Down-the-Hole Drilling Rig Operation Technology Strategy

Table of Contents

With the continuous development of modern engineering construction, DTH drilling rigs, as efficient drilling equipment, are widely used in various foundation engineering, mining, and other fields. However, for many beginners, mastering the efficient and safe operation of DTH drilling rigs can be challenging. This article provides a practical strategy for operating DTH drilling rigs, helping you acquire the necessary skills and enhance work efficiency.

Difference between a DTH drilling rig and a conventional drilling rig

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Conventional drilling rigs use the power of an electric motor or a diesel engine, which is transmitted to the turntable through the operating system to drive the drill bit connected to the drill rod to grind and cut the rock to achieve the purpose of drilling. This kind of drill first solves the ground power. This type of drilling rig primarily relies on ground power, utilizing electricity as its power source. Additionally, it requires a transmission system to function. Moreover, it consumes a significant amount of circulating water, making it particularly challenging to operate in areas with limited access to electricity or water. Therefore, the limitations of this drilling method are significant. Conventional drilling rigs have cumbersome groundwork in bedrock drilling, frequent lifting and lowering of the drill, large labor consumption, slow speed, and comprehensive calculation of capital consumption, and these disadvantages are difficult to change.

DTH drilling rigs mainly use compressed air. Its basic principle is that several air compressors, a booster, the output of high-pressure air through the drilling rig’s drill pipe to the bottom of the hole in the hammer, which blows the hammer piston to hit the carrying bit and then breaks the rock at the bottom of the hole, and then by the rotating drilling tool through the connection of the drill bit will be broken rock shear into debris, carried by high-pressure air out of the hole.

Operation technology of the DTH drilling rig

Mastering the rotational speed of the drilling rig, wind pressure, wind volume, and pressure on the drill bit

The impact force of the DTH hammer, the pressure of the drilling tool on the drill bit, and the speed of the drilling rig are directly related to the drilling speed of the drilling rig. Its impact force is related to the air volume and air pressure supplied (the air volume and air pressure specifications can be found in the user manual of the hammer). In practice, the air pressure and air volume can be slightly higher than the specified values in the manual to increase the impact force of the hammer on the drill bit, but not too high, or else the piston of the hammer will have the consequence of breaking the drill bit. The pressure of the drilling tools on the drill bit should not be too high. No matter how deep the hole is or how heavy the drilling tool is, it must always maintain a consistent and uniform pressure to work. Otherwise, it will not be able to make the drilling speed and quality to receive good results.

The operation method of continuous drilling tools release

During drilling, the operator swings the drilling tools down the hole intermittently according to the sound of the hammer and the stability of the drilling rig turntable.

Specific operation method: whenever drilling begins, the operator must swing the drilling tools gradually to the bottom of the hole. When the frequency down the hole reaches 700~900 times/min and the pressure of the drilling tool on the drill bit reaches about 3kN, it can be the best impact speed. At this point, the operator should halt the swinging of the drilling tools until the impact frequency decreases significantly and the rotary disk of the drilling rig shakes slightly. It is considered the interval time for swinging the drilling tools back to the bottom of the hole again. After re-swinging the drilling tools, the process described above is repeated. It is the drilling method of intermittent tool swinging. This method of slagging times and slagging requirements with other methods are no different, generally about half a meter to clear the hole, slagging once.


  • Through the impact sound of the hammer at the bottom of the hole and the change in the smoothness of the drilling rig’s turntable, we can judge the size of the pressure of the drilling tool on the drill bit and decide the time of swinging the drilling tool. We can also adjust the time interval of swinging the drilling tool at any time according to the softness and hardness of the rock at the bottom of the hole.
  • The verticality of the drill hole is relatively high.

In addition, since this method can intuitively listen and observe the situation, it is easier to master and more practical for beginners.

Disadvantages: the drilling speed is slightly slower.

The operation method of continuous swinging drilling tools

Before using the continuous volatile drilling tool drilling method, you should drill using the intermittent drilling method. After mastering the hardness of the rock to be drilled and the optimal feed rate, transition to the uniform drilling process.

In uniform drilling, the operator must accurately grasp the relatively uniform pressure and moderate speed to swing the drilling tools down the hole. It helps to maintain the impact frequency of the hammer within the fastest impact range down the hole, which benefits various factors related to drilling. Reaching this level can be regarded as reaching the best working state, and drilling can achieve significantly faster results.

To make good use of the method of drilling by continuously swinging and releasing drilling tools requires the operator to have a relatively skilled DTH hammer operation technology, concentrate on the work, listen carefully to the impact sound from the bottom of the hole to judge its frequency, observe the tightness of the lifting hook, observe the stability of the drilling rig turntable, and pay attention to various related factors related to drilling, whether they are within the optimal range. To accurately grasp this, it’s essential to drill for a period while periodically changing the drilling method to check if the volatile drilling tool speed is correct, making timely adjustments to maintain it in the optimal state. Beginners should avoid using continuous drilling methods initially, as it can lead to potential issues.


By mastering these operating skills, you can enhance your utilization of the DTH drilling rig for engineering construction work, improving work efficiency and safety. Additionally, I hope everyone continues to learn and explore new technical methods, making significant contributions to modern engineering construction.

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