Piping assembly with regard to the design trace of ship systems

The influence of design routing on the possibility of assembling pipelines of ship systems is considered. As a result, it is planned to manufacture pipes for the backlog, ensuring successful installation to reduce the labor intensity of pipeline work and shorten the construction time of the vessel as a whole. To exclude deviations during the installation of ship pipelines systems, it is proposed to use direct pipes made with an admissible mixing and connection. According to the proposed approach, in which the joints are not installed perpendicular to the pipe axis, but mutually parallel, a line consisting only of straight pipes (or having straight sections in its composition) can be moved to eliminate possible deviations of rigidly fixed joints by the actually required value. The process of excluding pipeline deviations when using straight pipes made with an allowable offset of mutual arrangement of joints and pipe turning is simulated.

Comparison Between Yield Strength Results Obtained From Methods Using Both Flattened and Non-Flattened Specimens

Tensile properties of API 5L large diameter pipes are typically determined with the use of full thickness flattened strap samples extracted in the transverse direction with respect to the longitudinal pipe axis (TPA) [1, 2, 3, 4]. It has been well established that the process of sample flattening has a significant influence on determination of the yield strength of the pipe [5, 6]. The flattening process is sensitive to a number of variables such as method of flattening, equipment used, number/sequence of strokes, and operators conducting the flattening. As a result, issues with repeatability are frequently encountered and despite several efforts, the industry lacks any type of official standard for universal use. Historically, the industry has been focused on ensuring that the actual strength of pipes was safely higher than the specified minimum. Recently, there has been interest to also establish an upper limit on pipe strength particularly in the longitudinal direction with respect to the pipe axis (LPA) in order to avoid under matching between pipe and girth weld properties. These new requirements create the need for enhanced process control to minimize the variation due to flattening. Samples obtained from longitudinally welded (SAWL) and helically welded (SAWH) seam Grade X70M line pipe of various nominal wall thickness to diameter (t/D) ratios were flattened using different procedures, measured for curvature, and tensile tested, all in controlled laboratory environments with minimized repeatability variation. Special attention was given to the definition and measurement of different types of curvatures observed through the range of different t/D ratios and effort was made to assess criteria for curvature measurement prior to testing. Additionally, non-flattened specimens were tensile tested using round bar and full ring expansion test methods, and a comparison between the results obtained from both flattened and non-flattened specimen methods was made. The sample transverse yield strength results confirmed the expected variation between samples flattened by different methods. In addition, a much greater variation was observed when comparing the yield strength results between flattened and non-flattened samples. Considerations of extending the use of non-flattened specimens as a production test and benefits or limitations associated with such practice are discussed.

IMPROVEMENT OF APPROACHES AND METHODS OF TURBULENT FLOW THEORY IN THE PIPES

The article consideres the analysis of the literature about the development of the water turbulent flow theory in the pipes. According to the results of analysis and theoretical studies, we obtained mathematical models. These models described the kinematic structure of the water turbulent flow in the pipes for different regions of turbulence. For the first time, the hypothesis was accepted that the dependence obtained from the Navier-Stokes differential equation for constructing the velocity profile in the laminar regime is suitable for calculating the average velocities in the turbulent regime of flow, but for this, it is necessary to replace the molecular kinematic viscosity with the total turbulent kinematic viscosity, which includes kinematic viscosity on the inner surface of the pipe and turbulent kinematic viscosity , which occurs due to the movement of masses from one layer into another, as recommended in J.V. Boussinesq. Based on experimental data I. Nikuradze and F.O. Shevelev, we obtained a distribution of the total kinematic viscosity in the pipes, including the kinematic viscosity on the pipe inner surface and the kinematic turbulent viscosity. For the first time, we used the kinematic viscosity distribution equation in the pipes and obtained the averaged velocity profile equation. This equation corresponds to the boundary conditions on the pipe inner surface and on the axis of the pipe. The equation of maximum averaged velocity, the equation of distance from the axis of the pipe to the points having average velocity, the equation of the ratio of maximum velocity to average velocity was obtained. For the first time, the equation of the tangent stresses components ( , ) and the tangent stresses equation in radial coordinates ( ) were obtained. The equation of the maximum value of the tangent stresses located on the inner surface of the pipe was obtained. The tangent stresses assume a zero value on the pipe axis. The equation of the vortex components ( , ) was obtained. We have shown that vortex lines are concentric circles whose centers are located on the pipe axis. The equation of angular velocity of flow particles rotation relative to the vortex lines was obtained. The maximum value of the particle rotation angular velocity on the pipe inner surface is determined. It decreases monotonically to zero on the axis of the pipeline. It is zero on the pipe axis. In this article, all equations reveal the kinematic structure of the water flow. We described these equations by the Reynolds number and the pipe friction factor. Such equations are adopted to show the dependencies between the regimes and the flow kinematic structure. These equations make it possible to calculate the distribution profile of the total kinematic viscosity, averaged velocity, tangential stresses and angular velocity of flow particle rotation.

