Development of Design Formulas for Pipe Loops Used in Ships Considering the Curvature of Corners

J. Ocean Eng. Technol. 2009;23(4):91-99.

Park Chi-Mo,Yang Park-Dal-Chi

School of Naval Architecture And Ocean Engineering University of Ulsan,School of Naval Architecture And Ocean Engineering University of Ulsan

코너부 곡률을 고려한 선박용 파이프 루프 설계식 개발

박치모,양박달치

울산대학교 조선해양공학부,울산대학교 조선해양공학부

Keywords: Pipe loop, Design formula, Curvature of corners, Castigliano's theorem, Displacement load, Thermal load, Pipe stiffness

핵심용어: 파이프 루프, 설계식, 코너부 곡률, 카스틸리아노정리, 변위 하중, 열 하중, 파이프 강성

Abstract

Many longitudinally arranged pipes in ships are subject to considerable displacement loads caused by the hull girder bending of ships and/or thermal loads in some special pipes through which fluids with highly abnormal temperatures are conveyed. As these loads may cause failure in the pipes or their supporting structures, loops have been widely adopted as a measure to prevent such failure, with the idea that they can lower the stress level in a pipe by absorbing some portion of these loads. But since such loops have some negative effects, such as causing extra manufacturing cost and occupying extra space, the number and dimensions of the loops need to be minimized. This research developed design formulas for pipe loops, modeling them as a spring element, for which the axial stiffness is calculated based on the beam theory, incorporating the effects of the curvature of loop corners and the flexibility of the straight portion of the pipe. The accuracy of the proposed design formulas was verified by comparing two results respectively obtained by the proposed formulas and MSC/NASTRAN. The paper ends with a sample application of the proposed formulas showing their efficiency.