Pipe Spool Research Articles

A Simplified Failure Assessment to Identify Crack Growth Behavior in the Gas Pipeline by Post-Hydrostatic Pressure

Hydrostatic pressure tests on pipelines have been found to be an inadequate means of critical integrity management due to the frequency of false negatives, which result from the inability of these tests to detect crack growth. It can be argued that focusing on pipe leakage does not guarantee future operability. A study presents a failure assessment methodology based on the failure assessment diagram (FAD), which aims to predict crack growth during hydrotesting. The calibrated pipe spool is validated by the application of data from hydrostatic tests and analytical techniques to ascertain the potential growth in circumferential surface cracks. A variety of factors, including pressure, material grades, flaw dimensions, and elliptical flaw angles, were examined in an effort to assess cracks. The results demonstrate that there is no pipeline leakage and minimal trapped air. Despite its location within the plastic zone, with a normalized pressure index of ≤1, the pipeline is deemed to be within acceptable limits according to the criteria established by the FAD. The assessment point was found to be predominantly influenced by the toughness ratio of the material grade. The crack propagated in the opposite direction with a maximum length a/c= 0.125 and a crack depth a/t= 0.2, which limited the toughness ratio. The load ratio indicates uniformity in elliptical angle flaw results. In this simplified failure assessment, the parameter describing the flaw size, which exhibits a strong correlation with the toughness ratio, plays a pivotal role. Further research and recommendations are also proposed.

A Study on the Residual Stress of Seam Pipe Cutting and Girth Welding

Seam pipes are easier to manufacture and cheaper than seamless pipes, and are widely used in the manufacture of pipe spools for marine plant facilities. The manufacturing and assembly of seam pipes involve welding and cutting. The localized heating and cooling that occur during these processes may change the existing residual stress and cause deformation. Uncontrolled deformation can accumulate as assembly errors at the next step, potentially delaying the entire process and causing economic losses. Therefore, characteristics of residual stress redistribution caused by cutting and girth welding of seam pipes need to be studied further. In this study, we performed thermo-mechanical analysis of the manufacturing, cutting, and girth welding processes of seam pipes using the commercial finite element analysis (FEA) software MSC Marc and analyzed the characteristics of residual stress. Furthermore, we measured the residual stress in each process using the hole drilling method, analyzed the characteristics of redistributed residual stress, and ensured reliability. Based on the results of FEA and measured residual stress redistribution, we can provide a basis for reasonable mitigation when performing structural integrity evaluation if there is a defect in the weld of the pipe.

An analysis of pipe spool supply chain in shipbuilding using 2-stage queuing model and discrete event simulation

Pipe spool supply in Korean shipbuilding industry consists of a complex supply chain comprising manufacturing and painting vendors. Major Korean shipyards with the most competitive edge have applied various policies and techniques to control the pipe spool supply chain and prevent production delays related to supply delays in pipe spools. Although research has been done on implementing the policies and techniques, there has been a gap on the theoretical consideration of pipe spool supply chain characteristics using a simulation model. Therefore, this study proposes an analytical method based on queueing model to analyze the characteristics of the pipe spool supply chain and also proposes a simulation model based on discrete event simulation (DES) to verify it. In addition, a numerical experiment using DES for the M/G/1 queuing model is conducted to examine the effect of time variability in the spool supply chain. From the more reliable experimental results, control parameters and management insights to manage the supply chain optimality are proposed and the effectiveness of policies that have been implemented by major shipyards is verified.

Research on the Stress Characteristics of Wellhead Bolts

Bolts are important connectors in the wellhead oil pipe spool, and the safety of wellhead bolts is an important guarantee for the operation of the oil pipe spool. Taking the wellhead oil pipe spool as the research object, a three-dimensional fluid model and a structural model of the wellhead equipment and its bolts were established. Through finite element numerical simulation, combined with the basic theory of fluid solid coupling, the equivalent stress and dangerous bolt distribution of the oil pipe spool bolts were studied. The study showed that under two different working conditions, the average equivalent stress on the bolt as a whole increased as the bolt position approached the outlet of the side flow channel, The most dangerous bolt in the wellhead tubing spool appears near the outlet; The stress distribution of bolts in different sections is uneven, and the stress at the bolt head, thread, and smooth rod intersects is greater than that at the middle section of the bolt. The bolt also bears both axial and bending stresses.

