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STUDI OPTIMASI OFFSHORE PIPELINE REPLACEMENT DI AREA BEKAPAI TOTAL E&P
INDONESIE, BALIKPAPAN
Jurusan Teknik Kelautan Fakultas Teknologi Kelautan
INSTITUT TEKNOLOGI SEPULUH NOPEMBER SURABAYA
2011
Oleh :Ema Sapitri 4307 100 112
Dosen Pembimbing:1. Ir. Hasan Ikhwani, M. Sc2. Prof. Ir. Daniel M. Rosyid, Ph. D
Mentor :1. Faisal Akbar, HS ENG/CST/PWK TEPI2. Hendri Sudjianto, PE ENG/CST/PWK TEPI
OUTLINE
LATAR BELAKANG
PERUMUSAN MASALAH
DATA OFFSHORE PIPELINE
BATASAN MASALAH
METODOLOGI PENELITIAN
ANALISIS & PEMBAHASAN
KESIMPULAN
MANFAAT
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
Source : Intranet TOTAL E&P Indonesie
Field Pipeline Section Section TypePipeline Pigging Status
Pipeline From
Pipeline ToLenght (km)
Product
Bekapai8'' BK to
BP-1Offshore Pipelines
Offshore Pipelines
Piggable BP-1 BK 1.8 Oil
Bekapai8'' BK to
BP-1Riser BK (8" BK to
BP-1)Risers Piggable BP-1 BK 1.8 Oil
Bekapai8'' BK to
BP-1Riser 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 SystemAPI
Material
Pipeline Design Code
Design Safety Factor
Pipeline Design
Life (yrs)
Operating Pressure
(bar)
Operating Temperature
(deg C)Effluent
38 3000Sacrificial
AnodeX42
ASME B31.4
0.72 25 8 40 Oil
N/A N/ASacrificial
AnodeX42
ASME B31.4
0.72 25 8 40 Oil
N/A N/ASacrificial
AnodeX42
ASME B31.4
0.72 25 8 40 Oil
TABEL 1.2 DATA PIPA
Source : Intranet TOTAL E&P Indonesie
Date Commissioned
Pipeline Class
Pipeline Position
TypeAge
Design Temperature (deg
C)
Design Pressure
(bar)
Wall Thickness
(mm)
Corrosion Allowance
(mm)
Coating Type
Coating Thickness
(mm)
12/31/1985Flow Line
Offshore Laid on Seabed
24 80 9.52 5 CTE 6
12/31/1985Flow Line
Platform Riser
24 80 12.7 5 Fibreglass 0.3
12/31/1985Flow Line
Platform Riser
24 80 12.7 5 Fibreglass 0.3
9 8" BK BP In-Service Oil 03/2007 Not Fit for Purpose Repair the pipeline ENG/CST
Affirm future requirement or non-requirement for pipeline use based on cost AMB
Continue cleaning pigging routinelyAMB/BSP/BKP
Monitor SRB content regularly MNS/INS/CORReinstall access fitting for CC & ERP MNS/INS/CORPerform a full CP potential survey as baselin MNS/INS/CORSchedule next IP based on repair/replacement schedule (1) MNS/INS/PIM
Line
StatusFrom
Action byFitness-For-Purpose Status @
Design Pressure (DP)To
Product ActionLast IP
MAIN PIPELINE - INTEGRITY STATUS (IP Based - October 2010)
No Pipe Ø
P/L Segment
DATA PIPA
Source : Intranet TOTAL E&P Indonesie
DATA PRODUKSI/PROSES PIPA
Source : DEPT.ENG/PRO TOTAL E&P Indonesie
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 = 8 bar = 116.03 psiMaximum Operating Temperature, T = 40 0C = 563.67 0RDesign Pressure, Pd = 80 bar = 1160.30 psi
Pressure Drop, ΔP = 0.8 bar = 11.60 psi
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 optimumdengan 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 dankontribusi nyata bagi perusahaanTOTAL E&P Indonesie, Balikpapankhususnya dan instansi terkaitatau lembaga penelitian sertamasyarakat pada umumnya.
2. Memberikan informasi / datasebagai referensi bagi perusahaanmigas, lembaga penelitian atauinstansi lain yang terkait maupunpihak independent.
