Pipeline design

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Pipeline Design and Construction

Presented by: Engr. Md. Sanwar Hossain Dy. Manager , Operation Gas Transmission Co. Ltd.

Pipeline design
Qmmscfd=0.00128084((P12-P22)/Lmiles)0.51D2.53 For successful implementation of a pipeline project, the following steps are to be considered in general: 1. Market survey- Present & future demand 2. MAOP & Design pressure 3. Map of the preliminaryselected pipeline route (L) 4. Pipe Size (D) 5. Wall thickness (t)

Pipeline design ( contd.)
6. Pipe specification / grade 7. Bill of materials 8. Total cost estimate 9. Selection of ROW 10. Detailed survey and Preparation of alignment drawings

Pipeline design ( contd.)
Load consideration: In earlier days , pipeline design was done considering the present load and 15 to 30% increment of load.Now-a days, the use of natural gas increased tremendously. As a result the concept of pipeline design has also changed. Presently pipeline design is being done considering the present load as well as the assumed gas load of the that particular area for the next 20 years ( effective life of the pipeline)

Pipeline design (Contd.)
Modified Panhandle equation- most useful for transmission pipeline: Qmmscfd=0.00128084((P12-P22)/Lmiles)0.51D2.53 where , P1=Upstream pressure, PSIA P2=Downstream pressure, PSIA D=Inside pipe dia , inch

Pipeline design (contd.)
t= DP/(2YFL JT) where, t=Pipe wall thickness, mm P=design pressure ,psig D=outside dia of pipe in mm Y=minimum yield strength, psig F=design factor L= Location factor based on class location J=welding joint factor T=Temp. deratingfactor

Line Pipe: API 5L Grades
Grade B X42 X46 X52 X56 X60 X65 X70 X80 Minimum yield Minimum Tensile strength( MPa) strength( MPa) 241 289 317 358 386 413 448 482 551 413 413 434 455 489 517 530 565 620

Design and Location Factor
Canadian Standards association (CSA) suggests design factor of 0.8 While location factors are:
Area Deserted Village ASME Class Location 1 0.72 2 0.60 0.500.40 CSA 0.80 0.72 0.56 0.44

City 3 Metropolis 4

Joint factor :
Weld type Seamless ERW SAW But Welled Spiral seam ASME B31.8 1 1 1 0.6 0.8

Temperature factor:
Temperature ( ̊ F) Up to 250 251-300 301-400 401-450 451 and above ASME- B31.8 1.00 0.97 0.93 0.91 0.87

Pipeline Construction Process
DPP Land acquisition & Requisition Tender Document Preparation Tender Bid Evaluation TenderAward Procurement Mobilization Clearing, Grading and Stringing

Pipeline Construction Process (contd.)
Welding and NDT Trenching, Lowering & Backfilling Tie-in Hydrostatic Testing Cleaning Commissioning Operation

Pre construction
ROW Acquisition & Requisition -ROW Selection -DC Office -Compensation -Crop Compensation

Pre construction (Contd.) General Guideline for Pipeline RoutingMinimize overall pipe length. Parallel existing utility corridors (Highway, High tension Electric transmission line). Avoid areas of high population density. Minimize highways, railways, river, khals, canals, ponds, hills & mountains crossing to reduce the project cost. Cross highways, railways, river, khals, canals at or close to 90 deg. angle. Minimize crossover of existing facilities. Provideadequate construction area.

Pre construction (Contd.) General Guideline for Pipeline Routing
Avoid the following areas: • Swamps and Wetlands • Rocky areas • Unstable soil • Populated areas • Historical areas • Environmentally sensitive areas ( Forest, Tea garden , Rubber garden etc.) • Religious sensitive areas ( Mosque , Graveyard, temple etc.)

Pre construction (Contd.)
Land acquisition /Requisition:
Normally 10 m wide strip along the proposed pipeline route is to be acquisition and a 15 m wide strip on one side of the acquisition strip is to be requisition. Acquisition is permanent possession for use of land but requisition is completely a temporary affair , only for the working period. For scraper station and Valve station separate block lands of required size have to be...