L52273 Internal Repair of Pipelines

Abstract

External, corrosion-caused loss of wall thickness is the most common cause of repair for gas transmission pipelines. To prevent an area of corrosion damage from causing a pipeline to rupture, the area containing the corrosion damage must be reinforced. Since corrosion is a time dependent process, as pipelines become older, more repairs are required. Repair methods that can be applied from the inside of a gas transmission pipeline (i.e., trenchless methods) are an attractive alternative to conventional repair methods since pipeline excavation is precluded. This is particularly true for pipelines in environmentally sensitive and highly populated areas. Hydrostatic pressure testing was conducted on pipe sections with simulated corrosion damage repaired with glass fiber-reinforced composite liners, carbon fiber-reinforced composite liners, weld deposition, an adhesively bonded steel patch, and adhesively bonded/helically wound steel strip. To benchmark pipeline material performance, additional pipe sections were evaluated in the virgin and in the corrosion damaged/un-repaired conditions. Three repair technologies exhibited burst pressures that were greater than the burst pressures of the un-repaired pipe sections: adhesively bonded/helically wound steel strip repair exhibited the highest performance with burst pressures ranging from 0.4% to 144% higher; carbon fiber-reinforced liner repair had burst pressures ranging from 4% to 17% higher; and glass fiber-reinforced liner repair had burst pressures ranging from 1% to 7% higher. Two repair technologies exhibited burst pressures that were lower than the burst pressures of the un-repaired pipe sections: adhesively bonded steel patch repair was 1% lower and weld deposition repair was10% lower.