THE FUTURE IN FLEXIBLE CONVEYORS

Transcription

1 BOSMIN - INNOVATORS OF MINING EQUIPMENT Page 1 oaxial Pipe onveyors - Technical Bulletin #3 THE FUTURE IN FLEXIBLE ONVEYORS This document explains e operating principles behind e proposed BOSMIN oaxial Pipe meod of hauling and how e AP translates into a more flexible transport system. Scale model of a oaxial Pipe transporter showing dynamic stacking.

2 BOSMIN - INNOVATORS OF MINING EQUIPMENT Page 2 oaxial Pipe onveyors - Technical Bulletin #3 AP - What is it? The BOSMIN oaxial Pipe (AP) system for bulk material transporting is most suited to removing sized material from a loading unit, and can lower e operating costs relative to truck or common conveyor haulage. It involves progressively wrapping a flat belt into a pipe formation to enable material to be delivered along a curved paway. The return belt is also wrapped into a pipe shape, but is positioned outside e delivery pipe. The two belts are separated by an internal idler set wi a belt running on eier side of e idler. Bo belts open flat at e delivery and loading points, like a conventional conveyor. This design allows e AP to move rough two dimensions - while it is operating. Wheel mounting e unit enables it to move in ree dimensions. The process has emerged from desk studies as AP STRUTURE WITHOUT THE BELT e most cost-effective way of hauling material from an open cut, but e BOSMIN AP also has good potential to reduce cost at underground mines and has furer industrial applications. How does e AP differ from oer PIPE ONVEYORS? Pipe onveyors (P) differ from e BOSMIN AP in several ways; The P idler frame is a rectangular shape and mounts twelve idlers in each conveyor frame. The AP idler frame is square and mounts one external idlers and one internal idler spring. The AP frame is erefore lighter and more compact. The AP idler frame supports e empty belt against e loaded belt. This prevents e empty belt collapsing and allows e conveyor to negotiate a much tighter curve. Recommended curves for P steel cord and fabric belts are 1000:1 and 300:1 (curve radius:pipe diameter) while AP belts are expected to negotiate curves down to 25:1. AP idlers have a helical spring profile while e P idlers are cylindrical. The spring surface provides greater contact area wi e pipe and allows for a less rigid belt. This assists wi tight conveyor cornering.

3 BOSMIN - INNOVATORS OF MINING EQUIPMENT Page 3 oaxial Pipe onveyors - Technical Bulletin #3 The delivery side of e AP is in contact wi e return side, rough e action of e internal idler set. It provides drive in bo belt directions along every idler frame set. This differs from e P which must supply belt tension around e whole conveyor, before inertial forces can be overcome. The P conveyor calls for a specially designed belt, while e AP is suited to a lighter belt specification, wi e main criteria being sufficient belt elasticity to negotiate e curves. The softer AP belt does not tend to spring open like e P belt and does not require special sets of transition idlers. Only regular impact idlers are placed at e loading point. P belts experience very high breaking-in resistance wi empty belts initially 1.5 times e calculated full load running resistance. AP belts do not resist pipe formation to is extent and consequently do not suffer from e problem of high breaking-in resistance. The P belt has a transition distance (leng:diameter) of between 25:1 and 50:1 for nylon fabric and steel cable belts, respectively. The AP belt transition distance is only 8:1, providing more compact loading and unloading spaces. The softer AP belt uses more frequent idler spacing an P belts. The former supports e belt at 3:1 (idler distance:pipe diameter) while fabric and steel cord P ratios vary from 4.1:1 to 10:1. However, e AP idler frame is half e size of e P frame, and has fewer bearings. The BOSMIN AP is all about transport flexibility and productivity. For many open cut strip operations, a BOSMIN AP will significantly increase e output of e existing loading equipment by improving e utilisation of e available loaders. Using a oaxial Pipe onveyor reduces, or eliminates, trucks and can reduce e equipment spreads by mining bo waste and ore wi only one set of equipment. AP hauling conserves natural resources where steep dipping deposits result in lower mining recovery rates. AP hauling is also appropriate where limited space is available such as in narrow underground excavations, or along curved roadways. Why is a OAXIAL PIPE ONVEYOR special? The BOSMIN AP is an improvement over previous pipe conveyor designs because e return belt is supported internally by e delivery belt. The idler frame is square in shape and forms e spider in a universal joint between adjacent conveyor structures. This arrangement allows e AP to bend in two dimensions, and rough tighter curves an oer pipe conveyor designs. This principle is put to good effect when conveying material from an open cut, as once e material is sized, it can be removed wiout using any truck haulage. The loading unit can be close coupled to a suitable crusher ensuring e loading unit is highly utilised by not having to wait for trucks to spot. This arrangement ensures at all e material leaving e open cut is sized to feed directly into e processing plant. Any secondary blasting is carried out in e open cut, and not at e ROM hopper. The pipe conveyor design holds e load in a <sausage' which allows e AP to negotiate steep slopes (tested at +60o ), and prevents wind blown dust emanating from e conveyor.

