Performance Grade Drilling and Testing Services

What is Reverse Circulation Drilling and When is the Method Used?
We provide a wide range of drilling and testing services to mines, construction companies, and geological clients in Africa. One of the methods used is that of reverse circulation drilling. We also provide core drilling and testing services, depending on the type of project, the depth, purpose of drilling, and soil conditions, but for the purpose of this article we will briefly explain the basics of reverse circulation drilling.
RC drilling, as it is commonly referred to, entails the usage of rods consisting of inner and outer tubes. Using this method of drilling, the cuttings are brought back to the surface in the rods. The method entails a process whereby a pneumatic reciprocating piston drives an exceptionally hard steel drill bit made from tungsten into the drill surface. Depths of up to 500 m and even deeper can be reached because the inner tubes can be closed up together and with this method, it is possible to attain dry rock parts which are driven out through an air compression system. It is a method suited to large-scale projects and although it is expensive, the method allows for superb penetration power and is generally more cost-effective than diamond-core drilling. As such, RC drilling is frequently used in mine exploration projects.

How does Reverse Circulation Work?
The air is blown down the rod’s annulus and with the pressure created, the water is lifted and the cuttings driven up through the rod’s inner tube towards the deflector box at the upper end of the drill string, from where the cuttings are then transported through a hose at the cyclone top. The cuttings fall through the bottom of the cyclone for collection in the cutting bag. Several such sample bags are used and meticulous record is kept of where drilling took place as well as at what depth the sample cuttings were collected.
An alternative modern RC drill method entails the usage of a drill hammer that has a hollow centre for immediate collection of the sample cutting in the pipe without it having to move past the hammer system. Water may be used for cooling the drill bit. The dry rock samples are analysed in the relevant laboratories to determine the exact mineral content. The information is used by geologists to determine whether a specific area has sufficient amounts and the required quality of a specific mineral.

Types of RC Drilling and Track Record
The two main types used today include the hammer method, which is applied for drilling deep using thicker rods to penetrate medium to hard rock. The second method entails usage of the air core method for drilling into clay and lower depths. The drill method is widely used for mine exploration and has a long track record. The first system was developed over four decades ago and is now also used in oil exploration projects across the globe.

Space Requirements and Possible Complications
Because of the large machinery involved, ample space is needed for RC drilling. The large drill rig and the support vehicles must be able to enter and exit the work area. There is always the risk of the drill bits getting stuck in the drill area because of the wearing down of the bits. If this happens, operations stop to first recover the very expensive rods. To minimise the risk, the tungsten nodules are ground on an ongoing basis. However, it does remain a risk and when the drill is stuck, it can take a few days to recover the rod.

When is RC Drilling Used and how Cost-Effective is it?
We provide RC drilling and testing services at all the main stages involved in mine development, including the initial exploration mining for samples, when needed to go very deep, and when in-pit grade control is required. It is also used at the ore body development level. RC drilling is far less expensive than diamond-core drilling, but it is more expensive than rotary air blast drilling. That being said, RC drilling provides more accurate samples than air blast drilling.

Main Benefits

  • Good penetration rate.
  • Can reach deep.
  • Less water used than when using the diamond-core drill method.
  • Simplified processes, which help to reduce the overall need for additional contractors.
  • Less handling of the samples at the drill site as analysis normally takes place in the lab.

Make use of our extensive range of drilling and testing services in mining and exploration to ensure efficiency through all stages of mining development.

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