A simple power allowance added to a milling stage. Does not include any machine mechanical dimensions or throughput estimates.
This model consists of a motor, a mechanical efficiency (or utilization), and a DCS power indication efficiency.
- Motor power is the rated output power of the motor (the motor "name plate" power).
- Motor mechanical efficiency is the amount of power actually absorbed by the ore during crushing.
- Motor efficiency to DCS is the the electrical losses between the motor output and the power measurement signal to the DCS.
Motor mechanical efficiency
Unlike other mill power models, this value is used to "tune" the amount of power absorbed by the ore. It includes mechanical losses in the drive train, but most of this efficiency is related to how effective the crusher is at transmitted power into breakage. Typical values by type of machine:
- Pebble crusher, choke fed (with a bin) = 0.75
- Pebble crusher, moderately loaded (no bin) = 0.60
- Pebble crusher, lightly loaded = 0.25 to 0.50
- Tertiary crusher, choke fed (with a bin) = 0.75
- Tertiary crusher, moderately loaded = 0.65
- Secondary crusher, choke fed (with a bin) = 0.65
- Secondary crusher, moderately–lightly loaded = 0.55-0.40
Motor efficiency to DCS
Consists of electrical losses between the motor output and the sensor measuring the power. Usually consists of the motor efficiency (typically 0.96) and possibly allowance for transformers or conductors between the sensor and the motor input.
Throughput is NOT validated
The crusher model does not check the volumetric flow through the crusher, the specific energy requirements, nor confirm that the crusher size is suitable for such a flow. It is the responsibility of the engineer (that's you!) to check the crusher mass balance, motor size and throughput limitations in a separate calculation.
Pebble crushing is considered part of the SAG mill for the purposes of power modelling in SAGMILLING.COM. The crusher feed, product and closed side setting sizes are not used (nor estimated) as such parameters are internal to the SAG mill "black box".