Drilling evolution

25 April 2008

Contractors Leighton and Kumagai are using six Tamrock jumbo drilling rigs to construct the 2.1 km l

Contractors Leighton and Kumagai are using six Tamrock jumbo drilling rigs to construct the 2.1 km long dual three lane Eagle's Nest Tunnel for Hong Kong's Highway 8 project.

Drilling is used in a wide range of different applications from foundations and tunnels in construction through to exploration, quarrying and mining. But whatever the job, construction companies and quarry operators are constantly looking for ways to save time and money. Therefore the pressure is always on drill rig and component manufacturers to find innovative solutions that increase productivity without compromising safety.

Surface solutions

One innovation which has already delivered significant accuracy and efficiency benefits to other construction markets - and is soon to make its drilling debut - is satellite positioning technology. Atlas Copco has developed a Global Positioning System (GPS) option for its ROC D7C and ROC F9C in response to specific requests from clients in Scandinavia and global demand for greater productivity and accuracy.

According to Atlas Copco, GPS adds a new dimension to the existing automation on the D7C and F9C rigs. “GPS allows the rigs to accurately complete pre-planned drill patterns and can provide records of hole alignment, burden and spacing. The system also allows the operation of the rig to be integrated with other equipment on site,” said Atlas Copco product manager Lennart Lundin.

“The system has an in-cab display panel which guides the driller through a short series of displays which deliver instructions on the location, depth and orientation of the next hole.”

Use of GPS for hole positioning removes the need for surveyors to mark out positions on larger projects before drilling gets underway and, on smaller schemes, drillers will no longer have to refer to paper plans to set up each hole themselves. The system can also be used to create accurate drill logs and transmit them to the office at the end of a days work.

“We expect the system to deliver substantial saving in both time and money,” said Mr Lundin. “The GPS system will be particularly beneficial to operators when setting up in poor light or bad weather conditions. “More precise drilling patterns will also deliver better blasting results,” he added.

Reducing noise emissions is another issue which is being faced by the whole of the construction industry and the surface drilling sector is no exception. Atlas Copco is believed to be the first to address the problem with the launch of its Silenced ROC D7C rig which the company claims is 10dB(A) quieter than other rigs on the market.

“In many countries noise restrictions are imposed on drilling work in urban areas. But the Silenced ROC D7C's silencing system makes it possible to drill anywhere and is the ideal choice for small and medium sized quarries and civil engineering work,” said Atlas Copco Surface Drilling Equipment manager Anders Hedqvist.

“Drilling noise from a standard rig is generated by vibration in the drill stem, feed system, boom and body of the rig. The design of the new ROC D7C includes components selected specifically to reduce the overall noise level but the most noticeable difference from a standard rig is the hood that covers the mast.”

Tamrock's latest surface rig range - Ranger Rock Pilot series - has also been designed to improve both drilling and environmental performance. The rigs feature a customised version of Tamrock's Rock Pilot hydraulic control system, originally developed for the Pantera rigs. The company claims that the Rock Pilot system helps operators to maintain performance and achieve straight holes, even in difficult ground conditions.

To reduce dust emissions, the Ranger series features high suction capacity dust collectors which have been designed to reduce both noise and power consumption. The three model range is equipped with high rotation torque HL series hydraulic top hammer rock drills and can drill holes of between 64 and 127 mm diameter. The new rigs also have larger fuel tanks - +30% larger compared to the previous model - which Tamrock claims will allow the rig to continue operating for up to 12 hours without the need to refuel.

Atlas Copco has also announced an upgrade of the ROC D5 and ROC D7 rigs with the addition of the new Tier 3/Stage IIIA Cat 6.6 engines, which offer -10% lower fuel consumption. The rigs also now feature a stiffer boom for better collaring and more stable drilling and the D7 can also be fitted with Atlas Copco's Silencing Kit or soon to be launched Long Mast.

Boart Longyear's Minisonic exploration rig is now available worldwide and completed its first project outside of the US last year. Rio Tinto successfully used the rig for exploration of mineral deposits near Mandena on the Indian Ocean island of Madagascar and is now being trialled in Australia.

Boart Longyear's sonic drilling technique uses high speed vibration passed down through the drill head and rod to the drill bit to displace and fracture rock. The system can be used to extract core samples, which was key factor in Rio Tinto's use of the system in Madagascar.

Surface exploration is also the focus of the latest rig from Atlas Copco Craelius. The Christensen CS14 is a trailer mounted rig and replaces the CS1000 p6L but, according to the company, is still based on the Christensen concept which it claims uses simple technology to deliver high capacity and reliable performance.

The new rig is powered by a Tier 2/Stage II Cummins engine and can drill holes up to 1200 m deep using N-size (76 mm diameter) equipment. The rig is designed for use in extreme conditions and can operate at altitudes of up to 3500 m without alteration and in ambient temperatures of up to 50 °C.

Underground

Atlas Copco has also been looking at improving drilling productivity for tunnelling applications and will unveil the Rocket Boomer E-Series at Intermat in Paris, France in April. According to the company, the new rig has been designed to speed up the drilling cycle and to minimise both under and over break.

