DTH drilling

1. Anil Kilania
Anil.kilania.min10@iitbhu.ac.in

2. DTH
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.
 It is rotary cum percussive type drilling.


3. DTH





DTH is short for “Down-The-Hole”.
Since the DTH method was originally developed
to drill large-diameter holes downwards in
surface-drilling applications.
its name originated from the fact that the
percussion mechanism followed the bit down
into the hole.
Applications were later found for the DTH
method underground.
The direction of drilling is generally upwards
instead of downwards

4. Working of DTH
In DTH drilling, the percussion mechanism
commonly called the hammer is located directly
behind the drill bit.
 The drill pipes transmit the necessary feed force
and rotation to hammer and bit plus compressed
air or fluids for the hammer and flushing of
cuttings.
 The drill pipes are added to the drill string
successively behind the hammer as the hole gets
deeper.
 The piston strikes the impact surface of the bit
directly, while the hammer casing gives straight
and stable guidance of the drill bit.


5. Working of DTH
The impact energy therefore is not lost in
joints allowing for much deeper percussion
drilling.
 This means that the impact energy does not
have to pass through any joints at all.
 This is a Great break through for smaller
portable water well drilling rigs, that before
were limited.
 The DTH on smaller rigs now can get same
results as large heavy truck rigs.


6. DTH drilling

8. By DTH we can drill up to
4500 meter

9. Uses of DTH
Mining- Drill & Blast holes in Open Pit mining,
Where the drill operator will drill several holes.
 Then fill with explosives and detonate to lift rock
allowing access to ore body RC- Exploration & Pit
grade control GW- Geothermal Bore Holes &
Water wells Oil & Gas- Deep well Bore Holes
Construction- Piling, Footings.
 DTH drilling is used in the construction
industry to produce piles into rock, also water
wells, and drilling bores for geothermal ground
source heat pumps.


10. DTH Drilling Tool

11. Comparison

12. Comparison

13. Comparison

14. Parameters
DTH Hammer
Drilling
(cost/hour)(40 m)
Rotary
Drilling
(cost/hour)(24 m)
Depreciation
Rs.
Rs. 1441
Repairing
Rs. 1000
Rs. 785
Hammer
Rs. 993
Rs.-----------------
Drill Bits
Rs. 292.72
Rs. 397.00
Drill Tubes
Rs. 330.84
Rs. 74.5
Dust collection
Rs. 62.03
Rs. 62.03
Labour
Rs. 537.62
Rs. 537.62
Fuel
Rs. 893.27
Rs. 635.22
lubricants
Rs. 181.96
Rs. 165.42
Total cost
Rs. 6064
Rs. 4098
Cost/meter
Rs. 151.6
Rs. 170.75
1772