- Email: [email protected]
Pipe lining abrasion testing for paste backfill operations
Minerals Engineering 22 (2009) 1088–1090
Contents lists available at ScienceDirect
Minerals Engineering journal homepage: www.elsevier.com/locate/mineng
Technical Note
Pipe lining abrasion testing for paste backfill operations David Hewitt a,*, Sebastian Allard b, Peter Radziszewski a a b
Comminution Dynamics Lab., Department of Mechanical Engineering, McGill University, 817 Sherbrooke Street West, Montreal, Canada H3A 2K6 Canada Kalprotect Inc., 26, rue Canvin, Kirkland, Quebec, Canada H9H 4S4
a r t i c l e
i n f o
Article history: Received 30 October 2008 Accepted 17 March 2009 Available online 9 May 2009 Keywords: Mineral processing Waste processing Tailings Tailings disposal
a b s t r a c t Pipe wear in paste backfill mining operations represents a great cost to mining companies. The replacement of prematurely worn pipes results in the shut down of the entire paste system. Abrasion testing performed on various pipe lining samples yielded both quantitative and qualitative data. Both standard and non-standard methods were explored during testing. The pipe materials are ranked by their relative wear resistance as well as energy per unit mass loss. The latter may allow for better prediction of pipe wear, this in turn could prove worthwhile when scheduling maintenance downtime for such a system where cost savings would be beneficial. Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction Paste backfill is for safe storage of tailings underground, and provides the required surface support and reduces the footprint of the surface tailings storage area, if any. Beyond these advantages, the remaining ore can be mined from pillars that were initially left in place to support the mine (Jung and Biswas, 2002). Tailings exiting the mill are sent to the paste plant where they are combined with various additives and chemicals. This paste, when pumped underground and set, will have the desired strength to support the rock above. The paste, depending on the type of mineral present contains over 47 wt% solids (Sofrá and Boger, 2002). With this high concentration of solids, abrasive wear must be considered. Poor selection of piping materials and improper design of the system may result in premature failure (Solov’ev et al., 1986; Bikbaev et al., 1973). A failure in one section results in the shutdown of the paste system, lost productivity and higher maintenance costs. With the constant push to minimize costs while maximizing productivity, the need for highly abrasion-resistant and predictable materials has become increasingly important. This investigation focuses on the abrasion-resistant properties of numerous materials of this nature. 2. Background Abrasive wear in pipes results when solids make up a large percentage of the fluid being transported. These particles interact with each other, the fluid media and the pipe walls. This can be de* Corresponding author. Tel.: +1 514 880 6966. E-mail address: [email protected] (D. Hewitt). 0892-6875/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.mineng.2009.03.010
scribed by a measured mass of pipe lost and an energy term calculated from the applied force a particle is exposed to and the distance the particle slides along the pipe wall (Rabinowicz, 1995). This can all be modeled experimentally in a laboratory using the abrasion wheel test where the abrasive wear is determined as a function of the applied force on the wheel, the test specimen’s hardness and density, the abrasion angle of the abrasive used and the distance travelled (Radziszewski, 2002). Testing the wear resistance of pipe lining samples was completed using a modified version of the ASTM G65-04 (Standard Test Method for Measuring Abrasion Using the Dry Sand/Rubber Wheel Apparatus) abrasion test machine. This machine’s main differences stem from the wheel material (steel vs. standard rubber-lined), wheel speed (variable vs. standard speed), force applied to sample (variable vs. standard force), abrasive material (any sand/ore vs. Ottawa Sand), there is also a water tank beside the abrasive hopper which allows for tests run dry or wet and instrumentation on the shaft of the wheel, a strain gauge used to collect strain and torque of the drive shaft. This machine was originally developed for the Total Media Wear Model (Radziszewski, 2002). It has been used to predict tumbling mill media wear in mineral processing. In this case, the machine will be used to compare and contrast the pipe sample performances relative to each other as well as the current pipe material (Radziszewski, 2002). 3. Methodology Eight possible pipe materials were tested to determine which should be used to replace the current steel pipe. Initial tests were performed with Ottawa Foundry Sand used as the abrasive. As with
1089
D. Hewitt et al. / Minerals Engineering 22 (2009) 1088–1090
all previous testing, the abrasive is sized to fit the size fraction 20 to +50 Tyler Screen Numbers. The pipe samples were sized to 50 50 38 mm, the mass of the sample was recorded and the sample was loaded into the test machine, see Fig. 1. The abrasive was loaded into the machine, and introduced into the test chamber forming a flowing curtain between the rotating wheel and the sample. A load was applied to the sample such that the sample experiences a predetermined force against the wheel. The sample test was run for 2 min, after which, the mass loss is calculated. The following tables show the operating parameters of the machine and the sample names (see Tables 1 and 2). In addition to these tests, four samples were selected and tested with abrasives supplied by the mining company; these abrasives were constituents of their current and proposed paste mixture. The names of the abrasives and pipe samples for these extra tests are located in the tables below (see Tables 3 and 4). The Supplied Sand was run within the same size distribution as the Ottawa Foundry Sand. The tailing samples, unfortunately, did not fit this size distribution; they were too fine to flow into the test chamber with gravity alone, a slurry mixture had to be created. The slurry was just over 40% solids by mass; this allowed the abrasive to flow into the test chamber with greater ease.
