Haul Trucks

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113September 2012 www. .comRIGID HAUL TRUCK BODIESThere are currently about 35,000 mining haul trucks in use at surface operations across the globe with payload ratings in excess of 90t, and around 42,000 if you count those that are currently out of service. The Parker Bay Co, which provides market research for the mining equipment industry, estimates that around 4,500 new trucks are intro-duced to the market each year. While most of these are supplied with bodies by their original equipment manufacturers (OEMs), there is a steadily growing market for specialist body designs, particularly those made by independent manufacturers.SELECTIONWhen selecting haul truck bodies, there are a number of factors to be considered including: the characteristics of the material to be hauled; truck payload/design; the range of bodies available; which loading tools the truck will be matched with; haul road conditions, grade and average haul distance; plus environmental conditions at the site. Before we begin a design, we conduct an extensive review of the mine needs, operations (loading tools), facilities and production budget requirements, says Rich Peters, sales manager for North America at Westech. This includes maintenance facilities and road conditions. Once this is complete, we use the latest in engineering technology to design, model and measure the design. We use such software as Pro/E, Ansys, CF Design and EDEM. Once the design is complete, a full review is done with the customer.We spend a lot of time talking with customers, and use computer models to determine the optimal interaction between the truck body and the loading tools, explains Dowen Raynor, product manager for truck bodies at ESCO. This system approach creates value for miners and helps define the balance between payload and service life.Sizing the body to allow the customer to achieve the rated truck payload is crucial. An appropriately sized body is one that can reach target payload and minimise spillage when hauling all material types at a mine site. To minimise the risk of machine overload, Caterpillar uses the 10-10-20 policy. This dictates that no more than 10% of loads should exceed 110% of the target payload, and no load should ever exceed 120% of the target payload; the average of all loads should be the target payload. Javier Llano, large mining truck body product manager at Caterpillar, says: We collect mine-specific information, including information on the material, such as fragmentation, abrasion and cohesion, and information about the loading tool being used, as well as customer expectations and maintenance criteria. Caterpillar applica-tion specialists then review the information and determine the optimal body configuration for each mine site.Josh Swank, vice-president of sales at Philippi Hagenbuch, says design is the most important thing to look at when selecting bodies. However, body life is determined by both the design and the material the body is made from. Weve learned that not all steels are created equal, he says. Start with the best quality steel and welding consuma-bles, paired with the design that provides optimal performance and life, and you will arrive at the most efficient truck body to operate as well as maintain.DESIGNThe most important factor affecting truck body design is the material being hauled. This will not only determine the capacity and position of the body on the chassis due to the stated materials angle of repose (the stacking angle), but it will also determine which accessories/wear parts may be needed so that the body can achieve its specified life. For example, if the material being hauled is very abrasive or the particles are very large, it may be beneficial to add liners to protect the truck body from premature wear and/or localised denting. If the material is very light, such as coal, then it is unlikely that liners or heavy main plates would be needed. The loose density of the material affects the volumetric design of a truck body, and directly determines the payload of the truck: the weight of the final truck body design, plus the truck chassis weight, subtracted from the gross vehicle weight (GVW) will give the potential payload. The lighter the body, the greater the payload potential, and the heavier the truck body the less payload potential there is within the trucks GVW range.In addition, allowances must be made for environmental influences, such as the weather, on the material; moist material can have a tenancy to hang up (stick) in A DT HiLoad body on its way to Xstratas Mount Owen mineGood body imageSelecting the optimal body design and wear materials for each truck can have a huge impact on mine haulage profiles. Carly Lovejoy explores best practice and the current marketThe loose density of the material affects the volumetric design of a truck body, and directly determines the payload of the truck113,115-117,119,121-122,124,127-128,130-132MM1209.indd 113 20/08/2012 11:52RDO.indd 1 14/08/2012 15:36115September 2012 www. .comRIGID HAUL TRUCK BODIESthe truck body after dumping, so modifications may be needed to counteract this.Loading tools will also affect the way the truck body is designed, so as to off-set characteristics inherent to each type of tool. Dennis Frank, director of sales at Mine Rite Technologies, explains: Wheel loaders tend to discharge the material in a wave that splashes against the off-side of the truck body and may require additional plate thickness or structure to counteract this. Shovels typically drop their load in one area, creating impact, and can also have the same effect as a loader, but against the front wall of the truck body as the shovel bucket is swung into the truck body and emptied. Further considerations for tray design include:

road design and width restrictions;

workshop design (width and height restrictions);

loading and unloading equipment and or procedures;

legislative conditions (environmental, health and safety); and

the clients business plan.Barry Miller, vice-president, business development at Trinity Mining and Construction Equipment, says that no matter what marker a mine uses to determine the efficiency of its haul fleet, it all comes down to finding the lowest cost per tonne for hauling material. Our efforts begin with the customer providing basic operational information, such as material weights, loading tool information and any restrictions that might come into play, such as body height, width restrictions and even berm height at the dumping location, he tells MM. Our engineers are then able to custom-design a body that meets the requirements of each individual mine, while hauling the maximum allowable payload.John van Reenen, managing director of VR Steel, says that when selecting a new truck body, the question should be: which body will be the longest lasting, strongest and lightest that will work in the conditions specific to the mine? Lightweight bodies are more susceptible to fatigue failure, which puts more emphasis on the design and manufacturing, he explains. It is vital to choose a supplier with good manufactur-ing and excellent design capabilities. TRUCK PERFORMANCEAn optimal body design will maximise machine productivity and component life, resulting in the lowest operating cost per tonne for the customer. When designing a body for a specific application, it is important to make sure it is not only of the correct capacity, but also positioned correctly on the chassis to distribute the weight of the load properly on the tyres. This will prevent uneven tyre wear as well as braking, steering or dumping issues. Mr Swank explains: Every truck has a maximum GVW that must be maintained, plus correct distribution of weight between the front and rear axles to stay within warranty and for optimal performance.If the body is positioned correctly within the front/rear axle distribution range (usually 1/3 front, 2/3 rear), the likelihood of encountering tyre or stability issues is greatly reduced. Lighter-weight bodies allow for more material to be hauled. However, a body that is oversized can lead to loads in excess of the rated payload of the truck, and result in decreased braking and steering capability, and reduced component life. Conversely, if the body is undersized, the truck is not being fully utilised, which results in a higher cost per tonne. Mr Llano from Caterpillar says: We have seen incidents of incorrect weight splits, excessive debris build-up due to the lack of, or incorrect placement of guards, and interference with the frame or other chassis components when aftermarket bodies are mounted on a Cat chassis.Richard Lang, CEO of DT HiLoad, adds: If the body design is tough enough for the mine conditions and lasts an economic period, then a lighter body will carry more payload all day every day. We find that customers typically get a payback period on the DT HiLoad Hercules body in under a year.Selecting a truck body that is not designed for a customers site-specific conditions and use could lead to less than optimal payload deliveries. Exceeding the trucks GVW can lead to warranty denial, increased fuel and maintenance costs, increased downtime and less productivity.MAINTENANCE All truck bodies will require some amount of repair. However, the frequency will vary greatly depending on the application and the care taken by the customer. Knowing customer expectations and having an understanding of the application is the best way to ensure that payload and durability are balanced. Some customers, those who want to maximise production even at the expense of some additional costs, prefer a consumable lightweight body that will operate for a certain amount of time before being replaced, Mr Llano tells MM. Customers at the other extreme want a single body to last the life of the chassis with no major rebuilds. There is a middle ground too, where most customers fall a body that can be refurbished or