Technical Details
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. This means that the impact energy does not have to pass through any joints at all. The impact energy therefore is not lost in joints allowing for much deeper percussion drilling.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.
With recent advances in technology DTH hammers and bits can now be operated to run at up to 500Psi, increasing the Rate of Penetration (ROP)
Read more about this topic: Down-the-hole Drill
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