that has propagated along the first weld pass start-stop line.

Improved methods for sizing metal loss in dents for ECA

Dents interacting with metal loss remain as a significant challenge to operators. Existing regulations require that dents with metal loss within high consequence areas be treated as immediate repairs or 60-day conditions, resulting in costly excavations for many operators. At the time when these regulations were written, it was not clear whether inline inspection technologies could discriminate the nature of the metal loss (i.e. corrosion or mechanical damage) or provide accurate sizing. Furthermore, advanced analysis techniques such as finite element analysis were limited, and fitness- forservice evaluations were not common. While the technological hurdles involved with evaluating interacting dent and metal loss features have been overcome, sensor lift-off remains a challenging issue for magnetic flux leakage (MFL) inspection tools, as sizing accuracy degrades at larger lift-off distances. Until recently, the sensor lift-off issue limited the ability to perform fitness- for- service evaluations because the metal loss in dent features could not be confidently sized. This study demonstrates how integrated lift-off sensors can be used to quantify the lift-off as the MFL sensors pass over a dent. This technology integration has allowed the confident application of sizing specifications for many dents with metal loss, thereby permitting robust fitness- for- service evaluations. Several case studies are examined in this paper, demonstrating how the integrated MFL and lift-off technology can serve to reduce excavations while still ensuring safe pipeline operations.

Using deep learning to identify the severity of pipeline dents

With the advent of machine learning, data-based models can be used to increase efficiency and reduce cost for the characterization of various anomalies in pipelines. In this work, artificial intelligence is used to classify pipeline dents directly from the in-line inspection (ILI) data according to their risk categories. A deep neural network model is built with available ILI data, and the resulting machine learning model requires only the ILI data as an input to classify dents in different risk categories. Using a machine learning based model eliminates the need for conducting detailed engineering analysis to determine the effects of dents on the integrity of the pipeline. Concepts from computer vision are used to build the deep neural network using the available data. The deep neural network model is then trained on a sub set of the available ILI data and the model is tested for accuracy on a previously unseen set of the available data. The developed model predicts risk factors associated with a dent with 94% accuracy for a previously unseen data set.

Derivation of phenomenological turbulence theory in liquid with small additives of drag reducing agents

Paper considers the issue of deriving the phenomenological turbulence theory in liquids treated with small additives of drag reducing agent. It also proposes the concept that for practical purposes, it is the phenomenological theory, which is relevant, since it determines the parameters of the phenomenon in question in the absence of detailed knowledge of the mechanisms of additives action, which, despite many years of intensive studies, remain either unknown or not fully understood. Different additives have different effects on shear turbulence in pipes and channels and, accordingly, change the integral characteristics of the turbulent flow in different ways. Some additives affect only the narrow wall-bounded areas of the flow without changing the turbulent viscosity in the flow core, while others act throughout the entire flow volume and significantly change the turbulent viscosity. Additives of the first type affect a turbulent flow by changing the boundary conditions in known models without changing the model coefficients. Additives of the second type change both the boundary conditions and the coefficients of the model itself. It is shown that the von Karman modified theory (model) of shear turbulence is equally suitable for describing the turbulent flow of a liquid with additives of the both first and second types. The universal drag equation with experimentally determined transfer coefficients that follows from this model enables calculating the hydraulic drag coefficient depending on the properties of the drag reducing agent used.

Optimization modeling of degradation processes in crude oil spilled on the sea surface considering the wind conditions

The article describes an optimization model study of degradation processes in crude oil spilled on the sea surface considering the wind conditions. A new configuration of a simplified optimization model of the oil degradation process on the sea surface is proposed. Based on the proposed configuration, a simplified optimization model of oil degradation on the sea surface has been developed. The optimal relationship between the time dependence of the wind speed and the fractional volume of oil volatilization is established, at which the minimum fractional volume of oil dissolved in water is attained.

