Troubleshooting a 556m Long Sand Slurry Pipeline Dr Nigel Heywood, BHR Group, Cranfield, UK Dr Neil Alderman, Private Consultant, Peterborough, UK Dr Peter Harris, Sibelco Ltd, Newton Abbot, Devon, UK

Kingsteighton, Devon, UK

Background Sand slurry pipeline designed to transfer 90 t/h of sand/clay through 556m long horizontal HPPE (High Performance PE) pipe using Warman® 8/6 AH centrifugal slurry pump rubber-lined impeller first run at 878 rpm, using 75 kW motor. later run at 983 rpm, using a 90 kW motor.

Background Pipeline operated well below 2003 design target for years only 57 t/h and 63 t/h transported from two quarries Solids feed delivered with m/c 8.54% w/w to conical-bottomed hopper/sump of pump by belt conveyor substantially diluted with water flowrate of 318 m3/h giving relatively low target solids volume fraction of about 9%. reduced sand transfer tolerated for several years, but sand produced by quarries saw significant demand increase system reviewed in 2010 to decide what actions to take to boost sand throughput.

Objectives and Method of Study One option : run pump impeller at a higher speed But currently installed rubber-lined pump impeller could not be run above 1000 rpm Second option : use hardened steel impeller of same diameter and in same casing which can be run at up to 1300 rpm. Rather than use maximum impeller speed which may cause significant wear, 1200 rpm was selected Hydraulic analysis needed to determine what solids throughput could be achieved

Objectives and Method of Study Pipe hydraulic analysis used range of dry solids throughputs (60 to 120 t/h, in 10 t/h intervals) with an associated constant m/c of 8.54% constant water addition of 318 m3/h Both pump head and efficiency were derated when hardened steel impeller of diameter 510mm runs at 1200 rpm This allowed calculation of pump discharge pressure power imparted to slurry minimum motor size required for target solids throughput.

Sand Particle Size Distribution after Screen

Sand and Clay Slurry Properties Solids distribution contained 16.8% < 75 micron assumed to be all clay particles and the rest sand Coarse fraction (sand) 0.832 and fine fraction (clay) 0.168 From PSD, coarse fraction d50 estimated at 1.0mm Used in SRC 2007 Pipeflow software d50 of whole PSD estimated at 0.7mm Used in pump head and efficiency deration (ANSI/HI 2011)

Sand/Clay Slurry Supply to Pump, showing Conical-Bottom Feed Hopper

Sand/Clay Slurry Supply to Pump

Pipe showing Reduced Pipe Wall Thickness through Erosion at Lower Right

Original internal diameter 202.2mm (250mm OD). Pipeline Details Original internal diameter 202.2mm (250mm OD). wear increased estimated average internal pipe diameter to 206.3mm at 2010 . Contained 46, 5mm welds protruding into pipe Modelled as a tapered contraction followed by tapered expansion for friction estimation Net elevation increase of 14.95m, including 5.45m sloping upwards section 9.5m vertical section before discharge to atmosphere

Water Flow Alone (121 litre/s, 40C)   Case (e, mm) Number of weld protrusions Fanning friction factor for straight pipe, f Frictional pressure loss for straight pipe, bar Frictional pressure loss from weld protrusions, Predicted pump discharge pressure, barg 1 (0) 0.00330 2.30 3.77 2 (0) 46 0.223 3.99 3 (0.03) 0.00376 2.62 4.09 4 (0.03) 4.31 Includes 1.47 bar static head Measured pump discharge pressure = 4.18 bar Falls between cases 3 and 4

Estimates of Pump Key Parameters for 60 - 120 t/h of “Dry” Solids Dry Solids Rate t/h Dry Sand Transfer Rate Total Volume Flowrate m3/h Pipe Velocity V m/s Mass fraction of feed slurry Cm Feed slurry density kg/m3   Pf/L Pa/m Pf bar Pump Discharge Pressure Pdis barg 60 50.0 346.2 3.00 0.156 1108 717 3.99 5.18 70 58.3 351.0 3.04 0.177 1124 773 4.30 5.52 80 66.6 355.7 3.08 0.197 1140 827 4.60 5.84 90 74.9 360.4 3.12 0.216 1156 879 4.89 6.15 100 83.3 365.1 3.16 0.234 1171 930 5.17 6.45 110 91.6 369.8 3.20 0.251 1185 1078 5.99 7.31 120 99.9 374.5 3.24 0.267 1200 1130 6.28 7.62

Pump Characteristics for Installed Warman® 8/6 AH Pump with Rubber-Lined Impeller

Pump Characteristics for Recommended Warman® 8/6 AH pump with Hardened Steel Impeller

Head Deration Chart from ANSI/HI 2011 Standard

Volume Fraction of Feed Slurry Product of Ccv, Cs and Cfp Corrected Head Ratio (Hr) Values, assuming Impeller Speed of 1200 rpm and Diameter 510 mm Dry Total Solids (sand plus clay) Feed Rate, M, t/h   Volume Flowrate of Slurry litre/s Volume Fraction of Feed Slurry Ccv Product of Ccv, Cs and Cfp RH, % Corrected Hr 60 96.2 0.065 0.436 0.302 2.1 0.979 70 97.5 0.075 0.502 0.348 2.4 0.976 80 98.8 0.085 0.566 0.392 2.7 0.973 90 100.1 0.094 0.628 3.0 0.970 100 101.4 0.103 0.689 0.478 3.3 0.967 110 102.7 0.112 0.748 0.519 3.6 0.964 120 104.0 0.121 0.806 0.559 3.9 0.961

Pump Efficiencies for Slurry flow and Minimum Motor Size required for Pump with Hardened Metal Impeller at 1200 rpm Dry Total Solids Feed Rate, M, t/h Volume Flowrate litre/s Pump Efficiency Ratio Pump Efficiency, % Power imparted to Slurry, W, kW Minimum Motor Size Required for Pump, kW 60 96.2 0.979 54.8 49.9 91.0 70 97.5 0.976 54.6 53.8 98.5 80 98.8 0.973 54.5 57.7 106 90 100 0.970 54.3 61.6 113 101.4 0.967 54.2 65.4 121 110 102.7 0.964 54.0 75.1 139 120 104.0 0.961 79.3 147

Conclusions Use hardened steel impeller running at 1200 rpm, instead of the current rubber-lined impeller running at 983 rpm: 70 t/h of total dry solids is achievable with minimum motor size of 100 kW To achieve dry solids throughput of 90 t/h minimum motor size of 113 kW needed Hydraulic analysis indicated that currently-installed 90 kW motor inadequate if used with a hardened steel impeller running at 1200 rpm.

THANK YOU FOR YOUR ATTENTION Nigel Heywood nheywood@bhrgroup.co.uk