Factors Affecting DTH Hammer Drilling

Table of Contents

The DTH hammer is a working device that connects DTH drill bits and DTH drills. This efficient drilling tool finds widespread application in petroleum, geology, minerals, and other resource exploration and development fields. With the rapid development of the economy, the market demand for it is increasing. Due to the complex underground environment, the drilling efficiency of DTH hammers is affected by many factors.

DTH hammer

Geological conditions

Geological conditions are the primary factor affecting DTH hammer drilling. The hardness, abrasiveness, brittleness, joints, fissures, and other characteristics of the rock influence the drilling speed. For example, when drilling in hard rock, the wear of the hammer will be accelerated, thereby reducing drilling efficiency. Facing different geological conditions, we should choose the appropriate hammer and drill bit and adjust the drilling parameters.

Equipment performance

The impact of equipment performance on DTH hammer drilling should not be overlooked. Factors such as axial pressure, rotary speed, water injection, and lubrication of the equipment play a crucial role in determining drilling speed and efficiency.

Axial pressure

When drilling holes below φ200mm, the axial pressure is usually less than 16000N. Tests have shown that increasing axial pressure cannot significantly increase the drilling speed, but can only increase drilling wear and the chance of the alloy column falling off.

Axial pressure is primarily employed to counteract the counter-impact force during impact work, ensuring continuous contact between the drill bit and the rock at the bottom of the hole. Each DTH hammer has its axial pressure and a suitable axial pressure section, and there’s an appropriate axial pressure section for optimal performance. The required axial pressure varies with working air pressure, increasing as air pressure increases. In proper operation, the minimum axial pressure is the piston area of the DTH hammer multiplied by the air pressure. Operators can also make real-time adjustments based on factors such as drill bit type, geological conditions, and drilling efficiency.

When drilling holes below φ200mm, the axial pressure is usually less than 16000N. Tests indicate that increasing axial pressure doesn’t significantly boost drilling speed but only increases the chance of drilling wear and alloy column dislodgement. Therefore, maintaining an optimal axial pressure is crucial for efficient and sustainable DTH hammer drilling.

DTH drilling tools

Rotation speed

The rotation of the DTH hammer during the drilling process has two functions. Firstly, it rotates the drill bit edge to a specific angle in preparation for the next impact. Secondly, it contributes to cutting the rock. However, in hard rock, the cutting effect is relatively limited. The rotational speed of the DTH hammer is initially determined based on factors such as impact frequency, the characteristics of the rock, and the diameter of the hole being drilled. Additionally, it can be dynamically adjusted at any point during the drilling operation in response to changes in drilling speed. This adaptability ensures that the rotational speed remains optimized for efficient and effective drilling throughout the process, accommodating variations in geological conditions and operational requirements.

Water injection

Injecting water into the pressurized airflow during the rock drilling process is a beneficial practice, particularly for effective and economical dust removal. This method also helps in cooling the compressed air entering the DTH hammer. However, it’s not beneficial to the drilling speed or the service life of the drilling tools. For drilling with a DTH hammer, water injection is generally not required. However, if there is a small amount of water seepage during the drilling process, rock powder forms a viscous substance that gradually adheres to the hole wall, DTH hammer, and the outer diameter of the drill pipe, resulting in the formation of a very hard “rock wall,” it becomes necessary to inject 8-15L/min of water. Simultaneously, stop impacting and rotating, lifting up and down, and blowing to decompose the “rock wall.” Subsequently, inject water into the drilling in the pressurized airflow until there is a certain amount of water influx.


The primary objectives of lubrication encompass diminishing friction, thwarting corrosion, and sealing gaps. Upon the initiation of a new Down-The-Hole (DTH) hammer or the revival of a stored unused one, it is imperative to administer approximately 100ml of lubricant directly into the DTH hammer through the air inlet of the connector. Likewise, when the DTH hammer is in operation and the well is flushed with water or a foaming agent, it is necessary to inject oil directly into the DTH hammer post-operation. During rock drilling, lubrication for the DTH hammer is lubricated by lubricating oil mixed with compressed air. The mixing of lubricating oil and compressed air is achieved through an oil injector. In the DTH hammer, too much or too little lubricating oil will cause abnormal drilling and even weak or no impact.

DTH drilling tools

Method of operation

The impact of operational techniques on Down-The-Hole (DTH) hammer drilling holds significant importance. Adhering to correct operating procedures is pivotal in ensuring the smooth functioning of the equipment and enhancing drilling efficiency. Employing sensible drilling pressure and rotational speed, for instance, proves instrumental in mitigating equipment wear and circumventing potential failures. Furthermore, the proficiency and experience of the operator stand as crucial determinants influencing drilling efficiency.

Environmental factor

Environmental factors exert a notable influence on Down-The-Hole (DTH) hammer drilling. For example, climate conditions, topography, and groundwater conditions will all affect drilling efficiency. Adverse weather conditions, including heavy rain and strong winds, can potentially lead to equipment damage or failure. In the case of complex topography, more sophisticated drilling techniques become imperative, involving adjustments to the drill bit angle or altering the drilling direction. In the case of rich groundwater, waterproof measures need to be taken to avoid equipment damage by moisture.

In summary, DTH hammer drilling is subject to numerous influencing factors. Enhancing drilling efficiency requires taking into account relevant factors and implementing corresponding measures. Only in this way can the high efficiency of DTH hammer drilling be ensured.

Picture of Kelleg


Your reliable partner in the field of geotechnical engineering.

Get "Kelleg Company Profile and Product Brochure" now

  • 20.9Mb, we will send it to your email after submitting.
  • Your email information is absolutely safe, and we will not disclose it to third parties for any reason.

Can't get enough?

Get all latest news, exclusive offers and updates on new arrivals.



We will contact you within 1 working day, please pay attention to the email suffix “@kellegco.com