Estimation of Arc Welding Pressure Pipeline Weld Peaking Parameters Based on Data Prediction

Peaking parameter is the key content in the regular inspection of the pressure pipeline. Solving the problem of the peaking measurement method defined by a standard cannot be applied to a situation in which there exists a weld surface with reinforcement and misalignment. In this paper, a peaking estimation method based on data prediction was proposed to estimate the contour information of the base metal at the weld joint using the contour point set data of the base metal part of the weld. Herein, the longitudinal weld peaking estimation method based on a piecewise logistic regression (PLR) and the girth weld peaking estimation method based on a piecewise Bayesian linear regression (PBLR) were studied, and the midpoint of the two symmetrical points of the base metal on either side of the weld was used as a reference for calculating the peaking. Finally, we collected the surface profile data of longitudinal weld pressure pipes with diameters of 155 mm, 255 mm, 550 mm, and 600 mm and the surface profile data of girth weld pressure pipes with diameters of 120 mm, 130 mm, 140 mm, and 170 mm. This weld seam data used the data estimation method proposed in this article and traditional long short-term memory and fitting methods. The results showed that the proposed data prediction method could accurately predict the position of the base metal, and the theoretical mean absolute error of the peaking estimation based on the PBLR and PLR could attain 0.06 mm and 0.07 mm, respectively, which meets the parameter measurement requirements of related verification fields.

Introducing Compressive Residual Stresses into a Stainless-Steel T-Pipe Joint by an Overlay Weld

Microcracks are always present in the deposited metal of nickel-based alloys and austenitic stainless steels, which affects the safety of the pressure pipes. If compressive stress can be introduced into the cracked position by overlay welding, the time required with ordinary gouging repair welding technology will be significantly reduced, which is practical significance for pressure pipes repair welding. In this work, a stainless-steel T-pipe joint was fabricated using manual metal arc welding with an ER316L wire, and an overlay weld was fabricated using tungsten inert gas arc welding with an ERNiCrFe-7A wire. The overlay thickness was about 10 mm. The contour method was employed to measure the residual stress in the T-pipe joint. The results show that compressive residual stress about 50 MPa is formed in the original ER316L weld, which proves that the residual compressive stress can be obtained in the original weld by surfacing 10 mm thick nickel base alloy on the original weld surface.

Mechanical and System Simulation Modeling and Analysis of Surge Relief Valve

Surge pressure relief valve is widely used in oil transportation. When water hammer occurs in the pipeline, the valve shall be opened in time to release the high pressure so as to ensure the safety of the oil pipeline. This paper discusses the structure and principle of the surge relief valve. Combined with the working process, the stress and working state of the main valve and the pilot valve are analyzed. The mechanical model of the pilot valve is established. This paper focuses on the analysis of the parameters affecting the closing process of the main valve. The relevant laws of the structure and performance parameters of the pilot valve to the main valve closing are obtained. The model of relief valve is modeled and simulated in detail by the AMESim software. The dynamic characteristics of the surge relief valve are analyzed and the correctness of the main parameters and rules that affect the main valve closing is verified by using the model. According to the analysis and simulation results, the friction force of the pilot valve can only affect whether the two valves can close normally. The closing time of the main valve is inversely proportional to the diameter of the inlet pressure orifice. In the normal operating range, the closing time of main valve gradually increases with the diameter of outlet pressure pipes, but does not change with the length of outlet pressure pipes.

Thermomechanical Modeling of a Sleeve Rehabilitation System for Pressure Pipes

The thermomechanical modeling of a sleeve rehabilitation system for pressure pipes is studied including temperature effect on system behavior. The rehabilitation system consists of a multicylinder axisymmetric layer system, with an intermediate layer of epoxy resins and two outer steel covers that are longitudinally welded forming a sleeve. The analysis is conducted over several stages; initially, the incidence of temperature on the rigidity of three types of resins currently available on the market is experimentally evaluated. Then, nonlinear relationships between rigidity and temperature are established from the evaluation of the resins, which are typical of an inhomogeneous material. The resins exhibit a significant loss of rigidity with temperature, generating a risk of delamination that could drastically reduce the effectiveness of the rehabilitation system in the event of possible temperature rises. An analytical model was developed to calculate contact pressures between the resin layer and the external sleeve, internal pipeline displacements, stresses, and deformations. Finally, contour plots were developed for different temperature, pressure levels, and pipe thickness as a graphics tool to predict pipeline failure due to plastic deformation or rupture.