Rates
Use the Pit Optimiser > Analyse Pits > Rates tab to specify the rates at which material will be mined and processed, and the rates at which products will be sold, throughout the periods of the analysis.
As indicated by the = button on the left-hand side of each field, it is possible to specify the mining, processing and selling rates using expressions.
Mining Rate (tonnes per period)
(Optional.) Specify the rate (mass per period) at which material will be mined.
Processing Rate for All Methods
Select to specify the rate at which ore will be processed for all processing methods.
Specify the rate (mass or volume, per period) at which ore will be processed by all processing methods.
Processing Rate per Method
(Mine > Definition > Model > Block Model > Optimisation Value >Calculate from element revenues and costs only.) Select to specify the rate at which ore will be processed for individual processing methods.
Specify the following settings for each processing method (as defined on the Stope Optimiser > Processing Facilities tab):
Method
Select the processing method for which the processing rate is specified.
Rate
Specify the rate (mass or volume, per period) at which ore will be processed by the processing method.
Since it is not possible to specify the selling rate when optimisation values are sourced from a field in the block model of the mine, the processing rate should be set to the greater of the anticipated processing rate and the selling rate in this scenario.
Selling Rate (grade mass units per period)
(Mine > Definition > Model > Block Model > Optimisation Value > Calculate from element revenues and costs only.)
Specify the following settings for each customer (as defined on the Pit Optimiser > Customers tab) to which products will be sold:
Customer
Select the customer to which the product is sold.
Rate
Specify the rate (mass of element per period) at which the product is sold to the customer.
The selling rate must be expressed in units that are consistent with those specified for the elements by Mine > Definition > Model > Elements > Grade Representation. For example, if Grade Representation is set to “g/t” (grams per tonne), the selling rate must be expressed in grams per period.
Since it is not possible to specify the selling rate when optimisation values are sourced from a field in the block model of the mine, the processing rate should be set to the greater of the anticipated processing rate and the selling rate in this scenario.
Specifying Different Rates for Different Periods
Expressions can be used to specify different mining, processing and/or selling rates for different periods.
Example: To specify the following rates:
| Period | Rate (t/period) |
|---|---|
|
1 - 3 |
500,000 |
|
4 - 7 |
750,000 |
|
8 + |
1,000,000 |
click the = button next to the appropriate field and enter the following expression into the top left field in the Expression Editor:
if {PERIOD} <= 3 then
500000
elseif {PERIOD} <= 7 then
750000
else
1000000
endif
where {PERIOD} is a variable that is predefined within the context of the analysis to represent the “current” period.
Tip: Within the Expression Editor, the {PERIOD} variable can be selected from Variables > Time.