Reverse Circulation Drilling pipe RC drilling with dual wall

Reverse Circulation drilling, or RC drilling, is a method of drilling which uses dual wall drill rods that consist of an outer drill rod with an inner tube. These hollow inner tubes allow the drill cuttings to be transported back to the surface in a continuous, steady flow.

RC drilling

Unlike diamond drilling, it compiles sample rock cuttings instead of rock core. The drilling mechanism is most often a pneumatic reciprocating piston called a hammer, which in turn is driving a tungsten-steel drill bit, specifically made to be able to crush hard rock.

The hammer is used to remove rock samples which are pushed through the machine with compressed air. When air is blown down the annulus (ring-shaped structure) of the rod, the pressure shift creates a reverse circulation, bringing the cuttings up the inner tube. When the cuttings reach a deflector box at the top of the rig, the matter is moved through a hose attached to the top of the cyclone.

The drill cuttings will travel around the cyclone until they fall through the bottom opening into a sample bag. These bags are marked with the location and depth of the place where the sample was collected and can be transported directly to the assay lab for analysis.

Benefits of RC drilling

Reliable and uncontaminated samples:

When the cutting travels through the bit into the inner tube towards the cyclone, it is not introduced to other areas of the hole, keeping it free of cross-contamination. This creates the possibility of producing large quantities of high quality, reliable samples.

Sample cuttings are easier to catalogue and keep track of. Because the samples collected will have an exact location and depth at which they were found, surveyors and interested parties will be able to locate mineral deposits more precisely.

RC drilling is best for grade control

Grade control is used to define the ore grades and blocks in the pit. For an exploration program, the quality of the samples is imperative for mine planning and blasting—the samples must be reliably accurate.

RC drilling is the superior method used for grade control in open pit mining operations because:

1. samples obtained via RC drilling are free of contaminants

2. the samples are collected at the drill and sent directly to the lab to be assessed

3. RC sampling requires less handling than other methods

4. less handling results in cost reduction and faster turnaround times

The reliability of the cuttings produced during RC drilling is an industry asset. RC grade control is the most cost effective and efficient method to differentiate between waste rock and minerals.