PIPELINE FRICTION LOSSES OF COARSE SAND SLURRIES - COMPARISON WITH A DESIGN-MODEL

Friction losses in 0.2-0.3 m i.d. pipelines were investigated for thre e coarse sands with mass median particle sizes of 0.6-0.7 mm and size distributions of 1.4, 5.4 and 27.3, respectively, when expressed in te rms of the ratio of particle diameters 85 to 15% by mass finer. The pa rtially-stratified friction loss model proposed by K.C. Wilson, G.R. A ddie and R. Clift, Slurry Transport Using Centrifugal Pumps, Elsevier, Oxford, 1992 [1] predicted the observed friction losses reasonably we ll at volumetric concentrations of 12-15% for velocities of practical interest. Good agreement was found for concentrations of up to 31% for sand with the intermediate distribution. However, predictions for the narrowest sand underestimated friction losses at higher concentration s of 26-31%. Friction losses for the broadest sand were overestimated markedly at concentrations of 28-39%. With these two sands, observed l osses did not increase linearly with concentration, in disagreement wi th model assumptions. The different mechanisms involved are discussed in light of results demonstrating how particle size distribution, cont ent of particles 0.1-0.5 mm in size, and concentration affect friction losses. The flow conditions discussed here correspond to velocities t hat clearly exceed those for which there are risks of deposition at th e bottom of the pipe.