Thermoplastic lined carbon steel pipelines offer a cost-effective solution to the prevention of corrosion in flowlines transporting hydrocarbon fluids. Field experience and an earlier Thermoplastics Linings JIP demonstrated that liner collapse is the major technical hurdle preventing more widespread adoption of this technology - particularly for multi-phase hydrocarbon applications. Liner collapse results when permeated gases, through the thermoplastic liner, collect in the annular space between the liner and outer steel pipe. During depressurisation this accumulation could cause the liner to collapse. Venting these
permeated gases is the key to successful application of thermoplastic lined steel pipelines for multiphase hydrocarbon transport. Phase 1 of COREL JIP (April 1998-December 1998) identified 3 design concepts with the potential to provide a means to effectively vent the annulus. The main objective of COREL JIP Phase 2 project (March 1999-August 2000) is to verify the potential of these 3 design options through proof of concept testing and analysis. If possible a field trial of the most promising
technology will be undertaken towards the end of the project. Proof of concept testing within Phase 2 will be aimed at answering the following question as a priority: Can gas that has built up in the interface between the steel pipe and the liner vent at a sufficient rate to avoid liner collapse on depressurisation - or can the need for venting be eliminated? The three most promising concepts have been identified as a perforated liner, externally longitudinally grooved liner and a liner incorporating an impermeable barrier (alurninium). Theoretical and experimental work has been undertaken to date and learnings have been derived from earlier ,liPs and participants' in-house research. This paper sumrnarises findings to date.