About the Influence of the Corrosion Defect Geometry on Repaired Pipes Stress Distribution

This paper proposes a new approach in dealing with volumetric surface defects (VSD) in pipelines. Using three-dimensional (3D) scanning and reverse engineering techniques, along with finite element analysis, we studied and evaluated comparatively the stress distributions in the defect area for different shapes and positions of the machined VSD, in order to find the best solution for the repairing process using composite materials. Our main conclusion is that instead of machining the VSD such as to generate a rectangular shaped machined defect, with edges parallel/perpendicular to the pipe axis, it is better to mold the VSD. Another possible solution would be to machine the real VSD such as to generate an inclined rectangle that circumscribes the defect. This paper also studies the influence of the machined defect filet radius to the bottom of the VSD.

Development of Design Support System for Piping Route and Differential Pressure Flowmeter by Three-Dimensional Fluid Analysis

In power plants that becoming more compact, it will expend much time and effort to satisfy the requirement for the differential pressure flow measurement according to ISO’s standards. Therefore, it is difficult for engineers in the design phase to completely remove the potential for large errors in flow measurement. This paper presents the 3D fluid analysis system that is a lower cost than the conventional method to confirm the soundness of such measurement in the phase of piping route design. This system has the function to automatically generate the analysis models from general 3D piping CAD data. The analysis program is written by the open source code to reduce a license fee. Also, this system has the function of calculating the swirl strength along the pipe axis as one of the means for efficiently supporting the design change. In order to verify and validate the analysis system, we analyzed several flow paths, confirmed the response of the swirl strength and flow rate indication value of the differential pressure flowmeter model. The analysis result well simulated the increase or decrease swirl strength in the complex flow path, and fluctuation of the flow rate indication value. Also, the system supports to set the flowmeter in the appropriate position by providing visualization of the swirl strength along the pipe axis. In the flow path analysis in this validation, it took about one month to visualization of the swirl strength along the pipe axis from the generation of the analysis models. The 3D fluid analysis system collaborative with 3D piping CAD design system has been developed. This system enable to confirm the effects of swirl strength on flow measurement and the soundness of the differential pressure flow measurement at a lower cost in comparison with conventional method.

Analysis of steady flow in a circular cylindrical pipe with hydraulically smooth walls

Анализируются формулы для скоростей и сопротивлений при установившемся течении несжимаемой вязкой жидкости в круглой цилиндрической трубе. Используется закон подобия скоростей при турбулентном режиме течения для получения представления коэффициента сопротивления в явном виде. Рассматривается связь между числами Рейнольдса, вычисляемых по средней и по динамической скоростями. Сформулирован принцип нахождении профилей скорости по закону сопротивления. Приведены аналитические выражения для всего универсального профиля скоростей. Приводится алгоритм построения кривой сопротивления по профилю скоростей в универсальных координатах. Предлагается единая формула для коэффициента сопротивления при любом режиме течения и формула для учёта отклонения от логарифмики на профиле скоростей в области вблизи оси трубы. The formulas for the velocities and resistances in the steady flow of an incompressible viscous fluid in a round cylindrical pipe are analyzed. The law of similarity of velocities in the turbulent regime is used to obtain an explicit representation of the drag coefficient. The relationship between the Reynolds numbers calculated by the average and dynamic speeds is considered. The principle of finding velocity profiles according to the law of resistance is formulated. Analytical expressions are given for the for any flow regime and a formula for taking into account deviations from the logarithm on the velocity profile in the region near the pipe axis.

