• Geomechanics and Engineering
• /
• 제39권2호
• /
• pp.197-209
• /
• 2024

This paper investigated the deformation of a large-diameter pipeline caused by double shield tunnel construction in silty fine sand strata in Nantong, China, by on-site measurements and numerical simulations. Results indicate the pipe settlement curve was not symmetrical after the double tunnel construction in the silty fine sand strata. The construction of the subsequent tunnel had a significantly smaller impact on the stress and horizontal displacement of the pipeline than the preceding tunnel. There is a significant shading effect of the large-diameter pipeline, which would restrict the soil settlement above the pipeline. The adjusted settlement formula shows good agreement with the measured data, facilitating approximate calculations for both surface and pipe settlements. The correction factor a ranges from 0.50 to 0.90, while b ranges from 0.95 to 1.20.The elastic modulus and the burial depth of the pipeline had a great effect on the stress of the pipeline, but a smaller effect on its settlement. However, the soil loss rate greatly affected both the settlement and stress of the pipeline. Moreover, the pipeline risk level distribution map can quickly identify the risk status of the pipeline.

• Proceedings of the KSME Conference
• /
• 대한기계학회 2001년도 춘계학술대회논문집B
• /
• pp.235-240
• /
• 2001

This paper introduces developed prototype intelligent pig which detects corrosion on pipeline by using Magnetic Flux Leakage technology. The 8 inch developed MFL(Magnetic Flux Leakage) pig is composed of 5 yokes which magnetize pipeline wall and 45 Hall sensors which detect MFL signal. The designed MFL modules are analyzed by using magnetic circuit method in order to confirm whether pipeline wall is fully saturated. A variety of artificial defects are manufactured on 8 inch diameter steel pipeline in order to acquire MFL signals. So leakage flux of the axial, radial and circumferential component was acquired as defects. The results of this paper show that design technique for 8 inch MFL pig can be applied to large diameter MFL pig and 0.5mm defect depth can be detected.

• Journal of Mechanical Science and Technology
• /
• 제15권4호
• /
• pp.500-509
• /
• 2001

Offshore subsea pipelines must be stable against external loadings, which are mostly due to waves and currents. To determine the stability of a subsea pipeline on the seabed, the Morrison equation has been applied with prediction of inertia and drag forces. When the pipeline is placed in a trench, the force acting on it is reduced considerably. Therefore, to consider the stability of a pipeline in a trench, one must employ reduction factors. To investigate the stability of various trenches, we numerically simulated flows over various trenches and compared them with experimental data from PIV (Particle Image Velocimetry) measurements. The present results were produced ar Reynolds numbers ranging from 6$\times$10$^3$to 3$\times$10(sub)5 based on the diameter of the cylinder. Quasi-periodic flow patterns computed by large-eddy simulation were compared with experimental data in terms of mean flow characteristics fro typical trench configurations (W/H=1 and H/D=3, 4). The stability for various trench conditions was addressed in terms of mean amplitudes of oscillating lift and drag, and the reduction factor for each case was suggested for pipeline design.

• Journal of Korean Society of Water and Wastewater
• /
• 제32권1호
• /
• pp.37-45
• /
• 2018

This study develops a model to estimate the economic life of the large-diameter water supply pipeline in Korea by supplementing existing methods used to perform similar calculations. To evaluate the developed methodology, the model was applied to the actual target area with the conveyance pipe in P waterworks. The application yielded an economic life computation of 39.7 years, considering the cost of damages, maintenance, and renewal of the pipeline. Based on a sensitivity analysis of the derived results, the most important factor influencing the economic life expectancy was the predicted failure rate. The methodology for estimating the economic life of the water supply pipeline proposed in this study is one of the core processes of basic waterworks facility management planning. Therefore, the methods and results proposed in this study may be applied to asset management planning for water service providers.

• Journal of the Korean Institute of Gas
• /
• 제6권1호
• /
• pp.10-16
• /
• 2002

This paper introduces developed prototype intelligent pig which detects corrosion on pipeline by using Magnetic Flux Leakage technology. The 8 inch developed MFL(Magnetic Flux Leakage) pig is composed of 5 yokes which magnetize pipeline wall and 45 Hall sensors which detect MFL signal. The designed MFL modules are analyzed by using magnetic circuit method in order to confirm whether pipeline wall is fully saturated. A variety of artificial defects are manufactured on 8 inch diameter steel pipeline in order to acquire MFL signals. So leakage flux of the axial, radial and circumferential component was acquired as defects. The results of this paper show that design technique for 8 inch MFL pig can be applied to large diameter MFL pig and 0.5mm defect depth can be detected.

