API 5L Research Articles

A review of onshore and offshore pipeline construction and decommissioning cost in the USA - part 1: specifications, cost estimation and onshore construction

The cost to construct and decommission oil and gas pipelines varies widely between onshore and offshore regions as well as within each area, depending on numerous factors. The purpose of this review is to evaluate publicly available data sources for onshore and offshore pipeline installation and decommissioning activities in the USA. The activities and processes involved, factors that impact cost, cost statistics and limitations of analysis are presented for onshore and offshore pipeline installation and decommissioning. Similarities and differences between construction and decommissioning processes and the tradeoffs involved in design are described to better understand the cost differences that arise between projects. In the first part of a two-part review, an overview of pipeline manufacturing and API 5L specifications introduce relevant terminology and basic pipeline requirements, and a description of cost estimation procedures, normalisation, and data sources provides the evaluation framework. A description of onshore pipeline construction cost data and analysis concludes the paper. [Received: May 4, 2020; Accepted: June 3, 2020]

A review of onshore and offshore pipeline construction and decommissioning cost in the USA - part 1: specifications, cost estimation and onshore construction

The cost to construct and decommission oil and gas pipelines varies widely between onshore and offshore regions as well as within each area, depending on numerous factors. The purpose of this review is to evaluate publicly available data sources for onshore and offshore pipeline installation and decommissioning activities in the USA. The activities and processes involved, factors that impact cost, cost statistics and limitations of analysis are presented for onshore and offshore pipeline installation and decommissioning. Similarities and differences between construction and decommissioning processes and the tradeoffs involved in design are described to better understand the cost differences that arise between projects. In the first part of a two-part review, an overview of pipeline manufacturing and API 5L specifications introduce relevant terminology and basic pipeline requirements, and a description of cost estimation procedures, normalisation, and data sources provides the evaluation framework. A description of onshore pipeline construction cost data and analysis concludes the paper. [Received: May 4, 2020; Accepted: June 3, 2020]

Experimental and Analytical Investigation on the Effect of Heat Treatment Parameters on the Mechanical Properties of an API 5L X65 Steel

High Strength Low Alloy steels (HSLA) for oil and gas pipelines should display high mechanical strength, toughness, ductility and weldability. In this work we studied the influence of quenching and tempering temperature on the yield strength, ultimate tensile strength, percent elongation and hardness of API 5L steel pipes in order to optimize heat treatments to be performed after hot induction bending of the material. The thermal cycles involved soaking temperatures of 880, 920 and 960 °C, cooling water at 15, 23 and 31 °C and tempering at 530, 600 and 670 °C. From this, experimental design techniques were used to reduce the number of experiments. The results from contour maps suggest that soaking temperatures of 910 and 950 °C and tempering between 540 and 610 °C were the most suitable for treatment, regarding mechanical strength. The variation of the water temperature was not significant for the assumed cooling conditions. The prediction regression models of the mechanical properties from the variables involved in the heat treatments showed a good fit between the experimental and predicted results, with correlation coefficient between 0.89 and 0.94.

Assessment of corroded API 5L X52 pipe elbow using a modified failure assessment diagram

Pipe elbows (bends) are considered critical pressurized components in the piping systems and pipelines due to their stress intensification and the effect of bend curvature. They are prone and hence more exposed to different corrosion failure modes than straight pipes. Late detection of such elbow damages can lead to different dangerous and emergency situations which cause environmental disasters, pollution, substantial consumer losses and a serious threat to human life. A comprehensive safety and reliability assessment of pipe elbows, including usage of prediction models, can provide significant increases in the service life of pipelines. It is well known that the limit pressure is an important parameter to assess the piping integrity. In this paper, the integrity assessment of damaged pipeline elbows made of API 5L X52 steel was done within the framework of numerical modeling using the finite element method (FEM) and finite element analysis (FEA). The evaluation of numerically FEM modeled limit pressure in the corroded elbow containing a rectangular parallelepiped-shaped corrosion defect with rounded corners at the intrados section was done and compared to different codes for calculating limit pressure. Moreover, the area with the corrosion defects with different relative defect depth to wall thickness ratios was FEM modeled at the intrados section of the pipe elbow where the highest hoop stress exists. The results showed that the codes for straight pipes could not be applied for the pipe elbows due to the significantly higher error in the obtained limit pressure value compared with numerically FEM obtained results. However, the results for modified codes, adapted for the pipe elbow case using the Goodall formula for calculation of the hoop stress in pipe elbows with defects are pretty consistent with the numerical FEA results. The notch failure assessment diagram (NFAD) was also used for the straight pipe and pipe bends with different corrosion defect depth ratios, while the obtained critical defect depth ratios further highlighted the criticality of pipe elbows as an essential pipeline component.