Machine-Learning Approach to Predict Total Fabrication Duration of Industrial Pipe Spools

In industrial modular construction, components fabricated in the shop are assembled into modules before being transported to construction sites. This approach offers improved construction efficiency, higher quality products, and the opportunity to work in a controlled environment that offers more predictable schedules. A distinct category of modularized construction is that of piping structures where prefabricated segments of pipes, called pipe spools, are arranged and attached to a steel structure to speed up on-site assembly. Determining when a particular pipe spool is ready for delivery to the site is affected by many factors, including material availability, workforce performance and availability, shop loading conditions, and shop capacity. These factors combine to produce a high degree of uncertainty when estimating the fabrication duration. This paper investigates the improvement of delivery time prediction of pipe spools that are fabricated in a manufacturing facility. The study’s main contribution is to propose a data-driven machine-learning model that accurately predicts the total fabrication duration in a pipe spool fabrication facility. The developed model is expected to assist production managers to plan for the appropriate workforce and material delivery requirements. The proposed approach utilizes a combination of product composition and real-time loading status of the shop to develop and examine several tree-based machine-learning models. The approach was evaluated using records of 6,989 pipe spools. The overall prediction performance was improved by a reduction of 35% in the mean absolute percentage error compared to original heuristic estimates. The results also show a strong positive correlation of 0.8 between the actual and predicted values.

Complexity, Performance, and Search Efficiency: An Eye-Tracking Study on Assembly-Based Tasks among Construction Workers (Pipefitters)

Past studies have used eye-tracking glasses to analyze people’s perception of visual stimuli, usually regarding wayfinding, safety, or visual appeal. Some industries, such as the automotive industry, studied the effects of visual stimuli on task completion. However, the architecture and construction industries have mainly conducted eye-tracking experiments with surveys or search tasks instead of performing a task. This paper uses eye-tracking glasses to analyze people’s perception of visual stimuli while completing tangible tasks that simulate real-world applications. This research studies how people look at visual stimuli that influence their ability to interpret drawings with varying degrees of complexity, assess task completion performance, and inspect how people search for information. Twenty pipefitters wore eye-tracking glasses to record their eye movement patterns while completing a model pipe spool assembly. The eye-tracking glasses and Visual Eyes software measured visit metrics, fixations, fixation durations, convex hull coverage, assembly time, rework, and errors. Unlike previous studies, convex hull areas are calculated and used to measure search efficiency. This research found that people interacted more frequently with more complex visual stimuli but did not necessarily require more time to complete a task. People with lower search efficiency visited the drawings more frequently than people with higher search efficiency. People with higher search efficiency made fewer mistakes, redid less work, and completed tasks quicker than those with lower search efficiency. Search efficiency was found to be a good predictor of task performance.

Pulsating flow velocity profile measurement at an acoustically reflecting and non-reflecting open pipe end using laser doppler anemometry (LDA)

Depending on the geometry and operating condition, occasionally strong and destructive acoustic resonances occur in the pipe spool piece between the high-pressure discharge of screw compressors and the connected pulsation damper/silencer inlet. To avoid these resonances, the use of a nozzle with defined cross-section reduction is investigated. By designing the contraction ratio as a function of the nozzle inlet Mach number, a non-reflecting termination/transition can be provided. For a defined operating point, acoustic reflection from the nozzle can be avoided in this way, thus preventing the acoustic resonance in the spool piece.Within this paper the pulsating flow field directly downstream an acoustically reflecting open pipe end is investigated using laser doppler anemometry (LDA) at the air test rig at the Chair of Fluidics at TU Dortmund University. In the modified experimental setup an operating point-specific designed nozzle is installed at the open pipe end to create a non-reflecting termination. By means of LDA measurements, the velocity profile is determined experimentally at the nozzle outlet for the designed operating condition. The 2D measurement results (radius dependant velocity and phase distribution) extend established 1D decomposition of pressure measurement signals into upstream and downstream travelling waves and allow a deeper understanding of the acoustic behaviour of non-reflecting nozzles.

