How to Define Slurry Particle Size
Accessing and describing the make of a deposit or a slurry is important in the selection of pumping equipment. Particle size along with particle distribution will affect pump wear, material selection, pipeline settling velocity, and how a deposit will or will not flow and therefore affect production rates. Deposits with oversized wood or trash particles will also create a problem known as “bird nesting”. Oversized rocks will create an issue known as “paving stoning”. Both subjects for another day
Although it is important to be able to accurately describe both particle size and distribution, today we will only address particle size.
To the right are examples of the types of terms used to describe rock in the sand and gravel industry. Useful in obtaining a general feel for the makeup of a deposit but not very analytical. To be able to further clarify, and to easily describe the size of particles, some standards have been established. Unfortunately, as with most things in our industry, there are multiple standards!!
The basis or method of the various standards is however common, and that is “ to define a particle in accordance with the size of the particle that will pass through a specific size mesh”. Unfortunately, the sizes of mesh and the units of measure used to describe the mesh is not common. The four particle size standards I have worked with are; “Tyler”, “US Bureau of Standard Screens”, “British Standard Screens”, “I.M.M. Screens” and Wentworth.
| Diameter (mm) | Diameter (phi) | Wentworth Size Class | |
| 4096 256 | -12 -8 | Gravel | Boulder |
| 64 | -6 | Cobble | |
| 4 | -2 | Pebble | |
| 2 | -1 | Granule | |
| 1 | 0 | Sand | Very Coarse Sand |
| 0.5 | 1 | Coarse Sand | |
| 0.25 | 2 | Medium Sand | |
| 0.125 | 3 | Fine Sand | |
| 0.0625 | 4 | Very Fine Sand | |
| 0.0313 | 5 | Silt | Coarse Silt |
| 0.0156 | 6 | Medium Silt | |
| 0.0078 | 7 | Fine Silt | |
| 0.0039 | 8 | Very Fine Silt | |
| 0.00006 | 14 | Mud | Clay |
The Wentworth standard is rarely used but does contain a useful table that provides a clear cross-reference between common terms used to describe materials and the relative particle size in mm for that material.
| U.S. Bureau of Standard Screens | Tyler Screens | British Standard Screens | I.M.M. Screens | |||||||||
| Mesh | Aperture | Mesh | Aperture | Mesh Double Tyler Series |
Mesh | Aperture | Mesh | Aperture | ||||
| Inches | mm | Inches | mm | Inches | mm | Inches | mm | |||||
| 2.5 | .321 | 7.925 | ||||||||||
| 3 | .265 | 6.73 | 3 | .263 | 6.680 | |||||||
| 3.5 | .223 | 5.66 | .221 | 5..613 | 3.5 | |||||||
| 4 | .187 | 4.76 | 4 | .185 | 4.699 | |||||||
| 5 | .157 | 4.00 | .156 | 3.962 | 5 | |||||||
| 6 | .132 | 3.36 | 6 | .131 | 3.327 | 5 | .1320 | 3.34 | ||||
| 7 | .111 | 2.83 | .110 | 2.794 | 7 | 6 | .1107 | 2.81 | ||||
| 8 | .0937 | 2.38 | 8 | .093 | 2.362 | 7 | .0949 | 2.41 | 5 | .100 | 2.51 | |
| 10 | .0787 | 2.00 | .087 | 1.981 | 9 | 8 | .0810 | 2.05 | ||||
| 12 | .0661 | 1.68 | 10 | .065 | 1.651 | 10 | .0660 | 1.67 | ||||
| 8 | .062 | 1.574 | ||||||||||
| 14 | .0555 | 1.14 | .055 | 1.397 | 12 | 12 | .0553 | 1.40 | ||||
| 10 | .050 | 1.270 | ||||||||||
| 16 | .0469 | 1.19 | 14 | .046 | 1.168 | 14 | .0474 | 1.20 | ||||
| 12 | .0416 | 1.056 | ||||||||||
| 18 | .0394 | 1.00 | .039 | .991 | 16 | 16 | .0395 | 1.00 | ||||
| 20 | .0331 | .84 | 20 | .0328 | .883 | 18 | .0336 | .85 | ||||
| 16 | .0312 | .792 | ||||||||||
| 25 | .0280 | .71 | .0276 | .701 | 24 | 22 | .0275 | .70 | ||||
| 20 | .025 | .635 | ||||||||||
| 30 | .0232 | .59 | 28 | .0232 | .586 | 25 | .0236 | .60 | ||||
| 35 | .0197 | .50 | .0195 | .495 | 32 | 30 | .0197 | .50 | 25 | .020 | .508 | |
| 40 | .0165 | .42 | 35 | .0164 | .417 | 36 | .0166 | .421 | 30 | .0166 | .421 | |
| 45 | .0138 | .35 | .0138 | .351 | 42 | 44 | .0139 | .353 | 35 | .0142 | .361 | |
| 40 | .0125 | .317 | ||||||||||
| 50 | .0117 | .297 | 48 | .0116 | .295 | 52 | .0166 | .295 | ||||
| 60 | .008 | .250 | .0097 | .246 | 60 | 60 | .0099 | .252 | 50 | .01 | .254 | |
| 70 | .008 | .210 | 65 | .0082 | .208 | 72 | .0083 | .211 | 60 | .0083 | .211 | |
| 80 | .0070 | .177 | .0069 | .175 | 80 | 85 | .0070 | .177 | 70 | .0071 | .180 | |
| 100 | .0059 | .149 | 100 | .0059 | .147 | 100 | .0060 | .152 | 80 | .0065 | .157 | |
| 90 | .0055 | .139 | ||||||||||
| 120 | .0049 | .125 | .0049 | .124 | 115 | 120 | .0049 | .125 | 100 | .0050 | .127 | |
| 140 | .0041 | .105 | 150 | .0041 | .104 | 150 | .0041 | .105 | 120 | .0042 | .107 | |
| 170 | .0035 | .088 | .0035 | .088 | 170 | 170 | .0035 | .088 | 150 | .0033 | .084 | |
| 200 | .0029 | .074 | 200 | .0029 | .074 | 200 | .0030 | .076 | 170 | .0029 | .074 | |
| 230 | .0024 | .062 | .0024 | .061 | 250 | 240 | .0026 | .065 | 200 | .0025 | .063 | |
| 270 | .0021 | .053 | 270 | .0021 | .053 | 300 | .0021 | .053 | ||||
| 325 | .0017 | .044 | .0017 | .043 | 325 | |||||||
| 400 | .0015 | .037 | ||||||||||
This was a very basic short discussion today but next time we will use the terminology and the information on particle size discussed today to delve into “Particle Distribution” and how it affects deposit flow and therefore production .
Cheers,
RJ
