OFFSHORE PIPELINE

OFFSHORE

1. Pipe Selection
    1.1.Seamless pipe used on 1" through 6" pipeline.
    1.2. ERW pipe used on 4" through 12" pipelines.
    1.3 DSWS pipe used on 16" and larger pipeline.
    1.4 Pipeline wall thickness  Design F = 0.72
    1.5 Riser pipe wall thickness Design F = 0.5

2.Offshore Design consideration
    2.1 Determine minimum bending radius of steel pipe in laying outline and ordering material
    2.2 Assure line will not float--> Weight coatings to increase specific gravity (normally 1.35), Anchors
    2.3 Pipe Grade-Hight Strengh pipe used to decrease thickness requirements for pressure required
    2.4 Consider crushing of empty pipe in deep water
    2.5 Consider bending and longitudinal stress on riser

3. Offshore Construction consideration
    3.1 Determine stressed in sag bend and overbend--> Stinger and tension floats
    3.2 Spud barge --> Shallow water 5 to 50 ft
    3.3 Laybarge --> Deepwater, 50 to 2200 ft ; 2" through 48" pipe
    3.4 Jack up barge --> 12 to 200 ft; 2" through 6- 5/8" OD pipe
    3.5 Pipe reel barge --> 12 to 1000 ft ; 2" through 12 3/4" OD pipe

4. Offshore burrying
   4.1 Plow --> Deep water and stiff clays, Plow can be used concurrent with laying of pipe
   4.2 Jet --> Used in waterdepth to 300 ft, handjetting by divers, machine jet after pipeline is laid
   4.3 Dredge --> Used in shallow water (marsh and bays)
   4.4 Pipeline cover --> 3 ft minimum up to 200 ft water depth
   4.5 Cover near platform --> 5 ft for 300 ft outward from riser