STUDI OPTIMASI OFFSHORE PIPELINE REPLACEMENT DI … · MANFAAT. 1. Memberikan manfaat dan kontribusi nyata bagi perusahaan TOTAL E&P Indonesie, Balikpapan khususnya dan instansi terkait

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


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


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


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

METODOLOGI PENELITIAN

KLICK HERE

FLOW CHART.doc

Flow Chart.doc


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



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



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


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


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 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)



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



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 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



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



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



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


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


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


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


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


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


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


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

API RP-14E. 1991. Recommended Practice for Design and Installation of Offshore Production PlatformPiping 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, 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

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.

The End OF PRESENTATION

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STUDI OPTIMASI OFFSHORE PIPELINE REPLACEMENT DI … · MANFAAT. 1. Memberikan manfaat dan kontribusi nyata bagi perusahaan TOTAL E&P Indonesie, Balikpapan khususnya dan instansi terkait