Inspection and mitigation for pitting corrosion on stainless steel process piping to prevent process safety event and loss production opportunity in Medco E&P

Stainless steel piping has excellent corrosion resistant properties, both internal or external piping surface. In humid circumstances, sea vapor containing chlorine will be trapped on the pipe surface, especially pipes below deck with minimum sun exposure (more humid). Chlorine on the external pipe surface will damage the passive layer of stainless steel pipe. Damage speed is faster than recovery of passive layer stainless steel. This condition lead to a lot of localized pitting corrosion spread. The corrosion was detected visually and carried out with dye penetrant inspection to assure pitting condition. Actual dimension of pitting (depth, diameter) cannot be measured due to limitation of the NDE technique. This pitting corrosion can result hydrocarbon leakage as a process safety event that contributes loss of production opportunity. Without modification circumstances, this condition can be stopped immediately by application of a viscos elastic coating to prevent pitting corrosion propagation. Application of viscos elastic coating is simpler and faster when compared to conventional coating. Viscos elastic coating will protect stainless steel piping surface against oxygen and chloride in humid circumstances so that stainless steel can recover passive layer and stop pitting corrosion.

Flow-Induced Vibration Screening of a Thermoplastic Composite Pipe Water Injection Jumper

An active subsea field in the Gulf of Mexico has adopted a thermoplastic composite pipe (TCP) water injection jumper for its waterflood upgrade. The jumper assembly is composed of a TCP span attached to steel piping on either end. The TCP spool is lightweight and flexible relative to the traditional steel-only M-shaped subsea jumpers. As such, the flow-induced vibration (FIV) threat from internal fluid flow must be assessed for the intended service. A three-tiered approach is used to assess the level of FIV threat expected in this TCP subsea jumper application. A high-level screening based on widely used industry guidelines indicates a susceptibility to FIV fatigue failure for the steel piping in the TCP jumper assembly. A comprehensive screening based on structural finite element analysis and computational fluid dynamics shows that the vibration levels and stress cycling due to FIV will be acceptable for the intended water injection application and a 30-year design life, when adopting a factor of safety of 10 for subsea service. We evaluate the effect of doubling the length of the steel piping on either end of the TCP span, as a means to increase the overall span of the TCP jumper assembly. Lastly, we draw a comparison between a traditional all-steel M-shaped jumper and the TCP jumper in terms of FIV fatigue life, for the same operating conditions and the same total suspended span.