STUDI OPTIMASI OFFSHORE PIPELINE REPLACEMENT DI AREA BEKAPAI TOTAL E&P INDONESIE, BALIKPAPAN
Oleh : Ema Sapitri 4307 100 112 Mentor : 1. Faisal Akbar, HS ENG/CST/PWK TEPI 2. Hendri Sudjianto, PE ENG/CST/PWK TEPI
Dosen Pembimbing: 1. Ir. Hasan Ikhwani, M. Sc 2. Prof. Ir. Daniel M. Rosyid, Ph. D
Jurusan Teknik Kelautan Fakultas Teknologi Kelautan INSTITUT TEKNOLOGI SEPULUH NOPEMBER SURABAYA 2011
OUTLINE LATAR BELAKANG
DATA OFFSHORE PIPELINE PERUMUSAN MASALAH MANFAAT BATASAN MASALAH METODOLOGI PENELITIAN ANALISIS & PEMBAHASAN KESIMPULAN
LATAR BELAKANG • Offshore pipeline replacement merupakan aktivitas rutin di perusahaan migas (design life) • Selama ini di TOTAL E&P Indonesie, Balikpapan menggunakan studi komparasi utk melakukan desain pipa • Perlu adanya studi optimasi • Flowrate (produksi) pipa di area bekapai dari platform BK ke BP-1 menurun • Perlu adanya laying analisis sebelum dilakukan instalasi pipa
Source : Intranet TOTAL E&P Indonesie
LOKASI REPLACEMENT
Source : Intranet TOTAL E&P Indonesie
TABEL 1.2 DATA PIPA Field
Pipeline
Section
Section Type
Pipeline Pigging Status
Bekapai
8'' BK to BP-1
Offshore Pipelines
Offshore Pipelines
Piggable
BP-1
BK
1.8
Oil
Bekapai
8'' BK to BP-1
Riser BK (8" BK to BP-1)
Risers
Piggable
BP-1
BK
1.8
Oil
Bekapai
8'' BK to BP-1
Riser BP-1 (8" BK to BP-1)
Risers
Piggable
BP-1
BK
1.8
Oil
Concrete Coating Thickness (mm)
Concrete Coating Density (kg m3)
CP System
API Material
Pipeline Design Code
Design Safety Factor
Pipeline Design Life (yrs)
Operating Pressure (bar)
Operating Temperature (deg C)
Effluent
38
3000
Sacrificial Anode
X42
ASME B31.4
0.72
25
8
40
Oil
N/A
N/A
Sacrificial Anode
X42
ASME B31.4
0.72
25
8
40
Oil
N/A
N/A
Sacrificial Anode
X42
ASME B31.4
0.72
25
8
40
Oil
Pipeline From
Pipeline To
Lenght (km)
Product
Source : Intranet TOTAL E&P Indonesie
TABEL 1.2 DATA PIPA Date Commissioned
Pipeline Class
12/31/1985
Flow Line Flow Line Flow Line
12/31/1985 12/31/1985
Pipeline Position Type Offshore Laid on Seabed Platform Riser Platform Riser
Design Temperat ure (deg C)
Design Pressure (bar)
Wall Thickness (mm)
Corrosion Allowance (mm)
Coating Type
Coating Thickness (mm)
24
80
9.52
5
CTE
6
24
80
12.7
5
Fibreglass
0.3
24
80
12.7
5
Fibreglass
0.3
Age
MAIN PIPELINE - INTEGRITY STATUS (IP Based - October 2010)
P/L Segment No
Pipe Ø 9
8"
From
To
BK
BP
Line Status In-Service Oil
Product
Last IP
Fitness-For-Purpose Status @ Design Pressure (DP)
03/2007
Not Fit for Purpose
Action
Action by
Repair the pipeline
ENG/CST
Affirm future requirement or non-requirement for pipeline use based on cost
AMB
Continue cleaning pigging routinely Monitor SRB content regularly Reinstall access fitting for CC & ERP Perform a full CP potential survey as baselin Schedule next IP based on repair/replacement schedule (1)
Source : Intranet TOTAL E&P Indonesie
AMB/BSP/BKP MNS/INS/COR MNS/INS/COR MNS/INS/COR MNS/INS/PIM
DATA PIPA
Source : Intranet TOTAL E&P Indonesie
DATA PRODUKSI/PROSES PIPA Production/Process Data Oil Flow Rate, Qo
=
70.4
STBD
=
395.30 ft3/day
Gas Flow Rate, Qg
=
4.1
MMScfd
