Page 266 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

121243

Offshore Pipeline

Systems

Contents
E. Stabk; 121250
I Background 121243 Alternative scoring approach I21252
TI Third-party damage index 121244
A. Dcpth of cover 121245 A Design 121253
B Actnity level 121245 B. Conqtruction 12
C Aboveground facilitic$ 121246 C. Opeiations 1212
D Damage prevention I21246 D Maintenance 12
E Right-of-way condition I21247
F P&ol frequency 12’247
111 Coriocion index 121247
A Atmospheric corrosion 121248 Emergency response 12’255
B Internal corrosion I21248
C Submerged pipe corrosion 121248
IV Design index I2/249
A Safety factor I2/250
B Fatigue 121250

I. Background
accounting for 14% and natural forces 12% of the remaining
Since offshore pipelines were first installed in shallow waters known causes of 1047 recorded pipeline failures. Interestingly
in the early 1950s, the technical difficulties of operating and though, almost all of the deaths, injuries, damages, and pollu-
maintaining lines in the subsea environment have challenged tion episodes were caused by damages from vessels [71].
the industry. Today, these challenges are multiplied as pipelines Deaths and injuries are associated with gas pipelines, which,
coexist with busy harbors, industrial ports, commercial and because of the highly compressed flammable gas, have higher
recreational fishing areas, general recreational areas, environ- explosive potential than most liquid lines. Even though corro-
mentally sensitive areas, and other offshore facilities. Deep sion caused a greater number of leaks, most of the pollution (in
water had been defined as depths greater than 650 ft (the edge volume of spilled product) was caused by anchor damage [71].
of the Outer Continental Shelf) but is now typically considered In this data sample, therefore, the most prevalent cause was not
to be a depth greater than 1600 ft. Offshore pipelines are the most consequential cause. When shallow water accidents
routinely installed in water depths of up to 7000 ft, as of this are included in the analysis, it is thought that maritime activities
writing. Current technology is allowing installation at ever- (third-party damage) and natural forces play an even larger
increasing depths. role.
In the Outer Continental Shelf waters of the United The dynamic nature of pipeline operations offshore often
States, corrosion was the largest single cause of pipeline fail- makes the risk picture more complex than onshore operations.
ures (50%) between 1967 and 1990, with maritime activities Offshore facilities are normally built to facilitate the recovery