The technology and procedures for the inspection of pipelines from offshore production and process facilities to shore or other offshore installations has developed rapidly in recent years. This rapid development can be attributed to several factors including pipeline operators protecting their investment in their lines, heightened environmental protection concerns, and increasing regulatory requirements. A limited number of the offshore pipeline systems in the U.S. currently include the ability to inspect the trunkline using either an ultrasonic or magnetic particle inspection pig. This pig ...
The technology and procedures for the inspection of pipelines from offshore production and process facilities to shore or other offshore installations has developed rapidly in recent years. This rapid development can be attributed to several factors including pipeline operators protecting their investment in their lines, heightened environmental protection concerns, and increasing regulatory requirements. A limited number of the offshore pipeline systems in the U.S. currently include the ability to inspect the trunkline using either an ultrasonic or magnetic particle inspection pig. This pig is moved through the pipeline with the product flow from the trunkline's point of origin offshore to an onshore or nearshore facility. As the pig moves through the line, it takes and stores measurement readings which can be downloaded and interpreted after the pig is removed from the line. While inspection pig technology can provide the pipeline operator with valuable information, several factors can prohibit development of a successful trunkline inspection pigging program. Because inspection pigs have onboard data measurement and storage facilities, they are significantly longer and heavier than foam or scraper pigs, and must be articulated to negotiate pipe bends. The minimum negotiable bend radius varies among inspection pig vendors, but is typically between 3 - 5 pipe diameters. The drive cups on an articulated pig are located in the front to prevent buckling. The cups must maintain a close fit with the inside pipe diameter to propel the pig through the pipeline and can stall or jam in a multi-diameter pipeline. The scope of the project includes the development of several basic concepts which, in principle, meet the project objectives. These concepts have been evaluated from several technical viewpoints and two primary concepts selected for further development. A preliminary design effort, carried out on both primary concepts, includes: Structure stress calculations; Detailed layouts of major assemblies and components Step by step installation, operation, and maintenance procedures; Detailed capital and operating cost development. A basic scenario of a 12" ANSI 900# rated system in 400 ft. water depth is used for both concepts. A sensitivity analysis for the effects of greater and lesser water depths (800 ft. and 100 ft.) and a change in pipe size to 8" nominal is also included.