=
4189.91 ft3/day
Water Flow Rate, Qw
=
100
bwpd
=
561.50 ft3/day
Operating Pressure, P Maximum Operating Temperature, T
= =
8 40
bar 0 C
= =
116.03 563.67
psi 0 R
Design Pressure, Pd
=
80
bar
=
1160.30
psi
Pressure Drop, ΔP
=
0.8
bar
=
11.60
psi
Source : DEPT.ENG/PRO TOTAL E&P Indonesie
ENVIRONMENT DATA
Source : DEPT.ENG/SVY TOTAL E&P Indonesie
PERUMUSAN MASALAH 1. Bagaimana meminimalkan berat pipa untuk mendapatkan diamater luar pipa (Do) dan tebal pipa (t) yang optimum dengan mempertimbangkan constraint (kendala) berikut : 1. Stress Analysis, yang menjadi constraint adalah hoop stress. 2. Buckling Analysis, yang meliputi : system collapse check dan propagation buckling. 2. Bagaimana stabilitas pipa di dasar laut (on bottom stability : vertical stability dan lateral stability) ? 3. Berapa panjang bentangan pipa yang diijinkan dan panjang bentangan kritis pipa (free span analysis) ? 4. Bagimana laying analysis dan persentase yield stress yang dihasilkan dari pemodelan OFFPIPE ? 5. Berapa dimensi diameter luar pipa (Do) dan tebal pipa (t) yang optimum untuk dapat dioperasikan di BK-BP 1 platform area Bekapai tersebut ?
MANFAAT 1. Memberikan manfaat dan kontribusi nyata bagi perusahaan TOTAL E&P Indonesie, Balikpapan khususnya dan instansi terkait atau lembaga penelitian serta masyarakat pada umumnya. 2. Memberikan informasi / data sebagai referensi bagi perusahaan migas, lembaga penelitian atau instansi lain yang terkait maupun pihak independent.
BATASAN MASALAH 1. Studi ini dilakukan di perusahaan TOTAL E&P Indonesie, Balikpapan, yaitu studi optimasi pada pipa lepas pantai di area Bekapai yang menghubungkan platform BK ke BP1 dengan diameter original 8 inchi. 2. Variabel optimasi Diameter luar pipa (Do) dan tebal pipa (t) 3. Constraint yang dipertimbangkan stress analysis : hoop stress, buckling analysis : system collapse dan propagation buckling. 4. Parameter desain yang diperhitungkan meliputi : perhitungan on bottom stability, stress analysis, buckling analysis dan free span analysis. 5. Metode instalasi yang digunakan metode S-lay (pipa di area interfield offshore, d = 35 m). 6. Laying analysis dengan bantuan pemodelan software OFFFPIPE. 7. Pipeline design codes yang digunakan : • ASME B 31.4 2009 (Main Code) • DNV RP-F109 2010 – OBS (On Bottom Stability) • DNV RP-F110 2007 – Global Buckling • DNV RP-F105 2006 – Free Span • DNV RP-E305 1988 – OBS (On Bottom Stability) • DNV OS-F101 2010 – SPS (Submarine Pipeline System) • API RP-14E 1991 – Line Sizing 8. GS dari TOTAL yang digunakan : • GS EP COR 220 2010 -- Corrosion • GS EP PLR 100 2011 – Pipelnes-Risers
METODOLOGI PENELITIAN
KLICK HERE
ANALISIS & PEMBAHASAN Kalkulasi Dimensi Awal Pipa Erosional velocity
Dengan : Ve c ρm
= = =
kecapatan aliran tererosi, feet/second konstanta empiris mixture density dari gas/liquid pada tekanan dan suhu tertenti, lbs/ft3
P Sl
= =
R T Sg Z
= = = =
Tekanan pada saat beroperasi, psia Spesific gravity cairan (Air = 1, gunakan garvitasi rata-rata untuk campuran air hidrokarbon) pada kondisi standart Ratio gas/liquid, ft3/barrel pada kondisi standart Suhu pada saat beroperasi, 0R Spesific gravity gas (udara=1) pada kondisi standart Faktor kompresibilitas gas
