Testwork: Drop weight test

Testwork: Drop Weight Tests

The JK drop weight testing machine is used to generate data sets for two different comminution models:

A fitted "A" and "b" for the "E_CS versus T₁₀" test result, which is used in JK SimMet to generate particle size distributions (ergo, the appearance functions).
A fitted "drop weight index" (DWI) test result, which is used in the Morrell SMC power model to predict the specific energy consumption of particle breakage for "standard particle size distributions" of a process feed and product streams.

The test is a 'per-specimen' test where individual specimens of prepared rock are hand-picked by the test operator and placed into the apparatus. The size and quantity of the specimens is different in the JK SimMet and Morrell SMC (DWI) procedures. Generally, the DWI procedure requires fewer specimens of smaller sizes, but is much quicker (and less expensive) to operate.

Sample Requirements

The drop weight test for use in JK SimMet, referred to here as the "full drop weight test", requires approximately 100 kg of material with a top size of 75-100 mm. When using drill core, this requires whole-diameter PQ core.

The drop weight test for use in the Morrell SMC model requires minimum 8 kg with sized between 25-40 mm (though smaller dimensions can be substituted if the coarser material is not available).

Test Inputs

Not applicable

Test Outputs

The "full" JK DWT returns a separate value for the fitted parameters A and b (which are frequently multiplied together and reported as A×b),
- A table of Appearance values for a crusher model are provided.
- A companion tumbling test is conducted that returns a ta value.

The SMC test returns a Drop-Weight Index DWI value.
- Inferred A, b (, A×b) and ta are provided for people who intend to use the JK SimMet software.
- Derived output values for Mia (for SAG milling), Mic (for crushing) and Mih (for high-pressure grinding rolls) are provided for doing power-based calculations, such as those in SAGMILLING.COM.

Modelling

JK SimMet, which is a population-balance model, uses the A and b values to predict the t₁₀ generated by a certain breakage energy E_CS. This t₁₀ is then extended to create an appearance matrix used to predict the particle size distribution of a breakage event.

In the Morrell SMC model, the Mia value is used to predict the specific energy consumption of a SAG mill. When combined with an Mib value (obtained as a modified output of a Bond ball mill work index test), the total specific energy consumption of a grinding circuit can be predicted.

Trademarks & Licensing

JK SimMet and JK DWT are trade marks of the Julius Kruttschnitt Mineral Research Centre, Indooroopilly, Australia. Laboratories performing this test pay a royalty when submitting raw results for interpretation.
SMC Test and DWI are trade marks of SMC Testing Pty Ltd, Chapel Hill, Australia. Laboratories performing this test pay a royalty when submitting raw results for interpretation.

Testwork: Drop weight test

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