BATASAN MASALAH
1. Studi ini dilakukan di perusahaan TOTAL E&P Indonesie, Balikpapan, yaitu studioptimasi pada pipa lepas pantai di area Bekapai yang menghubungkan platformBK 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
ANALISIS & PEMBAHASAN
Kalkulasi Dimensi Awal Pipa
Erosional velocity
Dengan :
Ve = kecapatan aliran tererosi, feet/secondc = konstanta empirisρm = mixture density dari gas/liquid pada tekanan dan suhu tertenti, lbs/ft3
P = Tekanan pada saat beroperasi, psiaSl = Spesific gravity cairan (Air = 1, gunakan garvitasi rata-rata untuk
campuran air hidrokarbon) pada kondisi standartR = Ratio gas/liquid, ft3/barrel pada kondisi standartT = Suhu pada saat beroperasi, 0RSg = Spesific gravity gas (udara=1) pada kondisi standartZ = Faktor kompresibilitas gas
A = Minimum pipe cross-sectional area yang dibutuhkan, in2/1000barrels 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
di = Diameter dalam pipa, inchi
= Density gas/cairan pada aliran tekanan dan suhu tertentu, lbs/ft3
W = Jumlah cairan dan laju aliran uap air lbs/hr
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 = Diamater luar pipa, in (mm)F1 = Faktor desain hoop stress (Tabel 3.9)Pe = Tekanan eksternal pipa, psi Sh = Hoop stress, psiSy = Specified Minimum Yield Strength, psiT = Tebal pipa nominal, in (mm)Pe = Tekanan Eksternal pipa, psiw = 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 Do t min (mm) t req (mm) t selected (mm)
B4.5'' = 114.3 mm 2.516 5.516 6.02
6.625" = 168.275 mm 3.704 6.074 7.112
X-424.5'' = 114.3 mm 2.096 5.096 6.02
6.625" = 168.275 mm 3.086 6.086 7.112
X-464.5'' = 114.3 mm 1.914 4.914 5.563
6.625" = 168.275 mm 2.818 5.818 6.35
X-524.5'' = 114.3 mm 1.693 4.693 4.775
6.625" = 168.275 mm 4.693 5.493 5.563
X-564.5'' = 114.3 mm 1.572 4.572 4.775
6.625" = 168.275 mm 2.315 5.315 5.563
ANALISIS & PEMBAHASAN
Analisis Tegangan (Stress Analysis)
Hoop Stress
Dengan :Do = Diamater luar pipa, in (mm)F1 = Faktor desain hoop stress (Tabel 3.9)Pe = Tekanan eksternal pipa, psi Sh = Hoop stress, psiSy = Specified Minimum Yield Strength, psiT = Tebal pipa nominal, in (mm)
Longitudinal Stress & Combined Stress
Dengan :F2 & F3 = Faktor desain combined stress (Tabel 2.9)Sl = Longitudinal StressSt = 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 Do Check Sh (psi) Allowable Sh (psi) Presentase Sh Check
B4.5'' = 114.3 mm 10530.616 25200 0.420 OK
6.625" = 168.275 mm 13122.962 25200 0.520 OK
X-424.5'' = 114.3 mm 10530.616 30240 0.350 OK
6.625" = 168.275 mm 13122.962 30240 0.430 OK
X-464.5'' = 114.3 mm 11395.705 33120 0.344 OK
6.625" = 168.275 mm 14697.718 33120 0.444 OK
X-524.5'' = 114.3 mm 13276.295 37440 0.355 OK
6.625" = 168.275 mm 16777.011 37440 0.448 OK
X-564.5'' = 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 Do Longitudinal Stress Combined Stress (psi)Allawable Stress
(psi)Check
B4.5'' = 114.3 mm 70% 13968
≤ 31500OK
6.625" = 168.275 mm 83% 15959 OK
X-424.5'' = 114.3 mm 58% 13968
≤ 37800OK
6.625" = 168.275 mm 69% 15959 OK
X-464.5'' = 114.3 mm 55% 13722
≤ 41400OK
6.625" = 168.275 mm 65% 15392 OK
X-524.5'' = 114.3 mm 55% 15568
≤ 46800OK
6.625" = 168.275 mm 65% 17239 OK
X-564.5'' = 114.3 mm 52% 15568
≤ 50400OK
6.625" = 168.275 mm 61% 17239 OK
ANALISIS & PEMBAHASAN
Analisis Buckling (Buckling Analysis)
Karakteristik Collapse
Dengan :
Pc = Tekanan collapse, psiPel = Tekanan collapse elastic, psiPp = Tekanan collapse plastis, psifo = OvalityD = Diameter luar, int2 = Tebal minimum dinding pipaE = Modulus young (30022811,71 psi)αfab = Faktor toleransi fabrikasiv = Poisson ratio, 0.3
ANALISIS & PEMBAHASAN
Analisis Buckling (Buckling Analysis)
System Collapse Check
Dengan :p min = Tekanan internal minimum, psi
= Material resitance factor, (Tabel 2.14)= Safety class resistance factor
Pc = Tekanan collapse, psi
Propagation Buckling
Kondisi terjadinya propagation buckling jika :
Ppr < Pin < Pe
Dengan :Pe = tekanan eksternal, psiPpr = Tekanan perambatan buckling, psify = Tegangan yield, psiD = Diameter luar pipa, in t2 = Tebal minimum dinding pipa, inαfab = Faktor fabrikasi