A method to generate a pipe model to compensate for low congestion level of 3D geometry available at the early stage of detailed design

For a recent explosion risk assessment, a CFD (computational fluid dynamics)-based simulation has been widely employed using a 3D geometry model for a gas dispersion and an explosion simulation. For an accurate determination of explosion design loads, extensive scenarios covering various leak locations, leak directions, leak rate, wind directions and so on are treated in the simulation. In order to reflect the results of the risk assessment into detailed topside design, the time-consuming simulations should be begun from the early stage of the detailed design. However, the congestion level of 3D geometry modeling available at the early stage is considerably different from the as-built model due to the lack of modeling of small-sized piping, pipe supports, electrical supports, detailed structural outfitting and so on. This study proposes a method to generate 3D pipe modeling to compensate for the low congestion level. A random approach is made for the generation by randomly determining a starting point of a pipe spool, pipe diameter, pipe direction, a straight pipe length, number of pipes in a pipe spool and so on. For a pipe running through a given box range, it is cut out on the box boundary and a pipe type connecting with a neighboring module is also realized. For a longitudinally long pipe rack, the inside pipe spools have different features. The generation algorithm is adjusted to realize these features. The generated method doesn't include any algorithm to avoid existing other geometric entities such as equipment or structural members. Thus, the generated pipe length is generally reduced after combining with a module containing equipment and structural members. A study is also done about how much the pipe length of the as-built model needs to be increased considering the overlap. The proposed method is verified by combining the generated pipe model with a module containing only structure & equipment, and comparing explosion analysis results with the corresponding as-built model. A dispersion simulation is also performed for the validity of the proposed model in the dispersion simulation as well.

Using termination points and 3D visualization for dimensional control in prefabrication

To increase productivity, quality, and safety, heavy industrial construction projects are increasingly adopting prefabrication and modularization techniques. This shift, in turn, has resulted in fabrication shops fabricating more complex assemblies with tighter tolerances. However, most measurement in these shops is conducted using manual hand measurement tools, which can be costly and is known to cause significant rework due to geometric noncompliance of termination points in particular. Termination points are defined as the coordinate system points where assemblies connect or are constrained. Automated, 3D-scanning measurement and visualization systems can potentially be accurate, repeatable, and objective sources of termination point data. In this paper, a new framework for classification and calculation of termination points is presented that is based on automated, 3D-scanning measurement and visualization. The utilization of the framework enables fabrication shops and project owners to adopt effective 3D measurement solutions. To investigate the usefulness of the defined framework, a termination-point-based scan-vs-BIM method is developed for objects with circular cross sections, such as pipe spool assemblies. The method was validated in an industrial-scale experimental study. The study demonstrated that the new framework can be used to develop applications that are more accurate and provide superior visualization to craft workers during fabrication, and thus potentially improve productivity and reduce rework.