• Journal of Korean Society of Water and Wastewater
• /
• 제30권6호
• /
• pp.725-736
• /
• 2016

There is a growing concern on the improvement of water distribution pipeline for multi-regional water supply system in Korea along with its aging infrastructure. Rehabilitation of large diameter pipeline is more efficient in cost and time compared to replacement with trenching. The procedure for rehabilitation are diagnosis, cleaning, spraying coating material, and final inspection. The internal state of pipeline was carefully diagnosed and got C grade, which required rehabilitation. We found that 17,274,787,000 Korean won could be saved after pipe surface coating because of increased C coefficient of Hazen-Williams equation. Optimal coating material was D polyurea. We also found optimal distance between spraying nozzle and pipe wall to be 70 - 80 cm, which were critical factors for coating quality. This study also illustrated the time for spray drying to be more than 30 min. These results could be used in the quality control process during rehabilitation of aged pipelines.

• Journal of Welding and Joining
• /
• 제29권3호
• /
• pp.64-69
• /
• 2011

Since welding process for most pipelines with large diameter has been carried out by the manual process, automation of the welding process is necessary for the sake of consistent weld quality and improvement in productivity. Therefore the development of the optimized algorithm to decide the welding condition is an effective technique to prove the feasibility of interface standards and intelligent control technology to increase productivity and reduce the cost of system integration. In this study, the pipe welding experiment has been carried out using plused GMA welding process to select optimal welding condition. And necessary information in root-pass welding has been obtained by applying in the pipeline using the selected welding conditions through the welding experiment.

• Journal of Ocean Engineering and Technology
• /
• 제34권3호
• /
• pp.194-201
• /
• 2020

In this study, an optical-fiber sensor was used to measure loads that could act in an environment similar to the loading conditions that exist in an actual pipe. The structure and the installation method of the optical-fiber strain sensor were applied considering the actual large pipe and the buried pipe environment. Load tests were performed using a displacement sensor and sandbags to determine the deflection of the pipe according to the external load, and the linear measurement results were verified. Considering the conditions that could exist in the actual pipe, the test method was presented, and the strain of the buried pipe generated at this time was measured.

• Journal of Korean Society of Water and Wastewater
• /
• 제28권6호
• /
• pp.681-690
• /
• 2014

It is known that sewer problems are the major causes of road cave-in. The objective of this study is to analyze the risk of road cave-in due to storm sewer laterals. We investigated 174 storm sewer laterals using a zoom camera at O-dong area in Seoul. The causes of road cave-in were classified into five cases: breakage of rigid pipe, deformation of flexible pipe, out of pipeline alignment, changing pipe material or changing pipe diameter, and a poor linkage between lateral and sewer. In addition, all defects were sorted into five grades based on the severity rating at storm sewer laterals. In this study, the most fragile pipe materials were found to be concrete pipe and polyethylene pipe, which recorded 2.3 and 1.69 defect rates. With regard to the causes of road cave-in, deformation of flexible pipe has a large influence on road cave-in at present. On a long-term basis, the two causes, out of pipeline alignment and a poor linkage between lateral and sewer, could have more influence on road cave-in.

• Nuclear Engineering and Technology
• /
• 제53권1호
• /
• pp.69-78
• /
• 2021

Venturi meter is frequently used in feed water flow control system in a nuclear power plant. Its accurate measurement plays a vital role in the safe operation of the plant. This paper firstly investigates the influence of the length of each section of pipeline, the throat inner diameter of Venturi and the flow characteristics in a single-phase flow on the accuracy of Venturi measurement by numerical calculation. Then the flow and the accuracy are discussed in a multi-phase flow. Numerical results show that the geometrical parameters and the characteristics of complex turbulent flow in the single-phase flow have little impact on the accuracy of Venturi flow rate measurement. In the multi-phase flow, the calculated flow rate of Venturi deviated from the actual flow rate and this deviation value is closely related to the amount of steam in the pipeline and increases sharply with the increase of the amount of steam. The over-reading of Venturi flow rate is present.