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1、Crushing and Grinding 2002 Conference Page 1 CRUSHING AND GRINDING 2002 CONFERENCE New Developments And Practices In Lifters And Liners INTRODUCTION The mineral processing industry is in the midst of a revolution, a grinding plant revolution. Major breakthroughs in both metallurgical performance and
2、 overall grinding plant availability are undeniable. The full benefits of these developments are not widespread. Metallurgical performance is being enhanced by superior mill operating modelling by the discrete element method which, in certain applications, encourages the use of fewer, shell-lifter r
3、ows with higher lifter heights. This results in larger and heavier liners. Overall plant availability and utilisation are both enhanced by fundamental mill systems equipment quality and reliability (a credit to mill manufacturers and plant maintenance personnel) and faster, safer, reline times using
4、 RMEs worn-liner removal, new-liner-placement Mill Relining System. This paper defines, as RME believes, the final frontiers of large grinding mill relining practices with a particular emphasis on the team effort required of all interested parties. Mineral Grinding A Complex Game (offering worthwhil
5、e prizes) Grinding plant design, construction, operation and maintenance are each complex activities when each is reviewed individually. When combined, the complexities may seem overwhelming and some issues are perhaps overlooked, especially during the heavy workload of new plant design and construc
6、tion. This paper nominates all the involved parties (the Players) in a successful mill relining Team and provides a foundation document for future discussion in this area. RME will provide this paper, and subsequent updated versions, as a reference source at both the and .au websites. As in any com
7、plex Game, this Team of Players combine their individual skills to achieve a successful outcome, ie. a podium finish in the world-series, annual-mill-utilisation contest. The Players in a Successful Mill Relining Team For a greenfields grinding plant project, the Team players are: 1. Project Owner 2
8、. Project Manager 3. Mill Supplier 4. Liner Supplier Crushing and Grinding 2002 Conference Page 2 5. Plant Operating Personnel 6. Plant Maintenance Personnel 7. Mill Relining Crew 8. Mill Relining System Supplier (RME) For an existing grinding plant operation, the Project Manager has no further infl
9、uence, reducing the field to seven (7) Players. The Project Owner should however, nominate a remaining Player, probably the Plant Operator, to review the Project Managers areas of responsibility. The contribution of each Player to the Teams overall success is now discussed in detail. 1. PROJECT OWNE
10、R 1.1 Thinking before building The Project Owner, the ultimate beneficiary of world class grinding plant performance, will face many decisions regarding expenditure of Project Capital. Only the Owner, through those decisions, possesses the power to influence all other Players. Some decisions will ha
11、ve a positive influence on the final outcome. Some decisions will have a negative effect. Those decisions will determine plant performance, availability, utilisation and safety, sometimes for the entire duration of the grinding plants life. In other words, poor decisions may embody irreversible and
12、negative effects on operational and maintenance outcomes including mill relining. The Owner must first consider the importance of grinding plant performance and availability to the overall project. A few operations, notably alumina refineries, have been known to install a spare mill and are therefor
13、e not exposed to the usual grinding mill availability demands to maintain throughput. Usually, mill availability is critical and especially so in a modern grinding plant equipped with a single, large, primary mill. If, after consideration, grinding plant performance and availability are deemed impor
14、tant, the roles of each other Player must be considered and their potentials optimised. The Owner will be required to work especially closely with the (perhaps conservative) Project Manager. Both Owner and Project Manager should make themselves aware of all recent developments in this area, eg. a mo
15、ve toward significantly larger mill liners made possible, in part, by RMEs worn liner removal, new liner placement Mill Relining System. Simply thinking about relining issues at the beginning of the Project will reveal many opportunities. Given a little consideration, the full potential of all other