The study of corrosion behaviour api 5l steel in sea water using immersion test method

API 5L steel, a low carbon steel with a high alloy content, is often used as an underwater construction material or oil and gas pipeline. Banten has a wide sea area and has a long coastline where part of the coastline is used for petrochemical industries. There are three coast areas of Banten, namely Bayah Rangkasbitung, Anyer and Merak, that are used for petrochemical industries. Most of those industries use API 5L steel for underwater construction materials and pipes to channel seawater, chemical compounds, gas and oil. Whereas, seawater will greatly affect the lifetime of API 5L construction steel because it can cause corrosion. The purpose of this study is to analyze the corrosion characteristics of API 5L steel affected by the environment of seawater media and the temperature of seawater in accordance with its natural conditions. The samples of API 5L steel were immersed in seawater media with variation of immersion time of 5, 10, 15 Days and variation of immersion temperature of 20°C, 40°C, and 60°C. In this study, a series of tests were carried out, namely immersion test, weight loss test, and SEM test (Scanning Electron Microscopy). The highest corrosion rate on API 5L steel is 0.39 mmpy which belongs to Merak’s seawater media in the immersion time of 15 Days and the temperature of 60°C, while the lowest corrosion rate on the API 5L steel is 0.013 mmpy which belongs to Bayah’s seawater media with a time of immersion of 10 Days and a temperature of 20°C.

Burst capacity and development of interaction rules for pipelines considering radial interacting corrosion defects

Pipelines failures during its service life caused by the impact of multiple corrosion defects are most probable to occur, which may induce severe consequences as compared to single defect acting alone. Interaction rules were developed for multiple defects in the longitudinal and circumferential directions previously, but the knowledge on two or more defects aligned radially is still not well understood. This paper aims at investigating new interacting limits when corrosion defects are acting both on the internal and external wall, separated by a radial spacing, SR. The studies were carried out using burst test experiments as well as numerical modelling using pipe specimens of type API 5L X42. Six colonies of radial interacting corrosion defect arrangements were tested. The paper investigates the effects of the radial interaction by means of radial limit, SRLim. It was found that increasing the defect depths of internal and external defects would highly reduce the failure pressure, Pmultiple. Depending on the orientations of the multiple defects acting radially, the failure pressure may be less or more than the case of single defect, Psingle. Thus, the failure pressure ratio of Pmultiple/Psingle should be used as a measure, with any values larger than 0.99 depict no interaction taken place among those multiple defects. From the six colonies, only two colonies showed the significance of radial interactions. The paper then suggests that when radial interaction does not presence, multiple corrosion defects acting radially may then be treated as single defect.

Through-Thickness Inhomogeneity of Texture, Microstructure, and Mechanical Properties After Rough and Finish Rolling Treatments in Hot-Rolled API 5L X70 Pipeline Steel

The development of inhomogeneity in the microstructure, texture, and mechanical property in hot-rolled (API) 5L X70 pipeline steel after rough and finish thermomechanical control processing has been investigated by experimental measurements. Our investigations revealed that the rough rolling stage produced mostly large and coarse ferrite grains across the thickness, while the finish rolling stage led to a rather refined small-grained microstructure. EBSD investigations confirmed that after the rough rolling stage, recovered and deformed grains dominated the quarter and mid-thickness compared to the surface. Investigation of the finish rolled steel showed that in comparison with the quarter and mid-thickness sections of the plate, the surface section mostly consists of deformed grains. The texture components obtained from x-ray measurement showed that after rough and finish processing stages, the {001} , {110} , {123} , {112} , and {001} components were observed to be present. However, inhomogeneity of texture was observed at different depths of the rolled steel, such that in comparison with the surface, volume fractions of texture and intensities of the desired γ-fiber texture were seen to be highest at the mid- and quarter-thickness sections after both rolling stages. The room-temperature tensile stress–strain curves showed that the highest yield strength was observed for samples obtained from the near-surface section, while samples obtained from the mid-thickness section showed the highest elongation during tensile deformation. Overall, the final stage processing was observed to refine the final microstructure of the steel, thus improving the strength of the steel.