A
=
Minimum pipe cross-sectional area yang dibutuhkan, in2/1000 barrels liquid per day
ANALISIS & PEMBAHASAN Kalkulasi Dimensi Awal Pipa Pressure Drop
Dengan : Qg
=
Laju aliran gas, million cubic feet/day (14,7 psia dan 600F)
Sg
=
Spesific gravity gas (udara = 1)
Ql
=
Laju aliran cairan, barrels/day
Sl
=
Spesific gravity cairan (air = 1)
=
Penurunan tekanan, psi/100 feet
=
Diameter dalam pipa, inchi
=
Density gas/cairan pada aliran tekanan dan suhu tertentu, lbs/ft3
=
Jumlah cairan dan laju aliran uap air lbs/hr
di W
ANALISIS & PEMBAHASAN Kalkulasi Dimensi Awal Pipa Reference : API RP-14 E-1991 (Line Sizing) Dari erosional velocity criteria dihasilkan minimum pipe inside diameter sebesar 2.525 in Penurunan tekanan (pressure drop) sebesar 1.18 psi/100 ft. Karena diameter terlalu kecil, sehingga dipilih 4.5 in & 6.625 in dalam mechanical design Diameter original 8 in tetap dipakai sebagai batasan maksimum dalam optimasi
ANALISIS & PEMBAHASAN Kalkulasi Tebal Pipa (Pipe Wall Thickness) Reference : ASME B31.4 2009
Dengan : Do = F1 = Pe = Sh = Sy = T = Pe = w =
Diamater luar pipa, in (mm) Faktor desain hoop stress (Tabel 3.9) Tekanan eksternal pipa, psi Hoop stress, psi Specified Minimum Yield Strength, psi Tebal pipa nominal, in (mm) Tekanan Eksternal pipa, psi Massa jenis air, kg/m3
h
=
Kedalaman air laut, m
G
=
Percepatan gravitasi, m/s2
ANALISIS & PEMBAHASAN Kalkulasi Tebal Pipa (Pipe Wall Thickness) Material grade B, X-42, X-46, X-46, X-52, dan X-56 (API 5L-2000). Tabel 4.1 Tebal Pipa tiap Material Grade (API 5L 2000) Grade B X-42 X-46 X-52
X-56
Do
t min (mm)
t req (mm)
t selected (mm)
4.5'' = 114.3 mm
2.516
5.516
6.02
6.625" = 168.275 mm
3.704
6.074
7.112
4.5'' = 114.3 mm
2.096
5.096
6.02
6.625" = 168.275 mm
3.086
6.086
7.112
4.5'' = 114.3 mm
1.914
5.563
6.625" = 168.275 mm
2.818
4.914 5.818
4.5'' = 114.3 mm
1.693
4.693
4.775
6.625" = 168.275 mm
4.693
5.493
5.563
4.5'' = 114.3 mm
1.572
4.572
4.775
6.625" = 168.275 mm
2.315
5.315
5.563
6.35
ANALISIS & PEMBAHASAN Analisis Tegangan (Stress Analysis) Hoop Stress
Dengan : Do = F1 = Pe = Sh = Sy = T =
Diamater luar pipa, in (mm) Faktor desain hoop stress (Tabel 3.9) Tekanan eksternal pipa, psi Hoop stress, psi Specified Minimum Yield Strength, psi Tebal pipa nominal, in (mm)
Longitudinal Stress & Combined Stress Dengan : F2 & F3 = Sl = St =
Faktor desain combined stress (Tabel 2.9) Longitudinal Stress Torsional stress, psi (MPa)
ANALISIS & PEMBAHASAN Analisis Tegangan (Stress Analysis) Material grade B, X-42, X-46, X-52, dan X-56 (API 5L-2000). Tabel 4. 2 Tebal Pipa tiap Material Grade (API 5L 2000) Grade B
X-42
X-46
X-52
X-56
Do
Check Sh (psi)
Allowable Sh (psi) Presentase Sh
Check
4.5'' = 114.3 mm
10530.616
25200
0.420
OK
6.625" = 168.275 mm
13122.962
25200
0.520
OK
4.5'' = 114.3 mm
10530.616
30240
0.350
OK
6.625" = 168.275 mm
13122.962
30240
0.430
OK
4.5'' = 114.3 mm
11395.705
33120
0.344
OK
6.625" = 168.275 mm