16、 Team Players will be released at each and every reline and for the life of the plant. An extra 1-3% annual plant utilisation, won through efficient mill relining, is the prize on offer for such thought at the design stage. Crushing and Grinding 2002 Conference Page 3 1.2 An example of the consequen
17、ces of not thinking at the plant design stage The Owner of Project XYZ does not consider mill relining issues and does not brief the Project Manager regarding any particular wishes in this area. The XYZ Project Manager also does not consider mill relining issues and seeks grinding mill supply via a
18、Specification which does not contain mill relining requirements. The Mill Suppliers (all engaged in a competitive business) seek the lowest initial cost solution in order to win the mill supply contract. For some suppliers, their solution includes placing the mill motor alongside the mill shell. Thi
19、s arrangement is visually compact and appealing, promising a smaller plant building and significant cost savings. The Project Manager awards the supply contract to a Mill Manufacturer offering this compact arrangement and designs the grinding plant to suit. Another plant requirement is a through-pla
20、nt aperture for lifting equipment from the ground floor to other plant levels. This lifting well is placed next to the mill, denying the mill relining crew access to the non-motor side of the mill. Please refer to Figure 1.1. Platforms, within the through-plant crane well, are not possible since the
21、 whole clear aperture is required during shutdowns. Figure 1.1 Plan view of an ill-considered plant layout (with respect to mill relining activities) Crushing and Grinding 2002 Conference Page 4 Unfortunately and forever-more, mill relining crews are sentenced to working between the confines of mill
22、 shell and mill motor. They face constant exposure to increased physical risk and mechanized linerbolt removal is precluded. Relining times are always long and accidents not uncommon. 1.3 Summary the Project Owners opportunities The Project Owner must consider grinding plant availability and its imp
23、ortance to plant performance and ultimately, profitability. The Project Owner must work closely with the Project Manager to ensure all issues relating to grinding mill relining are considered and addressed via the supply specification documents relating to mill supply, associated plant supply and th
24、e detailed design of the adjacent plant. This paper, provided in a constantly updated format at and .au websites, can serve both as a set of guidelines and a checklist for the Project Owner and the Project Manager. Constructive criticism, toward developing a complete and accurate checklist, is welc
25、omed. 2. PROJECT MANAGER Project Managers are constantly developing their expertise in a wide range of areas, including those relating to grinding mill plant design and mill relining issues. Most modern grinding plants are easy to work within and produce excellent results. The Project Managers suppl
26、y specification documents, included in every Request for Quotation (RFQ), will define the future outcomes for his client, the Project Owner. In no particular order, the Project Managers key questions and responsibilities regarding the performance of future mill relining activities include: 2.1 Mill
27、supply contract - technical issues relating to mill relining 2.1.1 Obstacles Do the mill motors or other mill contract supply items impede Linerbolt removal/replacement including access for tools such as RMEs THUNDERBOLTTHUNDERBOLT recoilless hammers? Crushing and Grinding 2002 Conference Page 5 Ple
28、ase refer to Figure 2.1 (RME can supply THUNDERBOLTTHUNDERBOLT operating envelopes which clearly define THUNDERBOLTTHUNDERBOLT hammer operating clearances). The ability to apply powerful tools to remove worn liners easily is one of the greatest, single factors dictating overall grinding mill relinin
29、g speed and safety. Figure 2.1 Superimposing RME THUNDERBOLTTHUNDERBOLT recoilless hammer outlines, over each mill liner bolt hole, will reveal possible interference with mill components such as the ring motor. 2.1.2 Liner-knock-out holes Have mill-bolt-hole-sized, liner-knock-out holes been provide
30、d in the mill shell and perhaps mill ends for every liner? Please refer to Figure 2.2. Tiny knock-out holes are of no use. Figure 2.2 SAG mill shell liners need knock-out holes for every liner. SAG mill end liners/grates (outer rows) benefit from knock-out holes . All mills (SAG, AG, ball and Rod) b
