Halco Rock Tools
IntroductionHalco Rock Tools Ltd. is a world class manufacturer of down the hole (DTH) drilling equipment. Halco pioneered the development and distribution of DTH hammers in the 1950s, and now their precision-engineered range of performance hammers and drill bits is used globally. Predominantly used for mining, DTH is preferred in other applications such as construction, quarrying, formation sampling, and the drilling of water wells. Halco Rock Tools, in close cooperation with Stenuick Freres, actually established the development and distribution of the down the hole hammer in the 1950s throughout the UK, Australia, New Zealand, Africa, and India. Produced for more than 60 years, these products continue to be regarded as one of the most reliable and durable available today. This is due to the commitment to customers’ needs, design expertise, and rigorous product testing in extreme drilling conditions. Halco Rock Tools is located in Halifax, UK. Hammer OverviewWhat is DTH and How is it Used? The “Down the Hole” or DTH hammer is used for drilling holes through a wide range of rock types, the variety of which continues to extend well beyond the original conception of early blast hole drilling. “Down the Hole” refers to where the hammer action occurs when compared to drifter hammers, which hammer on top of the drill string. The DTH hammer piston always makes direct contact with the drill bit, and there is generally no loss of transmitted energy as the hammer drills deeper, as is the case with drifter (top hammer) rigs. What is Reverse Circulation? Reverse circulation hammers can in most instances carry out continuous sample collection in a fraction of the time necessary with conventional or wireline coring. Why is the DTH approach preferred today? Although DTH hammers started life in quarries, they are now appreciated throughout the drilling industry where they have become the preferred option due to their significant advantages over other systems, in particular –
Prior to DTH technology, blast hole drilling was normally carried out with drifter equipment. Water well drilling in hard formations was done by cable tool rigs or rotary rigs using roller cone bits. However, because drifter drilling becomes progressively slower with more depth, unlike DTH hammers, and because the latter can drill in one day what a cable tool rig takes weeks to complete, the quarrying, waterwell, site investigation, civil engineering, and mining industries throughout the world have become more and more aware of the advantages to be gained from using DTH hammers. This is not only as an alternative to drifters, but because of the higher performances when compared to conventional rotary drilling. The DTH hammer concept proved so popular that established manufacturers of drifter steels, bits, and accessories followed our lead and developed their own range of DTH hammers and bits.
How is DTH Better? Penetration rates with DTH hammers are almost directly proportional to air pressure therefore doubling the air pressure, which results in approximately double the penetration. The first ever hammers were of “valved” design and had an internal liner. This valved technology, together with compressor availability, limited the air pressure capability of the early hammers that were incapable of withstanding air pressures above 170 psi. The valve itself had operational problems because hammer malfunction occurred when large volumes of water The removal of the valve has eliminated the operational problems previously experienced. Modern hammers are also of a rigid construction, enabling them to withstand air pressures as high as 435 psi. Further development of DTH hammers will be in terms of their design, which will be related to achieving lower user drilling costs through increased rates of penetration and longer life in the hole. Increases in penetration rates will require the investigation of delivering yet higher air operating pressures to the hammer as in conventional designs, or the use of alternative power sources such as water or oil. To achieve longer life of the components of the hammer, research of wear- and impact-resistant materials not normally associated with traditional hammer manufacture is essential. Water-powered hammers are being developed for use in underground mines. Although performance results are encouraging, the design of the hammer is limited to use on sites where large amounts of water are available and can be tolerated and, most importantly, handled and cleaned for return to the hammer. Hydraulic oil-powered hammers have been tested in some quarries, but these need a specially adapted drill rig, drill tubes, and a coupling system. Spillage with potential contamination of the ground is a major consideration. Furthermore, a separate air supply is needed in order to flush the hole. Because of these limitations, water- and oil-powered hammers are slow to gain ground and air-driven hammers still have the competitive edge. The immediate opportunity for DTH hammers is in developing their use for applications normally drilled using other methods, for example shallow oil and gas field development, shallow wide hole piling, continuous