Jung Kwan Seo

A methodology for determining efficient gas detector locations on offshore installations

More than 70% of accidents that occur on offshore installations are result of hydrocarbon explosions and fires, which, because they involve blast effects and heat, are extremely hazardous and have serious consequences in terms of human health, structural safety and the surrounding environment. Most such accidents are caused by gas leaks, which, if undetected, can lead to the formation of a concentrated gas cloud that can ignite or explode. An effective gas detection system is important for preventing gas-related catastrophic accidents and can mitigate risk on offshore installations. The aim of this study is to develop a risk-based methodology to aid the initial placement of gas detectors for an efficient gas detection system that will function optimally in all possible scenarios on offshore installations.

Effects of Palm Kernel Expellers on Growth Performance, Nutrient Digestibility, and Blood Profiles of Weaned Pigs

This experiment was conducted to investigate the effects of palm kernel expellers on growth performance, nutrient digestibility, and blood profiles of weaned pigs. A total of 88 weaned pigs (6.94±0.76 kg body weight [BW]; 28 d old) were randomly allotted to 2 dietary treatments (4 pigs/pen; 11 replicates/treatment) in a randomized complete block design (sex as a block). The dietary treatments were a typical nursery diet based on corn and soybean meal (CON) and CON added with 20% of palm kernel expellers (PKE). Pigs were fed for 6 wk using a 3-phase feeding program with declining diet complexity and with phases of 1, 2, and 3 wk, respectively. Blood was collected from randomly selected 2 pigs in each pen before weaning and on d 7 after weaning. Pigs were fed respective dietary treatments containing 0.2% chromic oxide from d 29 to 35 after weaning. Fecal samples were collected from randomly selected 2 pigs in each pen daily for the last 3 days after the 4-d adjustment period. Measurements were growth performances, digestibility of dry matter, nitrogen and energy, white and red blood cell counts, packed cell volume, and incidence of diarrhea. The PKE increased average daily gain (ADG) (246 vs 215 g/d; p = 0.06) and average daily feed intake (ADFI) (470 vs 343 g/d; p<0.05) and decreased gain-to-feed ratio (G:F) (0.522 vs 0.628 g/g; p<0.05) during phase 2 compared with CON, but did not affect growth performance during phase 1 and 3. During overall experimental period, PKE increased ADG (383 vs 362 g/d; p = 0.05) and ADFI (549 vs 496 g/d; p<0.05) compared with CON, but did not affect G:F. However, no differences were found on digestibility of dry matter, nitrogen, and energy between CON and PKE. The PKE reduced frequency of diarrhea (15% vs 25%; p = 0.08) for the first 2 wk after weaning compared with CON. Similarly, PKE decreased white blood cells (8.19 vs 9.56×103/μL; p = 0.07), red blood cells (2.92 vs 3.25×106/μL; p = 0.09), and packed cell volume (11.1% vs 12.6%; p = 0.06) on d 7 after weaning compared with CON. In conclusion, addition of 20% palm kernel expellers to nursery diet based on corn and soybean meal had no negative effects on growth performance, nutrient digestibility, and blood profiles of weaned pigs.

A New Method for Determining the Design Sloshing Loads for LNG FPSOs

The aim of this study was to develop a new method for determining nominal values for sloshing loads in the design of storage tanks in LNG FPSO (liquid natural gas, floating production, storage and offloading units). Details of the procedure are presented in a flow chart showing the key sub-tasks. The applicability of the method is demonstrated using an example of a hypothetical LNG FPSO operating in a natural gas site off a hypothetical oceanic region. It is concluded that the developed method is useful for determining the design sloshing loads of storage tanks in ship-shaped offshore LNG installations in combination with virtual metocean data and operational conditions.Copyright