31、enefit from liner knock-out holes. Crushing and Grinding 2002 Conference Page 6 2.1.3 Liner design Does the mill liner pattern eg. number of rows, height of lift, etc. follow the latest/best understanding of grinding dynamics within the mill. This issue will have considerable influence on the mass o
32、f the heaviest liners. The old liner weight standard for (say) a 32 SAG mill was 4000 lb/1818 kg. The new standard is 7700 lb/3500 kg. 2.1.4 Mill entry diameter There are relationships between maximum liner weight, overall liner dimensions, overall mill dimensions (diameter and length) and the criti
33、cal mill entry diameter. RME can advise regarding minimum mill entry dimeter for a given mill and a maximum liner weight. Alternatively, RME can advise a maximum liner weight for a given mill, including a non-negotiable clear entry diameter. 2.2 Mill/plant interface issues 2.2.1 What is the relation
34、ship between the mill charge level and the plant floor level? This relationship has a major effect on mill relining crew access to liners and resulting mill relining efficiency. Please refer to Figure 2.3. Figure 2.3 Relationships between Mill Charge level and Plant Floor levels. Low Mill Format Hig
35、h Mill Format Crushing and Grinding 2002 Conference Page 7 2.2.2 How will mill bearings be replaced? In high mill formats, the entire bearing pedestal is exposed and the mill bearings are easily accessed. In low mill formats, the bearing pedestal is partially below floor level and a lift-in/lift-out
36、 floor section is required. Please refer to Figure 2.4. In some cases, this lift-in/lift-out floor precludes Mill Relining Machine operating forces from being resisted near the mill. The necessary off-set means additional cantilever for the Mill Relining Machines beam. Please refer to Figures 2.7 an
37、d 2.8 and to further discussion under Plant Structure Design Issues Mill Relining Machine front jack and rear tie down hard points. Figure 2.4 High Mill verses Low Mill Format 2.3 Plant structure design issues 2.3.1 Mill Relining Machine entry into plant (obstacles) Can the Mill Relining machine fit
38、 into the plant? Please consider the machines travel/transport route from delivery shipping container(s), site assembly/erection, erection site to outside plant, outside plant to Mill Relining Machine in-plant storage location. RME has experienced one major oversight in the areas which requires some
39、 machine disassembly and some plant structure disassembly to deliver the machine to its normal storage location. While difficult enough at ground level, this activity occurs three floors up from ground level. High Mill Format Low Mill Format Crushing and Grinding 2002 Conference Page 8 2.3.2 MRM tra
40、velling (obstacles) Can the Mill Relining Machine travel easily from its nominated storage location to each mill serviced by it ie. are there steps in the floor, process pipework (horizontal, vertical, oblique) etc. Please refer to Figure 2.5. Figure 2.5 An RME Mill Relining Machine negotiating plan
41、t structure and process piping obstacles. 2.3.3 Floor capacity 1 (for RME s Mill Relining Machine) Can the floor carry the weight of a travelling Mill Relining Machine? Consider loads of 12,000 to 25,000 kg depending upon mill size. Please refer to Figure 2.6. 2.3.4 Floor capacity 2 (for RMEs Powere
42、d Feed Chute Transporter) Can the floor carry the weight of the travelling Powered Feed Chute Transporter? Consider 30,000 to 100,000 kg depending upon mill size. Please refer to Figure 2.6 2.3.5 Floor capacity 3 (for stacked liners, new and old) Can the floor carry the weight of stacked mill liners
43、? Crushing and Grinding 2002 Conference Page 10 Figure 2.7 Typical RME Mill Relining Machine front jack hardpoint. 2.3.7 Mill Relining Machine rear (uplift) tiedowns The cantilevered arrangement of a working Mill Relining Machine demands robust rear-tiedown details. Please refer to Figure 2.8 for de
44、tails. The uplift forces will vary depending upon mill diameter, mill length, liner weight etc. Please refer to RME for exact values, once the mill parameters are know. The Project Manager must consider these point loads in the plant floor design. Figure 2.8 Typical RME Mill Relining Machine rear ti
