DYNAMIC FREE SPAN ANALYSIS USING ANALYTICAL AND FINITE ELEMENT METHOD IN OFFSHORE PIPELINE

• Main Author: AYUBI - NIM : 25515001 , RACHMAN
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/30077
• Institution: Institut Teknologi Bandung

<p align="justify">Subsea pipeline is one of distribution method that generally used in oil and gas industry to distribute fluids from one offshore platform to onshore facility or another offshore platform. One of key element to design offshore pipeline is free span analysis. Free span is a condition where the pipeline doesn’t have any support, so the pipeline will be hanging free. Free span length in offshore pipeline has standard design to prevent over stress that can cause cracks, fractures, and leaks. The purpose of this research is to get the value of maximum allowable free span length in static condition based on ASME B31.8 and dynamic condition based on DNV RP F105 and Buyon Guo approachment (Offshore Pipelies), after get the value of the free span length, this research also calculate the lifetime of this pipeline in the free span condition. Parameter that used for the assumption of calculating the pipeline lifetime is using the maximum current velocity in the seabed of the location. The model was developed using finite element method ABAQUS to find natural frequency of the pipeline. <br /> <br /> From the Guo approachment calculation, maximum allowable free span length for operating pipeline is 17.73 m (pinned-pinned condition), 22.22 m (pinned-fixed condition), and 26.59 m (fixed-fixed condition). From the DNV RP F105 calculation, the maximum allowable free span length is 17.09 m (pinned-pinned condition) and 21.02 m (fixed-fixed condition). <br /> <br /> From the maximum allowable free span length using Guo approachment, the value of the natural frequency is 1.11 Hz for pinned-pinned condition, 1.59 Hz for pinned-fixed condition, and 1.53 for fixed-fixed condition. However, based on DNV RP F105 free span length calculation, the value of the natural frequency is 1.45 Hz for pinned-pinned condition and 1.46 Hz for fixed-fixed condition. The value of this analytical approachment (Guo and DNV) is less than the value from the finite element method software analysis (ABAQUS) for the same free span length for each supporting type. <p align="justify"> <br />