Hui-Ryong Yoo

Feasibility Study on the Utilization of EMAT Technology for In-line Inspection of Gas Pipeline

If gas is leaking out of gas pipelines, it could cause a huge explosion. Accordingly, it is important to ensure the integrity of gas pipelines. Traditionally, over the years, gas-operating companies have used the ILI system, which is based on axial magnetic flux leakage (MFL), to inspect the gas pipelines. Relatively, there is a low probability of detection (POD) for the axial defects with the axial MFL-based ILI. To prevent the buried pipeline from corrosion, it requires a protective coating. In addition to the potential damage to the coating by environmental factors and external forces, there could be defects on the damaged coating area. Thus, it is essential that nondestructive evaluation methods for detecting axial defects (axial cracks, axial groove) and damaged coating be developed. In this study, an electromagnetic acoustic transducer (EMAT) sensor was designed and fabricated for detecting axial defects and coating disbondment. In order to validate the performances of the developed EMAT sensor, experiments were performed with specimens from axial cracks, axial grooves, and coating disbondment. The experimental results showed that the developed EMAT sensor could detect not only the axial cracks (minimum 5% depth of wall thickness) and axial grooves (minimum 10% depth of wall thickness), but also the coating disbondment.

Development of MFL system for in-pipe robot for unpiggable natural gas pipelines

This paper introduces a MFL system developed by a research project, which has been being conducted by KOGAS and initiated in 2011, to develop ILI (In-Line Ispection) Robot named “PIBOT” for the inspection of 16” to 14” unpiggable natural gas pipelines. All elements and functions in the proposed MFL (Magnetic Flux Leakage) system were designed to minimize friction between magnetizer and pipe wall and maximize defect detectability. To enhance driving performance and the ability of obstacle-negotiation, shunting system that can control direction of magnetic flux was developed. The performance of proposed MFL system was verified in the UPSF (Unpiggable Pipeline Simulation Facility) constructed to undertake several kinds of performance test about defect detectability, driving efficient and pressure resistance ability.

Implementation of High Magnetization System for Performance Enhancement of Magnetic Flux Leakage Tool

This paper discusses the effectiveness of high magnetization saturation in ILI (In-Line Inspection) using an MFL (Magnetic Flux Leakage) tool, and introduces a practical method for improving the magnetization level together with the piggability. Thin steel plates, replacing the conventional wire brushes were used as conductors to transfer the magnetic flux to the pipe wall. The newly designed MFL tool was compared with the conventional version by means of FEM (Finite Element Method) analysis and full-scale experiments. In the results, the newly developed magnetization system obtained a stronger MFL signal amplitude, specially 2.7 times stronger, than that obtained by the conventional magnetization system for the same defect dimensions.

Development of Third-Party Damage Monitoring System for Natural Gas Pipeline

In this paper, we develop a real time monitoring system to detect third-party damage on natural gas pipeline. When the damage due to third-party incidents causes an immediate rupture, the developed on-line monitoring system can help reducing the sequences of event at once. Moreover, since many third-party incidents cause damage that does not lead to immediate rupture but can grow with time, the developed on-line monitoring system can execute a significant role in reducing many third-party damage incidents. Also, when the damage is given at a point on natural gas pipeline, the acoustic wave is propagated very fast about 421.3 m/s. Therefore, the data processing time should be very short in order to detect precisely the impact position. Generally, the pipeline is laid under ground or sea and the length is very long. So a wireless data communication method is recommendable and the sensing positions are limited by laid circumstance and setting cost of sensors. The calculation and monitoring software is developed by an algorithm using the propagation speed of acoustic wave and data base system based on wireless communication and DSP systems. The developed monitoring system is examined by field testing at Balan pilot plant, KOGAS being done in order to demonstrate its validity through reactive detection of third-party contact with pipelines. Furthermore, the development system was set at the practical pipelines such as an offshore pipeline between two islands Yul-Do and Youngjong-Do, and a land branch of Pyoungtaek, Korea and it has been operating in real time.