drilling and casing systems, reverse circulation chip sampling, mole drilling, and applications where holes in excess of 36" diameter are required in mining, civil engineering, and construction applications. Drill Bit OverviewWhat are "Down the Hole" Drill Bits, and How are They Used? “Down the hole” (DTH) drill bits are used with “Down the hole” hammers for drilling holes through a wide range of rock types. In conjunction with DTH hammers, drill bits are designed with a splined drive for rotating the bit in the ground. Drill bits are available in different sizes and different styles so they can drill a wide range of hole sizes. How have DTH Drill Bits Developed? Rapid advances in drill bit technology have also occurred throughout the last 40 years. The first type of drill bit used with down-the-hole hammers was a “cross bit” design. Four chisel-shaped lengths of tungsten carbide were brazed into the bit body. The action of brazing preset stresses within the drill bit, thereby limiting its life. A further disadvantage of the cross bit was that the majority of the carbide was situated around the center of the bit face and not towards the outer edge of the drill bit where there is the most rock to cut. In the late 1960s, however, the button bit was introduced, and this was a landmark in the progress of DTH equipment which led to bit lives previously unheard of. The button bit design eliminated the primary shortcomings of the cross bit. Cylindrical button inserts are precision ground to extremely close tolerances and pressed into the drill bit as an interference fit. This resulted in improved carbide insert retention by eliminating brazing stresses and other defects associated with brazing and braze materials. Button inserts are distributed more efficiently than cross bit inserts by providing more cutting power where it is needed at the outer edge of the drill bit face In many cases, the need to sharpen the drill bit was eliminated with the arrival of the button bit, and the improved cutting action provided increased drilling rates particularly in hard rocks. While the cross bit design is still used in some rotary and drifter applications where the rock is very soft, the button bit is now used in virtually every DTH application. Applications - Overburden Systems - Soft soil is normally drilled with augers or by the rotary method, but DTH hammers have adapted to soft conditions by being able to drill and case the hole simultaneously using an eccentric bit which can be withdrawn on completion of the bore hole, leaving the casing in situ, thus preventing hole collapse. The systems achieve this by enabling the down-the-hole drill string and casing to be lowered simultaneously. A down the hole hammer is used, to which is fitted a driver and eccentric bit. Drill Bit Selection GuideAs with Halco hammers it is crucial that you choose the right drill bit, otherwise it will cost you in both time and money. With a comprehensive range on drill bits on offer, you can be sure that you will definitely find a suitable bit for any project you are undertaking. These carburized drill bits are among the best in the world, providing outstanding performance and durability. All drill bits are produced at a specialized plant where they are made out of high quality nickel chrome alloy steel, carburized, and heat-treated to offer extra protection against wear and fatigue. Every hole in the bit head is machined to within microns and fitted with carbide inserts that provide the cutting action of the rock. Three different bit heads are on offer -- Convex, Flat Face, and Concave -- also with three different inserts. The manufacturer guarantees they have a drill bit that can tackle any challenge and rock face formation. The two most important factors in choosing the right drill bit are productivity and reliability. For soft to medium rock formations where penetration rates are high, the ballistic and semi-ballistic inserts coupled with flat face or concave bit heads are more suitable. If the rock formation is on the hard to very hard side, it is more advisable to use a domed insert with convex head which will result in a longer drill bit life.
Hammer Selection GuideChoosing the right hammer is essential to your productivity and operating cost. All Halco hammers are built to last, manufactured to an exceptional standard, and provide the outstanding performance and productivity required today by customers. Versatility and variety are key to Halco products and you can be assured that all Halco hammers are suitable for a wide range of rock drilling applications. Every hammer is constructed at a state-of-the-art manufacturing plant using the highest quality heat-treated nickel chrome alloy steels. These processes meet the requirements for ISO9001:2008 standards. It is a Halco imperative that every hammer produced surpasses the customers' expectations and they're constantly striving to improve service and product quality. Four Different Types of Hammers:
GW500 and GW600 hammers are fitted with a reversible cylinder to maximize operating life and are suitable for operation at air pressures up to 435 psi. |
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