Driving Efficiency in Global Infrastructure — High Strength DTH Solutions for Large Scale Tailrace Tunnel Projects

• Project Type : International Hydropower   Dam Construction (Tailrace Tunnel Section).
• Geological Profile : Predominantly composed of highly abrasive granite and medium hard sandstone (Protodyakonov scale f =10 -14).
• Scale : Simultaneous excavation of parallel tunnels (Tunnels No. 1 and No. 2), requiring massive air circulation (as seen in the large ventilation ducts) and continuous mucking operations.

• Connection Failure : Standard drill rods suffered from fatigue cracks at the joints due to the extreme torque and high pressure impact required for hard rock penetration.
• Accelerated Wear : The high quartz content of the rock led to rapid thinning of the pipe wall, forcing frequent tool replacements and increasing the cost per meter.
• Operational Downtime : In a complex environment with synchronized ventilation and hauling systems, any tool failure caused expensive cascading delays.

• Premium 76mm DTH Drill Pipes : Manufactured from high strength 23CrNi3Mo alloy steel, offering superior impact toughness and fatigue resistance compared to standard R780 steel.
• Friction Welding Excellence : Utilizing advanced friction welding technology, we ensured a 100% metallurgical bond between the tool joint and the seamless pipe, achieving "Zero Breakage" under high torque loads.
• Nitrided Tool Joints : To combat the abrasive nature of the sandstone, all 2 3/8" API REG threads were nitrided to enhance surface hardness and prevent galling.

• Penetration Rate Increase : Stable tool performance allowed for a 22% increase in daily drilling progress.
• Extended Tool Life : Our drill pipes lasted 35% longer than the previous supplier’s products, significantly optimizing the procurement budget.
• Seamless Completion : The reliable supply chain ensured that Tunnel 1 and Tunnel 2 stayed on schedule, securing the contractor's reputation for timely delivery.

"Reliability is the heartbeat of tunnel construction. In hard rock formations, Henglong’s DTH pipes have proven to be the most durable component of our drilling rig setup." —— Lead Site Engineer