Down-the-Hole (DTH) drilling plays a pivotal role in industries such as, construction, water well, geothermal, mineral exploration and oil & gas related drilling markets. A crucial component of DTH drilling is naturally the DTH Hammer, which utilizes compressed air to power the drilling process. The efficiency of this process is heavily reliant on air pressure, as it directly impacts the performance of the DTH drilling tools. From drilling speed to tool longevity, the right air pressure is essential to optimize drilling performance. In this article, we will explore the significant role air pressure plays in DTH drilling and how it affects overall performance. Understanding these dynamics will enable drilling professionals, engineers, and project managers to make informed decisions to maximize drilling efficiency.
The compressor is responsible for supplying compressed air to the DTH Hammer. Selecting the right compressor to match the DTH hammer requirements are vital to ensure consistent delivery of the required air pressure for optimal performance. A high-quality compressor ensures that air pressure is maintained consistently throughout the drilling process, preventing fluctuations that could affect the drilling efficiency.
Altitude and temperature have a direct effect on the structure or air. CFM or m³/min air adjustments should always be properly considered when drilling at altitude. As altitude increases, the air density decreases, meaning that more air pressure may be needed to achieve the same drilling performance.
For example: Operating a DTH hammer at 10,000 ft elevation (or 3000 m) at a temperature of 40 F (4.4 C) would require around 50% more energy than at sea level to drill at the same air pressure.
Increased ambient air temperatures have a similar effect on air. At high temperatures the air becomes less dense and at low temps the air becomes more dense. These differences also require an adjustment to air supply.
For example: Using a DTH hammer at sea level with ambient temperature at 100 F (38 C) versus 0 F (-18 C) would require upwards of 20% more air volume at the same air volume.
Similarly, deeper boreholes require higher air pressure to overcome the increased resistance caused by the depth. These factors must be considered when setting the air pressure and volume pressure to ensure effective hole cleaning for efficient drilling.
Drilling under high heads of water typically requires different air pressure parameters. A DTH hammer needs sufficient air pressure to overcome the back pressure in the borehole and this pressure should be calculated in accordance with the depth of water in the hole.
1 foot (or 0.30 m) of water in the borehole is = to 0.434 psi (0.03 bar) So 100 ft (30.5 m) of water in the borehole there would be 43.4 psi (3 bar) of back pressure.
Once the head of water is overcome, the air pressure should reduce to the normal or usual operating pressure. However if the inflow of water in the borehole is high, the air pressure will increase and the DTH hammer performance will reduce. In some circumstances it may be necessary to utilize a high air pressure booster compressor to allow for continuation of drilling.
Different types of DTH bit face designs are designed for specific drilling conditions. The most common design being concave face shape which is suited for most drilling conditions as it holds a very straight hole due to the tapered recess or ‘dish’ in the face of the bit. It is also known for excellent penetration rates and hole flushing. The design of the drill bit plays a significant role in determining the ideal air pressure, so if you are drilling through soft rock formations you may not require as much air pressure as one designed for hard rock formations. Understanding the specific requirements of the drill bit helps to ensure that the right air pressure is applied for optimal performance.
Leaks in the air system, such as in hoses or connectors, can reduce the efficiency of the drilling process by allowing air to escape. The longer the compressed air hose, the more likely leakage can happen. This leads to a loss of air pressure and requires the compressor to work harder to maintain the desired pressure. Regular maintenance and inspection of the air system are critical to prevent this kind of unnecessary issue and ensure consistent compressed air delivery to where it’s needed.
To maximize drilling efficiency, it is essential to optimize air pressure based on the specific conditions of the drilling project. Here are some best practices to ensure air pressure is set correctly:
The correct air pressure setting depends on factors such as the rock type, borehole depth, and the drill bit design. Drilling professionals should work closely with engineers to determine the optimal air pressure based on these variables. In general, a higher pressure is required for harder rock formations and deeper boreholes. However, excessive air pressure can also cause unnecessary wear on the equipment, so it is essential to find the right balance.
To ensure consistent air delivery, a robust preventative maintenance schedule of the compressor is necessary. The compressor is a key part of overall operation and if not looked after properly it can lead to breakdowns, reduced efficiency and costly repairs. So daily checks of the oil level, draining of receiver tank, leak inspection of the hoses and couplings and watching for any unusual readings of the gauges and indicators are a must. By doing this and keeping a well maintained compressor you are less likely to experience pressure fluctuations, which can disrupt the drilling process and affect performance.
Many mining and construction projects over the years have demonstrated the benefits of optimizing air pressure in DTH drilling. For example, in a recent project in a limestone quarry, engineers increased the air pressure settings, which resulted in a 30% improvement in penetration rate and a reduction in fuel consumption by 15%. These kinds of improvements can have a significant impact on project timelines and costs, making it essential for drilling professionals to fine-tune their air pressure settings. The selection of a premium manufactured DTH hammer such as Drill King Int’l which will help ensure your drilling project has a positive outcome
Explore DrillKing International’s full range of DTH drilling solutions today to enhance your drilling efficiency and achieve optimal results.