4 BOSMIN - INNOVATORS OF MINING EQUIPMENT Page 4 oaxial Pipe onveyors - Technical Bulletin #3 How is e AP conveyor loaded? Ground preparation The AP can convey material wi maximum particle size up to 33% of e diameter of e pipe when e load cross sectional area does not exceed 75% of e pipe area. Lump sizes up to 66% of e pipe diameter are possible for belts loaded to around half e pipe area. These limitations require at over sized material be eier screened or crushed before loading onto e AP. A continuous mining machine may produce suitably sized material. Loading Units A AP conveyor may be loaded wi sized material, using a feeder to provide constant even flow. Wi lump materials, is can be achieved by eier scalping off e oversize, or crushing it down to undersize dimensions. Feeder-rusher after MMD Shoveller In mining applications, run of mine rock is fed onto an apron feeder using a front end loader, a shovel, or an excavator. The apron feeder conveys material to a scalping screen and e oversize passes into a mobile crusher. Bo e scalping screen undersize and e crusher product, feed onto e AP. The apron feeder and crushing unit can be close coupled to a loading shovel to form a shoveller unit. This arrangement permits e loading unit to operate continuously while e mobile crusher feeds e AP. How is e AP supported? AP stability considerations The AP can run on wheels located at e idler frames. This position ensures e wheels track along e circumference of a turning circle providing a good trailing profile. This arrangement is suited to underground applications, or surface mines where e conveyor travels directly up e dip slope. Alternately, e AP may be suspended at e midpoint, from a crane hook. The crane does not need to relocate for small movements of e loading unit, but needs to tram when e angle of suspension exceeds safe limits. rane tramming can be controlled automatically, or manually from e loading unit. This meod of support is suitable when e AP traverses several benches, or when e loader trams laterally while e face advances, and requires a sideways movement of e AP.

5 BOSMIN - INNOVATORS OF MINING EQUIPMENT Page 5 oaxial Pipe onveyors - Technical Bulletin #3 A AP may be supported from a wire rope. This has application for cross country travel or underground transport along a tunnel opening. Unloading e AP. The AP is suited to substantial automation, and may not require an operator, as e load can simply feed onto a trunk conveyor at a transfer station. However, if e AP is used to load trucks at e top of a slope and feed onto a stockpile between trucks, an operator is required. This operation of e AP provides an alternative to having a truck loading bin, or pausing e conveyor system between trucks. What are e AP broad design criteria? Idler Size and Belt Speed A AP idler is designed to limit e speed of bearing rotation to less an 1,000 rpm. However, where tight horizontal curves are required, e belt speed may be limited by e centrifugal forces developed by e load as it negotiates horizontal curves. If centrifugal forces are too high, e AP can rotate excessively in e idler frames, and e belt speed should be reduced accordingly. The idler speed of rotation is adjusted by forming e helical spring into a spring diameter matching e required belt speed. The spring pitch is adjusted to ensure it meets e British Standard for an infinite spring life. Indicated belt speed is calculated from: Belt speed (mps) = x AP internal pipe diameter (mm) 3 Belt apacities - Small Lumps (m per hour). AP Diameters Maximum Lump Size Maximum Belt Speeds (mps) Maximum Idler Diameter (mm) * Large Lump Belt apacity Maximum Lump Size Maximum Belt apacity (m per hour). is 88% of Small Lump Size Tabulations

