Treated Sewage Effluent is transferred from the DMC/Wafra Pumping Station to Abdally Reservoir via two parallel transfer mains with several offtakes to supply local facilities. One transfer main is constructed from Ductile Iron and the other from GRP. The aim of the study was to investigate the operation of the system and ensure that the proposed surge vessels can adequately protect the system following an uncontrolled pump shutdown event.
A simulator of the system was built and various shutdown scenarios were modelled. Particular focus was given to the different pressure ratings of the two pipe materials during the study. The project was hydraulically complex as the pipeline route passes through undulating terrain and hence large sections of the pipelines drain out when the pumps are not running. It was therefore necessary to optimise the pipeline air valve requirements and also pipe gradients in descending drained sections to ensure stable open channel flow is achieved to prevent air locking.
A detailed formal report was written which included a number of specific recommendations to ensure the secure operation of the system for a range of different operating conditions. This included the optimisation of the surge vessel control system to maximise the available protection to the pipelines whilst also prolonging the life expectancy of the surge vessel air volume compressors.