Double Head Drilling Method-
rotary/rotary percussion with hydraulic drifter
rotary/rotary with DTH
The special feature of this system that belongs to the overburden drilling methods is the array of the rotary heads. The double head drilling device is carried by a sled where the rear rotary head is adjustable to the front rotary head. The rotary heads are operating in counter-rotating directions.
Such counter-rotating direction of rotation makes accurate drilling possible and prevents inadvertent release of rod and casing when they are changed. With the adjustment of the rear rotary head or hydraulic drifter towards the front rotary head a control of the flushing and soil extraction is given. Drilling can be done with flushing and also without.
Drilling under the ground water level can be managed with special crown bits.
Double head drilling with two rotary heads and DTH hammer offers the same advantage. The DTH hammer is driven by the rear rotary head. With this drilling system it is possible to reach much deeper holes than with a hydraulic top hammer. Both rotary head are operating in counter-rotating directions.
Hydraulic drifter (mm / inch) |
| Casing |
Internal Rod |
| Ø 88,9 / 3,5 |
Ø 1 1/2" - T38 |
| Ø 101,6 / 4 |
Ø 1 3/4" - T45 |
| Ø 108,0 / 4,25 |
Ø 1 3/4" - T45 |
| Ø 114,3 / 5,23 |
Ø 1 3/4" - T45 / Ø 2 1/4" - T51 |
| Ø 152,4 / 6 |
Ø 2 1/4" - T51 or Ø 88,9 / 3,5 |
| Ø 177,8 / 7 |
Ø 114,3 / 4,5 |
DTH (mm / inch) |
| Casing |
Internal Rod |
| Ø 108,0 / 4,25 |
Ø 63.5 " / 2,5 |
| Ø 114,3 / 4,5 |
Ø 76,1 / 3 |
| Ø 133,0 / 5,23 |
Ø 88,0 / 3,5 |
| Ø 139,7 / 5,5 |
Ø 88,9 / 3,5 |
| Ø 152, 4 / 6 |
Ø 88,9 / 3,5 |
| Ø 177,8 / 7 |
Ø 114,3 / 4,5 |
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