PprPe
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 Ouside Diameter (Do)
Caracteristic
Collapse
Pressure (Pc), psi
Check Collapse
(psi)
Syarat (Check
Pe - Pmin <
1109.260 psi)
B4.5'' = 114.3 mm 14883.07 2695.345
OK6.625" = 168.275 mm 8442.583 1806.31
X-424.5'' = 114.3 mm 15665.777 2837.094
OK6.625" = 168.275 mm 8959.642 1916.936
X-464.5'' = 114.3 mm 13636.79 2282.162
OK6.625" = 168.275 mm 7343.278 1402.778
X-524.5'' = 114.3 mm 10636.163 1527.86
OK6.625" = 168.275 mm 6042.704 1011.267
X-564.5'' = 114.3 mm 10950.234 1572.976 OK
6.625" = 168.275 mm 6253.288 1046.509 NOT 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 Outside Diameter
(Do) Ratio Do/t
Ppropagation
Presssure (psi)
Check
Propagation
Pressure (psi)
Check (Syarat
> Pe (1109.260
psi))
B
4.5'' =
114.3 mm34.428 169.097 129.21
OK6.625" = 168.275
mm38.14 130.902 100.024
X-42
4.5'' =
114.3 mm25.743 160.69 121.58
OK6.625" = 168.275
mm24.638 115.46 92.34
X-46
4.5'' =
114.3 mm39.923 153,473 117.272
OK6.625" = 168.275
mm46.103 107.097 81.835
X-52
4.5'' =
114.3 mm55.084 77.584 59.283
OK6.625" = 168.275
mm58.776 65.97 50.409
X-56
4.5'' =
114.3 mm55.084 83.552 63.843
OK6.625" = 168.275
mm58.776 71.044 54.286
ANALISIS & PEMBAHASAN
Stabilitas Pipa (On Bottom Stability)
Stabilitas Vertikal (DNV-RP-F109 2010)
Dengan := Safety factor
b = Gaya apung pipa tiap satuan panjang, N/mws = Berat pipa yang terpendam tiap satuan panjang, N/msg = 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 := Masa jenis air laut (1025 kg/m3)
g = Percepatan gravitasi (9,81 m/s2)Dc = 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 secaravertikal 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 Do Installation Condition Operation Condition
Ratio Syarat DNV Check Ratio Syarat DNV Check
B4.5'' = 114.3 mm 0.414
≤ 1.0 OK0.346
≤ 1.0 OK6.625" = 168.275 mm 0.436 0.353
X-424.5'' = 114.3 mm 0.401
≤ 1.0 OK0.337
≤ 1.0 OK6.625" = 168.275 mm 0.408 0.335
X-464.5'' = 114.3 mm 0.420
≤ 1.0 OK0.350
≤ 1.0 OK6.625" = 168.275 mm 0.446 0.360
X-524.5'' = 114.3 mm 0.430
≤ 1.0 OK0.357
≤ 1.0 OK6.625" = 168.275 mm 0.457 0.367
X-564.5'' = 114.3 mm 0.430
≤ 1.0 OK0.357
≤ 1.0 OK6.625" = 168.275 mm 0.457 0.367
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 Do Design
Criterion (DC)
Syarat DNV
CheckRation DC dg Passive
Soil ResistanceSyaratDNV
Check
B4.5'' = 114.3 mm 0.447
≤ 1.0 OK0.070
≤ 1.0 OK6.625" = 168.275 mm 0.573 0.351
X-424.5'' = 114.3 mm 0.430
≤ 1.0 OK0.068
≤ 1.0 OK6.625" = 168.275 mm 0.529 0.323
X-464.5'' = 114.3 mm 0.455
≤ 1.0 OK0.072
≤ 1.0 OK6.625" = 168.275 mm 0.589 0.361
X-524.5'' = 114.3 mm 0.469
≤ 1.0 OK0.074
≤ 1.0 OK6.625" = 168.275 mm 0.606 0.371
X-564.5'' = 114.3 mm 0.469
≤ 1.0 OK0.074
≤ 1.0 OK6.625" = 168.275 mm 0.606 0.371
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 Do Design
Criterion (DC)
Syarat DNV
CheckRation DC dg Passive
Soil ResistanceSyarat DNV
Check
B4.5'' = 114.3 mm 0.700
≤ 1.0 OK0.112
≤ 1.0 OK6.625" = 168.275 mm 0.860 0.465
X-424.5'' = 114.3 mm 0.700
≤ 1.0 OK0.112
≤ 1.0 OK6.625" = 168.275 mm 0.860 0.465
X-464.5'' = 114.3 mm 0.712
≤ 1.0 OK0.113
≤ 1.0 OK6.625" = 168.275 mm 0.884 0.478
X-524.5'' = 114.3 mm 0.773
≤ 1.0 OK0.117
≤ 1.0 OK6.625" = 168.275 mm 0.911 0.493
X-564.5'' = 114.3 mm 0.773
≤ 1.0 OK0.117
≤ 1.0 OK6.625" = 168.275 mm 0.911 0.493
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
GradeOutside Diameter
(Do)
Span Lenght,
Ls (m)
The Critical
Span Lenght for
In-Line Motion,
LC-IL (m)
The Critical
Span Lenght for
Cross Flow
Motion 1, LC-CF
(m)
Check Ls
< LC-IL & LC-
CF
B4.5'' = 114.3 mm 8,819 12,617 17,889
OK6.625" = 168.275 mm 12,430 14,000 27,832
X424.5'' = 114.3 mm 8,775 12,554 17,800
OK6.625" = 168.275 mm 12,305 13,859 27,552
X464.5'' = 114.3 mm 8,692 12,436 17,632
OK6.625" = 168.275 mm 11,855 13,703 27,241
X524.5'' = 114.3 mm 8,443 12,080 17,128
OK6.625" = 168.275 mm 11,855 13,352 26,544
X564.5'' = 114.3 mm 8,443 12,080 17,128
OK6.625" = 168.275 mm 11,855 13,352 26,544
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 Do
Percent
Yield Stress
(Overbend)
Max.
