RE531 RE004 RE542 RE543 RE545 RE547 RC Drilling Reverse Circulation Drilling Equipment

Reverse Circulation, or RC, drilling is a fast and cost efficient method of retrieving high quality samples from exploration and mine drilling. The system has been continuously developed since its inception in Australia in the early 1970s, and is now a preferred method for initial exploration, ore body development and in-pit grade control.

The RC method employs dual wall drill rods that comprise an outer drill rod, with an inner tube located inside the drill rod. The inner tubes overlap, and seal on the tube below with O rings when the drill rods are screwed together. These inner tubes provide a continuous sealed pathway for the drill cuttings to be transported from the bit face to the surface. The circulating medium, in most cases high-pressure air, enters the annulus between the rod and tube via the air swivel, which is normally part of the drill string, or sometimes mounted on top of the rotation head. The air travels down the annulus to the drilling tool,

which is usually an RC hammer, or can be a blade bit or tricone roller bit. As in conventional open hole drilling, the air powers the drilling tool and the exhaust air carries the cuttings. In RC drilling the cuttings are returned to the surface through the inner tubes in the drill string and rotation head. Once through the rotation head, the air and cuttings comprising the sample change direction at the discharge blast box and are transported through the sample hose to the cyclone. The cyclone slows the sample, separates it from the air, and collects it.

RC drilling provides virtually uncontaminated cuttings to the cyclone. As the cuttings travel directly from the drill bit through the steel inner tubes and sample hose, there is no cross contamination from other areas of the hole. Using good sample splitters and sampling procedures, RC results rival the accuracy of diamond core assays. Drilling penetration rates are similar to open hole drilling, and are often faster at greater depths. The sample velocity through the inner tubes can be up to 250 m/sec, so retrieval of the sample and hole cleaning is rapid. Production rates of up to 200-300m/ day are common at rates exceeding 10 m/h, many times faster than diamond drilling, and achieving rapid results for the customer. Unconsolidated formations can often be drilled and sampled without casing. Washing and scouring of the hole is minimized, because there is normally no fluid or cuttings flow against the walls after the drill bit has passed. Low impact bits, such as RC blade or RC roller, are ideal in these soft or loose formations. With good drilling techniques, samples can be kept dry, even several hundred metres below the water table. Dry samples are preferred as they split more accurately for assay, and are easier to handle. RC sample content ranges from dust to 25 mm chips, and is already partially processed for analysis. Wireline surveying of the hole is still possible through the drill rods. With the use of a stainless steel rod at the bottom of the string, hole azimuth

readings are also possible.

1. Drop Center Bit

For high penetration rates in soft to medium hard and fissured rock formations. Low to medium air pressures. Maximum hole deviation control.

2. Concave Face

The all-round application bit face specifically for medium hard and homogenerous rock formations. Good hole deviation control and good flushing capacity.

3. Flat Face Bit

This kind of face shape is suitable for hard to very hard and abrasive rock formations in applications with high air pressures. Good penetration rates an resistance to steel wash.

4. Double Gauge Face

This kind of face shape is suitable for fast penetration rates in medium to hard rock formations. Designed for high air pressures and good resistance to steel wash step gauge bit.

5. Convex Face

For high penetration rates in soft to medium-hard with low to medium air pressures. It is the most resistance to steel wash, and may reduce the load and wear on the gauge buttons, but poor hole deviation control.