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Iron Ball Mill: Grüson Drum with a Stepped Die Ring and Two Screens (Richards, 1903)
The Grüson ball mill: a drum turning on a horizontal axis, charged with chilled iron or steel balls of mixed sizes. The balls grind the ore against each other and against a stepped die ring. The ground ore passes out through a coarse and a fine screen; the oversize is carried back in.
Result: a mill for fine grinding of cement, fertiliser, clay and soft ores, wet or dry. Sizes from 0.66 m to 1.83 m across.
Source: R. H. Richards, Ore Dressing, vol. I (1903), § 225, Figs. 172a-b and Table 149. Unknown: dimensions beyond the table, and the materials of the side plates, screens and shaft. Picture: Richards, Figs. 172a-b.
Advanced
Unknown
Instructions
1
1
Make the drum and the die ring
Make the drum and the die ring
The drum is two side plates (b) joined round the edge by the die ring (a). The die ring is five perforated, spiral plates of chilled iron. Each plate laps the next, so they form steps: the balls drop from one step to the next, and the space under each step lets the oversize from the screens back in. Not given: the side-plate material, sizes, hole sizes.
Materials for this step:
Iron Castings5 die plates, chilled iron
Unknown Material2 side platesTools needed:
Unknown Dimensions
Adjustable Spanner2
2
Put the two screens round it
Put the two screens round it
Outside the die ring, fit a coarse perforated screen (c) to take the wear. It is in five parts with spaces between them and has back-deflecting holes (g). Outside that, fit a fine gauze screen (d). At the end of each section of fine screen, fix a deflector or shovel (f). As the drum turns, it carries the oversize up and back into the grinding space. Not given: the screens' metal and mesh.
Materials for this step:
Perforated Screen Plate1 coarse screen, 5 parts
Woven Wire Screen Cloth1 fine screenUnknown Material5 deflectorsTools needed:
Unknown DimensionsAdjustable Spanner3
3
Mount and house it
Mount and house it
Carry the drum on a horizontal shaft in two bearings; the figures show them on masonry piers. Enclose the drum in a plate iron housing with a discharge spout (e) below, a feed hopper (h) at one end, a manhole (i) and a dust pipe (k) on top. Ours: steel sheet for the plate iron.
Materials for this step:
Steel Shaft1 mill shaft
Bearing Block2 pieces
Mild Steel Sheet1 housing, spout, hopperTools needed:
Adjustable SpannerUnknown Dimensions4
4
Fit the drive
Fit the drive
Drive the mill by gear and pinion. In the figure, the gear is on the mill shaft and the pinion on a countershaft that carries tight and loose pulleys. A belt from the line shaft runs on the pulleys: on the tight pulley the mill turns, on the loose pulley it stops.
Materials for this step:
Gear Wheel1 on the mill shaft
Pinion1 pieceSteel Shaft1 countershaftBearing Block2 pieces
Tight and Loose Pulleys1 pieceTools needed:
Drive BeltAdjustable Spanner5
5
Charge the balls (size sets the charge)
Charge the balls (size sets the charge)
Load chilled iron or steel balls in mixed sizes; mixed sizes grind better than one size. Size is the variable: No. 0 (0.660 m drum, 45 rev/min) takes 15 kg of 40 mm and 45 kg of 80 mm balls, 60 kg in all. No. 2 (1.330 m, 30 rev/min) takes 100 kg each of 100, 115 and 125 mm, 300 kg. No. 4 (1.830 m, 25 rev/min) takes 217 kg each of the same three sizes, 650 kg. The bigger the drum, the slower it turns and the heavier its charge.
Materials for this step:
Grinding Media (Steel Balls)300 kg for No. 2; 60 kg No. 0, 650 kg No. 4Tools needed:
Platform Scale6
6
Grind
Grind
Feed the ore, egg-size, through the hopper and run the mill wet or dry. Power, and output per 24 hours: No. 0 takes 1/4 horse power and grinds 1,680 kg of copper ore to 15 mesh, or 840 kg of chrome iron ore to 130 mesh. No. 2 takes 2 1/2 to 3 horse power: 14,400 kg of brick bats to 20 mesh, or 1,920 kg of emery to 200 mesh. No. 4 takes 9 to 11 horse power: 12,720 kg of gold ores to 40 mesh, or 10,800 kg of chrome iron ore to 130 mesh. Wear: 1,345 kg of balls for 102,400 barrels of cement, about 0.139 lb a ton. The end plates last 18 months. Hard quartz ores wear the balls too much.
Tools needed:
Drive Belt
WaterMaterials
11- 5 die plates, chilled ironPlaceholder
- 5 deflectorsPlaceholder
- 1 coarse screen, 5 partsPlaceholder
- 1 fine screenPlaceholder
- 1 countershaftPlaceholder
- 2 piecesPlaceholder
- 1 housing, spout, hopperPlaceholder
- 1 on the mill shaftPlaceholder
- 1 piecePlaceholder
- 1 piecePlaceholder
- 300 kg for No. 2; 60 kg No. 0, 650 kg No. 4Placeholder
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