Using 3D Scanning for Accurate Estimation of Termination Points for Dimensional Quality Assurance in Pipe Spool Fabrication

Increased prefabrication and modularization have resulted in fabrication shops producing more complex assemblies with tighter tolerances. Most measurements in fabrication shops are still done using manual tools that are not accurate enough for engineering tolerance specifications, which can lead to rework. Three dimensional (3D) scanning and measurement systems can provide increased accuracy and digital integration capabilities, however they do not sufficiently support fast and accurate dimensional quality assurance (DQA) of pipe spool fabrication. This is because no dimensional quality assurance methods to date have focused solely on termination points for pipe spool assemblies. In the present article, a new scan-vs-BIM method is developed to accurately estimate termination points for 3D scanned cylindrical assemblies. This method relies on statistically fitting circular features at termination points and thus eliminating conventional issues with target placement for laser trackers and measurement readings for tape measures. The method is tested in an industrial-scale experiment, where 30 pipe spool assemblies were fabricated, and more than 400 quality control steps completed. The accuracy of termination point detection was benchmarked against results from a laser tracker and compared against commercial scan-to-BIM software. Results show that the developed method has an average accuracy of 1.01 mm and is significantly better than the scan-to-BIM software with an average accuracy of 4.75 mm.

The concept of digital twin used to investigate geometrical variations in the production of pipe spools

The fourth industrial revolution comprises the digital transformation of manufacturing by means of an intensive integration of advanced information and communication technologies. The possibility of creating interactive virtual replicas of the physical entities to predict and detect physical issues and optimize processes is one of the key benefits of the manufacturing digitization. In the oil and gas industry, one of the essential activities that can take advantage of innovative digital technologies is the geometrical quality assurance of pipe spools. In this sense, this work focuses on the development of digital twins of pipe spools that embrace attributes of their physical counterparts to manage dimensional variation and to assist the geometrical quality assurance process. Based on data available in the design stage of the product realization loop, i.e., dimensional tolerance, it was possible to estimate the process capability and to predict, by sensitivity analysis, the behavior of the spool elements when assembling them to each other.

Corrosionfracture kinetics in welded pipes in chlorine-saturated carbon dioxide oilfield media

Bypass tests of Ø219×8mm 13KhFA, 08KhMFChA, 20-ksh (steel 20 corrosion resistant cold resistant) and Grade steel 20 piping spools were carried out on an oil-gathering line of one of the oilfields in the Stavropol region. Tubing condition was checked after 7, 15, 17 and 23 months of testing. After two years in service no change was found in mechanical properties of the base metal or weldments manufactured from 13KhFA and 08KhMFChA steels. It has been demonstrated that the formation of chromium-containing phase in corrosion products inhibits the penetration of chlorine ions from corrosive media to the surface of metal and thus reduces corrosion rates. Estimated, laboratory and comparison passivation coefficients have been proposed. These coefficients make it possible to predict the level of steel self-passivation with regard to operating conditions of particular oilfields.

Application of isometric transformation and robust estimation to compare the measurement results of steel pipe spools

Abstract Production of prefabricated pipe spools for the needs of the oil and gas industry requires precise determination of their shape and dimensions. The crucial moment of production is to measure the spool being built, compare it with the design and define the geometry corrections that should be applied at the construction stage. At present, the comparison of spools is usually done in a manual manner in a CAD program or other software dedicated for this purpose and is implemented by combining variously defined translations and rotations. This approach is time-consuming and the results strongly depend on the survey engineer’s experience. In this article, a method of comparing the shape of two spools, based on isometric transformation and robust estimation, has been proposed. This method can be used to automate the comparison process. In standard approach, applied by both design engineers and assemblers, spools are described by a set of coordinates and, in the case of flanges, by sets of appropriately defined angular values. A method of flange description suitable for use in the isometric transformation process has been proposed, and potential problems that may appear at the implementation stage of the algorithm have been discussed. The proposed method makes it possible to determine the elements of a spool that do not fit into the design project in a way that allows minimizing the number of corrections at the construction stage.

