Offshore Flowline Rehabilitation with Spoolable Steel-Reinforced Bi-Modal HDPE Pipe [PE]

This paper demonstrates an approach for rehabilitation of an offshore welded steel flowline with a spoolable steel-reinforced thermoplastic pipeline system. Traditional thermoplastic materials provide an established low pressure technology for pipeline applications offering enhanced corrosion resistance over traditional rigid metallic pipes. Despite the advantages of flexibility and corrosion resistance, applications of monolithic thermoplastic pipes are limited in pull through rehabilitation applications by tensile capacity. The flexible steel pipe design overcomes this limitation and delivers a high integrity pipeline system with operating pressures up to 3,000 psi and nominal diameters up to 8-inch. The flexible steel pipe system is analogous to those deployed in the offshore oil and gas industry but designed and optimized for onshore and shallow water applications. The construction consists of a flat steel strip reinforcement helically wrapped around a thermoplastic liner, combining the advantages of bimodal high density polyethylene pipe with the established properties and strength of steel. The steel reinforcement is isolated from the pipe contents and external fluids by the thermoplastic corrosion-resistant liner and external cover. The resultant system properties are demonstrated by testing and illustrated with a case study of pipeline rehabilitation of a five mile pipeline in an environmentally sensitive area.