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Wearing out the welcome

To some of the more astute people in the industry, an investment in wear parts depends on many factors other than the ground conditions that a machine works in. These include the price of the steel being protected, the price and availability of labour, the volume of work and the price of hard facing and ground engaging tools.In any market there are Holdens and there are Rolls Royces, and there is a legitimate place in the market for each. In some applications and market conditions, the most economic decision might be to run cheap, light buckets that cost less but hold more, and will need to be replaced more often than a stronger, heavier bucket.When the price of steel is high, it can make sense to spend more on a protection package that prolongs the life of the bucket. It can pay to spend more on hard facing to protect the underlying steel, and it may pay to spend more for an attachment that uses higher tensile steel that will last longer with no weight penalty.Some of the better-known attachment makers say customers are prepared to pay the right money to get an attachment made from good-quality steel that provides endurance without a weight or performance penalty.Makers such as Esco, Hensley, Metalogenia (MTG) and CRD (Combi) offer sophisticated tooth and lip protection systems along with locking systems that hold them in place in severe applications but allow quick change-outs of components.These systems, which can form a significant proportion of the total cost of a bucket, are largely aimed at the quarry and mining markets where owners generally have sophisticated reporting systems that can quantify the benefits of a good GET and wear protection system.However attention to ground engaging tools, and bucket design itself, is at least as important on smaller machines because of their limited hydraulic horsepower and breakout force. Differences in efficiency between buckets can make a significant difference to productivity and fuel consumption.Teeth and side cutters reduce the initial resistance when a bucket engages with the earth in applications where good penetration and high breakout forces are required, and they also extend the lift of the bucket itself. Design factors such as tapered side walls can assist in reducing resistance, as can bucket profiles that encourage material to roll into the bucket.There are a few different basic tooth designs, but many look-alikes – if not perform-alikes. Sorting out the most economical option is an unenviable task for contractors, but there are a few stories out there of contractors who have bought on the basis of “it’s cheaper but it does the same job” only to be disappointed.Good quality teeth are designed to wear so that they roughly maintain their original shape and efficiency. Those that wear to an inefficient shape can cause a significant penalty in bucket fill and fuel consumption.Phil Polmear has built his business, Grade Control, around products that improve and broaden the capabilities of graders. One such product is Sandvik’s System 2000 blade system comprising a one-piece board, a row of tungsten carbide tools that mount in the bottom of the board, and end protectors. The tools typically last for around 500 hours and the boards for around 4000 hours. A key to achieving this life is setting the tools up at the correct angle so they wear evenly by rotating rather than dragging.According to Polmear, perhaps the most impressive aspect of the system is that it works in virtually all conditions from sand to hard rock. He says the button shape of the tool that Sandvik offers has proven effective in fracturing rock to create gravel during maintenance grading. This has impressed councils that use the system – many resisted at first but have subsequently converted after seeing it working elsewhere or following a demonstration on their roads.The Sandvik system cuts corrugations and potholes out of the road to provide an even surface. Blade mixing of gravel created and recovered by the Sandvik system and soil recovered from the drains produces a surface that holds together. Some councils have been able to save time and fuel by reducing the number of maintenance grades required per year. The longer interval between changes of cutting edge compared to a conventional straight blade also means the grader has reduced downtime.Grade Control also represents Maddock Industries from the US. Among that company’s range of innovative products are a backhoe-mounted milling attachment for patching or removing the road surface prior to digging a trench to lay a pipe; a grader-mounted milling attachment; a towed road recycler and roadside drain cutters. BRS Civil Australia was one of the first contractors to undertake rock sawing in Sydney sandstone using excavator-mounted attachments. The saws evolved over a number of years as more was learnt about the ideal tooth patterns, cutting speeds and ground engaging tools.The early saws all used tungsten carbide teeth and were limited in the hardness of rock they could cut. Largely through trial and error, patterns and materials were found that could cut most Sydney sandstone economically. BRS also did some work with diamond matrix cutting tools in harder rock.Tungsten carbide and diamond matrix each have their own applications. Tungsten carbide is economical but limited in the hardness of rock that it can cut, while diamond matrix will cut harder rock but is brittle and considerably more expensive. Diamond matrix saw blades can also cut a narrower slot and create less dust when cutting. Dust control is a significant issue with rock cutting and generally requires watering of the trench, or spraying a mist on the blade.BRS has worked on a number of high-profile projects in Sydney, including the M5 tunnel and basement excavation for the Bondi Junction shopping centre, but moving to Brisbane meant the company had to re-establish its credentials in a new market and in a different rock.In the past hammers have been used for rock excavation in Brisbane. Getting work in the Brisbane Tuff rock meant not only proving the rock sawing method, but also developing economical and productive tooth patterns and GET specifications.“Although the Brisbane Tuff is harder than the Hawkesbury Sandstone of Sydney, it is less abrasive,” BRS director Brian Daizli said. “We have developed a tooth pattern that chips the rock out, rather than pulverises it, and have been able to use Betek tungsten carbide picks supplied by Hard Metal Industries. At present we are happy that tungsten carbide provides the most economical option, but we can move to diamond matrix if the conditions warrant it.”In Queensland BRS has completed service trench work for Abigroup on the first stage of the Northern Busway project and drainage trench work at Caloundra for FRH.Hard Metal Industries is Australian supplier for Betek tungsten carbide picks and holders supplied into applications other than those served by Wirtgen equipment. In Australia the main civil applications are foundation drilling, trenching and rock sawing, and tunnelling. HMI also has its own hard facing technology and builds machines to apply hard facing.Although a relatively recent entrant to the Australian market, HMI has made significant inroads, supplying tools for road headers working in the North South Bypass Tunnel and for many of the foundation machines working on the Gateway Bridge Upgrade project. Betek works closely with leading foundation equipment manufacturer Bauer and has an unrivalled range of tools for this application.The tools that HMI is supplying to the Brisbane foundation drilling market are larger than those traditionally used in Sydney sandstone, according to director Andrew Dry. “The torque of modern foundation drilling machines allows larger tools to be used,” he says. “Less tools are used in total, and they have a significantly longer life than the smaller tools that have been used in the past. While the larger tools cost more individually, less are required and their longer wear life, and the reduced time spent changing picks, make them a better economic proposition. We believe that the foundation drilling market in Sydney could also benefit from a move to larger picks.”While the same size pick is used for rock sawing in the Brisbane and Sydney environments, HMI supplies a different pick insert to Brisbane customers to better match the local rock conditions.