ABSTRACT

An important concern of the pipeline designer is what inclination to specify as the maximum for construction. It is well-known that if the inclination exceeds the angle of repose of the slurry in a pipe then the solids can slide to the bottom of the slope and cause a plug. The rheological properties of this settled material can be investigated to see if it is still in a liquid, and therefore theoretically pumpable form; generally a slope limitation is imposed which will prevent sliding. The maximum slope, which may be of the order of 10 per cent (14), cannot be predicted at present and it is necessary to determine its value from test results such as those described by Olada et al. (15). In certain instances the cost of restricting the maximum slope can be excessive and arrangements have to be made to back flush or inject water in the event of a shut-down with slurry in the pipe. Experience gained with early pipelines has allowed slope limitations to be relaxed by as much as 50 per cent for some iron and copper concentrates (16). This has a substantial effect on capital costs by shortening pipeline length.