Hydrogen embrittlement of API 5L X65 pipeline steel in CO2 containing low H2S concentration environment

The basic corrosion mechanisms in CO2 environments are widely investigated and reported by scientific community. However, cracking failure mechanisms in CO2 environment or in environments where CO2 coexist with other gases need a better understanding. Cracking susceptibility of API 5L X65 in pure CO2 was recently reported and the basic mechanism was attributed to hydrogen embrittlement. The influence of hydrogen permeation and the detrimental effect of cathodic polarisation support the assumption of hydrogen embrittlement as the determining factor for the loss of plasticity and strength. The loss of strength of an API 5L X65 steel when CO2 and H2S coexist in the same environment is the focus of the present work. Hydrogen embrittlement (HE) and hydrogen induced cracking (HIC) of pipeline steels are failures modes expected to occur in CO2 with traces of H2S environments. The present work aims to approach the performance in laboratory of an API 5L X65 steel in CO2 with traces of H2S environment (slightly sour), using as baseline the performance of the material in pure CO2 environment (sweet), already reported. Hydrogen permeation and Slow Strain Rate Tests (SSRT) were carried out in CO2 environment containing low concentration of H2S. It was observed that traces of H2S in CO2 environment promote much more intense hydrogen permeation, much higher than in purely CO2 environment. Loss of ductility was also much more severe than in CO2 environment, with and without the influence of cathodic polarisation. Hydrogen generation enhancement promoted by traces of H2S in solution, corresponding to an average content of 21 ppm in solution, had a heavy effect on hydrogen embrittlement of the steel, confirmed by the lower ratio of reduction in area (RRA) and time to fracture in comparison with sweet service conditions.

Fracture assessment of pipeline girth weld at low temperature

The results of long-distance oil and gas pipeline failure analysis are important to the industry in order to maintain the reliability and safety of them. Seam welding in these pipes is done with good accuracy at place of work, while girth welding is carried out in the installation site and usually causes the main failure problem. Therefore, the most vulnerable and crucial part of these pipes is the girth welding. Investigating the fracture behavior of girth weld in high-pressure gas pipeline systems at low temperatures is important because these products are hazardous and may lead to explosion, leading to economic losses and environmental pollution. In the present study, the fracture behavior of girth-welded API 5L X65 natural gas transportation pipes was experimentally investigated at low temperatures. The fracture parameters were obtained using Arcan fixture in which all of the in-plane modes including pure tensile mode to pure shear mode can be created by altering the loading angle from 0° to 90°. Finite element analysis was also conducted by ABAQUS finite element software in order to determine geometrical coefficients which are required in calculating the fracture toughness. Results revealed that by decreasing the temperature and increasing the mode II loading contribution, the fracture toughness values were also decreased.

Design and assembly of an apparatus system based on the Villari effect for detecting stress concentration zone on ferromagnetic materials

This paper presents the study results on the fabrication of a structural integrity assessment apparatus by determining stress concentration zones in pressure pipeline and equipment. The apparatus uses a triaxial magnetic field sensor to measure magnetic field components in three axes Ox, Oy, and Oz, in the working range of the magnetic field from -300 µT to 300 µT. The investigation of the selfmagnetic leakage field by this apparatus in the API 5L steel specimens under tensile stress shows a high variation of the magnetic field at a steel elongation lower than 1 mm (corresponding to the elastic deformation state of the material). In the case of an artificial defect, the apparatus can detect a change in the magnetic field caused by stress concentration.

Composite patch repair of damaged tubular members from flare boom structures subjected to compressive loads

Conventional repair method for steel structures requires cutting and welding processes, which in offshore platforms may impose several disadvantages. Composite material repair has become an alternative for the rehabilitation of damaged structures and has been widely applied in other industries. In this work a numerical-experimental investigation evidences the effectiveness of the composite patch repair for flare boom corroded tubular elements subjected to axial compressive loads. A finite element model developed to determine the minimum composite laminate thickness that recovers the structural element strength is validated through numerical simulations. Twelve API 5L grade B reduced scale steel tubes with central perforations and similar longitudinal and transverse slenderness, respectively defined by length to radius of gyration of the cross-section area and diameter to thickness ratios, are tested covering the range of interest for full scale members. The composite material consists of a hybrid fabric made of carbon and glass fibers impregnated with epoxy resin. Severe localized corrosion is considered conservatively, idealized as a circular perforation in half the element length. In many cases the maximum load of the repaired tube even exceeded the intact tube capacity. Moreover, it is shown that sufficient load capacity recovery is achieved for the conditions assumed.