Numerical method for identifying the flow model in the line pipe

With high availability of measuring tools and wide opportunities of modern computer technology, the existing methods of predictive estimations of hydraulic parameters for the fluids’ pipeline transport seem to be too approximate. Due to this, it is relevant to adapt the most accurate relationships available in the scientific and technical literature to real conditions. Based on the review of analytical solutions for calculating friction losses in the pressure lines, the structure of relationships most accurately reflecting the experimental data of I. Nikuradze is determined, where the hydraulic drag coefficient ? is described by the piecewise-continuous relations, given by O. M. Ayvazyan. The hydraulic drag coefficient structural relationship shall be selected with the highest capability to summarize the experimental data available in the scientific and technical literature. Using the pressure measurement data, free parameters included in the selected relationship for the hydraulic drag coefficient shall be identified. The numerical computation algorithm is proposed that enables to recover the values of parameters in the structural relationship of hydraulic drag coefficient ? through multiple application of the well-known method of sensitivity functions and pressure measurement data in the line pipe. The procedure is described for generating the computing system of ordinary differential equations that enables for every fixed set of experimental data (pressure and flow rate) to determine (or correct, if necessary) the corresponding parameters in the unified structural relationship for hydraulic drag coefficient ?. The feature of the proposed algorithm is the absence of embedded cycles. Dynamic control of variable parameters in the hydraulic drag coefficient ? based upon the proposed approach enables to improve the predictive estimations accuracy of flow parameters while pumping fluids and to acquire additional data on the state of the fluids filling the inner pipeline space.

Method for determining technological parameters to repair pipeline with out-of-spec curvature

When performing in-line inspection of trunk pipelines, line pipe sections are detected with curvature exceeding the values required by specifications. To prepare a repair work project that entails bringing the pipeline into the standard conditions, it is necessary to determine the technological parameters of the repair. The corresponding technique is known for cases of moving an initially straight pipeline. The authors of the paper have developed the method for determining the technological parameters to repair pipeline with out-of-spec curvature of the axis. The method is based on simulation of pipeline deformation with the initial curvature of the axis, taking into account the actual operating conditions of the pipeline and in-line inspection data. Examples of calculations of repair technological parameters and stress-strain state of pipeline sections with out-of-spec curvature are given. The simulation results confirm the possibility for applying this method to assess the technological parameters of repair, the length of trench excavation, the size and limits of the pipeline additional burying or lifting, and to determine the stress-strain state of the pipeline section under repair during and after repair work.

The cross-disciplinary approach to analysis and forecast of operational damage tolerance of the oil pipeline system – part 2

The paper presents the cross-disciplinary approach to the analysis of the oil pipeline system based on the methodologies of tribo-fatigue and mechano-thermodynamics. The pipeline section is analyzed as a complex system pipe-soil- flow of liquid subject to the set of mechanical, thermal and friction loads. It is shown that theses loads are mainly repeatedlyalternated, and the pipe metal works in the multi-cycle fatigue conditions. The procedure of resonance accelerated fatigue tests is proposed, and their results are presented. Also, the unorthodox method of integrated wear-fatigue tests of the pipeline steel was proposed with the model of simultaneous pressure and wall friction actions. The presented field test results of pipes subject to the long-term operation showed that their fracture may occur not only in the near-weld zone, but also in the vicinity of internal corrosion damages. New models of three-dimensional stress-strain state and volumetric damage tolerance for the system pipe-soil-liquid flow were developed. These models were applied with regard to the pipe internal corrosion damages, defined using the inline inspection technique. A new efficient method to describe static and cyclic elastic-plastic fracture of the pipe steel with crack using the transverse strain is proposed and tested. Results of the computer-simulated propagation of the crack-like damage are based upon the model of deformed solid with dangerous volume. The new model is proposed for risk and safety assessment with regard to the ultrasonic inspection data. The algorithm of the ‘oil line pipe’ problem solution is presented for drafting a short-term plan of particular R&D actions.

Flexural dynamic response of monopile foundations under linear wave loads

An analytical solution for the dynamic response of submerged slender circular cylindrical structures subjected to linear wave loads is presented. A double Laplace transform with respect to temporal and spatial variables is applied both to motion equation and boundary conditions. The dynamic deflection of the beam is obtained by inversion of the Laplace transform. The latter with respect to spatial variable is obtained analytically, while the one concerning the temporal variable is numerically calculated using Durbin numerical scheme. Results in the case of a representative example for a monopile foundation subjected to Airy waves are presented and discussed, and the analytical result is compared against numerical dynamic and static solutions.