Papers by Author: Song Chun Choi

Abstract: The thickness of the process equipment increases in proportion to pressure for the methane hydrate transportation and storage. The pressure is one of the most important factors, because a material must be selected in the way of proper pressure and temperature to design the process equipment. Therefore, we tried to figure out whether the phase equilibrium temperature & pressure can be applied to the designed temperature and pressure or not, and carried out the thickness calculation of the pure methane hydrate container in accordance with “Boiler and Pressure Vessel Code - Division I of Section VIII, ASME”. Also, we studied on the effect of the container’s thickness using the results of the phase equilibrium temperature and pressure measurement including the inhibitor and promoter of the methane hydrate on some related references.

Abstract: Goal setting safety legislation for high pressure systems was first introduced in 1973 and retained in the High Pressure Safety Management Law in Korea. This has enabled a move towards inspection strategies based on the risk of failure. This trend towards a risk based approach is being supported by extensive plant operating experience, improved understanding of material degradation mechanisms, and the availability of fitness-for-service assessment procedures. RBI (Risk-Based Inspection) is very effective and efficient of the inspection and maintenance techniques. In particular, RBI will be found how to apply both inspection interval as a result of RBI implementation and re-inspection interval of pressurized equipment defined by the High Pressure Safety Management Law in Korea. The objectives of this paper are to develop an enhanced KGS-RBITM program to resolve shortcoming inclusive of the above issue and to evaluate the risks of equipments in Naphtha Cracking Center (NCC) which is a typical facility of petrochemical plant using the KGS-RBITM program. The results of the risk assessment and re-inspection interval of internal opening using KGS-RBITM program are useful in determining the inspection planning.

Abstract: The nondestructive evaluation technique for the material degradation is necessary because of the limitation of conventional destructive methods. In this study, an ultrasonic velocity measurement method was attempted for the estimation of the creep damage of degraded modified 9Cr-1Mo steel. The specimens with seven different kinds of aging periods were prepared by an isothermal heat treatment at 690
. The ultrasonic velocity was measured by an immersion method. The correlation between the measured ultrasonic velocity and tensile properties were studied. The ultrasonic velocity has an declining tendency with the increase of heat treatment time. A correlation between the ultrasonic velocity and aging parameter were established, which allows one to estimate the material degradation of modified 9Cr-1Mo steel.

Abstract: Risk-based inspection (RBI) guideline based on API 581 provides a methodology for calculating the risks of equipment in refinery or petrochemical plant. However, there is a major limitation of its application to the petrochemical plant directly since only a representative material is considered in calculating the risk, especially in part of the consequence of failure, even though the equipment is composed of numerous materials. The objectives of this paper are to develop an enhanced RBI program to resolve shortcoming inclusive of the above issue and to evaluate the risks of equipment in petrochemical plant using the program. In this respect, the mole fractions of materials were used to fully incorporate the characteristics of different materials. The proposed RBI program consists of qualitative, semi-quantitative and quantitative risk evaluation modules in which toxic materials as well as representative materials were selected automatically for comparison with those in the current guideline. The RBI program has been applied to evaluate the risks of equipment in Naphtha Cracking Center (NCC) which is a typical facility of petrochemical plant. Thereby, promising evaluation results were obtained and applicability of the proposed RBI program was proven.

Abstract: Recently, regulatory bodies quite often encourage to adopt risk-based inspection (RBI) and management programs because they can enhance safety simultaneously with deregulation in Korea. RBI is an integrated methodology that factors risk into inspection and maintenance decision making. This paper describes an example of how to use known risk assessment codes (API 580, API 581 BRD) to address such safety analysis requirements for risk management in the refining industry. Specifically, this paper reports the methodology and the results of application to the refinery units using the KGS-RBITM program, developed by the Korea Gas Safety Corporation in reference of API Codes and ASME PC (Post Construction) with a suitable consideration of Korean situation. The results of the risk and reliability assessment using KGS-RBITM program are useful in determining whether the detected defects are tolerable or required to be repaired. The subsequent decisions are to manage the future inspection, repair and maintenance planning in the risk reduction control.

Abstract: Pipelines have the highest capacity and are the safest and the least environmentally disruptive means for transmitting gas or oil. Recently, failures due to corrosion defects have become a major concern in maintaining pipeline integrity. A number of solutions have been developed for the assessment of remaining strength of corroded pipelines. In this paper, a Fitness-For-Purpose (FFP)type limit load solution for corroded city gas pipelines is proposed. For this purpose, a series of burst tests with various types of machined defects were performed. Finite element simulations were carried out to derive an appropriate failure criterion. Based on such solution along with existing solutions, an integrity evaluation program for corroded city gas pipeline, COPAP-CITY, has been developed.