Table 1 Test parameters.
4. Results
Table 3 Abrasives supplied by mining company.
Fig. 2 shows the results for all pipe materials when tested with the Ottawa Foundry Sand. The primary y-axis denotes the wear rate (g/kWh) calculated for each sample, the secondary y-axis is the actual wear (g) of the sample. The results are presented in order of increasing wear rate. Most proposed pipe materials outperformed the current pipe material, the Kalprotect samples were more abrasion resistant than the current pipe material, also they occupied four of the top six rankings. Fig. 3 shows the results of the extra tests that were performed with four of the pipe samples and the abrasives supplied by the mining company. These results are presented alongside the Ottawa Foundry Sand results. A trend was noticed in the performance of the samples when subjected to different abrasives, the Ottawa Foundry Sand being the most abrasive results in the highest wear rate. The Proposed tailings were the least abrasive, giving the low-
Abrasive name
Abrasion test parameters Wheel material Wheel speed Abrasive used Applied force Time of test
Steel 155 RPM Ottawa Sand 300 N 2:00
Table 2 Pipe sample names. Sample name
Supplier
Current pipe material Competitive sample 1 Competitive sample 2 Competitive sample 3 Competitive sample 4 Competitive sample 5 Competitive sample 6 Competitive sample 7 Competitive sample 8 Competitive sample 9
Mining company Mining company Mining company Mining company Mining company Kalprotect Canada Kalprotect Canada Kalprotect Canada Kalprotect Canada Kalprotect Canada
Ottawa Foundry Sand Supplied Sand Current tailings Proposed tailings
Table 4 Pipe samples used in slurry tests. Sample name Current pipe material Competitive sample 1 Competitive sample 7 Competitive sample 8
est wear rate. This wear trend appears consistent for all four abrasives tested; it is not possible to conclude that this trend will be maintained for any tailings abrasive material. 5. Conclusion
Fig. 1. Abrasion test machine (Misra and Finnie, 1980).
With abrasion being the primary source of wear in paste backfill systems, proper design and selection of materials will be of critical importance. The pipe material will be directly responsible for the availability of the paste backfill system. The tests performed with the steel wheel abrasion machine replicated the abrasive wear phenomenon present in the paste backfill piping system. Having determined experimentally pipe lining material wear rates, it is possible to use these rates to estimate liner performance in the field. However, further modeling and validation work is required in order to use this experimental data to predict pipe system wear life. Based on the experience predicting steel media wear in tumbling mills, it is conceivable to tie these wear rates with paste pipe flow to the development of pipe liner wear model that could predict wear and help schedule downtime for maintenance. Once validated against industrial data, such a model could contribute to reducing overall paste backfill operating costs.
