Determination method for the design pressure of offshore multiphase pipeline

The main design codes for the offshore multiphase pipeline include DNV OS-F101-2000, ASME B31.4, ASME B31.8, API RP1111, GB50253 and GB50251. However there is no specific design pressure stated in these documents. Different points of view lead to different results in the design pressure. Therefore the current decision to use 1.1 or 1.0 times of the maximum operating pressure as the design pressure has its own limitation after analyzing the definitions and regulations in the design pressure stated in these codes. The paper discusses the relationship among design pressure, pipe wall thickness, pressure switch, the set pressure point and the reserve of throughput increase based on the designed pipeline by CNPC Offshore Engineering Company Ltd. It is recommended that determination on a design reasonable pressure should follow the general design layout combined with the structure and process design result of offshore pipeline.