INVESTIGATION OF HELICAL STRAKES PROTECTION EFFECTIVENESS WITH A COMPARATIVE STUDY OF RIGID RISER NUMERICAL MODELS IN THE NATUNA SEA
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...
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| Format: | Theses |
| Language: | Indonesia |
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| Online Access: | https://digilib.itb.ac.id/gdl/view/61683 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | 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.
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