INVESTIGATION OF HELICAL STRAKES PROTECTION EFFECTIVENESS WITH A COMPARATIVE STUDY OF RIGID RISER NUMERICAL MODELS IN THE NATUNA SEA

• Main Author: Muhammad Faiq Fagmi, Rifqi
• Format: Theses
• Language: Indonesia
• Subjects: Teknik (Rekayasa, enjinering dan kegiatan berkaitan)
• Online Access: https://digilib.itb.ac.id/gdl/view/61683
• Institution: Institut Teknologi Bandung

Riser is a part in the subsea pipeline system to deliver fluid in oil and gas drilling and processing areas in the sea, such as the Natuna Sea. Riser is usually vertical pipe located near offshore platform and far from the support, so that it is prone to damage due to environmental loads, such as ocean current that causes the vortexshedding phenomenon and gives fatigue loads during operation. To reduce the vortex-shedding that occurs, suppression devices are used, such as helical strake that commonly used. Based on this, a study was conducted to determine the effectiveness of helical strakes protection on the riser to reduce the vortexshedding. This research is carried out by performing numerical simulations of current flow with a maximum speed in the Natuna Sea of 0.96 m/s passing through a riser with a diameter of 8.625 inches to determine the flow patterns and forces that occur. In addition, simulations were carried out in several variations of helical strakes protection configurations, 100% along the riser, 80%, 60%, 40%, and 0%. The results of the simulation of several variations are compared based on the measured lift coefficient, so that the 100% configuration has the maximum effectiveness, 66.9% reduction in lift coefficient. In addition, a comparison of the stresses that occur in each configuration of the riser with stress analysis. The analysis was carried out by modeling a riser with a thickness of 22.23 mm as a result of wall thickness design which was given a current load at the speed of the numerical simulation results that have been carried out. From the results of the analysis, it was found that riser with 80% or more helical strakes protection provided optimal protection.