Principle, Advantages, and Cost of Air Reverse Circulation Drill Bit

When choosing a drilling method, especially in terms of exploration and grade control, many factors such as cost, time, environmental impact, drilling depth, and sample quality must be considered. This article will introduce the advantages, costs, and safety of reverse circulation drill bit and explain why it is the best method for grade control.

What is Reverse Circulation Drill Bit

Reverse circulation drill bit is a drilling method that uses dual-wall drill rods, consisting of an outer drill rod and an inner tube. These hollow inner tubes allow rock cuttings to flow continuously and steadily back to the surface. Unlike diamond drilling, reverse circulation drill bit obtains rock chips instead of core samples. The drilling principle involves using a pneumatic hammer to drive a tungsten steel drill bit to crush the rock layers. The hammer, which operates through pneumatic reciprocating motion, drives the tungsten steel drill bit used to break hard rocks. When compressed air blows out, the pressure shift creates a reverse circulation, allowing rock cuttings to move up into the inner tube. Once the cuttings reach the surface, they are connected via a hose to a cyclone separator for sample splitting, after which the sample drops into a sample bag from the bottom opening. These sample bags are labeled with the location and depth of the collected sample and can be sent directly to the laboratory for analysis.

Benefits of Reverse Circulation Drill Bit

Reliable and uncontaminated samples

Rock cuttings enter the sample collector through the inner tube of the drill rod without contacting other areas, avoiding cross-contamination, thus obtaining high-quality, reliable samples. Samples are easy to classify and track, with precise location and depth, allowing accurate mineralization positioning.

Fast drilling speed

Reverse circulation drill bit can drill 200-300m per day, allowing for quicker drilling results and less time spent.

Low site requirements

Reverse circulation drill bit does not require water during drilling, making it suitable for water-scarce areas.

Low cost

Compared to diamond drilling, reverse circulation drill bit can reduce costs by up to 40%.

Rreverse Circulation Drill Bit is most suitable for mine grade control

Reverse circulation drill bit is the best method for grade control in open-pit mining:

• Samples obtained through reverse circulation drill bit are not contaminated;

  
  

• Collected samples are sent directly to the laboratory for testing without complex pre-treatment;

  
  

• Costs can be reduced, and the mining process time can be shortened.

The reliability of rock cuttings generated during reverse circulation drill bit is an industrial asset. RC grade control is the most cost-effective method to distinguish between waste rock and minerals. Due to the small footprint of RC drill rigs, extensive earthworks are not required. This means reverse circulation drill bit has minimal environmental impact.

Safety Considerations for Using Rreverse Circulation Drill Bit

Reverse circulation drill bit comes with some operational safety considerations that need special attention. The noise level is high, with the sound of the drill bit hammering rock combined with the noise of compressed gases, which can cause hearing damage. Therefore, workers need to wear hearing protection devices as well as all other appropriate personal protective equipment. This includes not only earplugs or earmuffs but also respirators, safety shoes, hard hats, and industrial gloves. Reverse circulation drill bit personnel usually require at least one operator and two sampling workers. The risks they face could come from strains while handling samples, injuries from falling objects, potential harm from broken compressed gas hoses, or crushing or impact injuries from machinery.