Settlement in backfill pipelines: its causes and a novel online detection method

Abstract

Many predictive models exist for the calculation of the critical deposition velocity for settling slurries and pastes. However, unforeseen variability of backfill operations as well as changing properties of source materials used for a particular backfill recipe may result in unexpected pipeline blockages. Although quality control procedures are often in place to ensure consistency of the backfill recipe, the large number of factors influencing pipeline blockages and their interdependence cannot always be determined reliably. This paper addresses what are considered to be the dominant parameters affecting backfill pipeline blockages. In particular, backfills with low water content and high cement content may undergo significant rheological changes during extended pipeline transportation, which may affect the settling characteristics. Various methods and types of instrumentation are used in laboratories to measure the velocity and flow conditions at the pipe invert, but no simple instrumentation is readily available as an industrial monitoring tool. A novel method to detect the onset of a stationary bed with an all-metal pipe spool is presented. This instrumentation has been shown to detect the existence of a stationary bed at the pipe invert reliably over a wide range of slurry compositions and slurry densities. Its non-intrusive nature makes it an ideal tool for abrasive and coarse backfill types.