One-bed RFECT system for inspection of circumferential cracks in 16 inch gas pipeline

Inspection of unpiggable pipeline becomes one of major issues in the gas pipelines industry. Remote field eddy current testing (RFECT) has strong potential for inspecting unpiggable pipelines among the various NDE methods. Thus, in this study, design of RFECT system including driving coil, sensing coil and passive scanning module and intial experimental results obtained from fabricated one-bed testing system isdicussed.

A Study on the Measurement of Axial Cracks in the Magnetic Flux Leakage NDT System

From among the NDT (Non-Destructive Testing) methods, the MFL (Magnetic Flux Leakage) PIG (Pipeline Inspection Gauge) is especially suitable for testing pipelines because the pipeline has high magnetic permeability. MFL PIG showed high performance in detecting the metal loss and corrosions. However, MFL PIG is difficult to detect the crack which occured by exterior-interior pressure difference in pipelines and the shape of crack is very long and narrow. Therefore, the new PIG is needed to be researched and developed for detecting the cracks. The CMFL (Circumferential MF) PIG performs magnetic fields circumferentially and can maximize the magnetic flux leakage at the cracks. In this paper, CMFL PIG is designed and the distribution of the magnetic fields is analyzed by using 3 dimensional nonlinear finite element method (FEM). By Simulating and Measuring the magnetic leakage field, it is possible to detect of axial cracks in the pipeline.

Optimal Design of RFECT System for Inspection of 16-inch Ferromagnetic Pipe

An effective approach to optimal design of Remote Field Eddy Current Testing (RFECT) system was introduced in this paper. Although the RFECT technique has unique advantages over other nondestructive testing methods, related information is not easy to be accessed by public. Designing approaches to two major components of the RFECT system – exciter and receiver coil - are documented in this paper. Simple equations including some novel investigation to predict performance of the coils are introduced. Then, to validate the proposed approach, performance of the RFECT system equipped with the designed coils was evaluated by an experiment. The experiment was conducted on 16-inch ferromagnetic pipe using the RFECT system showed good performance by detecting all defects machined on the pipe.

Diameter-Adjustable Controller Design of Wheel Type Pipe Inspection Robot Using Fuzzy Logic Control Method

To make the pipe-inspection robot move inside the specific dimension pipeline, the crucial problem is to adjust the diameter of the robot inside the pipeline. This paper proposes a fuzzy logic controller design method for diameter control of a wheeled-type pipe inspection robot. To do this task, the following steps are executed. Firstly, a wheeled-type pipe inspection robot that can work in 150–250 mm radius pipeline is developed. The robot is developed with two modules: active module and passive module such that each module has three wheel configurations with different mechanism to expand the wheels. Secondly, kinematic models of 4 bar linkage of the robot and dc motor are presented. Thirdly, the PI controller and the fuzzy logic controller are presented for the robot to track the given robot diameter. Finally, simulation is performed to verify the performance of two proposed control methods. The results show that the proposed fuzzy logic controller can track the reference diameter better than using PI controller.

Development of RFECT System for In-line Inspection Robot for Unpiggable Natural Gas Pipeline

This paper focuses on the RFECT (Remote Field Eddy Current Testing) technology for use on the ILI (In-Line inspection) robot platform to inspect unpiggable natural gas pipeline. An effective design for RFECT system is proposed to minimize the system architecture modification that is required in implementing large diameter of RFECT system of which sensor channel must be increased according to the increase in diameter of pipeline to be inspected. The parallel digital LIA (Lock-In Amplifier) is designed considering the increase in sensor channel. The performance of proposed RFECT system is verified through the pull-rig experiment including a set of artificial defects simulating metal loss on the pipeline.

Introduction of In-Line Inspection Technology in KOGAS

This paper focuses on the introduction of the development of in-line inspection technology in Korea Gas Corporation to keep maintaining the integrity of pipeline facilities. There are pipeline systems in oil and gas industry with various installations such as valves, tees, miters and bends as well as many operating condition such as operational pressure, flow-rate and temperature which result in piggable and un-piggable. This paper introduces results of research and development of in-line inspection technology for verifying the integrity of piggable and un-piggable pipeline in KOREA. KOGAS has produced results with values in the development of robotic inspection technology equipped with NDE (Non-Destructive Evaluation) for un-piggable pipeline and as well as the development of conventional in-line inspection technology for piggable pipeline since 2000.