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The purpose of this study is to investigate the influence of welding sequence on the risk of burn-through, cold cracking and residual stresses during in-service sleeve repair welding of gas pipelines. Based on ABAQUS software, axisymmetric finite e1ement models were conducted to calculate transient temperature distributions and resulting residual s...
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... B36.10 [6]. This pipeline specification is widely used for transportation of natural gas. The repair sleeve chosen for the present work has a length, diameter and wall thickness of 400 mm, 952.4 mm and 24 mm, respectively. The repair sleeve is connected to the pipe by a fillet weld of 6 passes deposited on both sides of the sleeve as shown in Fig. 1. The repair process is performed according to API 1104 [5] using Manual Shielded Metal Arc Welding (SMAW) with 70% efficiency. All welding parameters are indicated in Table 1. The effect of welding sequence on residual stresses was investigated by welding both sides of the sleeve either simultaneously or sequentially. Two axisymmetric ...
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EFFECT OF WELDING SCHEME ON RESIDUAL STRESSES DURING IN-SERVICE SLEEVE REPAIR WELDING OF GAS PIPELINES
Ahmed R. Aliana, Mostafa Shazlyb, Mohammad M. Megaheda
aFaculty of Engineering, Cairo University
Giza, Egypt
bFaculty of Engineering, The British University in Egypt
Al-Shorouk City, 11873, Cairo, Egypt
ABSTRACT
The sleeve-repair welding is a...
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Citations
... All electrodes were preheated for 2 h at 350 C, then held at 100 C in a portable heat box before use. A clock spring method was chosen to minimize the weld-induced distortions [20,21]. The sequence of tack welding is illustrated in Fig. 1. ...
In-service patch welding is frequently used to repair corroded or damaged steel structures. However, the repair welding may adversely affect the long-term mechanical integrity of the structure. Fatigue treatment techniques could reduce such drawbacks. However, the effectiveness of treatment techniques in the case of in-service fillet welded steel patch repairs has not received due attention. This paper deals with the fatigue behavior of fillet welded patch repairs made on normalized A516 GR.70 carbon steel plates. The test specimens received different thermal treatments, including post-weld heat treatment (PWHT), TIG-dressing (TD), and temper bead (TB) welding. The pros and cons of these treatments were evaluated through quasi-static tensile tests, high-cycle constant amplitude fatigue testing, microstructural assessments, and hardness measurements. The TD treatment provided the most significant fatigue improvement, owing to beneficial changes it made to the geometry, microstructure and hardness of the weld toe area. The fatigue life and the fatigue-prone locations in the PWHT and TB specimens did not significantly vary from those in the untreated welded specimens. However, there was a reduction of the ultimate tensile strength in the PWHT specimens. The microstructure of the heat-affected zone plus the hardness of the weld toe areas significantly contributed to the fatigue performance. The fatigue lives of the fillet welded patch repairs were also interrelated to the geometrical changes caused in the weld toe by the treatment method.
... In contrast to the simultaneous welding operation, sequential welding allows the axial thermal expansion of the sleeve during the deposition of the right fillet weld [33]. Fig. 20a and b shows contour plots for the longitudinal residual stresses at the first and second welding passes, respectively. ...
The present work investigates the influence of welding sequence and scheme on residual stresses induced during in-service sleeve repair welding of gas pipelines. For this purpose, a 3D thermo-mechanical FE analysis is conducted on an 8″-Schedule-20, API 5L-X65 steel pipe. Two welding sequences for the sleeve-pipe circumferential fillet welds are compared in the present study: sequential welding in which one side of the sleeve is welded first and then the other side is welded by the same welder, and simultaneous welding in which both sides of the sleeve are welded concurrently by two welders. Within the simultaneous welding sequence, four different welding schemes, designed to investigate the influence of the number of welders and welding directions on residual stresses, are investigated. The results show that the sequential welding sequence induces less residual stresses and distortions. Within the simultaneous welding sequence, the back-step welding scheme is found to induce the least average residual stresses as compared to other welding schemes.
This work investigated stress response of a corroded X80 steel pipeline repaired by a type-B sleeve to internal pressure by finite element modeling. Firstly, a three-dimensional numerical model of corroded pipeline reinforced with type-B sleeve was developed, and its accuracy and reliability were verified by the burst test results and the theoretical analytical solution, respectively. Second, the von Mises stress of the pipe body, sleeve and fillet weld was simulated under various affecting factors, i.e., internal pressure, corrosion defect dimension (depth, length and width) and sleeve length. Finally, a parameter sensitivity study was conducted to determine the effects of corrosion geometry and sleeve length on the repair efficiency. The main investigation results show that the type-B sleeve repair method is effective to restore the pressure-bearing capacity of the pipeline at the corrosion defect, and the burst failure of repaired pipeline always occurs at the region far away from the defect and sleeve. At the limit state of burst, the local defective region shows the highest stress, followed by the fillet weld, and the repair sleeve has the smallest stress, thus the maximum equivalent stress of the corroded zone is suggested to be used for measuring the repair efficiency of the repaired pipe by type-B sleeve. The sleeve-repair effectiveness is affected by depth of the corrosion defect, a deep corrosion defect reduces the performance of the sleeve repair compared with a shallow defect. The effect of the corrosion defect length on sleeve repair depends on the defect depth. Furthermore, there exist a critical length of the defect that affect the repair efficiency. The corrosion defect width shows limited effect on stress level at the defect of the repaired pipe. At last, a new method based on stress analysis is proposed to optimize the sleeve length for repairing a corroded pipeline.
