Setting up for RC Drilling

When setting up or buying a rig to commence RC drilling there are a lot of factors to consider. Initial costs are high so you need to get it right the first time. Talking to peers in the industry plus rig and consumable manufacturers is a great way to get firsthand experience so that costly mistakes can be avoided. Harley Hollier from Harlsan Industries, a leading consumable supplier highlights the importance of paying careful attention to initial equipment purchases.

Choices like the type, configuration and setup of a rig has downstream affects on production rates, downtime, profitability and operator safety.

There are two types of RC Drilling

RC with hammer, used in medium and hard rock and can reach depths up to 800m. Rods are usually 4’’ and 4 ½’’ diameter.

Aircore, to drill softer oxide and clay ground to depths of 100m using Air Core & Vacuum Bits. Rods are normally 3’’ to 3 ½’’. Some companies will specialise in Aircore Drilling.

Rig Carrier Type – Truck v Track Mounted

Track based, deep hole RC exploration rigs are a more stable platform therefore giving better hole alignment and less hole deviation. Track based rigs are appealing to clients as they can reach depths of up to 800m and also reduce the impact on the environment because they are more manoeuvrable with a smaller footprint.

A truck mounted rig has the primary advantage in that it can be driven long distances between drilling sites whereas a track mounted rig needs transporting on a low loader. Modern eight wheel drive trucks can also access increasingly rugged terrain.

Ancillary equipment like support trucks & vehicles

As well as the drilling rig, reverse circulation setups usually consist of a support vehicle, an auxiliary vehicle & 4wd light vehicles.

The support vehicle is normally a truck in the range from a 3 tonne 4WD truck (which can hold 1,000 litres of fuel & 750 litres of water) up to a full sized 8 x 8 which can carry 6,000 litres of fuel, 2,500 litres of water, 300m of 4 ½’’ spare rods and other supplies needed for maintenance.

The auxiliary vehicle is normally required to transport auxiliary compressor & booster units when drilling deeper holes requires boosted air. If drilling is to continue at night lighting plants will also be needed.

Compressors

RC rigs have their own compressor and sometimes a booster to generate air pressure. Compressors on an RC rig normally have an output of around 1000 cfm at 500 psi (500 L·s-1 at 3.4 MPa). The depth of hole that can be drilled will be determined by the amount of air.

If extra air pressure is needed to drill deeper holes the engines are mounted on the auxiliary vehicle. A fairly standard set up would be an RC rig with on-board air of 1350cfm/500psi which would achieve drilling depths of 300-400metres. If required an Auxiliary Booster Air Truck can be added upping the capabilities to 2700cfm/1000psi and increasing hole depth to 800metres.

Drillstring

Once a drilling company has purchased a new rig they will need to fit it with a drill string. The drill string covers the consumables and includes Wear Bend/Deflector Box, Hydraulic Blowdown, Inlet Swivel, Adapter & Saver Subs, RC Drill Rods, DTH hammer or Air Core Bits

There are a number of different variations to how the drill string can be set up, so taking the time talking to a supplier who knows the industry is critical.

A good starting point would be to vist Harlsan Industries at www.harlsan.com.au. They regularly help drillers can make the right decisions based on their years of experience designing, manufacturing & supplying RC drilling consumables.

Sampling

The sole purpose of RC drilling is to obtain accurate samples of the ground being drilled. The sample travels up the inner tube and is usually diverted 90 degrees at the wear bend or deflector box to slow down the speed of the sample.

A knock on nut connects the sample hose to the deflector box which usually has a ceramic or metal wear plate that is easily replaced in the field. The sample then travels through the sample hose to the cyclone which further slows down the sample and also separates the sample from the air which goes out through a dust collector.

A good cyclone is critical to obtain accurate samples. At the bottom of the cyclone is the dump box. As one sample is in the dump box another is collecting in the cyclone so there is no need to stop drilling during the sampling process. From the dump box the sample is dropped into the splitter which reduces the size in a range from 6.25% to 12.5%.

A list of equipment for a standard RC drilling rig

• Top Hydraulic Drive
• Compressor (preferably around 750 HP, 1250CFM/350psi)
• 200 metre capacity automated rod handler
• Hands free automated breakout system
• Down hole survey 400mtr x 6mm non rotating wire line
• Heavy duty 2 metre mast dump feed system with 19000kg variable pull back
• 12,300kg variable pull down
• Cyclone sample & SP1 horizontal
• Support truck

These specifications are suitable for any RC drilling requirements, including grade control, mineral exploration, resource definition and water bores etc.

For RC Sampling the cyclone and splitter can be mounted on the drilling rig or on a separate truck or trailer. The advantage of a separate trailer mounted cyclone & splitter with dust suppression is that it provides accurate sampling in a hazard free environment away from the rig.

Personal Protective Equipment – PPE

Drilling companies provide PPE. An example of equipment that may be required is listed below from the “NT Government Geological Survey 2004/2007, Drilling Manual.”

• Head: hard hats (AS1800, 1801, 2210) must be worn within 30 m of the rig. Note that metal hard hats are not permitted; allowable accessories include sun brim, visor-type face shield, earmuff attachments, lampholder. Long hair must be restrained, even when a hard hat is worn.
• Eye: safety glasses (AS1336:1982, AS1337), tinted or otherwise; welding shields (AS1338): a full-face shield is to be worn when cutting core. Filters in fluoroscopes and UV boxes (AS1338 Part 2)
• Hearing: hearing protection device shall provide protection to a level not exceeding 85 dB (AS1270). This can be earmuffs, disposable ear plugs or both, such that they do not compromise other safety equipment
• Respiratory: respiratory protection against dust (AS1715, AS1716). Breathing apparatus may be carried on some rigs and its use requires formal training
• Skin: sunscreen and insect repellent will be supplied by the employer
• Hand: general work gloves (AS2161), welding gloves (AS1558)
• Foot: safety boots (AS2210) with a steel toe cap must be worn by all personnel within 30 m of an operating drill rig;
• Clothing: safe and adequate clothing, no loose clothing, a UPF (UV) rating of 50+. Some companies stipulate that long-sleeved shirts and long trousers be worn on drill rigs; welding apron, raincoats
• Harness: all personnel aloft must have a safety belt or safety harness (AS1891, AS2626). Note that these standards forbid the use of harnesses made from leather or natural fibre webbing. No tools to be hand carried into the mast

 
Source http://www.nt.gov.au/d/Minerals_Energy/Geoscience/Content/File/Pubs/Record/NTGSRec2004-007.pdf