Ulfah, Noni Nabila (2016) Analisis Operabilitas Common Spare CALM Buoy Studi Kasus PT.PERTAMINA (Persero) Pada Lokasi Operasi Terminal Transfer Utama Tuban. Undergraduate thesis, Institut Technology Sepuluh Nopember.
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Abstract
Dalam operasi offshore, penggunaan single point mooring sebagai sistem tambat
merupakan salah satu pilihan populer, CALM Buoy merupakan SPM yang paling
banyak dipakai di Indonesia terutama oleh PT Pertamina (persero). Seperti
struktur lainnya, buoy membutuhkan perawatan berkala dan pada saat tertentu
perawatan harus dilakukan di darat sehingga mengharuskan owner untuk
menyewa buoy lain. Strategi ini membutuhkan biaya yang cukup besar dan
karenanya PT Pertamina (persero) melakukan studi penggunaan buoy SPM
IMODCO sebagai common spare yang digunakan saat buoy menjalani perawatan
di dok. Hanya buoy dari common spare yang akan dipindahkan antar lokasi
sementara tali tambat menggunakan yang tersedia di lokasi. Buoy common spare
memiliki empat mooring line, sementara pada beberapa lokasi terdapat enam
mooring line. Perbedaan ini akan mempengaruhi respon gerak dan nilai
operabilitas. Dengan mempertimbangkan respon gerak, tension mooring line, data
sebaran gelombang serta kriteria batas operasi, akan didapatkan nilai operabilitas
dari common spare SPM CALM Buoy. Analisis dinamis berbasis ranah waktu
dilakukan untuk kedua SPM di TTU Tuban masing-masing berkapasitas tambat
150.000 DWT dan 35.000 DWT. Analisis dilakukan dengan variasi ukuran kapal,
muatan dan posisi kapal inline serta between line. Kemudian diambil kasus
dengan respon terburuk yang akan dijadikan acuan analisis operabilitas. Analisis
operabilitas dilakukan pada tiga variasi Hs yaitu 1.25 m, 2.5 m, dan 3.5 m. Kriteria
yang ditinjau adalah tension mooring line serta moda gerak heave, roll, pitch pada
buoy. Pada semua kasus, nilai tension telah memenuhi kriteria SF API RP 2SK
untuk kondisi intact dinamis sebesar 1.67. Sementara untuk dinyatakan operable,
buoy tidak diperbolehkan tercelup ke dalam air dengan intensitas kejadian
melebihi 20%. Pada tanker 150.000 DWT dan 100.000 DWT presentase tercelup
pada Hs 2.5 m secara berturut-turut adalah 30.35% dan 33.25% sehingga
dinyatakan tidak dapat beroperasi pada Hs tersebut. Pada tanker 35.000 DWT dan
17.500 DWT presentase tercelup pada Hs 3.5 m secara berturut-turut adalah
66.17% dan 76.91% sehingga dinyatakan tidak dapat beroperasi pada Hs tersebut.
Berdasarkan analisis yang dilakukan dapat disimpulkn bahwa nilai operabilitas
untuk tanker 150.000 DWT dan 100.000 DWT adalah 99.893% sementara untuk
tanker 35.000 dan 17.500 adalah 99.996%.
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CALM buoy is one of SPM commonly used in Indonesia, especially by PT
Pertamina (Persero). Like any other offshore structure, CALM buoy requires a
periodical maintenance. Sometimes the maintenance need to be carried out
onshore, thus it requires the owner to charter another buoy for replacement. In this
respect the owner should allocate certain amount of budget, which to some degree
is relatively costly. PT Pertamina (Persero) has therefore initiated to conduct a
study on utilizing an old SPM IMODCO’s buoy as a common spare, to replace the
buoy at any site when it is put under maintenance in onshore yard. Only the
common spare buoy will be moved to the site, without the the accompanying
mooring system. The problem arises because the common spare is configured
with 4 mooring lock points, whereas in most sites they used 6 or 8 mooring lock
points. These differences will certainly affect the motion responses and the
operability rates of the common spare buoy. Analyses are then performed to
acquire information on motion responses and mooring line tensions. Combining
these with the wave scatter diagram and operation limit, the operability rate of the
common spare SPM CALM buoy could be predicted. Time domain dynamic
analysis was conducted for SPM operating in TTU Tuban, combined with 35,000
DWT tanker, as the lowest operational capacity, and 150,000 DWT, as the
maximum operational capacity. The analysis was conducted by varying of tanker
capacity, loading condition and tanker position, ie. inline and between lines. Then
the worst case was selected for further evaluation in the operability analysis,
conducted in three significant wave height variations, namely 1.25 m, 2.5 m, dan
3.5 m. Operability criteria so considered are mooring line tension, and buoy’s
heave, roll and pitch motions. All of the cases were found to satisfy API RP 2SK
requirements of safety factor for tension in intact dynamic simulation of 1.67.
Further, to be declared as operable, the buoy is not allowed to be fully or partially
submerged with intensity more than 20% of the total cycles. For the 150,000
DWT and 100,000 DWT tankers the percentage of submerging on Hs 2.5 m are
30.35% and 33.25%, respectively, thus both condition are classified as not
operable on the corresponding Hs. For 35,000 DWT and 17,500 DWT tankers the
percentage of submerging on Hs 3.5 m are 66.17% and 76.91% thus both
condition are classified as not operable the corresponding Hs. Based on those
analyses, it can be concluded that the operability rate for 150,000 DWT and
100,000 DWT tankers are 99.893%, whilst the 35,000 DWT and 17,500 DWT
tankers has a 99.996% operability rate.
| Item Type: | Thesis (Undergraduate) |
|---|---|
| Additional Information: | RSKe 627.924 Ulf a |
| Uncontrolled Keywords: | common spare SPM, operabilitas, respon gerak bangunan apung, SPM CALM Buoy, |
| Subjects: | T Technology > TC Hydraulic engineering. Ocean engineering > TC1680 Offshore structures |
| Divisions: | Faculty of Marine Technology (MARTECH) > Ocean Engineering > 38201-(S1) Undergraduate Thesis |
| Depositing User: | Mr. Tondo Indra Nyata |
| Date Deposited: | 27 Feb 2020 02:13 |
| Last Modified: | 27 Feb 2020 02:13 |
| URI: | http://repository.its.ac.id/id/eprint/75209 |
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