14697.718
33120
0.444
OK
4.5'' = 114.3 mm
13276.295
37440
0.355
OK
6.625" = 168.275 mm
16777.011
37440
0.448
OK
4.5'' = 114.3 mm
13276.29505
40320
0.329
OK
6.625" = 168.275 mm 16777.01066
40320
0.416
OK
ANALISIS & PEMBAHASAN Analisis Tegangan (Stress Analysis) Material grade B, X-42, X-46, X-52, dan X-56 (API 5L-2000). Tabel 4.3 Tebal Pipa tiap Material Grade (API 5L 2000) Grade B
X-42
X-46
X-52
X-56
Do
Longitudinal Stress Combined Stress (psi)
4.5'' = 114.3 mm
70%
13968
6.625" = 168.275 mm
83%
15959
4.5'' = 114.3 mm
58%
13968
6.625" = 168.275 mm
69%
15959
4.5'' = 114.3 mm
55%
13722
6.625" = 168.275 mm
65%
15392
4.5'' = 114.3 mm
55%
15568
6.625" = 168.275 mm
65%
17239
4.5'' = 114.3 mm
52%
15568
6.625" = 168.275 mm
61%
17239
Allawable Stress (psi)
Check OK
≤ 31500
OK OK
≤ 37800
OK OK
≤ 41400
OK OK
≤ 46800
OK
OK ≤ 50400
OK
ANALISIS & PEMBAHASAN Analisis Buckling (Buckling Analysis) Karakteristik Collapse
Dengan : Pc Pel Pp fo D t2 E αfab v
= = = = = = = = =
Tekanan collapse, psi Tekanan collapse elastic, psi Tekanan collapse plastis, psi Ovality Diameter luar, in Tebal minimum dinding pipa Modulus young (30022811,71 psi) Faktor toleransi fabrikasi Poisson ratio, 0.3
ANALISIS & PEMBAHASAN Analisis Buckling (Buckling Analysis) System Collapse Check Dengan : p min = = = Pc =
Tekanan internal minimum, psi Material resitance factor, (Tabel 2.14) Safety class resistance factor Tekanan collapse, psi
Propagation Buckling Kondisi terjadinya propagation buckling jika : Dengan : Pe Ppr fy D t2 αfab
Ppr < Pin < Pe
= = = = = =
tekanan eksternal, psi Tekanan perambatan buckling, psi Tegangan yield, psi Diameter luar pipa, in Tebal minimum dinding pipa, in Faktor fabrikasi
Pe
Ppr m sc
ANALISIS & PEMBAHASAN Analisis Buckling (Buckling Analysis) Tabel 4.5 System Collapse Check pada Material Grade B, X-42, X-46, X-52, dan X-56
Grade
B X-42
Ouside Diameter (Do) 4.5'' = 114.3 mm
14883.07
6.625" = 168.275 mm
8442.583
4.5'' = 114.3 mm
15665.777
1806.31 2837.094
6.625" = 168.275 mm
8959.642 13636.79
1916.936 2282.162
4.5'' = 114.3 mm
X-46
6.625" = 168.275 mm
X-56
Syarat (Check Pe - Pmin < 1109.260 psi)
2695.345
OK OK OK
7343.278 10636.163
1402.778 1527.86
4.5'' = 114.3 mm
6042.704 10950.234
1011.267 1572.976
OK
6.625" = 168.275 mm
6253.288
1046.509
NOT OK
4.5'' = 114.3 mm
X-52
Caracteristic Check Collapse Collapse (psi) Pressure (Pc), psi
6.625" = 168.275 mm
OK
ANALISIS & PEMBAHASAN Analisis Buckling (Buckling Analysis) Tabel 4.6 Propagation Buckling pada Material Grade B, X-42, X-46, X-52, dan X-56 Grade
B
X-42
X-46
X-52
X-56
Outside Diameter (Do) 4.5'' = 114.3 mm 6.625" = 168.275 mm 4.5'' = 114.3 mm 6.625" = 168.275 mm 4.5'' = 114.3 mm 6.625" = 168.275 mm 4.5'' = 114.3 mm 6.625" = 168.275 mm 4.5'' = 114.3 mm 6.625" = 168.275 mm
Ratio Do/t
Ppropagation Presssure (psi)
Check Propagation Pressure (psi)
34.428
169.097
129.21
Check (Syarat > Pe (1109.260 psi))
OK
38.14
130.902
100.024
25.743
160.69
121.58
24.638
115.46
92.34
39.923
153,473
117.272
OK
OK
46.103
107.097
81.835
55.084
77.584
59.283 OK
58.776
65.97