6 BOSMIN - INNOVATORS OF MINING EQUIPMENT Page 6 oaxial Pipe onveyors - Technical Bulletin #3 Internal Idlers The first model AP internal idler set consisted of cylindrical polymer rollers mounted on a stiff but flexible axle, (see cover picture.) More recent developments show at a helical spring design is low friction, and very effective in supporting bo e inside and outside belts while providing a ready means to add intermediate drive power along e leng of e AP as seen in e second model AP. Belt Thickness and Wid The belt ickness increases wi AP size, and is 3.3% of e pipe diameter. The belt needs to be sufficiently wide to provide sufficient overlap for e Model 2 internal pipe. This is given by: Belt Wid = 1.13 ð AP internal pipe diameter (mm) and 10% wider if e AP slope angle exceeds 30 o External Idlers The external idlers are helical springs of similar specification to e internal idler, but suitably longer. AP alignment For a dynamically moving AP, idler frames are connected to e AP intermediate structures, as shown on page 3. These are box sections and join e idler frames, at two opposing fulcrum points, to from a universal joint. The universal joints may be given stiffness by including self centring actuators across e hinge joints. This design has e effect of evenly spreading any curve e AP negotiates over a range of idler frames. Drive Power Requirements The AP installed drive power requirements can be approximated from: kw = 205 Ln(L) (tgh 3600) Where L is for conveyor lengs greater an 250m, t is tonnes-per-hour conveyed, g is 9.81, and h is e transfer height difference. Power for APs less an 250m are based on specific bearing friction characteristics. The drive power may be applied to e belt rough driven head and tail pulleys, using pinch rollers as required. Preferably, e power is supplied by driving e idler spigot shafts as illustrated. This arrangement provides for an intermediate drive system and allows for AP to be extended over an indefinite leng. AP IDLER FRAME What are e osts? The AP system may not require any operating labour, depending on e meod of suspension and unloading process. A loader driver can also control e AP operation. This results in very favourable running costs compared to truck haulage. Maintenance costs are confined to periodic belt and idler replacements togeer wi bearing maintenance at e various joining points. The frequency of ese services depends on e application, but is expected to be low. Energy costs depend on e transport elevating requirements togeer wi friction losses. The balanced haulage inherent in a belt conveyor provides a substantial energy saving when compared to e trucking alternative.

7 BOSMIN - INNOVATORS OF MINING EQUIPMENT Page 7 oaxial Pipe onveyors - Technical Bulletin #3 How does a AP affect ore reserves? By reducing e cost of transporting mined materials, it is possible to move e economic limits for mining furer down dip or into more marginal areas of reserve, ereby increase mineable reserves. The AP will transport material up steep slopes, making it an ideal tool for mining steep dips, or conveying out of open cut or underground excavations. BOSMIN AP - How does it work? Equipment maintenance The shoveller, AP, and trunk conveyor must operate concurrently. The mechanical availability (MA) for e system is erefore e product of each unit's availability. However, all e units are expected to have high MA, when correctly matched to e prevailing mining conditions. In hard rock applications, a standby crusher unit may be justified so at wearing crusher parts are replaced offline. Under ese circumstances, a system MA above 90% is anticipated. Belt leaning The AP runs wi e clean side always against e internal idlers. To prevent excessive wearing to ese idlers e underside of e belt must be protected at e loading and unloading points. This is achieved by enclosing e gap between e two belts, providing a belt plough, or a blower system to ensure ere is positive air flow out of is space. The outer belt surface is cleaned at e discharge point wi a conventional belt scraper and by action wi e helical spring idlers. These idlers may be powered ereby providing a live cleaning action to e belt. Belt hanges When a steeply sloping belt is changed or e structure maintained, e belt should be run in reverse or cleaned by passing a pig rough e pipe to remove e fixed charge of material present in e pipe. This is only o present in conveyors sloping greater an 35. Pit Access While e AP eliminates truck haul ramps from an open cut, ere is still a need to provide pit service access via a less expensive roadway. In an underground situation eliminating trucks can impact ventilation and road size. What are e key AP environmental factors? The BOSMIN AP system of hauling offers benefits ahead of traditional open cut mining meods. The key factors include: Less power and diesel fuel used in mining. The AP uses much less energy an truck hauling meods. There is an operating cost benefit, and ere is a significant environmental benefit in at using fewer kilowatts, results in smaller generating impacts. Much of e diesel truck fuel used for open cut mining can be replaced wi locally generated electric power. Low noise emissions. The AP is a significantly less noisy operation an e haul truck alternative. The operating machinery is electrically powered, and only emits a low hum while operating. Large overburden trucks can be a source of noise impact which is avoidable where truck and shovel mining is replaced by e BOSMIN AP and Shoveller system. Low dust emissions. BOSMIN AP greatly reduces dust release when compared to haul trucks and some open conveyors. The load travels in an enclosed <pipe' isolating e opportunity for dust generation to e loading and delivery points. This reduces e cost associated wi haul road dust suppression. Is e BOSMIN AP a wise use of human resources? Introducing new mining equipment can result in severe HR problems due to e need for very specialised skills or for people prepared to work in unfamiliar surroundings. The AP requires few or no operators and a limited number of customary conveyor maintenance personnel. This minimises potential HR difficulties.

