A renewed approach to surface mining
cost estimating
Sam Blakely| May 8, 2022 | 12:25 pm
Sherpa for Surface Mines has been reinvented as Costmine’s Sherpa Surface, an
improved, cloud-based mining-cost-estimating application. The transition of this
unique application to the web gives anyone with an internet connection, and a
need to estimate the capital and operating cost associated with surface mining,
instant access to a powerful engineering-based tool with a new easy-to-use
interface.
The original Sherpa for Surface Mines was created to allow mining cost
estimators to use advanced cost engineering procedures at the pre-feasibility level
and earlier. The program was designed to be both highly flexible, so experienced
engineers could fully utilize their expertise, and easy to use, so that those not
fully versed in cost engineering techniques could produce reliable estimates.
These design principles have endured the application’s transformation into the
new Sherpa Surface.
Figure 1.
Minimum Required Data to Estimate Costs
Rather than relying on obscure statistical relationships, Sherpa Surface takes a
cost engineering approach. As it was with Sherpa, this updated application uses
established engineering procedures and algorithms to calculate all the
engineering parameters necessary to estimate the costs associated with surface
mining and development. Haul cycle times, excavator productivity, explosive
consumption rates, pumping requirements, and a host of other engineering
parameters are determined using accepted mathematical procedures. Finally,
these engineering parameters are coupled with up-to-date itemized cost data,
provided by Costmine’s Mining Cost Service and a variety of other sources, to
arrive at complete surface mining capital and operating cost estimates.
Sherpa Surface can accomplish all of this (including data entry, determination of
engineering parameters, application of itemized costs, and detailed reporting) in a
matter of seconds. However, when site-specific data is available and/or the user
is experienced, the application encourages you to overwrite any and all
intermediate calculations, estimates, and costs that it provides. This allows the
user to tune his or her cost estimate to their project’s specific characteristics,
bolstering the reliability of their cost estimate; and making the Sherpa Surface
capable of estimating the costs of projects located around the globe.
Equipment selection
Figure 1 shows us the minimum amount of data entry required to estimate the
capital and operating costs associated with a surface mining project, covering
basic project, production and deposit data. After the minimum data entry has
been saved, the Sherpa Surface begins the process of selecting the primary
equipment fleet. You can request that the application specify the fleet for you, or
you can specify your own fleet if more appropriate for your project.
If you choose to let the Sherpa Surface determine your fleet, standard
engineering techniques are used to select the types and determine the sizes of the
excavators and haulers. The application then goes through an optimization
process to determine the most economically attractive excavator-hauler
combination. Equipment availability, bucket fill factors, material densities and
swell, fixed cycle times, and travel speeds (adjusted for load and gradient) are all
considered when determining productivity.
Figure 2.
Ore, Waste, and Ancillary Equipment Summary
Once excavators and haulers have been selected, the Sherpa Surface examines
the specified powder factors, bench heights, and production requirements to
select the type and determine the size of the blasthole drills. Requirements for
ancillary equipment, including graders, pumps, dozers, lighting plants, water
tankers, pick-up trucks, maintenance trucks, and explosives loaders are also
provided. A summary of the primary and ancillary equipment fleets is displayed
on the Settings Summary page of the application, shown in Figure 2. As with all
fields in the application, you may alter any or all of the fleet related parameters,
or even specify new equipment, by simply overwriting the values suggested by
the application.
With the equipment fleet specified, the Sherpa Surface begins the task of
determining the requirements for all other aspects of the operation. The numbers
of hourly and salaried workers required to meet the specified production rate are
estimated. Consumption rates for all pertinent supplies are calculated. The sizes
of the shop, mine office, change house, and warehouse are provided, as are
requirements for explosives storage facilities and the electrical distribution
system. The Sherpa Surface also estimates pre-production development and haul
road requirements, as well as working capital, engineering, and management
parameters.
Figure 3.
Total Project Cost Summary
Once all necessary engineering parameters have been determined, they are used
in conjunction with the information contained in the itemized cost database to
calculate all relevant capital and operating costs. Overall costs are displayed in an
easy-to-read Executive Summary. Detailed costs are displayed in four menus,
including a Total Project Cost Summary (see Figure 3) displaying annual average
operating costs by category and a schedule of annual capital costs incurred. All
the reports and the Executive Summary are downloadable as a PDF with one
click. Finally, the data can also be transferred to other applications, such as your
favourite spreadsheet application, for further analysis.
A unique approach to mining cost estimating
The cost estimating techniques used by the Sherpa Surface rely on numerous
project-specific engineering parameters, along with user entered resource data
and ore and waste production rates, provide the foundation upon which the cost
estimate is based.
Sherpa Surface will suggest entries that allow you to complete reasonable
estimates with a minimal amount of information in a small amount of time. The
only items that absolutely must be specified are daily production rates, shift
schedules, and the total resource size. CMJ
Sam Blakely is a mining engineer and cost analyst at Costmine
(www.costmine.com).