A Work on Welding Productivity and Economy for Smaw & Fcaw Processes

Every welding process possess its own advantages and limitations and selected after careful analysis and study of variables related to the process /product form and application criteria. Factors governing the selection of welding process includes the type of the product to be welded, material, joint geometry, field and service conditions, productivity expectations, capital cost, availability of resources, quality requirements, net cost savings etc. Currently in India, shielded metal arc welding is the major welding process dominates the welding industry and plays a key role compared to other welding processes. To achieve the higher productivity and cost savings, it is necessary to adopt suitable welding process, which can be superior to SMAW and can be justified fully in terms of productivity, quality and cost. Comparative production studies were conducted to establish the facts and to arrive conclusion. This concept will be applicable for pipe spools welding in a fabrication shop for welding groove and fillet weld joints in out of position. Process will be applied for large bore spools welding i.e. for Pipe diameter equivalent or greater than 168 mm OD and wall thickness of 7.11 mm and above. For study purpose only two welding processes were taken into account i.e. SMAW and FCAW. Since carbon steel pipe spools fabrication is 85% of the total scope, selection of the high productive and cost economic welding process plays a vital role.

Коррозионно-механическое разрушение электросварных труб в нефтепромысловых средах высокой агрессивности

Pipes welded from specially prepared sheet steel, in comparison with the seamless drawn ones, are characterized by the low cost, higher corrosion resistance, and dimensional stability. When ensuring the properties of a welded joint at the base metal level, they can compete with seamless pipes. To start using welded pipes made of new steels, long-term field tests in fields with high aggressiveness of extracted fluids are required. It is necessary to have the comparative results on corrosion resistance of the base metal and welded joints. The paper aimed at obtaining information on the mechanisms and kinetics of stress-corrosion fracture and the operating ability of electric-welded pipes during continuous service. The authors carried out the field (bypass) tests of the electric-welded pipe spools made of 08HMFChA, 13HFA, 09GSF, and 20-KSH steels on the operating oil gathering main of Mamontovskoye oilfield of Western Siberia with the high content of H 2 S and CO 2 dissolved gases and bacterial contamination. The study identified the rates of general and local corrosions of base metal, welded joints, and the area of low generating lines of the pipe. The study showed the peculiarities of corrosion fracture initiation and development and change in the rate of general and pit corrosions depending on the chemical composition of steel and its running time. The authors identified the interrelation of the dependence of change in the rate of corrosion fracture with the increase in the running time on the composition and structure of the corrosion products. For the chromic steels (08HMFChA and 13HFA), chromium concentration in the corrosion products is the main factor of surface passivation. The authors proposed the passivation coefficient, in other words, the criterion for evaluation of change in the corrosion rate during running time.

Impact of augmented reality and spatial cognition on assembly in construction

Abstract Applications of augmented reality have the potential to help radically improve construction productivity, reduce rework and improve communication of design intent. A hand-held augmented reality application that has been developed to assist in assembly and inspection of pipe spools using 3D scanning, scan-vs-BIM, flexible workflow, and a touch sensitive user interface is described here. Representing a class of augmented reality applications, it is used to examine the impact of augmented reality and its relation to human spatial cognitive abilities. Experiments are conducted with 21 professional pipe fitters and 40 engineering students, whose spatial cognitive abilities are measured, and who are then asked to assemble a complex pipe spool using conventional or augmented reality assisted means. Statistical analysis of the experimental results for these groups of subjects validates several observations. Augmented reality can help save substantial time in pipe spool assembly over the conventional methods for both untrained engineers and for well trained professional pipe fitters. Those whose cognitive abilities are measured as low experienced more benefit than the other subjects from the augmented reality application. More applications of augmented reality need to be studied to understand its potential impact on construction work.

Experimental studies of operational properties of asphaltene-resin-wax deposits formed in oil trunk pipelines

The paper presents the results of experimental laboratory studies of the properties of asphaltene-resin-wax deposits (ARWD) affecting the efficiency and reliability of pumping. The analysis of negative and positive properties of deposits, including corrosion impact of ARWD on the oil pipeline wall, was carried out. The thermal conductivity coefficient of heavy oil deposits samples taken from existing oil trunk pipelines (OTP) was measured. To assess the influence of the deposit layer on the smoothness of the inner surface of the pipe wall, tests were carried out to determine the roughness coefficient using the samples of pipe spool segments. The samples were cut from the sections of OTP under repair, the inner surface of which is covered with a layer of ARWD, accumulated and hardened during the long-term operation of pipelines, periodically affected by in-line cleaning pigs. The results of laboratory studies of the ARWD thermophysical properties confirmed the relatively high thermal insulation properties and smoothing ability of the deposit layer. Tests to assess the corrosion properties of ARWD showed the possibility of reducing the corrosion rate due to the passive protection of the deposit layer formed on the inner surface of the pipe wall.

