Journal of the Korean Society of Marine Environment & Safety (해양환경안전학회지)

The Korean Society of Marine Environment and safety (해양환경안전학회)
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Study on the Change of Relative Humidity in Subsea Pipeline According to Drying Method

건조 공법에 따른 해저 파이프라인 내부 상대습도 변화 특성 연구

  • Yang, Seung Ho (Department of Mechanical Engineering, Ulsan College)
  • 양승호 (울산과학대학교 기계공학부)
  • Received : 2022.03.17
  • Accepted : 2022.04.27
  • Published : 2022.04.30
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Abstract

The subsea pipeline pre-commissioning stage consists of the following processes: Flooding, Venting, Hydrotesting, Dewatering, Drying, and N2 Purging. Among these processes, drying and nitrogen purging processes are stipulated to reduce and maintain the relative humidity below dew point to prevent the generation of hydrate and the risk of gas explosion in the pipeline during operation. The purpose of this study is to develop an analysis method for the air drying and nitrogen purging process during pre-commissioning of the subsea pipeline, and to evaluate the applicability of the analysis method through comparison with on-site measurement results. An analysis method using Computational Fluid Dynamics (CFD) was introduced and applied as a method for evaluating the relative humidity inside a subsea pipeline, and it was confirmed that analysis results were in good agreement with the on-site measurement results for the air drying and nitrogen purging process of the offshore pipeline. If the developed air drying and nitrogen purging analysis method are used as pre-engineering tools for pre-commissioning of subsea pipelines in the future, it is expected to have a significant impact on the improvement of work productivity.

해저 파이프라인 예비커미셔닝(Pre-commissioning) 단계는 입수(Flooding), 배수(Venting), 하이드로테스팅(Hydrotesting), 탈수(Dewatering), 건조(Drying), 질소충진(N2 Purging)의 공정과정으로 구성된다. 이 중 건조와 질소충진 과정은 운용 중 파이프라인 내부에 하이드레이트(Hydrate)의 발생과 가스 폭발의 위험을 방지하기 위해 상대습도를 이슬점 아래로 감소 및 유지되도록 규정되어 있다. 본 연구의 목적은 해저 파이프라인 예비커미셔닝 중, 공기건조(Air Drying)와 질소충진 공정과정에 대한 해석법을 개발하고 현장계측 결과와의 상호 비교를 통해 해석법의 활용가능성을 평가하는 데 있다. 해저 파이프라인 내부 상대습도 평가를 위한 방법으로 전산열유체(CFD)를 활용한 해석기법을 도입·적용하였고 해양공사 해저 파이프라인 공기건조와 질소충진 공정과정에 대한 현장계측 결과와 잘 일치함을 확인하였다. 개발된 공기건조와 질소충진 해석법 및 평가방법을 향후 해저 파이프라인 예비커미셔닝 작업의 사전 엔지니어링 도구로 활용할 경우, 작업생산성 향상에 크게 기여할 것으로 사료된다.

Keywords

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