1090
D. Hewitt et al. / Minerals Engineering 22 (2009) 1088–1090
Sample Wear Performance with Ottawa Foundry Sand 2.50 2.00
1.00
50
0.50
0
0.00 pl e
er ia l
8
m
at
Sa iv e tit
tP C
om
pe
ur re n C
pe om C
ip e
Sa
M
m
m iv e tit
tit C
om
pe
tit pe om C
pl e
pl e
5 iv e
Sa
Sa
m
pl e m
iv e
Sa iv e tit
C
om
pe
pe om
pl e
1
7 m Sa
iv e tit
tit pe om C
pl e
pl e
6 Sa iv e
Sa iv e tit pe
om C
m
pl e
9 m
pl e m Sa iv e tit
4
100
3
1.50
2
150
pe om C
Wear
Wear [g]
Wear Rate
200
C
Wear Rate [g/kWh]
250
Sample Material Fig. 2. Pipe sample abrasion performance.
Wear Rate for Different Abrasives
Wear Rate [g/kWhr]
80 70 60 50 40 30 20 10 0 Competitive Sample 8
Competitive Sample 7
Current Pipe Material
Competitive Sample 1
Sample Material Ottawa Foundry Sand
Supplied Sand
Current Tailings
Proposed Tailings
Fig. 3. Wear rate with different abrasives and materials.
References Bikbaev, F.A., Krasnov, V.I., Maksimenko, M.Z., Berezin, V.L., Zhilinski, I.B., Otroshko, N.T., 1973. Main factors affecting abrasive wear of elbows in pneumatic conveying pipes. Chemical and Petroleum Engineering 9, 73–75. Misra, Finnie, 1980. A classification of three-body abrasive wear and design of a new tester. Wear 60, 111–121. Jung, S.J., Biswas, K., 2002. Review of current high density paste fill and its technology. Mineral Resources Engineering 11, 165–182.
Rabinowicz, E., 1995. Friction and wear of materials. Wiley, New York. pp. 315. Radziszewski, P., 2002. Exploring total media wear. Minerals Engineering 15, 1073– 1087. Sofrá, F., Boger, D.V., 2002. Environmental rheology for waste minimisation in the minerals industry. Chemical Engineering Journal 86, 319–330. Solov’ev, Yu. G., Yushkevich, P.M., Bondar’, N.P., Kravchenko, N.V., 1986. Determination of basic factors affecting the abrasive wear of pipes. Metal Science and Heat Treatment 28, 214–216.
Contents lists available at ScienceDirect
Minerals Engineering journal homepage: www.elsevier.com/locate/mineng
Technical Note
Pipe lining abrasion testing for paste backfill operations David Hewitt a,*, Sebastian Allard b, Peter Radziszewski a a b
Comminution Dynamics Lab., Department of Mechanical Engineering, McGill University, 817 Sherbrooke Street West, Montreal, Canada H3A 2K6 Canada Kalprotect Inc., 26, rue Canvin, Kirkland, Quebec, Canada H9H 4S4
a r t i c l e
i n f o
Article history: Received 30 October 2008 Accepted 17 March 2009 Available online 9 May 2009 Keywords: Mineral processing Waste processing Tailings Tailings disposal
a b s t r a c t Pipe wear in paste backfill mining operations represents a great cost to mining companies. The replacement of prematurely worn pipes results in the shut down of the entire paste system. Abrasion testing performed on various pipe lining samples yielded both quantitative and qualitative data. Both standard and non-standard methods were explored during testing. The pipe materials are ranked by their relative wear resistance as well as energy per unit mass loss. The latter may allow for better prediction of pipe wear, this in turn could prove worthwhile when scheduling maintenance downtime for such a system where cost savings would be beneficial. Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction Paste backfill is for safe storage of tailings underground, and provides the required surface support and reduces the footprint of the surface tailings storage area, if any. Beyond these advantages, the remaining ore can be mined from pillars that were initially left in place to support the mine (Jung and Biswas, 2002). Tailings exiting the mill are sent to the paste plant where they are combined with various additives and chemicals. This paste, when pumped underground and set, will have the desired strength to support the rock above. The paste, depending on the type of mineral present contains over 47 wt% solids (Sofrá and Boger, 2002). With this high concentration of solids, abrasive wear must be considered. Poor selection of piping materials and improper design of the system may result in premature failure (Solov’ev et al., 1986; Bikbaev et al., 1973). A failure in one section results in the shutdown of the paste system, lost productivity and higher maintenance costs. With the constant push to minimize costs while maximizing productivity, the need for highly abrasion-resistant and predictable materials has become increasingly important. This investigation focuses on the abrasion-resistant properties of numerous materials of this nature. 