50.409
55.084
83.552
63.843
58.776
71.044
54.286
OK
ANALISIS & PEMBAHASAN Stabilitas Pipa (On Bottom Stability) Stabilitas Vertikal (DNV-RP-F109 2010)
Dengan : b ws sg
= = = =
Safety factor Gaya apung pipa tiap satuan panjang, N/m Berat pipa yang terpendam tiap satuan panjang, N/m Pipe spesific density
Gaya apung pipa tiap satuan panjang (b) dan berat pipa yang tenggelam tiap satuan panjang (ws) dapat dihitung dengan formula berikut :
Dengan : g Dc
= = =
Masa jenis air laut (1025 kg/m3) Percepatan gravitasi (9,81 m/s2) Diamater luar pipa termasuk seluruh coating, m
ANALISIS & PEMBAHASAN On Bottom Stability Stabilitas Lateral (DNV-RP-F109 2010)
Dengan : = = = = = =
Faktor keselamatan (safety factor) Beban hidrodinamis pada arah horisontal, N/m Beban hidrodinamis pada arah vertikal, N/m Tahanan tanah pasif, N/m Koefisien gesek berat pipa yang tenggelam tiap satuan panjang, N/m
Dari kalkulasi tidak pipa diameter 4.5 in dan 6.625 in masih stabil secara vertikal maupun lateral
ANALISIS & PEMBAHASAN On Bottom Stability Vertical Stability
Material grade B, X-42, X-46, X-52, dan X-56 (API 5L-2000). Tabel 4.7 Tabel Hasil Kalkulasi Stabilitas Vertikal pada Pipa dalam Kondisi Instalasi dan Operasi
Grade B X-42 X-46
X-52 X-56
Do
Installation Condition Ratio
4.5'' = 114.3 mm
0.414
6.625" = 168.275 mm
0.436
4.5'' = 114.3 mm
0.401
6.625" = 168.275 mm
0.408
4.5'' = 114.3 mm
0.420
6.625" = 168.275 mm
0.446
4.5'' = 114.3 mm
0.430
6.625" = 168.275 mm
0.457
4.5'' = 114.3 mm
0.430
6.625" = 168.275 mm
0.457
Syarat DNV Check ≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
Operation Condition Ratio 0.346 0.353 0.337 0.335 0.350 0.360 0.357
0.367 0.357 0.367
Syarat DNV Check ≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
ANALISIS & PEMBAHASAN On Bottom Stability Lateral Stability (Installation Condition)
Material grade B, X-42, X-46, X-52, dan X-56 (API 5L-2000). Tabel 4.8 Tabel Hasil Kalkulasi Stabilitas Lateral pada Pipa dalam Kondisi Instalasi
Grade
B X-42 X-46 X-52 X-56
Do
Design Criterion (DC)
4.5'' = 114.3 mm
0.447
6.625" = 168.275 mm
0.573
4.5'' = 114.3 mm
0.430
6.625" = 168.275 mm
0.529
4.5'' = 114.3 mm
0.455
6.625" = 168.275 mm
0.589
4.5'' = 114.3 mm
0.469
6.625" = 168.275 mm
0.606
4.5'' = 114.3 mm
0.469
6.625" = 168.275 mm
0.606
Syarat DNV
Check
≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
Ration DC dg Passive Syarat Check Soil Resistance DNV 0.070 0.351 0.068 0.323
0.072 0.361 0.074 0.371 0.074 0.371
≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
ANALISIS & PEMBAHASAN On Bottom Stability Lateral Stability (Oparation Condition)
Material grade B, X-42, X-46, X-46, X-52, dan X-56 (API 5L-2000). Tabel 4.9 Tabel Hasil Kalkulasi Stabilitas Lateral pada Pipa dalam Kondisi Operasi Grade B X-42 X-46 X-52 X-56
4.5'' = 114.3 mm
Design Criterion (DC) 0.700
6.625" = 168.275 mm
0.860
4.5'' = 114.3 mm
0.700
6.625" = 168.275 mm
0.860
4.5'' = 114.3 mm
0.712
6.625" = 168.275 mm
0.884
4.5'' = 114.3 mm
0.773
6.625" = 168.275 mm
0.911
4.5'' = 114.3 mm
0.773
6.625" = 168.275 mm
0.911
Do
Syarat DNV ≤ 1.0 ≤ 1.0