Application of Seeds from Psidium Guajava as Organic Inhibitor

Corrosion is the process of natural changes in the nature of a material due to the influence or reaction with the surrounding environment. One way to control it is by adding inhibitors. In this study, seeds from guava (Psidium Guajava) were used as organic inhibitors. The test material used is API 5L grade B steel. For corrosive media, a solution of 1 M H2SO4 is used. In experiments used variations in the concentration of extracts 0, 2, 3, 4, 5 and 6 ml. The results of the experiments showed a decrease in the corrosion rate of API 5L grade B when there were additional inhibitors. This is supported by the experimental results of Potentiodynamic Polarization. The rate of corrosion without the presence of an inhibitor shows 75,018 mmpy whereas in the presence of 2,8845 mmpy inhibitors. Based on the calculation, the inhibition efficiency is 96.155%. This is also indicated by the results of the testing of weight loss that has been done. The efficiency shown is 90.130%.

Experimental and theoretical study on the corrosion inhibition of API 5L X52 steel in acid media by a new quinazoline derivative

For the first time, the synthesis, characterization, and electrochemical assessment as corrosion inhibitor of steel API 5L X52 immersed in 0.5 M HCl of the molecule 2-bromo-6(2′,6′-dichlorophenyl) dihydrobenzo [4, 5] imidazo [1,2c] quinazoline, 2Br2′,6′diClDHBIQz is reported. To evaluate the corrosion inhibition efficiency, IE, of this synthesized compound the following were assessed: inhibitor concentration, temperature, hydrodynamic conditions and steel exposure time to the corrosive medium. At 25 °C, EIS indicated the IE increased to 92.7% having added 15 ppm (0.03 mM) concentration, remaining practically constant (91.9 ± 0.78) % in the whole electrode angular speeds range considered; IE values higher than 85%, were attained even after 280 h acid exposure in stagnant conditions. SEM and AFM images revealed the steel-protective capacity of 2Br2′,6′diClDHBIQz while XPS analysis proved its presence onto the steel surfaces. The theoretical results are in complete agreement with the experimental XPS analyses.

Burst Pressure Prediction of API 5L X-Grade Dented Pipelines Using Deep Neural Network

Mechanical damage is recognized as a problem that reduces the performance of oil and gas pipelines and has been the subject of continuous research. The artificial neural network in the spotlight recently is expected to be another solution to solve the problems relating to the pipelines. The deep neural network, which is on the basis of artificial neural network algorithm and is a method amongst various machine learning methods, is applied in this study. The applicability of machine learning techniques such as deep neural network for the prediction of burst pressure has been investigated for dented API 5L X-grade pipelines. To this end, supervised learning is employed, and the deep neural network model has four layers with three hidden layers, and the neural network uses the fully connected layer. The burst pressure computed by deep neural network model has been compared with the results of finite element analysis based parametric study, and the burst pressure calculated by the experimental results. According to the comparison results, it showed good agreement. Therefore, it is concluded that deep neural networks can be another solution for predicting the burst pressure of API 5L X-grade dented pipelines.

Correction to: Fatigue Behavior of Welded API 5L X70 Steel Used in Pipelines

Correction to: Fatigue Behavior of Welded API 5L X70 Steel Used in Pipelines

Finite element modeling of HIC propagation in pipeline steel with regard to experimental observations

In this research, hydrogen induced cracking (HIC) phenomenon in pipeline steel has been investigated by finite element modeling (FEM) with the help of experimental observations. Abaqus software has been utilized to model the crack. To this, first an API 5L X70 pipeline steel was electrochemically charged by hydrogen for 8 h to create different types of HIC cracks. Then, SEM was used to observe different types of hydrogen cracks. Based on the observations, most of HIC cracks were observed at the center of cross section where center segregation of some elements occurred. The results showed that HIC cracks propagated in stepwise, sinusoidal, straight and disordered manner. Moreover, HIC crack nucleated from a point with high stress concentration factor which was between non-metallic inclusion or void and metal matrix. The initiated micro-cracks from two neighbor inclusions link together to form a long HIC crack. Based on the experimental observations and FEM modeling, it was concluded that the driving force for the HIC crack propagation is the presence of hydrogen at the crack tip after it is initiated. Crack tip usually acts as a very small void and the combination of hydrogen atoms makes a high pressure which propel the crack forward. Moreover, the HIC crack propagation path was predicted by fracture mechanics approach showing that the J-integral had its maximum amount when the HIC crack tended to propagate horizontally.

External surface cracked offshore steel pipes reinforced with composite repair system subjected to cyclic bending: An experimental investigation

In this paper, we experimentally studied the external surface crack growth in steel pipes reinforced with Composite System Repaired (CRS). CRS reinforced surface cracked API 5L X65 pipes were tested, containing three initial notch sizes and four reinforcement schemes. During the tests, the crack growth results, as well as the strain on the external mid-bottom composite laminate around the cracked area, and the vertical deflection of the specimens were recorded. The results showed that within the surface crack growth stage, the composite laminates were adequately bonded on the steel substrate, which significantly decreased the crack growth rate and prolonged the residual fatigue life. In addition, CRS reinforcement has increased the stiffness of the surface cracked pipes. Through the analysis on applying different reinforcement schemes, we indicated that increasing the amount of composite layers evidently facilitated the reinforcement effectiveness, while increasing the bond length did not; and the inversely diagonal wrapping pattern performance less effective.

