Metso Minerals Industries, Inc.
240 Arch Street, P.O. Box 15312
York, Pennsylvania , USA 17405-7312
Phone: + 1 717 843 8671
Fax: +1 717 845 5154
24 ft. x 30 ft.- 14,000 HP Ball Mills
Metso Ball Mills
Brochure No.2040 06/02
Testing of the Material Automatic operation saves power, grinding media,
and liner wear, while increasing capacity. software
Three types of tests are available for mill power de-
can be developed to suit the most complicated cir-
cuits and complex ores.
In most cases one of two bench scale tests is ade-
All equipment adheres to the applicable standards
quate. First, a Jar Mill Grindability Test requires a
set by ASTM, NEMA, AGMA, AWS, and ANSI.
5 lb. (2 kg) sample and produces a direct measured
Metso mills are equipped with all normally required
specific energy (net Hp-hr/t) to grind from the design
safety features. Designs to meet other codes and
feed size to the required product size. The second
local or state safety regulations will be quoted on
test, a Bond Work Index determination, results in a
specific energy value (net Hp-hr/t) from an empirical
If time permits and the user wishes, grinding circuits Ball mills operate either in open or closed circuit.
are set up and continuous tests are run to simulate
Open circuit operation is best utilized when:
plant operation. These tests require two or three
days for each ore type and approximately 1,000 • Another stage of grinding follows the mill
pounds of material for each day of testing. Varia- • Reduction ratio is small
tions in ore hardness or circuit design may require • Feed material is already fine and one pass
larger samples. through the mill produces the desired results
• Product size control is not critical and oversize
Grinding Circuit Design
material can be tolerated in the product
Metso process engineers welcome the opportunity
Where size control of the final product is important,
to assist you with circuit and circuit control design as
closed circuit grinding is the most efficient method of
well as start-up, operation, and optimization of the
18 ft. x 22 ft.- 5,500 HP Ball Mills operation. The production of a higher quality prod-
uct at a lower cost justifies the additional capital in-
Productive grinding systems are the result of the vestment.
efforts of disciplines ranging from mechanical de-
Common wet grinding flowsheets include:
Grinding of materials in a tumbling mill with the The feed to a ball mill is prepared by... sign and metallurgy of materials to process engi-
presence of metallic balls or other media dates • Single or multistage crushing and screening neering and instrument application. Desired grind- • Open circuit
back to the late 1800's. Since that time, Metso • Crushing, screening, and/or rod milling ing results are achieved only through careful and • Closed circuit with hydro cyclones
Minerals and its predecessor companies, MPSI, • Primary crushing and autogenous/ skillful attention to detail. • Closed circuit with vibrating screens
Sala, Marcy, Hardinge, Kennedy Van Saun semiautogenous grinding Our engineers can specify or supply computer con- • Two stage variations of the above utilizing two
(KVS), Denver Equipment, Allis Chalmers, Bo- trol systems for the sophisticated circuits. The cost mills in series
liden Allis, and Dominion Engineering, have de- Normal feed sizes:
• 80% passing 1/4" (6 mm or finer) for hard ores of computer hardware decreases almost daily, mak- Let our engineers review your specifications and
signed and manufactured more than 8,000 grind- ing these controls feasible for smaller installations.
ing mills. • 80% passing 1" (25 mm or finer) for softer ores recommend the optimum circuit for your application
(Larger feed sizes can be tolerated depending
Metso Overflow Ball Mill sizes range from 5 ft. x
8 ft. with 75 HP to 26 ft. x 41 ft. with 20,000 HP. The length to diameter ratio of cylindrical mills range
Larger ball mills are available with dual pinion or from 1 to 1 through 3 to 1. When the L/D ratio is 2
ring motor drives. Our mills incorporate many to 1 or greater, we refer to the mill as a Tube Mill.
of the qualities which have made the Marcy The two most popular types of ball mills are…
name famous since 1913. These heavy-duty ma-
chines are designed for long life and minimum Grate or Diaphragm Discharge
In the discharge end of this mill, a slotted full di-
ameter or partial diameter grate with discharge
Variations of the standard designs are available lifter assembly conveys the material to the dis-
to suit any appropriate application. These may charge trunnion opening. The grate serves to
include but not be limited to: grate discharge, retain balls, tramp, and coarse material. A gradi-
peripheral discharge, dry grinding, special ent created between the feed opening and the
length to diameter ratio, high temperature mill- discharge slots eases the flow of material.
ing operations, or pebble milling.
Trunnion Overflow Discharge
A trunnion overflow mill has an open discharge
Application end. Material flows through the trunnion as a re-
sult of the pulp gradient between the feed and
A ball mill grinds ores and other materials to a typi-
discharge openings. A reverse helix in the dis-
cal product size of 35 mesh or finer.
charge trunnion liner retains balls in the mill. 22 ft. x 36 ft.- 12,500 HP Ball Mill