Pipe radius estimation using Kinect range cameras

Abstract In the heavy construction industry, pipe spool assembly is geometrically complex and suboptimal fabrication processes inevitably lead to fabrication errors and costly rework. In an attempt to mitigate fabrication risks and improve product quality, computer aided tools are being developed to provide an additional layer of control. In this paper, the data acquisition capabilities of two low-cost range cameras are investigated for the eventual purpose of pipe fitting process monitoring in a smart fabrication facility environment. Range images of various pipes are systematically taken at varying distances from the sensor. By using the proposed radius estimation algorithm, the utility of the data for accurate geometrical pipe feature detection is evaluated by a radius feature metric. Results show that the algorithm reliably extracts radius information from point clouds representing piping. In conjunction with the algorithm, the low-cost range camera hardware was able to characterize pipes, of radius ranging from 2.41 cm to 8.78 cm at a distance from the sensor ranging from 0.5 m to 3.75 m, with an average error of 18% for Kinect 1 and 10% for Kinect 2.

Enhancing the safety of construction crew by accounting for brain resource requirements of activities in job assignment

Abstract Safety management is regarded traditionally as an aggregate attribute for Human Resources (HR) in which the focus is placed on safety of construction crew by assuming same behaviour, capabilities and thus level of exposure to risk for all workers in the crew. In line with this, a team-based approach is generally adopted for task assignment to workers in construction operations. However, this approach tends to disregard the differences between skill level, experience, capabilities, learning rates and fatigue rates of different individual workers forming the team. In particular, due to differences in visual, auditory, cognitive and psychomotor capabilities of different workers and brain resource demands of different activities, the traditional approach may result in inconsistent workloads and uneven fatigue rates within a crew, affecting the workers' and crew's safety negatively. This paper proposes a novel framework for task assignment to construction workers in which safety of individual workers and thus the crew is ensured through optimizing workload distributions within a crew. The framework computes visual, auditory, cognitive, and psychomotor requirements of the jobs assigned to a worker and minimizes the identified workload imbalances through collaborative execution of shared tasks. The application of the proposed framework is examined on a pipe spool fabrication operation of a refinery project in a simulation environment.

Time-of-flight dependency on transducer separation distance in a reflective-path guided-wave ultrasonic flow meter at zero flow conditions.

Transit-time flow meters based on guided ultrasonic wave propagation in the pipe spool have several advantages compared to traditional inline ultrasonic flow metering. The extended interrogation field, obtained by continuous leakage from guided waves traveling in the pipe wall, increases robustness toward entrained particles or gas in the flow. In reflective-path guided-wave ultrasonic flow meters (GW-UFMs), the flow equations are derived from signals propagating solely in the pipe wall and from signals passing twice through the fluid. In addition to the time-of-flight (TOF) through the fluid, the fluid path experiences an additional time delay upon reflection at the opposite pipe wall due to specular and non-specular reflections. The present work investigates the influence of these reflections on the TOF in a reflective-path GW-UFM as a function of transducer separation distance at zero flow conditions. Two models are used to describe the signal propagation through the system: (i) a transient full-wave finite element model, and (ii) a combined plane-wave and ray-tracing model. The study shows that a range-dependent time delay is associated with the reflection of the fluid path, introducing transmitter-receiver distance dependence. Based on these results, the applicability of the flow equations derived using model (ii) is discussed.