DESIGN AND ANALYSIS OF BURST PRESSURE WITH INTERNAL CORROSION USING FINITE ELEMENT METHOD ON SUBSEA PIPELINE AT SOUTH CHINA SEA

• Main Author: Mary, Joanna
• Format: Final Project
• Language: Indonesia
• Subjects: Teknik (Rekayasa, enjinering dan kegiatan berkaitan)
• Online Access: https://digilib.itb.ac.id/gdl/view/80501
• Institution: Institut Teknologi Bandung

Indonesia has great potential in the oil and gas sector, which requires the development of supporting facilities for offshore activities, such as subsea pipeline systems to support effective production and distribution. To ensure that subsea pipelines can operate safely and have a low level of risk of failure, careful design and analysis stages are needed that are in accordance with standards, and are adapted to the environmental conditions in which the subsea pipeline operates. The first stage in subsea pipeline design is the design of pipe wall thickness using the DNV-ST-F101 design standard. The pipe wall thickness is designed based on the failure criteria of internal pressure containment, external overpressure, and propagation buckling under installation, hydrotest, operation, and shutdown conditions. Determination of pipe wall thickness is adjusted to the availability of pipes in API 5L Specification for Linepipe. The pipe wall thickness that has met all criteria is 15.9 mm. The next step is the on-bottom stability analysis to determine the thickness of the concrete coating based on the DNV-RP-F109 standard. The onbottom stability analysis was conducted by checking the stability of the lateral and vertical directions of the pipe without using trenching. The selected concrete coating thickness that met the criteria was 85.7 mm. Next, a dynamic installation analysis of the subsea pipeline was conducted using OFFPIPE and MOSES software. The installation analysis was carried out in two water conditions and considered the response of the barge movement when exposed to waves from 12 angles of wave incidence. The subsea pipeline installation was carried out using the S-Lay method and obtained a roller, tensioner and stinger configuration that met the stress criteria in the DNV-ST-F101 standard with a maximum stress received by the pipe of 84.72% in the overbend region and 64.1% in the sagbend region with a trim angle of 1º and a hitch of -3º. The free span analysis was conducted based on the DNV-RP-F105 standard by considering the amount of VIV and direct wave loading on the subsea pipeline. The permissible free span length is 31.13 m based on fatigue and ultimate limit state screening criteria. Pipes operating underwater are inseparable from corrosion which is a natural process when a metal interacts with its environment. Corrosion on the pipeline can cause significant thinning of the pipe wall thickness, reduce the bearing capacity of the pipeline, and affect the structural integrity of the pipeline. Corrosion analysis was conducted using the finite element method with the help of ABAQUS software to determine the burst pressure value that occurs when there is an influence of different corrosion depths and widths with idealized corrosion forms (uniform corrosion) and complex corrosion geometry forms (random corrosion). The analysis found that as the corrosion depth increases, the burst pressure value will be smaller. Every increase in the corrosion depth ratio (d/t) by 0.15, the burst pressure value will decrease by 15-20% of the internal pressure applied to the pipe for uniform corrosion and decrease by 20-23% for random corrosion. This indicates that the deeper the corrosion in the pipe, the easier the pipe will experience bursting. The decrease in burst pressure value of pipes with random corrosion is 3-5% greater than that of uniform corrosion. It is known that the burst pressure value in uniform corrosion modeling has a value that is 18% greater than random corrosion with an average burst presssure value of uniform corrosion of 18.28635 MPa and random corrosion of 14.8963 MPa.