The rig will be equipped with COP 3038 rock drills, which Atlas Copco claims are the fastest in the world, and the new BUT 45 booms, which have a 2.5 m extension and provide improved stability and positioning. Operator comfort has also been improved with arm rest controls and an ergonomically designed control panel and a colour display panel.

Tamrock's latest offering for the underground drilling market is the Axera range of mining jumbos. The new Axera 7 is a twin boom jumbo replaces the D07 model and the largest machine in Tamrock Axera range.

The Axera 7 is designed for applications where the heading size ranges from 4 by 4 m up to 6 by 6 m. The machine features the new Tamrock HLX5-series hydraulic rock drill which has a percussive power rating of 20 to 22 kW and can drill holes between 43 and 64 mm in diameter for blasting, rock bolting or cross cuts.

Tamrock has also upgraded and renamed the full power single boom D05 and compact twin boom D06 models as the Axera 5 and Axera 6.

Drills and hammers

Atlas Copco has recently added three new rock drills to its range - the heavy duty 21 kW COP 2160 and 25 kW COP 2560 and smaller 11 kW COP 1132.

The COP 2160 and COP 2560 are designed for continuous drilling in the 89 to 127 mm range and built for use on any Atlas Copco ROC surface drill rig with Secoroc T51 or the new ThunderRod T60 drill steel. Both drills are equipped with a dual damping system which enables a higher impact without compromising the service life. The high drill steel torque of 1810 Nm also helps minimise the risk of jamming.

Hydraulic oil lubrication of the gear mechanism has replaced manual lubrication, which reduces maintenance and improves cooling, allowing higher power use and decreasing wear under prolonged loading. Separate lubrication of the shank adaptor and front bushing ensures both adequate lubrication and cooling during heavy use and also prevents contaminants from entering the drill at the front end.

The lighter weight COP 1132 offers the same 33 to 51 mm hole range as its predecessors but has +30% more speed and Atlas Copco also claims that it is the smallest rock drill in the world with a hydraulic double damper. According to the company this feature helps to combine fast drilling with good drill steel economy.

The COP 1132 is also 200 mm shorter than the previous COP 1032 model which allows use of longer rod and fewer changes or joints and makes the drill -30% lighter too. The cutting angle of the COP 1132 is also smaller than it was on the COP 1032 which improves operation in confined spaces.

Halco Drilling International has recently launched a new range of down the hole (DTH) hammers and bits. According to Halco, the NT4, NT5 and NT6 hammers have a simple but robust design which very few parts to create them both user friendly and reliable. The NT4 hammer features Halco's new shank which has a simple geometry to withstand the extra power and 12 splines to increase the contact drive area and reduce wear.

The standard NT hammer is designed for high production drilling of blast holes, water wells and geotechnical applications but Halco has also developed additions to the range for specialist applications. The NT HD has been designed for the same applications as the standard NT range but has an increased outer diameter to give extended service life in abrasive conditions. The NT E hammer has been designed for use on deep hole drilling for geothermal and deep water well applications where high volumes of air are needed to remove ground water from the hole.

Consumables

According to International Construction Equipment product manager Simon Duck, innovation in drilling equipment sector is enabling smaller rigs to be used to drill bigger holes but this also brings some disadvantages.

“Smaller rigs generally have shorter masts, which means more drill rods and couplings are needed,” explained Mr Duck. “This becomes a problem on holes where you are using a multi pass system, such as installing conventional casings, because each time a new section of casing is installed the drill stem needs to be pulled out to fit the final drill system. This process takes time and hence more money.”

Single pass systems - which can drill through the overburden, leave the casing behind and continue drilling into the rock - are becoming increasingly popular. “The single pass systems which are now available can drill holes up to 1.27 m diameter,” said Mr Duck. “Handling drill rods that size is not easy, so single pass systems are an advantage.”

Robit Rocktool's is currently developing a new casing system which is also aimed at improving productivity on site. The new system - RoX Multi-Use - allows the same ring bit assembly to be used several times. According to Robit, this helps to improve the overall drilling efficiency and can save time and cost on temporary casing drilling applications where the casing cannot be left in the hole.

Atlas Copco Secoroc has added a new heavy DTH drill string - the ThunderRod T60 system - to its range. According to Secoroc the ThunderRod is built to deliver more energy and can be used with the most powerful hydraulic hammers on the market to drill holes in the 102 to 152 mm range. The ThunderRod has a cross section which is +40% greater than the conventional T51 rods, which helps prevent hole deviation.

Several new ranges of drill bits have been launched by Atlas Copco companies.

Atlas Copco Craelius's new Golden Jet Bits are a range of impregnated diamond core drilling bits which offer extended service for wire line drilling. The design is based on a 16 mm high cutting matrix, which Atlas Copco Craelius claims make it the most productive diamond core bit on the market.

Atlas Copco Secoroc's Rocket Bits are aimed at achieving higher productivity in soft to medium hard rock formations, such as shale and limestone. The bits feature a wide spacing between the ballistic buttons which minimises recrushing of rock and allows the cuttings to escape easily. The bits are currently available in 110 and 115 mm diameters and Secoroc has said that it plans to add more sizes to the range later this year.

Secoroc's other recent launch is also aimed at the button bit market. According to the company, the Grind Matic Jazz provides a quick and efficient way to grind worn spherical and ballistic button bits. The machine features profiled diamond grinding wheels and is semi-automated.

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