DESAIN DAN ANALISIS TEGANGAN PADA PERSILANGAN PIPA GAS BAWAH LAUT DENGAN STRUKTUR PENYANGGA TIPE CONCRETE SLEEPER
Design and Stress Analysis of Subsea Gas Pipeline Crossing with Concrete Sleeper as The Support
Ichsan Pradana Soewono 1, Ricky Lukman Tawekal 2, dan Jessica Rikanti Tawekal 3
Program Studi Teknik Kelautan
Fakultas Teknik Sipil dan Lingkungan
Institut Teknologi Bandung
Jl. Ganesha 10, Bandung 40132
1 ichsansoewono@gmail.com, 2 ricky.tawekal@gmail.com, dan 3 jessica.rikanti@gmail.com
Abstract: Nowadays the world’s demand for oil and gas is increasing while the reserves are running low. This has prompted the industry to undertake offshore search exploration. One of the facilities used to support the operation is a subsea pipeline. At the stage of detailed engineering, the piping design process started from the design and analysis of the pipe thickness. Analyzes were performed using the DNV-OS-F101 standard taking into account failures against pressure containment, external overpressure, propagation buckling, and local buckling. Then performed on-bottom stability analysis using the DNV-RP-F109 standard. If the weight of the steel pipe is not sufficient to withstand the environmental load, then concrete coating and/or trenching design is required to maintain pipeline stability. The next step is to perform an installation analysis using the OFFPIPE software. The goal is to determine the position of suitable rollers configuration so that there is no yield failure during the installation. Moreover, the subsea pipeline that is laid does not fully rest on the seabed due to the uneven bathymetric contours of the seabed. Therefore, the free span analysis is carried out based on the DNV-RP-F105 standard to determine the allowable free span length that meets the screening fatigue and Ultimate Limit State (ULS) criteria. Inevitably, subsea pipelines sometimes run into existing pipelines. So that a support structure is required to cross the existing pipeline, one of which is a concrete sleeper support type. The structure must be analyzed for vertical stability, overturning, sliding, and bearing capacity checks. Settlement calculations on the support structure also need to be carried out so that the design of the structure height still has a safe distance between the crossing pipeline and the existing pipeline. After that, the pipeline crossing analysis was carried out using CAESAR II software based on the ASME B31.8 standard to ensure that the pipe did not pass the allowable stress. The design and analysis process that has been carried out resulted in a pipe wall thickness design of 7.1 mm, a thickness of the concrete coating layer of 41 mm, and a maximum allowable free span of 6.3 m. The stability of the support structure final design is safe against various failures and the pipeline crossing stress does not exceed the allowable stress according to ASME B31.8.
Keywords: Offshore Pipeline, Subsea, Crossing, Stability, Concrete Sleeper
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