Drilling has a great impact on the productivity and economy of a mining company, for this reason, if the blasting process does not produce the expected results, the productivity of the project can be affected. It is at this point where the weight test or Pull Down makes its appearance since it allows the drilling parameters to be met so that the work can be executed successfully.
Definition of Pull Down
The Pull Down or weight test is the study of the amount of force that the push must have to break a rock. Some variants within this calculation are also taken into account such as The study of the optimal weight on the bit, the number of revolutions per minute (RPM) of the bit, the air pressure levels, the sweep speed, and penetration speed. These variables are taken into account when developing a weight test or Pull Down.
To produce rock failure, the bit teeth must create enough compressive force to produce rock failure. When the rock has low compressive strength, then the Pull Down necessary to produce rock failure will be less, on the other hand, if the rock has high compressive strength, then the greater the Pull Down necessary to produce the rock fault.
Variants that are taken into account when determining a Pull Down
Optimum weight on the bit
This indicator is calculated taking into account the weight on the bit (W) which is expressed in pounds, the level of compression of the rock (C), the diameter of the hole (D), and the variants (5) that are taken in the study. This calculation is represented by the following formula: W = (C x D) / 5.
Drill revolutions per minute
This indicator is required to move the cutting insert to the next insert break position; the faster this change of position is, the faster the penetration speed will be. The harder the ground to be drilled, the lower the required RPMs, while on the other hand, the softer the ground, the higher the RPMs required.
Drill revolutions per minute
This gauge is used to provide sufficient volume and pressure to optimize bit life. The bit requires minimal levels of air pressure to ensure the cooling and lubrication process of the bearings in the bit is adhered to.
Sweep speed
This indicator reflects how fast the air is leaving the drill. Compressor losses due to the effect of high elevation and temperatures cause a decrease in sweep speed. This part of the study also calculates the rate of fall of particles and the rate of exit of the detritus.
Penetration speed
This indicator reflects the speed with which the drill bit can fracture the rock below it, thereby deepening the excavation hole. This speed is generally expressed in feet or meters per hour. The penetration speed will depend on the external factors that make up the drilling area, such as the geological characteristics of the soil, in addition to the specific properties of the rocks that are within the drilling area.