A Simulation of the Post-Bending Process of the Pipe Billets for Welded Pipe Manufacturing

The paper presents a result of the simulation of the post-bending process of the pipe billet, using the MSC.Marc software package. It was shown that the use of a standard method for carrying out post-bending process leads to the formation of various defects, such as a variable gap between the edges along the pipe axis, vertical waves and bends at the edges, as well as a decrease in a sheet thickness on the edges.

Shadow-Based Operation Assistant for a Pipeline-Inspection Robot Using a Variance Value of the Image Histogram

This paper presents a shadow-based operation assistant method for a pipeline-inspection robot using a variance value of the image histogram. By displacing the position of the head camera relative to that of the illuminator, a crescent-shaped shadow appears in the images captured in a bent pipe. The size, position, and orientation of the shadow depend on the robot’s orientation around the pipe axis. By applying the pathway direction of the bent pipe obtained from the image processing to the rolling movement, the robot can automatically adjust its roll-orientation. Experiments were conducted in four types of pipeline environments to verify the autonomous navigation. These include a complex winding pipeline, a long straight pipe, and pipelines with replicated dust and dirt.

Assessment of Pipeline Spiral Weld Cracks Subjected to Internal Pressure

Spirally welded pipelines can make up significant portions of operator transmission systems, and may contain manufacturing anomalies that are susceptible to fatigue growth. Modifications to inputs of crack assessment models, such as CorLAS®, are required to account for the angle these cracks make with respect to the longitudinal pipe axis, given that these crack assessment models were developed for longitudinally orientated cracks. Two such modifications were investigated and are discussed in this paper. One approach considered the normal stress component perpendicular to the angled crack, for which a stress transformation calculator was developed. Another approach, adapted from API 579 and BS7910 standards, used an effective crack length calculated as the longitudinal projection of the full length of an angled crack. Failure pressures calculated using these approaches were compared to validated finite element (FE) results. For both modifications, the pressure capacity increased for angled cracks versus longitudinal cracks. The transformed normal stress approach resulted in non-conservative failure pressure predictions with respect to the FE models, whereas the modified crack length approach was conservative. Additionally, the extended finite element method (XFEM) was used to investigate the propagation behavior of angled cracks. It was found that the general tendency was for propagation parallel to the longitudinal pipe axis; however, when considering weld residual stresses, the crack propagation would be directed toward the direction of the spiral seam.

Standardization of Flattening Procedure of Transverse to Pipe Axis Strap Tensile Samples

Tensile testing on large diameter line pipe is generally done using strap samples obtained in the transverse to pipe axis (TPA) orientation of a pipe. The strap samples are then flattened and machined prior to testing. Although the standardized tensile testing is well documented, the variability in the reported TPA tensile properties of the same material tested within a lab or at different labs has always been an issue. Recent work conducted at EVRAZ NA research lab has identified flattening as the main source of the variability in reported yield strength (YS) values for line pipe. The lack of a standard procedure for flattening TPA strap samples is a major obstacle to obtaining consistent results. Therefore, the main objective of this current study was to establish a standardized flattening procedure for TPA strap samples. Both finite element analysis (FEA) and experimental approaches were adopted. Various flattening methods and fixtures were studied. Extensive flattening experiments were conducted on TPA samples from different line pipe products. Results showed that the spring back after flattening in a TPA sample is different for pipes with different gauge and grades. It was established that consistent flattening can be achieved using appropriate fixtures for differerent ranges of tubular products defined by grade, diameter and gauges. Evaluation of the flattening fixture designs and experimental results are discussed in this paper.