Mannes Wolters

Influence of physical aging on impact embrittlement of uPVC pipes

Abstract Most failures of unplasticised poly(vinyl chloride) (uPVC) pipes used in the Dutch gas distribution network originate from third party damage. Brittle pipes should therefore be replaced to ensure safe operation of the network. In this study, the relation between physical aging and embrittlement of uPVC is investigated using instrumented falling weight impact tests. The ductile to brittle transition temperature was first measured for a water pipe grade uPVC at different stages of aging. As a hypothesis, a critical stress criterion is proposed above which failure is brittle. The evolution of the ductile to brittle transition temperature that followed from the use of this hypothesis and a model for the polymer yield stress agrees qualitatively with the experimental data. A minor increase in transition temperature was observed for the water pipe grade with aging. Applying the same hypothesis to a uPVC gas pipe grade shows a more pronounced influence of physical aging.

Development options for the Dutch gas distribution grid in a changing gas market

The Dutch gas distribution grid faces several changes in the near future. Among others, the share of green gas will grow, the interaction with the electricity distribution grid and local heat grids will increase, and the grid will transform from a mono-gas system to a multi-gas system. The gas distribution grid is likely to be expanded with novel components, e.g. blending stations, gas storage sites, and gas compressor stations. Furthermore, these changes require the currently passive gas distribution grid to become a smart gas grid that monitors and controls the gas pressure, gas flow, and gas quality. Therefore, the distribution service operators need to make investments in the gas distribution grid. When looking at for example the introduction of green gas, a decision tree on the optimal green gas supply configuration can be identified. Decisions in this respect consider, among others, the location of several process steps (perform the process step locally at a small scale or centrally at a larger scale) and the addition of components like a gas storage site or a compressor station. Due to the multitude of development options for the gas distribution grid and the fact that the best solution is largely dependent on the local situation and performance criteria (e.g. CO2 emission minimization or cost minimization), a tool is required that can generate situation specific solutions. Each solution generated by the tool should have its own advantages and disadvantages. Generating multiple options and showing the advantage and disadvantage of them provides the distribution service operators insight in the available options and eases the decision making on investments of the gas distribution grid.