June 28, 2016
Large size DTH hammers and bits, are most commonly used within construction projects for piling and foundation drilling. This market segment is one of our weak spots in China, and therefore one of our key focus areas for improvements this year.
On Christmas Day last year, the China CC received an order for a QL 300 with a drill bit of 1m in diameter. The products were manufactured in Zhangjiakou factory on time, in late February. Delivery in March, and start-up led by our own Product Specialist Yan-Po Wang, who also assisted and oversaw the drilling the first two weeks on site.
The drilling site is located in Hunan province, in central region of China. This large project by Hunan Environmental Protection Group is the building of a waste incineration power station. Incineration basically means the burn of waste materials to generate heat and electricity. Commissioning of the power station is scheduled for 2017.
The customer is a drilling contractor named Chongqing TED pile foundation co. LTD. They were previously using another brand of drilling consumables, made in South Korea. They realized that they were going to struggle to complete all the required holes on time. They knew about our powerful QL 300 hammer, and decided to try it, with the aim of improving the drilling productivity. At this stage of the project, their task was to drill 120 root pile holes, 1m in diameter with a hole depth of between 9 m and 25 m each. The rock consisted of Granite with a high content of quartz/silica (<50 %), and a hardness ranging from 60 to 130 MPa. The rock had a development of longitudinal cracks.
The desired hole size of 1 m (1000 mm) is actually outside the recommended hole size range for the Kukje (South Korean manufacturer) hammer. The oversized bit has a negative impact on the drilling speed due to the K640 hammers’ relatively light piston. The K640 hammer is shorter in length, and has a smaller outer diameter, which restricts the capacity and efficiency in flushing. With less than ideal flushing you will experience low penetration rate as well as excess of abrasive wear on the drill bit and the hammer.
The QL 300 require slightly more air volume to hold equally high air pressure as the K640 hammer. However, with the current air package available on the drill rig, the QL 300 still performed at a >20 % higher penetration rate, yet working on a lower air pressure than the K640 hammer.
The Atlas Copco drill bit has several advantages over the Korean made bit. The shank of the bit (the part that mounts inside the hammer) is of a different design. The bit is much heavier and stronger to start with. The 1 m diameter of the bit head is bang in the middle of the recommended hole sizes, which assures good service life and high reliability with a minimum risk of failures. Our drill bit also does not use a foot valve, which minimizes the risk for failure. The Secoroc bit also has a unique design of the flushing grooves, for more efficient evacuation of the cuttings. This adds to faster penetration rate as well as improved wear characteristics of the drill bit. Furthermore, our L-type design of drive pins helps reduce spline wear and heat to build-up.
The higher productivity from using the QL 300 helped the customer to complete the 120 root pile holes on time. “The customer is impressed by the productivity from the QL 300, who also commented on the clean holes created, which helps with the concrete pouring.” says Yan-Po Wang, our DTH Product Specialist based in China. “And for the next project the customer plans to add one more air compressor to further increase the penetration rate. To maximize the benefits from drilling with the QL 300!” adds Yan-Po.
Claes Hillblom, Regional Business Manager
“I want to congratulate and thank Yan-Po, who has done a fantastic job in supporting the Customer centre throughout the entire process in this project; from winning the order to start-up and problem solving on site. Based on this success story and the new-found knowledge about the potential business to be won in China, the Customer centre has decided to invest in their own technical sales engineers with specific focus on the construction industry and the use of large DTH products in China”
|Recommended hole size:||700-960 mm||760-1210 mm|
Hammer outer diametre:
|640 mm||660 mm|
|2200 mm||3500 mm|
|3800 kg||5100 kg|
|Piston stroke:||150 mm||101 mm|
|520 kg||1002 kg|
Air flow needed for 12 bar:
|120 m3/min||135 m3/min|
|1970 kg||3500 kg|