GRE failures – What Is Piping

Materials for surface facilities: Piping: GRE, FBE coated CS / HDPE lined CS, DSS / SDSS Well hook-up: FBE coated CS, DSS / SDSS Bulk injection lines: HDPE lined CS, GRE Injection flowlines: Coated CS, HDPE lined CS, GRE Valves: bodies DSS / SDSS or CS with coating or 825 / 625 weld overlay; trim DSS / SDSS Pumps: bodies & impellors DSS / SDSS Materials for sub-surface facilities: Tubing: Coated CS, GRE lined CS Metallic materials for piping & well hook-up: DSS / SDSS DSS PREn > 34 SDSS PREn > 40 Coated CS FBE coated pipe, spools & fittings HDPE lined CS Loose fit liner and roto-lined spools & fittings Metallic materials for valves & pumps: Valves: CS, CS with 825 / 625 overlay for Bodies; & DSS / SDSS, 825 for trim Pumps: CS, CS with 825 overlay for Bodies & DSS / SDSS impellors Non-metallic materials: GRE: First used in 1982 for low pressure water systems and fire fighting systems >1300 km GRE pipelines, 113 km water service & remainder in multiphase service On-plot piping Successful use requires: Proper design: standards (ISO/company), qualification testing, stress analysis (supports/anchors), eliminate vibration Manufacture: QC during production Installation: experienced crews, supervision & inspection Installation of adhesive bonded joint (Fig. 1): Fig. 1: Installation of adhesive bonded joint GRE Failures: Most occur during installation due to: Poor workmanship Insufficient anchoring Poor flange alignment In-service failures are rare & only 2 have occurred: One involved a flowline and second was on flange connected to a pump In service failures (Fig. 2): 6” production flowline operating at 5 bar and 60 deg C with > 98% water-cut failed after 4 years due to Insufficient wetting of fibers during manufacture. Flange on 250 mm diameter piping in oil service directly connected to a pump cracked causing a leak due to pump vibration causing mechanical failure at flange/pipe interface HDPE: Loose fit liner has been used for water injection lines since 1988 >205 km HDPE lined CS pipelines in water service Rotolined spools and some HDPE lined CS pipe used for on-plot piping No limit on pressure; temperature 70 deg C for liner, 60 deg C for rotolined spools Successful use requires: Proper design & installation: standards (company) Installation: experienced crews / supervision for butt fusion welding of pipe & flanges, & for applying correct tension Fig. 2: Examples showing failures for GRE and HDPE Failure modes: Radial collapse: HDPE liner collapses inwards radially due to vacuum conditions occurring during shutdown procedure or a pressure build-up in the annulus between the liner and the CS pipe. Axial collapse: HDPE liner buckles inwards due to compressive axial stress resulting from differences in thermal expansion between the steel pipe and the PE liner itself.