DRY DRILLING

For our Horizontal Directional Drilling projects we use what are known as ‘dry’ drilling rigs.

Most of drilling companies, particularly the very large contractors, use drill rigs where bentonite is used as a lubrication. Bentonite is an imported material from Russia or Turkey that is used as a lubrication for drilling. It’s mixed with water and then injected down to the drill head to lubricate, to help reaming to actually remove the ground and to wash the ground out. They also then have to have a process of pumping that washed ground out, sifting it, recycling the fluid and pumping it back in.

Mole Engineering do not rely on that system for a number of reasons, including potential leaks into the water course and streams. A lot of companies don’t want bentonite used on their site because it can break out into river beds or underground reservoirs – all it needs to do is find a track or a fissure through ground and it can break out from the bore.

Here at Mole we use a unique (we may be the only contractors in the UK doing it) hammer reaming technique known as dry reaming. When we drill we use a compressed air jet to clear the head, with a pure water spray mist to keep the head cool. We use a pneumatic hammer rather than a rotating cutter and large pump motors to wash out the ground with water only – all of which helps us reduce the environmental impact of drilling.

Effectively we just expand the ground so once we drill through to our reception pit we can change the drill head into the back reaming hammer (like a torpedo with a piston inside), fit a cone to suit the diameter of the pipe (usually 30 or 50% larger than the pipe to reduce drag) and then pump down compressed air through the drill rods to this back reamer. When we start to pull back with our drill rig the head engages into the expansion cone and a hammer action cuts in, giving us a 6 tonnes pull with a hammer action – a very high tonnage which widens and displaces the ground ready for the pipe or conduit.

If you want to know more about our dry drilling rigs, give us a ring and ask – our engineers love talking about drilling!