Down the Hole Hammers (DTH) | 電影影評網
![Down the Hole Hammers (DTH)](https://i.imgur.com/FK6P5g9.jpg)
Asaruleofthumb,aDTHhammerusedinproductiondrillingshouldbereplacedwhenithaslost10%innetpenetrationrate.Thetotaldrillingcostpermeter ...
![Down the Hole Hammers (DTH)](https://i.imgur.com/FK6P5g9.jpg)
Selecting the right hammer
The optimum range of hole size for DTH drilling is 90 mm (3.5”) to 254 mm (10”). Smaller holes are generally drilled using tophammer drill rigs, and larger holes generally use rotary drill rigs.
As a rule of thumb, the smallest hole diameter a DTH hammer can drill is its nominal size. i.e. standard 102 mm (4”) hammer will drill a hole down to a minimum diameter of 102 mm (4”). The limiting factor is the outside diameter of the hammer, because as the hole diameter reduces due to diameter wear of the bit, airflow is restricted. Maximum hole size for production drilling is the nominal hammer size plus 25 mm (1”), so for a 102 mm (4”) hammer the maximum hole size is 127-130 mm (5”).
Choosing the right hammer is largely determined by type of application, hole size and type of rock formation. Ideally, the ...
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![](https://i.imgur.com/FK6P5g9.jpg)
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