8 BOSMIN - INNOVATORS OF MINING EQUIPMENT Page 8 oaxial Pipe onveyors - Technical Bulletin #3 Who is responsible for developing new mining machines? Long term equipment owners (industrialists, contractors or mine operators) benefit most by initiating development of new equipment designs. They own e machine for e longest time and have e best opportunity to depreciate e development cost over an acceptable period. Equipment owners also benefit most by e introduction of more efficient machines rough reduced owning and operating costs. Original Equipment Manufacturers (OEMs) can help build reliable machines at meet an operator's specific materials handling needs. Where to from here? 1. A desk study quantifies e site specific benefits of using a BOSMIN AP haulage system. Significant benefits must be defined before making e effort required to build new mining equipment. BOSMIN engineers can assist wi evaluating pit layouts and help in quantifying e benefits. 2. Determine e strategic advantages of developing a cheaper transporting meod. 3. Design and build a prototype unit and conduct field trials to evaluate productivity sensitive factors. 4. Select equipment suppliers for oaxial Pipe components. 5. Assemble and install AP components. Adding it all togeer. The BOSMIN AP is a new energy efficient equipment design to ensure mining stays competitive. The loader is highly utilised, and e transport system is counter balanced, providing energy efficient elevation of e mined materials. Trucks and haul ramps are eliminated or reduced from metalliferous mines, and tramming cars from underground mines. In deep mines e bottom line is machine efficiency and e AP offers anoer tool in achieving at aim as well as delivering significant environmental plusses. References 1. A description of e BOSMIN oaxial Pipe proposed mining conveyor, and model trials, can be viewed at e WWW home page, listed below. 2. Pipe onveyor Apparatus - Patent: Australian Letters Patent No , Inventor: Robert Arur Beatty, Priority Date 14 October Pipe onveyor Apparatus - Patent: United States Patent No.5,042,646, Date of Patent, 27 Aug Pipe onveyor - Patent: Australian Letters Patent No , Inventor: Robert Arur Beatty, Priority Date 5 May R&D From Rhetoric to Reality. R.A. Beatty, AusIMM Bulletin Feb Reserve calculations, mining, and milling of Homestake Mining's Open ut project described. Gary Loving, David G. McDowall, and Jerry D. Pfarr, Society for Mining, Metallurgy and Exploration Inc. Mining Engineering, October 1987.Feb Transportation System, Pipe onveyor, Japan Pipe onveyor o. Ltd. A technical brochure, cir.' Pipe conveyor - a new concept of materials handling. I.Faulkner (Ass.M.Inst of Quarrying), GM Projects Division, and J.ostin hief Engineer, Projects Division, Noyes Bros. P/L, Institute of Quarrying, NSW, 11 October Feb Technical Transfer Presentations - Revolutionary deep open cut equipment designs, and eir introduction to operations. R.A. Beatty, Presenter, MTE onference, Per, WA. 15 September Feb Deep Stripping Equipment Designs. R.A. Beatty, Presenter, AJM Open ut oal Operations onference, Mackay, Qld. 17 June ontacts:- Bob Beatty BE(Min) MAusIMM Principal Phax. Int BobBeatty@BOSMIN.com Web: R.A. Beatty & Associates Limited Hayes Avenue AMIRA Queensland 4300 Australia