Check OK OK
≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
Ration DC dg Passive Syarat Check Soil Resistance DNV 0.112 0.465 0.112 0.465 0.113 0.478 0.117 0.493 0.117 0.493
≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
≤ 1.0
OK
ANALISIS & PEMBAHASAN Free Span Analysis Material grade B, X-42, X-46, X-52, dan X-56 (API 5L-2000). Tabel 4. 10 Tabel Hasil Kalkulasi Free Span Analysis pada Material Grade B, X42, X46, X52, dan X56
Grade
B X42 X46 X52 X56
Outside Diameter (Do) 4.5'' = 114.3 mm 6.625" = 168.275 mm 4.5'' = 114.3 mm 6.625" = 168.275 mm 4.5'' = 114.3 mm 6.625" = 168.275 mm 4.5'' = 114.3 mm 6.625" = 168.275 mm 4.5'' = 114.3 mm 6.625" = 168.275 mm
Span Lenght, Ls (m) 8,819
The Critical The Critical Span Lenght for Span Lenght for Cross Flow In-Line Motion, Motion 1, LC-CF LC-IL (m) (m) 12,617 17,889
12,430
14,000
27,832
8,775
12,554
17,800
12,305
13,859
27,552
8,692
12,436
17,632
11,855
13,703
27,241
8,443
12,080
17,128
11,855
13,352
26,544
8,443
12,080
17,128
11,855
13,352
26,544
Check Ls < LC-IL & LCCF
OK OK OK OK OK
ANALISIS & PEMBAHASAN Laying Analysis Analisis laying pipa pada saat instalasi dilakukan dengan bantuan software OFFPIPE untuk pengecekan terhadap besarnya yield stress maksimum yang terjadi baik pada daerah over bend maupun sag bend. Berikut tabel bending stress maksimum yang dijinkan pada daerah over bend maupun sag bend. Tabel 8. Maximum Allowable Bending Stress (Referensi : Laying Analysis PT. Dwi Satu Mustika Bumi)
LAYING ANALISYS Gambaran Proses Laying Analysis
Gambar 2.20 Tegangan pada Daerah Overbend (Bai. Y, 2001)
LAYING ANALISYS Laying Analysis Hasil Pemodelan Software OFFPIPE Material grade B, X-42, X-46, X-52, dan X-56 (API 5L-2000). Tabel 4.10 Persentase Yield Stress sebagai Output dari (Hasil Pemodelan) software OFFPIPE
Grade
B
X-42
X-46
X-52
X-56
Do
Percent Yield Stress (Overbend)
4.5'' = 114.3 mm
103.08%
6.625" = 168.275 mm
311.01%
4.5'' = 114.3 mm
81.64%
6.625" = 168.275 mm
82.10%
4.5'' = 114.3 mm
74.66%
6.625" = 168.275 mm
78.64%
4.5'' = 114.3 mm
66.04%
6.625" = 168.275 mm
67.82%
4.5'' = 114.3 mm
72.60%
6.625" = 168.275 mm
66.75%
Max. Allowable Yield Stress (Overbend)
Check
≥ 85%
NOT OK
≤ 85%
OK
≤ 85%
OK
≤ 85%
OK
≤ 85%
OK
Percent Yield Stress (Sagbend) 49.28% 70.06% 44.88% 65.54% 40.97% 65.11%
36.24% 59.77% 33.34% 49.41%
Max. Allawable Yield Stress (Sagbend) ≤ 70%
Check OK NOT OK
≤ 70%
OK
≤ 70%
OK
≤ 70%
OK
≤ 70%
OK
PEMODELAN OPTIMASI Pemodelan optimasi hanya dilakukan pada material grade B, X-42, dan X52 , karena : Mengacu ke desain lama (diameter in, material grade X-42) Material grade B tidak lolos laying analysis pada pemodelan OFFPIPE Material grade X-56 terlalu tinggi grade-nya Material Grade X-52 Tabel 4.11 Data Diameter dan Tebal Pipa Material Grade X-52 Hoop Stress (Psi)
System Collapse (Psi)
Propagation Buckling (Psi)
D (in)
t (in)
D (in)
t (in)
D (in)
t (in)
4,5
0,0755
4,5
0,139
4,5
0,183
6,625
0,11
6,625
0,25
6,625
0,22
8
0,133
8
0,125
8
0,243
PEMODELAN OPTIMASI Kemudian akan diplot dalam grafik untuk mencari titik optimum.
.
