Iranian Journal of Oil and Gas Science and Technology

Abstract In the event of a main source outage, in the gas distribution network, the high-pressure gas stored in pipes, known as linepack, can be used as a short-term reserve to supply gas to consumers. Moreover, during the redesign of the distribution network, it is possible to convert a tree-structured network into a looped network by connecting two or more nodes. In reliability analysis approaches for networks under real conditions, due to the need to examine multiple and complex states and consequences, the computational burden in proposed network structures is very high, and therefore, simulation techniques are often used. In this paper, a novel approach is proposed to evaluate gas supply reliability in both tree-structured and loop-connected networks, considering the effect of linepack. Hydraulic analysis of the network was performed using the GP-NET software, and the overall reliability of gas supply in the pipeline network was determined, taking into account the random occurrence of failures in critical components that lead to network disruptions. The proposed approach was applied to the gas distribution system of a city in Kurdistan Province, Iran, and, through sensitivity analysis, the effect of changes in model parameters on the overall network supply reliability was also analyzed. The results indicate that creating loops and considering the effect of linepack lead to increased supply reliability and enhanced stability in providing services to consumers.

Abstract The purpose of this study is to investigate bending moment and the axial load capacity of a pressurized pipe suffering from a through-wall circumferential crack repaired by a composite sleeve. The three-dimensional finite element method (FEM) was adopted to compute the results, and the failure assessment diagram (FAD) was employed to investigate the failure behavior of the repaired pipe. The findings revealed that, for the investigated range of applied loads and angles of the crack, the interaction of brittle and ductile failure modes is negligible. Additionally, the yield strength of the cracked pipe was considered as reference stress to achieve a conservative design. Two cases of the combined loading state consisting of internal pressure/bending moment and internal pressure/axial tensile force were investigated. Repairing the crack under combined loadings using carbon-epoxy composites was studied where the influences of various parameters, including internal pressure, crack angle, and the composite patch thickness on the capacity of the cracked pipe to withstand bending moment and axial load were included. The results indicated that the bending moment and axial load capacities of the cracked pipe depend on internal pressure, crack angle, and the composite patch thickness; nevertheless, the crack angle is the main parameter. A composite sleeve can increase both bending moment and axial load capacity of the cracked pipe, but bending moment can be increased further than axial load. Using the composite patch to repair the cracked pipe caused the bending moment capacity to improve from 14.28% to 120%. On the other hand, the composite patch raised the axial load capacity from 5.1% to 93.5%. Additionally, an increase in the composite patch thickness caused the axial load capacity to extend more than bending load capacity.

Abstract The effect of adding extra inlet channels on the operation of the Stairmand Cyclone has been investigated numerically. The Reynolds stress model (RSM) and Eulerian-Lagrangian method were used to investigate the complex turbulent flow and cyclone performance. The impacts of one-way coupling and two-way coupling models on the cyclone efficiency and the calculation of cut-off size diameter were examined. The results showed that a rise in channel number increases the tangential velocity and extends the Rankine vortex region. Moreover, in the four-inlet cyclone, the direction of flow changes unlike the one-inlet and two-inlet cyclones, and it behaves like a jet flow. According to the results, the collection efficiency and cut-off size diameter of the four-inlet cyclone are respectively about 10.78% higher and 35% lower than those of one-inlet configuration. Therefore, the performance of four-inlet cyclone is the highest among the three investigated configurations due to high tangential and axial velocities. A cyclone with more inlets has a more symmetrical flow pattern. Consequently, the four-inlet cyclone has the lowest flux of erosion among the others. The results of cyclone performance reveal a slight difference between one-way coupling and two-way coupling models.