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Title: Determination of wall shear stress characteristics exhibited by high ice fraction ice pigging slurries
Author: Dean, Timothy John
ISNI:       0000 0004 2737 0458
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2012
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Ice pigging is a novel pipe cleaning concept, patented and developed at the University of Bristol, where thick ice slurry is pumped through a pipeline forming an 'ice pig' capable of displaying both solid and fluid like properties. The ice pig is able to displace material within a pipeline and apply elevated levels of shear stress at the pipe wall compared to simple water flushing, whilst still being able to negotiate complex topologies. Ice pigging has been demonstrated to show increased cleaning capability over equivalent water flushing. The work carried out for this thesis has been funded by the Nuclear Decommissioning Authority to assess the feasibility of using ice pigging as a decommissioning technique. Due to the nature of the decommissioning process it is important to understand the rheological properties of ice slurry in order to be able to engineer the composition of the ice pig for the desired application. A fully instrumented laboratory rig, developed over the duration of the thesis, allowed a series of experiments to be undertaken on simple horizontal pipe sections in order to determine the wall shear stress exhibited by flowing ice slurries of varying ice fraction and flow velocity. Results were obtained for flowing ice slurries above 35% ice fraction for which no data currently exists within the literature. Increasing ice fraction to a maximum of 50%, it was found that the wall shear stress increased with an exponential like fashion. A series of field experiments were also undertaken measuring pressure drop in large potable water pipes. Results are presented that can be used to help optimise the process for effective pipeline cleaning. Interesting flow characteristics were observed in the largest diameter pipe where pressure drop reduced significantly at very high flow rates. It is suggested that the 'operational limit' of the ice pig for that particular situation had been exceeded. This thesis has demonstrated that it is possible to manufacture and handle thick ice slurry in excess of 35% ice fraction, capable of delivering pipeline wall shear rates in the order of 10 to 500 times that of simple water flushing. Ice pigging presents a new, low risk innovative solution for pipeline cleaning in the nuclear industry. v
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available