2. Background Abrasive wear in pipes results when solids make up a large percentage of the fluid being transported. These particles interact with each other, the fluid media and the pipe walls. This can be de* Corresponding author. Tel.: +1 514 880 6966. E-mail address: [email protected] (D. Hewitt). 0892-6875/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.mineng.2009.03.010
scribed by a measured mass of pipe lost and an energy term calculated from the applied force a particle is exposed to and the distance the particle slides along the pipe wall (Rabinowicz, 1995). This can all be modeled experimentally in a laboratory using the abrasion wheel test where the abrasive wear is determined as a function of the applied force on the wheel, the test specimen’s hardness and density, the abrasion angle of the abrasive used and the distance travelled (Radziszewski, 2002). Testing the wear resistance of pipe lining samples was completed using a modified version of the ASTM G65-04 (Standard Test Method for Measuring Abrasion Using the Dry Sand/Rubber Wheel Apparatus) abrasion test machine. This machine’s main differences stem from the wheel material (steel vs. standard rubber-lined), wheel speed (variable vs. standard speed), force applied to sample (variable vs. standard force), abrasive material (any sand/ore vs. Ottawa Sand), there is also a water tank beside the abrasive hopper which allows for tests run dry or wet and instrumentation on the shaft of the wheel, a strain gauge used to collect strain and torque of the drive shaft. This machine was originally developed for the Total Media Wear Model (Radziszewski, 2002). It has been used to predict tumbling mill media wear in mineral processing. In this case, the machine will be used to compare and contrast the pipe sample performances relative to each other as well as the current pipe material (Radziszewski, 2002). 3. Methodology Eight possible pipe materials were tested to determine which should be used to replace the current steel pipe. Initial tests were performed with Ottawa Foundry Sand used as the abrasive. As with
1089
D. Hewitt et al. / Minerals Engineering 22 (2009) 1088–1090
all previous testing, the abrasive is sized to fit the size fraction 20 to +50 Tyler Screen Numbers. The pipe samples were sized to 50 50 38 mm, the mass of the sample was recorded and the sample was loaded into the test machine, see Fig. 1. The abrasive was loaded into the machine, and introduced into the test chamber forming a flowing curtain between the rotating wheel and the sample. A load was applied to the sample such that the sample experiences a predetermined force against the wheel. The sample test was run for 2 min, after which, the mass loss is calculated. The following tables show the operating parameters of the machine and the sample names (see Tables 1 and 2). In addition to these tests, four samples were selected and tested with abrasives supplied by the mining company; these abrasives were constituents of their current and proposed paste mixture. The names of the abrasives and pipe samples for these extra tests are located in the tables below (see Tables 3 and 4). The Supplied Sand was run within the same size distribution as the Ottawa Foundry Sand. The tailing samples, unfortunately, did not fit this size distribution; they were too fine to flow into the test chamber with gravity alone, a slurry mixture had to be created. The slurry was just over 40% solids by mass; this allowed the abrasive to flow into the test chamber with greater ease.
Table 1 Test parameters.
4. Results
Table 3 Abrasives supplied by mining company.