Tracking local brittle zone in the heat affected zone of girth-welded API 5L x46 pipe

In this study, microhardness variation as well as macro and micro structural examination of the heat affected zone (HAZ) of a girth welded API 5L X46 pipeline material were conducted as a means of tracking local brittle zone (LBZ) in the HAZ region. The weldment analysed were built from heat input range of 695 J/mm – 2567 J/mm. Analysis of the results revealed that the HAZ profile changes with variation in the heat input and becomes shallow but wider as the heat input increases. Defects free welds were achieved under the heat input range of 1650 J/mm – 2017 J/mm welding condition. Localized high hardness values were obtained at certain locations within the HAZ of intermediate heat input welds produced at 1467 J/mm due to thermal stresses induced strains at this heat input in the resolidified weld. Other than this, non-equilibrium rapid heating/cooling that is common during welding as well as the magnitude of mechanical strain generated on cooling vary with heat input and was attributed to the development of high hardness value at localized region within the HAZ of the welds in low heat input welding condition. The macrographic profile at these locations, contrasted against that of a failed pipeline material of similar specification obtained from typical oil and gas infrastructure, established that crack initiation and propagation followed the trend of microhardness variations in the girth welded pipe. The crack initiates at specific location in the HAZ with very high hardness in the range 186-216 Hv within a radius of about 3-5 mm from the edge of the fusion zone.
 Keywords: API 5L X46; Girth welding; Heat input; Heat affected zone; Local brittle zones

Investigation into Mechanism of Hydrogen Induced Cracking Failure in Carbon Steel: A Case Study of Oil and Gas Industry

Abstract Although the hydrogen induced cracking (HIC) is recognized as one of the destructive modes for pipeline and component steels serving in sour environments, the behavior of the HIC is still not fully understood. On the other hand, although many efforts have been made to identify the effects of hydrogen on laboratory steel specimens, the study of actual industrial samples has received less attention. In this paper, we have studied the mechanism of the HIC in a damaged pipe of a real case study of the oil and gas industry (finger type slug catcher) using detection, characterization, and microstructural investigation methods. The detection of the HIC in the specimens by advanced ultrasonic techniques, failure analysis using tensile tests, chemical composition analysis, optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), and energy-dispersive spectroscopy (EDS) techniques and their correlation with the microstructure, type, and morphology of the inclusions were conducted. The results indicated that the value of elements, especially carbon (0.13 wt %) and manganese (1.44 wt %), satisfies the requirement of API 5L specification. Furthermore, the inclusions, such as elongated manganese sulfide and spherical aluminum oxide, and the pearlite grains or the interfaces of the ferrite–pearlite phases played an essential role in the HIC phenomenon as nucleation and propagation places of cracks. It was also observed that HIC cracks were mostly initiated and propagated through the center or near the center of a cross-section of specimens. This region was a segregated zone where the center segregation of elements has occurred. Finally, we recognized a linear correlation between the HIC susceptibility and hardness value in steel, where by moving away from the cracks (1800 µm) to the crack edges, the hardness value increased significantly (179–203 HV), confirming the diffusion of hydrogen into hydrogen traps.

Effects of depth in external and internal corrosion defects on failure pressure predictions of oil and gas pipelines using finite element models

This study presents, for the first time, the mechanical behavior of API 5L pipeline steels X42, X52, X60, X70, X80, and X100 with external and internal corrosion defects as well as a combination of both defects that has been named external–internal corrosion defects. The conventional methods to predict failure pressure in corroded pipes, such as B31G, RSTRENG-1, SHELL, DNV-99, PCORRC, and FITNET FFS, have also been discussed in this article. In addition, pipeline failure pressure has been estimated using the finite element method, considering that it is the best approach to calculate actual failure pressure. The external and internal corrosion defect investigated in this research manifests as a rectangular shape with spherical ends at the edges. When the external–internal corrosion defect appears, failure pressure data decrease dramatically because of severe damage. This is due to the decrease in the ligament (effective area) caused by the corrosion defect. To have a good estimation of the pipeline failure pressure with an external–internal corrosion defect, DNV-99 method can be used with acceptable certainty.