Blast holes are drilled so that rock can be loaded with explosives and broken. In quarries and mines, DTH (down-the-hole) drilling is a standard way to make them.
How DTH drilling works
- Compressed air drives a pneumatic hammer that sits at the bottom of the drill string
- The hammer strikes the rock directly while the rig rotates the string
- The same air blows the cuttings out of the hole
Because the hammer works at the bottom of the hole, little energy is lost along the rods, so drilling stays fast and the hole stays straight in hard rock.
Surface and underground
- Surface quarries and open pits usually use a crawler mounted DTH rig, which works on rough, uneven ground
- Underground mines use compact machines that fit in a drift. Our underground DTH production drilling machine drills 115 mm to 165 mm holes with a 150 metre capacity
What to consider when choosing a rig
- Hole diameter and depth you need
- Rock type and how abrasive it is
- Carrier: crawler for rough ground, or another carrier for easier sites
- Compressed air and power available on site
- Spares and service close to where you work
Keep the rig working
Blast hole drilling is hard on equipment. Regular service of the hydraulics and a stock of common spares keep a rig earning. Jai Ambey Hydraulics builds DTH rigs and supplies accessories, spares and repair from Bhilwara, Rajasthan.