Fig. 2 shows the results for all pipe materials when tested with the Ottawa Foundry Sand. The primary y-axis denotes the wear rate (g/kWh) calculated for each sample, the secondary y-axis is the actual wear (g) of the sample. The results are presented in order of increasing wear rate. Most proposed pipe materials outperformed the current pipe material, the Kalprotect samples were more abrasion resistant than the current pipe material, also they occupied four of the top six rankings. Fig. 3 shows the results of the extra tests that were performed with four of the pipe samples and the abrasives supplied by the mining company. These results are presented alongside the Ottawa Foundry Sand results. A trend was noticed in the performance of the samples when subjected to different abrasives, the Ottawa Foundry Sand being the most abrasive results in the highest wear rate. The Proposed tailings were the least abrasive, giving the low-
Abrasive name
Abrasion test parameters Wheel material Wheel speed Abrasive used Applied force Time of test
Steel 155 RPM Ottawa Sand 300 N 2:00
Table 2 Pipe sample names. Sample name
Supplier
Current pipe material Competitive sample 1 Competitive sample 2 Competitive sample 3 Competitive sample 4 Competitive sample 5 Competitive sample 6 Competitive sample 7 Competitive sample 8 Competitive sample 9
Mining company Mining company Mining company Mining company Mining company Kalprotect Canada Kalprotect Canada Kalprotect Canada Kalprotect Canada Kalprotect Canada
Ottawa Foundry Sand Supplied Sand Current tailings Proposed tailings
Table 4 Pipe samples used in slurry tests. Sample name Current pipe material Competitive sample 1 Competitive sample 7 Competitive sample 8
est wear rate. This wear trend appears consistent for all four abrasives tested; it is not possible to conclude that this trend will be maintained for any tailings abrasive material. 5. Conclusion
Fig. 1. Abrasion test machine (Misra and Finnie, 1980).
With abrasion being the primary source of wear in paste backfill systems, proper design and selection of materials will be of critical importance. The pipe material will be directly responsible for the availability of the paste backfill system. The tests performed with the steel wheel abrasion machine replicated the abrasive wear phenomenon present in the paste backfill piping system. Having determined experimentally pipe lining material wear rates, it is possible to use these rates to estimate liner performance in the field. However, further modeling and validation work is required in order to use this experimental data to predict pipe system wear life. Based on the experience predicting steel media wear in tumbling mills, it is conceivable to tie these wear rates with paste pipe flow to the development of pipe liner wear model that could predict wear and help schedule downtime for maintenance. Once validated against industrial data, such a model could contribute to reducing overall paste backfill operating costs.
1090
D. Hewitt et al. / Minerals Engineering 22 (2009) 1088–1090
Sample Wear Performance with Ottawa Foundry Sand 2.50 2.00
1.00
50
0.50
0
0.00 pl e
er ia l
8
m
at
Sa iv e tit
tP C
om
pe
ur re n C
pe om C
ip e
Sa
M
m
m iv e tit
tit C
om
pe
tit pe om C
pl e
pl e
5 iv e
Sa
Sa
m
pl e m
iv e
Sa iv e tit
C
om
pe
pe om
pl e
1
7 m Sa
iv e tit
tit pe om C
pl e
pl e
6 Sa iv e
Sa iv e tit pe
om C
m
pl e
9 m
pl e m Sa iv e tit
4
100
3
1.50
2
150
pe om C
Wear
Wear [g]
Wear Rate
200
C
Wear Rate [g/kWh]
250
Sample Material Fig. 2. Pipe sample abrasion performance.
Wear Rate for Different Abrasives
Wear Rate [g/kWhr]
80 70 60 50 40 30 20 10 0 Competitive Sample 8
Competitive Sample 7
Current Pipe Material
Competitive Sample 1
Sample Material Ottawa Foundry Sand
Supplied Sand
Current Tailings
Proposed Tailings
Fig. 3. Wear rate with different abrasives and materials.
References Bikbaev, F.A., Krasnov, V.I., Maksimenko, M.Z., Berezin, V.L., Zhilinski, I.B., Otroshko, N.T., 1973. Main factors affecting abrasive wear of elbows in pneumatic conveying pipes. Chemical and Petroleum Engineering 9, 73–75. Misra, Finnie, 1980. A classification of three-body abrasive wear and design of a new tester. Wear 60, 111–121. Jung, S.J., Biswas, K., 2002. Review of current high density paste fill and its technology. Mineral Resources Engineering 11, 165–182.
Rabinowicz, E., 1995. Friction and wear of materials. Wiley, New York. pp. 315. Radziszewski, P., 2002. Exploring total media wear. Minerals Engineering 15, 1073– 1087. Sofrá, F., Boger, D.V., 2002. Environmental rheology for waste minimisation in the minerals industry. Chemical Engineering Journal 86, 319–330. Solov’ev, Yu. G., Yushkevich, P.M., Bondar’, N.P., Kravchenko, N.V., 1986. Determination of basic factors affecting the abrasive wear of pipes. Metal Science and Heat Treatment 28, 214–216.