Coating and insulation selection for corrosion protection and flow assurance of offshore pipelines and risers

The installation of offshore hydrocarbon pipeline systems is gradually approaching water depths of 10,000 feet for design lives of 30 years and more. As a consequence of these requirements external parent and field polymeric coating systems must have superior mechanical and physical properties that include the considerations below: Impact/abrasion resistance, adhesion/resistance to disbanding, tensile strength, elongation, and flexibility Temperature/pressure resistance and Thermal Insulation property requirements Resistance to chemical and biological deterioration Easily repair-able, resist mechanical damage and compatibility with the cathodic protection system Hydrate, wax and emulsion management solutions in these ultra deepwater pipeline systems has also prompted the development of insulation systems such as Pipe in Pipe technology or wet insulation material application, with the added design considerations of high pressure-high temperature design parameters and the method of installation. This has resulted in the development of new or modified coatings and insulation materials to provide the required properties at elevated temperatures up to 320 degrees F (160 degrees C) and also for LNG pipeline systems to minus 260 degrees F(-160 degrees C). The design of field joints for the selected parent coating and insulation system must be compatible and achieve similar mechanical and physical properties to the parent coating or insulation system. The achievement of a water tight (hydrophobic) field joint can also provide an extension to the fatigue life and less conservative weld defect acceptance criteria by allowing the use of fatigue crack growth rates for steel in air instead of the more severe rates for steel in seawater. This paper discusses the development and selection option methodology of current and future external coating/insulation systems, particularly the important influences affecting their performance and the merit of internal flow coatings.