A down-the-hole drill, usually called DTH by most professionals, is basically a jackhammer screwed on the bottom of a drill string. The fast hammer action breaks hard rock into small cuttings and dust that are evacuated by a fluid (air, water or drilling mud). The DTH hammer is one of the fastest ways to drill hard rock. The system is thought to have been invented independently by Stenuick. Origin of the nameDTH 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 mechanis. .
In DTH drilling, the percussion mechanism – commonly called the hammer – is located directly above the drill bit. The drill pipes transmit the necessary feed force and rotation to the hammer and the bit, along with the flui. .
A is first thought to have been used for rock drilling in 1844. Many quarries used hand held tools that required the driller to suspend himself from a rope over the quarry face in order to place the drill hole in.
[pdf] When the temperature of the oil measured by the sensor of the temperature control valve is lower than the action value (generally 70 - 85 degrees), the lubricating oil directly returns to the main engine from gas cylinder; when the oil temperature is higher than the action value, the temperature sensor of the temperature control valve is driven by the sleeve to push away the valve core, open the bypass valve, and let the lubricating oil enter the cooler for cooling (the higher the temperature, the larger the bypass valve is opened), and then the cooled lubricating oil to the main engine, so as to control the exhaust temperature of the air compressor during operation.
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