Investigation on the Burst Strength Capacity of Aging Subsea Gas Pipeline

Precisely evaluation of the reliability of aging structure is essential, particularly in the oil gas industry where inaccurate predictions of structural performance may have significant hazardous consequences. Related to this issue, it is important to predict the corrosion behavior of the gas pipeline structure used in the production of gas in subsea area. As corrosion is concerned, the effects of pipeline failure due to significant reduction of burst strength will make it hard for the pipeline operator to maintain the serviceability of pipelines. Therefore related to this problem, the resistance service of the pipeline is assessed by means of burst strength capacity. In this study, the critical part of the corrosion along 2.4 km pipeline is assessed using two approaches; empirical design codes formula and ANSYS numerical analysis. The future integrity of the pipeline is then assessed to predict the remaining year in service for the aging pipeline. The results and outcomes of the present study will be useful for evaluating the pipeline integrity as well as the prediction of the remaining life of in service aging pipeline structures.Copyright

Effects of Palm Kernel Expellers on Productive Performance, Nutrient Digestibility, and White Blood Cells of Lactating Sows

This experiment was conducted to investigate the effects of palm kernel expellers on productive performance, nutrient digestibility, and changes in white blood cells (WBC) of lactating sows. A total of 14 sows (200±12 kg of average body weight [BW]; 2.5 of average parity) were used and moved from gestation room to farrowing room on d 109 of gestation. Sows were randomly assigned to 2 dietary treatments in a completely randomized design. The treatments were a diet based on corn and soybean meal (CON) and CON added with 20% of palm kernel expellers (PKE). Sows were fed the treatments for 28 days (weaning) after farrowing. Blood was collected from each sow and 4 randomly selected piglets from each sow before farrowing or on d 3, 7, or 14 of lactation. Sows were fed respective treatments containing 0.2% chromic oxide from d 15 to 21 of lactation. Fecal samples were collected daily for the last 3 days after the 4-d adjustment period. Measurements were performances and WBC changes of sows and litter, nutrient digestibility of sows, and daily diarrhea of litter. Sows fed PKE had greater average daily feed intake (7.38 vs 7.10 kg/d; p<0.05) and lost less BW (−6.85 vs −8.54 kg; p<0.05) and backfat depth (−0.42 vs −0.71 mm; p<0.05) than those fed CON. However, there were no differences on digestibility of dry matter, nitrogen, and energy and weaning to estrus interval of sows fed either CON or PKE. Piglets from sows fed PKE gained more BW (203 vs 181 g/d; p = 0.08) and had less frequency of diarrhea (6.80 vs 8.56%; p = 0.07) than those from sows fed CON. On the other hand, no difference was found on preweaning mortality of piglets from sows fed either CON or PKE. Sows fed PKE had lower number of WBC (9.57 vs 11.82 ×103/μL; p = 0.09) before farrowing than those fed CON, but no difference on d 3 and 7. Similarly, piglets from sows fed PKE had also lower number of WBC (7.86 vs 9.80 ×103/μL; p<0.05) on d 14 of lactation than those from sows fed CON, but no difference on d 3 and 7. In conclusion, addition of 20% palm kernel expellers to lactation diet based on corn and soybean meal had no negative effects on productive performance, nutrient digestibility, and WBC changes of lactating sows.

Collision Tests on Steel-Plated Structures in Low Temperature

The aim of the study reported herein was to investigate the effects of low temperatures on the crashworthiness of steel-plated structures. A series of material tensile tests were performed to examine the material behaviors at low temperatures. Then, unstiffened steel-plated structure and stiffened steel-plated structure were collided with a cone-shaped drop object to estimate the crashworthiness of steel-plated structures. The material tensile test specimens and test structures were made of Polar class steel for ships and offshore structures which is a sufficient condition of the IACS requirements concerning Polar Class and Strength of Ships. The tests considered room and low temperatures relevant to an Arctic environment and a cryogenic condition. LS-DYNA nonlinear finite element simulations applying a practical approach of modeling techniques were performed to investigate the structural crashworthiness of the steel-plated structures numerically with results of material tensile tests.Copyright

Test Facilities for Safety Studies of Ships and Offshore Structures Associated With Extreme and Accidental Conditions