Grafik Optimasi tiap Constraint (Psi) 0,3
y = -0,0002x2 + 0,0196x + 0,0988 0,25
Tebal Pipa (in)
y = -0,0409x2 + 0,5072x - 1,3153 0,2 Hoop Stress X-52 System Collapse X-52
0,15
Propagation Buckling X-52 Poly. (Hoop Stress X-52) Poly. (System Collapse X-52)
0,1
Poly. (System Collapse X-52) Poly. (Propagation Buckling X-52)
y = 0,0001x2 + 0,0147x + 0,0066
0,05
0 0
1
2
3
4
5
6
7
8
9
Diameter Luar Pipa (in) Gambar 4. 3 Grafik Optimasi tiap Constraint pada Material Grade X52
PEMODELAN OPTIMASI Sehingga titik optimumnya adalah : (7.2 , 0.1132). Hal ini berarti pada material grade X-42 diameter luar pipa yang optimum adalah 7.2 in dan tebal pipanya optimum adalah 0.1132 in. Dengan berat pipa = 36.029 lb/in. Karena diameter luar ini tidak disediakan dalam schedule pipa (API 5L 2000), maka dipilih yang mendekati diameter luar dan tebal pipa dalam schedule pipa, yaitu diameter luar pipa 8.625 in dan tebal pipa 0.125 in.
KESIMPULAN 1. Meminimalkan berat pipa dilakukan dengan bantuan Microsoft Excel dengan membuat persamaan objektif tiap constraint dengan memplotkan 2 variabel diameter luar dan tebal pipa pada grafik. 2. Pipa dengan Ø 4.5” dan Ø 6.625” pada masing-masing material grade (B, X42, X-46, X-52, dan X-56 masih stabil baik kondisi instalasi maupun operasi. 3. Panjang bentangan pipa masih memenuhi (kurang dari) panjang bentangan kritis pipa. 4. Laying analysis (pemodelan OFFPIPE) menunjukkan bahwa pada material grade B dengan Ø 4.5” dan Ø 6.625” persen yield stress-nya melebihi maximum yield stress yang diijinkan, sementara pada material grade pada X42, X-46, X-52, dan X-56 masih memenuhi. 5. Diameter pipa (Do) dan tebal pipa (t) yang optimum untuk dapat dioperasikan di BK-BP 1 platform area Bekapai adalah Ø 8.625’’, dan tebal 0.125 in dengan berat minimal pipa 36.029 lb/in dan material grade X-52.
DAFTAR PUSTAKA API RP-14E. 1991. Recommended Practice for Design and Installation of Offshore Production Platform Piping System. Northwest Washington, DC. American. API Spec-5L. 2000. Spesification for Line Pipe. American Petroleum Institute, American. ASME B31-4. 2009. Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids. The American Society of Mechanical Engineers, American. Bai,Y. 2001. Pipeline and Risers. Oxford. Elsevier Science Ltd. DNV OS-F101. 2010. Submarine Pipeline Systems. Det Norske Veritas, American. DNV RP-F109. 2010. On-Bottom Stability Design of Submarine Pipelines. Det Norske Veritas, American. DNV RP-F110. 2007. Global Buckling of Submarine Pipelines Structural Design Due to High Temperature/High Pressure. Det Norske Veritas, American DNV RP-F105. 2006. Free Spanning Pipelines. Det Norske Veritas, American DNV RP-E305. 1988. On-Bottom Stability Design of Submarine Pipelines Det Norske Veritas, American. GS EP COR 220. 2011. Corrosion, Three Layer Polyethylene External Coating for Pipelines. TOTAL E&P Indonesie. Guo, B., Song, S., Chacko, J., dan Ghalambor, A. 2005. Offshore Pipeline. Elsiver, United State. Halliwell, R. (1986). An Introduction to Offshore Pipeline. University College, Cork. Intranet TOTAL E&P Indonesie. Mouselli, A. 1981. Offshore Pipeline Design, Analysis and Methods. PenWell Books, Oklahoma. Rosyid, D.M. 2009. Optimasi, Teknik Pengambilan Keputusan secara Kuantitatif. ITS Press, Surabaya. Tahrizi, A. 2010. Report of On the Job Training Bekapai Pipeline Analysis BKP-SNP 12” Pipeline Depressurisation Study and BK-BP1 New Pipeline Design, Balikpapan. Santosa, B. 2008. MATLAB untuk Statistika dan Teknik Optimasi. Graha Ilmu, Yogyakarta.
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