45、e-down hardpoint. Crushing and Grinding 2002 Conference Page 11 2.3.8 Thunderbolt Recoilless Hammer support systems 2.3.8.1 Support methods Thunderbolt hammers can be supported by any of three methods: Type A hammer suspended by plant overhead crane* Type B hammer(s) supported by RMEs twin-tube mono
46、rail arrangement Type C hammer(s) supported by RMEs telescoping jib(s) Independent studies have shown that, during a grinding plant shutdown, the most important piece of equipment is the overhead crane (The second most important is RMEs Mill Relining System). Using the overhead crane for Thunderbolt
47、 hammer support is a misuse of this vital resource when alternatives are available (monorails and jibs). Type A (overhead crane supported) Thunderbolt hammer solutions are not recommended. 2.3.8.2 Optimum Thunderbolt hammer support management For ball mills, gear driven or ring gear driven, the pref
48、erred method is circumferential twin-tube monorails. Please refer to Figure 2.9 and 2.10. All liner bolts are relatively short permitting the use of a standard length Thunderbolt hammer moil and a standard mill shell to monorail tube distance. Figure 2.9 Ball Mill Thunderbolt Hammer Support (Preferr
49、ed) RMEs Circumferential AA twin-tube monorail (sectional view) Crushing and Grinding 2002 Conference Page 12 An alternative for ball mills is the jib. Figure 2.10 Ball Mill Thunderbolt Hammer Support (alternative) RME Thunderbolt Telescoping Jib For gear driven SAG and AG mills, RME recommends the
50、following arrangement: twin-tube monorails for mill feed end and mill shell telescoping jibs for the discharge end Mill feed end and mill shell shell linerbolts are both relatively short permitting the use of a standard length Thunderbolt hammer moil and a standard mill shell to monorail tube distan
51、ce. Discharge end bolts are long and require the special long moil and the jibs telescoping facility. 2.4 Storage location for Mill Relining Machine (MRM) A Mill Relining Machine is exposed to an unusual and difficult duty cycle: months of inactivity punctuated by relatively brief periods of intense
52、 activity. To achieve maximum reliability and maximum asset life, protection of the MRM, from the typical concentrator environment, is critical. RMEs Mill Relining Machines, if protected and maintained adequately, are life of mine quality assets. Parking the MRM, without protective covers, directly
53、under Crushing and Grinding 2002 Conference Page 13 (say) the primary cyclones, guarantees periodic drenching with corrosive, abrasive, slurry spillage. RMEs large-rubber-tyred MRMs provide considerable scope for travel about the concentrator away from spillage sources. Protective covers are a stand
54、ard option and are also recommended. 2.5 Power supply and other services 2.5.1 Mill Relining Machine Provide suitable electrical power outlets, within robust, slurry-proof enclosures, as close as possible to the Mill Relining Machine and preferably near the mills feed-end trunnion. This location min
55、imises the length of power cable exposed and reduces the possibilities for tripping hazards, damage by forklift and damage from falling liners. Water, compressed air etc should also be provided nearby and for the same reasons. Please refer to Figure 2.11. Figure 2.11 Placement and protection of elec
56、trical and other supply services Crushing and Grinding 2002 Conference Page 14 2.5.2 Thunderbolt Recoilless Hammers Provide suitable electrical power outlets, within robust, slurry-proof enclosures, as close as possible to the Thunderbolt Powerpack locations to minimise exposed cable. Please conside
57、r a protected (roofed) area well away from the obvious spillage sources. Thunderbolt powerpack locations will vary from site to site, depending upon the Thunderbolt hammer support systems. Please contact RME for details. 2.6 Mill inching Mill inching is best controlled by the reline crews foreman, p
58、ositioned at the mill entry on the MRMs beam. The beam provides a safe, stable platform and the MRMs lights illuminate the interior of the mill. A remote, mill-inching control, in the reline foremans possession, permits fast, accurate control of the mill and the mill charge rille, which exposes the
59、next liners for replacement. Please consider specifying remote control for mill inching when producing the mill supply specification document. 2.7 Radio control frequencies Many RME Seven (7) Axis Liner Placement Mill Relining Machines are controlled via a remote, radio-control system. Productivity
