How to Select a DTH Drilling Rig for Quarry Development
A down-the-hole (DTH) drilling rig should be selected as one component of a drilling system. The hammer, bit, rods, compressor and carrier all have to match the task and each other; a rig bought on its own merits, and then fed by an air supply that was sized for a different hammer, is the most common and most expensive configuration fault in the field.
This page covers the selection sequence and, importantly, when DTH is not the right method for the hole you need.
1. Define the drilling task first
- Blast holes — pattern drilling for fragmentation; diameter and depth driven by the blast design and bench height.
- Quarry development and bench work — including pre-split and production holes.
- Holes for diamond wire — the through-holes that let a wire loop pass around a block. Here the requirement is usually a straight, clean hole of modest diameter on a specific geometry, and DTH may not be the appropriate or most economical method: the wall roughness and deviation a blast-hole-class hammer permits can make threading a wire difficult, and a dedicated arrangement may be specified for the project. Confirm the method against the hole geometry before choosing a rig.
- Other applications — anchor, dewatering or exploration holes, each with their own straightness and flushing requirements.
2. Confirm the hole requirement
| Requirement | What it drives |
|---|---|
| Hole diameter | Hammer size class, bit size, and air consumption. |
| Hole depth and inclination | Rod string, feed stroke, pull-up capacity, and the rod handling equipment. |
| Straightness tolerance | Method choice (wire holes, pre-split) and drilling practice. |
| Pattern and production rate | Number of rigs, mobility requirement, crew size. |
Write down the largest diameter and the deepest hole you expect over the next few years, not only the current job. A rig that covers today's requirement with nothing in reserve will be replaced early.
3. Evaluate the rock
Hardness sets the impact energy required per blow; abrasiveness sets bit life and therefore cost per metre — the two are frequently confused. Fracturing, voids and changing formation affect stability, flushing and deviation. Where possible use measured site information (uniaxial compressive strength, a simple petrographic description, and what neighbouring quarries achieve) rather than a generic rock name.
4. Match the air supply — the step most often under-specified
A DTH hammer consumes air at a stated working pressure. The compressor has to deliver that pressure and enough free air volume to drive the hammer and to lift cuttings out of the hole. Insufficient air means fewer and weaker blows and reground cuttings, which shows up as slow penetration and destroyed button life.
- Confirm the hammer's rated working pressure and its air consumption at that pressure.
- Size the compressor for delivered volume at working pressure, not for free air delivery at zero pressure.
- Add margin for hose losses, leakage, hole cleaning and altitude.
- Account for every other consumer sharing the compressor.
If there is one sentence to take from this page: ask for the air requirement of the hammer you have chosen, and size the compressor from that number.
5. Check the complete equipment package
| Element | Check |
|---|---|
| Rig configuration and mobility | Crawler for rough, soft or sloping ground and low ground pressure; wheeled or truck-mounted where moves are frequent and the ground is firm. Match the carrier to the terrain and the move frequency. |
| Hammer, bit, rods and connections | Confirm they are all one matched set — same shank family, compatible threads, correct rod diameter for the hole. |
| Compressor | Pressure, delivered volume, and whether it can be maintained where it will run. |
| Power and fuel | Diesel engine specification, consumption, refuelling logistics. |
| Feed force, rotation torque, pull-up capacity | Checked against the deepest planned hole, not the average one. |
| Dust control | Dry collection versus wet suppression — often a regulatory requirement, not an option. |
| Operator access and transport | Transport dimensions and weight, site access, set-up time. |
| Spares and support | Hammers, bits, shanks, feed components; agreed response time; operator training included in the package. |
6. Comparing quotations
Price the matched package rather than the rig alone: rig + compressor + hammer + starting set of bits, installed and commissioned. Confirm in writing that the compressor's pressure and delivered volume match the hammer at your altitude, and get the spares and service arrangement specified before signing.
Conclusion
The correct rig is the one that matches the real hole requirement, the rock, the available air supply and the project logistics. Confirm the complete system configuration before ordering — and if the hole is a wire hole, confirm the drilling method too.
Related KEENOVA pages
- Choosing a DTH Hammer and Drill Bit — the next level of the same matching exercise.
- DTH Drilling Machine — listed with pneumatic, pneumatic+electric and pneumatic+hydraulic drive options.
- Crawler DTH Drill and Rock Drill Machine.
- Drilling Equipment & Tools — hammer, bit, rod and accessories range.
- Rock Drilling Steel & Button Bits, Tapered Drill Rods.
Tell us the hole diameter and depth, the rock and the compressor you have — ask KEENOVA for a matched DTH package.