Allowable
Yield Stress
(Overbend)
Check
Percent
Yield
Stress
(Sagbend)
Max.
Allawable
Yield Stress
(Sagbend)
Check
B
4.5'' = 114.3 mm 103.08%
≥ 85% NOT OK
49.28%≤ 70%
OK
6.625" = 168.275 mm 311.01% 70.06% NOT OK
X-424.5'' = 114.3 mm 81.64%
≤ 85% OK44.88%
≤ 70% OK6.625" = 168.275 mm 82.10% 65.54%
X-464.5'' = 114.3 mm 74.66%
≤ 85% OK40.97%
≤ 70% OK6.625" = 168.275 mm 78.64% 65.11%
X-524.5'' = 114.3 mm 66.04%
≤ 85% OK36.24%
≤ 70% OK6.625" = 168.275 mm 67.82% 59.77%
X-564.5'' = 114.3 mm 72.60%
≤ 85% OK33.34%
≤ 70% OK6.625" = 168.275 mm 66.75% 49.41%
PEMODELAN OPTIMASI
Pemodelan optimasi hanya dilakukan pada material grade B, X-42, dan X-52 , 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..
Gambar 4. 3 Grafik Optimasi tiap Constraint pada Material Grade X52
y = 0,0001x2 + 0,0147x + 0,0066
y = -0,0409x2 + 0,5072x - 1,3153
y = -0,0002x2 + 0,0196x + 0,0988
0
0,05
0,1
0,15
0,2
0,25
0,3
0 1 2 3 4 5 6 7 8 9
Teb
al P
ipa (
in)
Diameter Luar Pipa (in)
Grafik Optimasi tiap Constraint (Psi)
Hoop Stress X-52
System Collapse X-52
Propagation Buckling X-52
Poly. (Hoop Stress X-52)
Poly. (System Collapse X-52)
Poly. (System Collapse X-52)
Poly. (Propagation Buckling X-52)
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 denganmembuat persamaan objektif tiap constraint dengan memplotkan 2 variabeldiameter luar dan tebal pipa pada grafik.
2. Pipa dengan Ø 4.5” dan Ø 6.625” pada masing-masing material grade (B, X-42, X-46, X-52, dan X-56 masih stabil baik kondisi instalasi maupun operasi.
3. Panjang bentangan pipa masih memenuhi (kurang dari) panjang bentangankritis pipa.
4. Laying analysis (pemodelan OFFPIPE) menunjukkan bahwa pada materialgrade B dengan Ø 4.5” dan Ø 6.625” persen yield stress-nya melebihimaximum yield stress yang diijinkan, sementara pada material grade pada X-42, X-46, X-52, dan X-56 masih memenuhi.
5. Diameter pipa (Do) dan tebal pipa (t) yang optimum untuk dapat dioperasikan diBK-BP 1 platform area Bekapai adalah Ø 8.625’’, dan tebal 0.125 in denganberat minimal pipa 36.029 lb/in dan material grade X-52.
DAFTAR PUSTAKA
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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, AmericanDNV RP-F105. 2006. Free Spanning Pipelines. Det Norske Veritas, AmericanDNV 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
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Depressurisation Study and BK-BP1 New Pipeline Design, Balikpapan.Santosa, B. 2008. MATLAB untuk Statistika dan Teknik Optimasi. Graha Ilmu, Yogyakarta.
The End OF PRESENTATION