Pipelines are a practicable means for delivering large quantities of gaseous hydrogen over long distances and for distributing it as a transportation fuel at fueling stations in urban and rural settings. Glass-fiber-reinforced polymer (GFRP) pipelines are a promising alternative to the present-day use of low-alloy steel in pipelines for hydrogen transmission. GFRP pipelines offer advantages of lower capital cost and improved lifecycle performance, compared to steel pipelines. The technical challenges for adapting GRFP pipeline technology from oil and natural gas transmission, where it is in extensive service worldwide, to hydrogen transmission consists of evaluating the hydrogen compatibility of the constituent materials and composite construction, identifying the advantages and challenges of the various manufacturing methods, testing polymeric liners and pipelines to determine hydrogen permeability and leak rates, selecting options for pipeline joining technologies, establishing the necessary modifications to existing codes and standards to validate the safe and reliable implementation of the pipeline.
We performed examined the technical feasibility of using a commercially available spoolable glass-fiber-reinforced polymer (GFRP) pipeline for hydrogen transmission. We used an accelerated aging process based on the Arrhenius model to screen for hydrogen-induced damage in the pipeline and in the pipeline’s constituent materials. We also measured hydrogen leakage rates in short lengths of the pipeline. The accelerated aging process involved immersing GRFP pipeline specimens in pipeline-pressure hydrogen (6.9 MPa/1000 psi) at an elevated temperature (60°C) to promote an accelerated interaction of hydrogen with the pipeline structure. To assess specific effects on the constituent materials in the pipeline, specimens of fiberglass rovings, resin matrix and liner materials were immersed together with the pipeline specimens, and specimens of all types were subjected to either a one-month or an eight-month exposure to hydrogen at the elevated temperature. At the conclusion of each exposure interval the pipeline specimens were evaluated for degradation using hydrostatic burst pressure tests to assess the overall integrity of the structure, compression tests to assess the integrity of the polymer matrix, and bend testing to assess the integrity of the laminate. The results of these tests were compared to the results obtained from identical tests performed on un-conditioned specimens from the same manufacturing run. Tensile tests and dynamic mechanical analysis were performed on multiple specimens of constituent materials.
We measured the hydrogen leak rate in GFRP pipeline lined with pipeline-grade high-density polyethylene (PE-3408). The thickness of the liner was 0.526 cm and its inside diameter was 10.1 cm. The hydrogen pressurization during the leak rate measurements was 10.3 MPa (1500 psia) — the maximum recommended pressure — and all measurements were done at ambient temperatures in an air-conditioned laboratory. The pipeline was closed on each end using a steel cap with elastomer (O-ring) seals. The leak rate was calculated from the temperature-compensated pressure decay curve. Changes in pipeline volume that occurred due to pressure-induced dimensional changes in the pipeline length and circumference were measured using strain gauge sensors. These volumetric changes occurred at the earliest measurement times and diminished to near zero at the long measurement times during which the steady-state leak rate was determined. Leak rate measurements in three different lengths of pipeline yielded a leak rate was significantly lower than the predicted rate from the standard analytical model for a cylindrical vessel.
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