Ultimate Mechanical Performance of a Filament Wound Glass Fibre

The use of glass fibre reinforced epoxy pipelines in the high pressure transport of fluids is becoming more widespread; this is due to the high strength to weight ratio and the corrosion resistant properties of these material systems. A 12-inch internal diameter glass fibre reinforced epoxy pipeline with winding angles of fSSO and a wall thickness of approximately 1.5 inches has being designed to operate at working pressures of at least 70 bar, with a working life of 20 years. The jointing system for the pipeline is based on an integral helically wound key-lock that is assembled between the male and female pipe joint ends. This key-lock consists of a groove with 10 helical windings in the male and female pipe ends and the groove contains a cylindrical polyamide key to carry the axial load due the internal pressure within the pipe. The hydrostatic seal to prevent leakage of fluid through the joint is provided by means of an elastomeric O-ring situated in a groove on the male component of the joint. A 3-metre long jointed section of pipeline was tested by varying the internal pressure of the pipe from zero to 150 bar and by monitoring the strain behaviour at three different sites along the pipe. The pipe was instrumented with strain gauges for the measurement of axial and hoop strains. Readings were taken at three sites on the female end of the pipe, namely, at the O-ring region, the neck and on a uniform section remote from the joint. The axial and hoop strain response to internal pressures up to 150 bar was linear. Burst pipe testing was subsequently carried out by bringing the internal pressure from zero to a critical burst value within a time of approximately 60 seconds. The results of the burst pipe test saw the pipe fail near the O-ring, at a pressure of 292 bar.