60、is enhanceed and radio control is always recommended. The Project Manager must ensure the frequency band offered to RME is permitted at the actual minesite location (country and region). 3. MILL SUPPLIER There are currently 5 major suppliers of grinding mills. In alphabetical order these are: ANI FF
61、E Minerals and Vecor Metso Outokumpu Polysius (Krupp) Tyzahmash in Russia and Chinese mill manufacturers do not appear to supply outside their home markets. Mill supply is a competitive business and it is to the suppliers credit that their product reliability seems to be increasing despite cost pres
62、sures. RMEs Mill Relining System elements (Mill Relining Machines, THUNDERBOLTTHUNDERBOLT Recoilless hammers, Powered Feed Chute Transporters) must interface perfectly with the Mill Suppliers elements (mill shell, mill drive, mill liners, mill feed chute etc). Crushing and Grinding 2002 Conference P
63、age 15 It is relatively easy to interface the design and manufacture of RMEs Seven (7) Axis liner placement Mill Relining Machine with the mill shell and associated plant. RMEs Mill Reline Machine Specification Sheet defines all the critical values. Please find a copy of RMEs Mill Reline Machine Spe
64、cification Sheet as Figure 3.1. Interfacing RMEs Thunderbolt Recoilless hammers and their support systems falls more in the area of the Project Manager and the detailed plant design. Interfacing RMEs rail-based Powered Feed Chute Bases (PFCB) and large-rubber-tyred feed chute, requires close coopera
65、tion. Figure 3.1 Copy of RMEs Mill Relining Machine Specification Sheet (April 2000) The key issues for Mill Manufacturers in relation to mill relining practices are: 3.1 Clear entry diameter into the mill Clear mill entry diameter is the single most important limitation to a fully mechanised and op
66、timised grinding mill relining. Please refer to RMEs Design Loading vs Entry Diameter Comparison graph included as Figure 2.13 and to a more detailed discussion below. Crushing and Grinding 2002 Conference Page 16 Figure 2.13 Design Loading verses Entry Diameter Comparison 3.2 Provision of working c
67、learances for mechanised liner and linerbolt removal The location and orientation of linerbolts, particularly relative to placement of motors/gearboxes/couplings, ring gears or ring motors, is of great importance for mechanised liner and linerbolt removal. Please refer to THUNDERBOLTTHUNDERBOLT Reco
68、illess hammer operating clearances, illustrated as Figure 2.1. Precise envelope details are available from RME. 3.3 Provision of linerbolt diameter liner knock-out holes for every liner Linerbolt diameters of M36, M42, M50, 2” etc should be considered minimums for liner knockout holes. RME has obser
69、ved 20 mm diameter knock-out holes, which are worthless. The impact from the THUNDERBOLTTHUNDERBOLT hammer destroys 20mm diameter pins instantly. RME would welcome discussion regarding the merits of standardising on 2” bolts for all mills. Please refer back to Figure 2.2 Crushing and Grinding 2002 C
70、onference Page 17 3.4 Liner design issues Points to consider are: 3.4.1 Bolt hole placing and spacing eg. 36 rows, 48 rows, 72 rows? Mill modelling should indicate the optimum arrangement. Fewer rows means larger, heavier liners with ramifications on mill entry diameter and Mill Relining Machine des
71、ign. 3.4.2 Liner weight and overall size Review liner weight and physical liner size relative to the mill entry diameter. Please refer to Figure 2.14 Figure 2.14 Cross-section showing the machine and liner mill entry problem 3.4.3 Application of liner accessories eg. between-liner rubber (wedge-its)
72、? 3.4.4 Liner/mill shell rubber Rubber glued to mill shell fails sooner or later by detachment. Is there a better way eg. specifying a bare shell with rubber glued to the back of each new liner? Crushing and Grinding 2002 Conference Page 18 Clear entry diameter detailed discussion (an expansion of 3
73、.1) Modern SAG and AG mills usually offer large clear entry diameters bought about by large mill bearings and large-bore mill feed chutes. The large-bore mill feed chutes are essential to minimize the risk of chute blockage. Ball mills however present special problems which are discussed in detail b
74、elow. Also, for sites where a single, combination SAG/ball Mill Relining Machine is required to service both the primary SAG or AG mill plus the associated ball mill(s), the ball mill entry diameter can be the limiting factor in the overall MRM design. Ball mill entry diameters have two problems: 1.
