SHERPA for Surface Mines

The cost estimating techniques used by SHERPA rely on a number of project-specific engineering parameters, such as material densities and swell, powder factors, rolling resistance, drill penetration rates, drill bit and rod wear, and bench heights. These parameters, along with user specified haul profiles and ore and waste production rates, provide the foundation upon which the cost estimate is based. You may, of course, enter all these values directly into SHERPA and manipulate them as needed. However, in cases where some or all of this information is unavailable, SHERPA suggests reasonable entries. In addition to its suggested entries, SHERPA’s help screens provide guidance in determining alternate values.

SHERPA’s suggested entries allow you to complete reasonable estimates with a minimal amount of information. The only items that absolutely must be specified are daily production rate, shift schedules, haul distances and gradients for both ore and waste, and the total resource size.

Once production and deposit data have been entered, SHERPA begins the process of selecting equipment. With SHERPA, you either specify you own fleet, or request that the software perform the task. If SHERPA suggests the fleet, standard engineering techniques are used to select the types and determine the sizes of the excavators and haulers. The program then goes through an optimization process to determine the most economically attractive excavator/hauler combination.

Excavator and hauler productivities are determined using widely accepted engineering techniques. 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.

Once excavators and haulers have been selected, the program 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. You may, of course, alter any or all of the fleet selected by SHERPA by simply overwriting the suggested values.

With the equipment fleet specified, SHERPA begins the task of determining 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, including blasting materials, drill bits and rods, diesel fuel, electricity, repair parts, lubricants, and tires 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. SHERPA also estimates pre-production development and haul road requirements, as well as working capital, engineering, and management parameters.

Once all necessary cost engineering parameters have been determined, they are used in conjunction with the information contained in the cost database to calculate all relevant capital and operating costs. The results are then displayed on the screen or sent to a printer.