Today we are going to discuss dust control for both drilling and blasting. Why are they important and how do they work? Let’s get into it.
Drilling Dust Control Systems
All the drills at McCallum Rock Drilling are equipped with two-phase dust control systems. These systems reduce airborne dust and create a safer work environment for our employees. As the hole is drilled, the bit grinds the rock into a fine powder. This powder, or rock “cuttings”, are then flushed out of the borehole by a high-pressure air system run by the large compressor mounted on the drill rig. When the dust laden air reaches the surface it is sucked into a separator hose and into the first phase of the air/dust separation system.
Phase one of this system is the air cyclone which removes up to 90% of the coarser dust particles by blowing high pressure air through the cone chamber. As the air is circulated, the larger dust particles are forced to the outside walls of the chamber and fall to the ground, creating a pile of drill cuttings next to each borehole. These coarse drill cuttings will then be placed back into the borehole once it has been loaded with explosives. The finer dust particles are blown through an opening in the cone to the second phase of the system.
Phase two of the air/dust separation system removes the remaining fine dust particles from the air by use of several air filters. The dust/air mix is blown through these filters, allowing the clean air to be exhausted out of the back of the drill rig. This fine dust collects on the filters, compressing the particles together. The collected particles then drop to the ground through another cone at the rear of the drill and are consumed in the blast.
This system is regularly inspected and tested by MSHA (Mine Safety and Health Administration) to confirm all dust limits are adhered to.
Blasting Dust Control
Now onto the blasting side of things. How do we minimize dust created by the blast? McCallum Rock Drilling and McCallum Powder utilize an emulsion-based explosives product for a vast majority of production blasting. This product is transported by custom-designed pump trucks from a secured off-site explosive storage facility to the rock quarry, following all ATF (Bureau of Alcohol, Tobacco, Firearms and Explosives) and DOT (Department of Transportation) regulations. There are two main reasons this is the exclusive product we use for production blasting.
The first reason we use this product is it’s not sensitized until it’s pumped off the truck and mixed with other solutions. The truck is computer-controlled with a number of pumps and valves that mix these solutions as they are pumped out of the truck and into the borehole. Therefor, this product is not technically an explosive until it reaches its final destination, the borehole. This allows for a safer and more secure storage and transport of the explosive material used in quarry blasting than ever before.
Second, this emulsion solution has a density greater than 1.0, making it heavier than water. The explosive product is also completely waterproof. Therefor when the emulsion is pumped down the borehole, it displaces any water that may have collected in the borehole since it had been drilled. This allows us to maximize the entire borehole with explosive energy.
We not only use this emulsion product in the wet winter months but also in the dry summer months. Even when we are not concerned about water in the borehole, the waterproof nature of the product allows us to load and charge the boreholes on the bench and then bring over a water truck and soak the entire area. By soaking the entire surface of the blast, we are able to mitigate a majority of the dust that would have been generated by the detonation of the otherwise dry material. A majority of the dust from blasting is generated by the dirt on the bench surface that has dried and is displaced by the blast. This specialized explosive product allows us to use as much water as necessary to eliminate the dry dirt on the surface of the blast without compromising the integrity of the explosive product or the blast.
What questions do you have about drilling and blasting dust control? Leave us a comment!