1. 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

2. Kingsteighton, Devon, UK

3. 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.

4. 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.

5. 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

6. 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.

7. Sand Particle Size Distribution after Screen

8. 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) 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)

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

10. Sand/Clay Slurry Supply to Pump

11. Pipe showing Reduced Pipe Wall Thickness through Erosion at Lower Right

12. 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
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

13. 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)
2.30
3.77
2 (0) 46
0.223
3.99
3 (0.03)
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

14. 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

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

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

17. Head Deration Chart from ANSI/HI 2011 Standard

18. 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

19. 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

20. 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.

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