Ships and offshore structures can face extreme and accidental events that can result in catastrophic consequences in association with casualties, property damages and pollution. Because the mechanism and its responses of structures in extreme and accidental events are highly nonlinear, it is essential to take advantage of experimental approaches as well as computational approaches in terms of identifying such nonlinear responses. Relevant test facilities are then required to meet the needs where full scale or at least large scale models should be dealt with. The objective of this article is to introduce test facilities recently built in the Korea Ship and Offshore Research Institute (KOSORI) at Pusan National University in Korea in terms of specifications and capabilities of various test facilities. Those facilities include test infrastructures in association with ultra-high subsea pressure, fires, explosions, structural failure and dropped object as well as high speed material test.Copyright

Effects of Wind on the Heat Flow of FPSO Topsides Subject to Fire: An Experimental and Numerical Study

The aim of this paper is to examine the effect of wind on the thermal diffusion characteristics of floating production storage and offloading (FSPO) topside models subject to fire. It is motivated by the need to identify the fire loads on FPSO topsides, taking into account the effects of wind speed and direction. The results of an experimental and numerical study undertaken for these purposes are reported here. This paper is part of Phase II of the joint industry project on explosion and fire engineering of FPSOs (EFEF JIP) [1]. An experiment was performed on a 1/14-scale FPSO topside model using a wind tunnel test facility. The locations of the heat source of the fire were varied, as were the speed and direction of the wind, and the temperature distribution was measured. Computational fluid dynamics (CFD) simulations using the ANSYS CFX program were performed on the test model, with the results obtained compared with the experimental results. It is concluded that wind has a significant effect on the thermal diffusion characteristics of the test model and that the CFD simulations are in good agreement with the experimental results. The insights developed in this study will be very useful for the fire engineering of FPSO topsides.Copyright

A Research on the Verification Test Procedure for Quantitative Explosion Risk Assessment and Management of Offshore Installations

해저에 매장된 원유, 가스 등을 탐사, 시추, 생산하는 해양플 랜트 설비에서 발생할 수 있는 각종 사고는 인명, 재산, 환경에 심각한 피해를 초래한다. 그 중에서 다양한 공정설비가 밀집되어 설치, 운영되고 있는 상부구조(topsides)에서 발생하는 가연성물 질의 누출 및 폭발화재 사고는 매우 심각한 위험요소로 인식되고 있다. 이러한 해양플랜트 폭발화재 사고에 대한 안전설계기법은 1988년 북해에서 발생한 Piper Alpha 사고를 계기로 Fig. 1에서 요약한 바와 같이 다양한 국제공동연구 등의 노력을 통하여 사고 발생 빈도(frequency)와 피해규모(consequence)를 정량적으로 평가하는 정량적 위험도평가(Quantitative Risk Assessment, QRA) 기준의 설계기법으로 발전되었다 (Paik & Czujko, 2011). Fig. 2는 해양플랜트 폭발사고에 대한 정량적 위험도평가와 관리 절차의 예를 보여주고 있다 (Paik et al., 2011). 폭발사고 에 대한 정량적 위험도평가를 위해서는 폭발사고의 발생 빈도와 피해규모를 정량적으로 산출해야한다. 현재 해양플랜트 산업에서 적용하고 있는 정량적 위험도평가 방법에서는 폭발사고의 발생 빈도를 가연성 물질의 누출빈도(leak fequency)와 점화확률 (ignition probabilisty)의 동시 확률로 정량화하고 피해규모는 전 산유체역학(CFD)과 유한요소해석(FEA) 기법을 활용하여 정량적 피해규모를 산출하고 있다. 그러나 전산유체역학 및 유한요소해석 기법의 적용은 실재 폭 해양플랜트 폭발사고 위험도 평가/관리를 위한 실증시험기법에 관한 연구 김봉주 .하연철 .서정관† 부산대학교 선박해양플랜트기술연구원

Applicability of CO₂ Extinguishing System for Ships

The offshore installations and ships are the structures most likely to be exposed to hazards such as hydrocarbon fire and/or explosion. Developing proactive measures to prevent the escalation of such events thus requires detailed knowledge of the related phenomena and their consequences.