Reverse Circulation Rotary Drilling Rig
RC drilling is similar to air core drilling, in that the drill cuttings are returned to surface inside the rods. The drilling mechanism is a pneumatic reciprocating piston known as a "hammer" driving a tungsten-steel drill bit. RC drilling utilizes much larger rigs and machinery and depths of up to 500 meters are routinely achieved. RC drilling ideally produces dry rock chips, as large air compressors dry the rock out ahead of the advancing drill bit. RC drilling is slower and costlier but achieves better penetration than RAB or air core drilling;
Drilling capacity with Reverse Rotary Rigs 1200 feet to 2000 feet
Direct Circulation Rotary Drilling Rig
Direct push technology includes several types of drilling rigs and drilling equipment, which advances a drill string by pushing or hammering without rotating the drill string. While this does not meet the proper definition of drilling, it does achieve the same result — a borehole. Direct push rigs include both cone penetration testing (CPT) rigs and direct push sampling rigs such as a Power Probe Direct push rigs typically are limited to drilling in unconsolidated soil materials and very soft rock. CPT rigs advance specialized
Drilling capacity with Direct Rotary Rings up to 1500 feet
A Down-The-Hole Drill is called DTH in most drilling terms. The down-the-hole drill is basically a mini jack hammer that screws on the bottom of a drill string. The fast hammer action breaks hard rock into small flakes and dust and is blown clear by the air exhaust from the DTH hammer. The DTH hammer is one of the fastest ways to drill hard rock. Now smaller portable drillcat drilling rigs with DTH hammers can drill as fast as much larger truck rigs
This drilling is used most frequently in the mineral exploration industry. (This tool is also known as a Down-the-hole drill.) The drill uses a pneumatic reciprocating piston-driven "hammer" to energetically drive a heavy drill bit into the rock. The drill bit is hollow, solid steel and has ~20 mm thick tungsten rods protruding from the steel matrix as "buttons". The tungsten buttons are the cutting face of the bit. The cuttings are blown up the outside of the rods and collected at surface. Air or a combination of air and foam lift the cuttings.