In the mining industry, with continuous technological advancements and increasing resource scarcity, enhancing extraction efficiency, reducing costs, and ensuring operational safety have become crucial for sustainable development. Down-the-hole (DTH) hammers are advanced drilling tools that play an increasingly vital role in mining due to their efficiency, energy-saving properties, and adaptability. They enable rapid rock fragmentation and efficient drilling while reducing tool wear. This extension of their lifespan provides significant economic and social benefits to mining companies. This article explores the efficient application of DTH hammers in mining, analyzing their working principles, advantages, key construction points, and factors affecting drilling performance, providing valuable insights for mining operations.
Overview of the Working Principle of DTH Hammers
A DTH hammer generates high-frequency impact forces through compressed air, effectively breaking rocks during drilling. Unlike traditional rotary drilling methods, DTH hammers utilize impact energy to achieve volumetric rock fragmentation while using exhaust gases to expel cuttings from the hole, enhancing drilling efficiency and reducing tool wear.
Advantages of DTH Hammers
High Drilling Efficiency: DTH hammers use high-frequency impacts to fracture rock, significantly increasing drilling speed, particularly in hard and abrasive formations.
Reduced Energy Consumption: Compared to traditional rotary drilling, DTH hammers require less energy for the same drilling depth, helping companies lower operational costs.
Improved Hole Quality: DTH hammer’s drilled holes feature smooth walls and minimal deviation, enhancing the efficiency and safety of subsequent operations.
Strong Adaptability: DTH hammers are suitable for various geological conditions, including hard rock, soft rock, frozen ground, and fractured zones, offering broad applicability.
Ease of Operation: The operation of DTH hammers is relatively straightforward, requiring lower technical skills from operators, which facilitates training and promotion.
Construction Steps and Key Operational Points
The construction process for DTH hammers includes hole opening, drilling, rod connection, and hole relocation. Key operational points to consider during the process include:
Hole Opening: Before drilling, verify the drilling position to ensure it meets design requirements. Open the water valve first, followed by the air valve, and initiate the rotary head at low pressure or floating advancement. Once the drill bit reaches a certain depth (e.g., 500mm to 800mm), operate the “advancement” handle to retract the rotary head for cuttings removal. After cleaning out the cuttings, correct the drilling angle and continue drilling.
Drilling: Monitor the equipment’s performance closely during drilling and adjust the advancement pressure as needed to avoid issues like jamming. Record the drilling footage for subsequent analysis.
Rod Connection: When one drill rod is fully in the hole, connect another rod to continue drilling. Ensure that the rods’ threaded connections are lubricated to minimize wear and ensure sealing. Also, prevent debris from entering the airline to avoid safety accidents.
Hole Relocation: Before moving the rig, raise the guide rails and check the air and water supply lines and control box connections for potential damage. During relocation, stop supplying air and water to the drill rig and ensure the equipment is stable and safe.
Factors Affecting DTH Hammer Drilling Performance
Drilling Pressure
The static weight applied to the drill bit is a crucial factor affecting drilling efficiency. When using pneumatic DTH hammers, one must consider drilling pressure, rock hardness, drill rig performance, and tool compatibility.
- Rock Hardness: In soft to medium-hard rock formations, increasing drilling pressure can significantly enhance efficiency. However, excessive pressure in hard rock can lead to rapid bit wear and decreased efficiency.
- Drill Rig Performance: The drilling capacity and stability of the rig determine the acceptable range for drilling pressure. High-performance rigs can handle greater pressures for more efficient drilling.
- Tool Compatibility: The material, size, and structure of the tools should match the drilling pressure to ensure stability and durability during the drilling process.
Rotary Speed
The rotational speed of the drill bit during drilling is critical for optimizing impact position and preventing repetitive fracturing.
- Impact Interval: An appropriate rotary speed ensures optimal impact intervals on the rock. Excessively high speeds may lead to repeated fracturing at the same spot, reducing efficiency, while too low speeds may not fully fracture the rock.
- Rock Layer Characteristics: Different rock layers require varying rotational speeds. Higher speeds may improve efficiency in soft formations, while lower speeds may reduce wear and improve efficiency in hard rock.
Air Speed and Volume
Airspeed and volume are two essential factors in the pneumatic DTH drilling process. They directly impact the flow of air within the hole and influence cutting removal and drilling efficiency.
- Air Speed: The upward airspeed is critical for effectively removing cuttings. Insufficient airspeed can lead to cuttings accumulation, hindering drilling, while excessive airspeed may increase energy consumption and noise. Typically, the upward speed for full drilling is controlled between 20 m/s and 25 m/s, while for core drilling, it ranges from 10 m/s to 15 m/s.
- Air Volume: The amount of air affects the flow rate and velocity within the hole. Sufficient air volume ensures efficient removal of cuttings while maintaining hole cleanliness. However, excessive air volume may lead to increased energy consumption and wall washing, while inadequate volume may fail to meet cutting removal needs. In practice, air volume selection should be calculated based on hole diameter, rod outer diameter, and hole depth.
Adjusting parameters such as drilling pressure, rotary speed, air speed, and volume is crucial for optimizing drilling performance.
Applications of DTH Hammers in Mining
Iron Ore Mining: In iron ore extraction, DTH hammers can efficiently drill through hard iron ore layers, increasing mining efficiency. Their low energy consumption and high-quality drilling results also help reduce extraction costs and improve ore recovery rates.
Gold Mining: Gold mining often encounters complex geological conditions, such as faults and fractured zones. DTH hammers, with their robust breaking capabilities and adaptability, can maintain stable drilling under these challenging conditions, ensuring smooth mining operations.
Coal Mining: In coal mining, DTH hammers enhance drilling speed and minimize damage to the coal seam roof, reducing safety risks. Their low noise and environmentally friendly features meet modern coal mining’s sustainability requirements.
Non-Metallic Mineral Mining: In the extraction of non-metallic minerals like limestone and gypsum, DTH hammers also perform exceptionally well. Their efficient drilling speeds and good hole quality contribute to improved extraction efficiency and product quality.
Conclusion
The use of DTH hammers in mining significantly improves drilling speed and efficiency, lowers energy consumption and costs, and demonstrates strong adaptability and flexibility to handle various complex geological and rock conditions. By precisely controlling key parameters such as drilling pressure, rotary speed, air speed, and volume, DTH hammers achieve effective rock fragmentation and rapid cuttings removal, bringing unprecedented convenience to mining operations. With ongoing technological advancements and deepening applications, DTH hammers will play an increasingly important role in future mining operations, driving the industry toward greater efficiency, environmental sustainability, and innovation. We believe that with the support of advanced technologies like DTH hammers, the mining sector is poised for a brighter future.