75、 Available Clear Entry Diameter 1 (defined by the mill, feed-end, trunnion bore or the trunnion liner details or mill-cavity liners) Typically, the ball mill feed chute is, in effect, a pipe of relatively small diameter. Ball mills can be pipe fed due to the small particle size. Chute blockage, from
76、 mill feed alone, is impossible. However, no mill relining machine will fit a sub-metre entry (pipe) diameter. Fortunately for Mill Relining Machine designers, the weight of balls plus charge within ball mills, demand very large bearings and correspondingly large trunnion journals. Occasionally the
77、ball mill bearings and the SAG mill bearings are identical, despite the somewhat larger diameter of the SAG or AG primary mill. Significant capital spares savings are then possible. The ball mills large trunnion bore is reduced to the feed chute (pipe) diameter by the feed end trunnion liner. Please
78、 refer to Figure 3.2 Crushing and Grinding 2002 Conference Page 19 Figure 3.2 Typical ball mill feed-end trunnion liner installed (left hand side) and removed (right hand side). Removing and re-installing a conventional feed-end, trunnion liner risks damaging the seals which can subsequently leak an
79、d damage the trunnion casting. The ball mill feed-end trunnion liner is a large and awkward component with rubber seals at each end. It is a major undertaking to remove and re-fit this piece. Furthermore, any mishap with the rubber seals risks catastrophic damage to the mill shell, specifically the
80、trunnion bearing casting. If the seals are damaged during re-fitting, slurry will leak into the space between the trunnion liner and the inner bore of the mills trunnion bearing/mill end casting. This slurry will erode the casting and, given enough time, will destroy the mill journal from the inside
81、. RME (and presumably the mill manufacturers) cannot recommend removal of the ball mill feed-end trunnion liner as part of the planned relining methodology. The solution to the dilemma of (i) requiring a large, clear-entry diameter for Mill Relining Machine access and (ii) not removing the feed-end
82、trunnion liner, is to provide a removable annulus feed end trunnion liner as standard supply. Please refer to Figure 3.3 This type of trunnion liner provides an easily removable annulus which: (i) provides a large clear entry diameter for MRM access and (ii) leaves the large, cylindrical trunnion li
83、ner (and its seals) securely in place. Crushing and Grinding 2002 Conference Page 20 Figure 3.3 Proposal for a removable annulus feed-end, trunnion liner. This solution provides a large, clear-entry diameter while leaving the trunnion liner securely in place. 2. Clear Entry Diameter 2 (defined by ba
84、ll charge height) The second problem when relining ball mills is charge height. Most ball mills seemed to be filled-to-overflowing with grinding balls. In mills equipped with removable-annulus-type, feed-end, trunnion liners the situation can be worse. When the trunnion liner annulus is removed, bal
85、ls cascade out the feed end. Relining crews are presented with the following image and the obvious problem of fitting the Mill Relining Machine into the mill. Please refer to Figure 3.4. Crushing and Grinding 2002 Conference Page 21 Figure 3.4 The problem of inserting a Mill Relining Machine into a
86、full charge ball Mill. Regrettably, this already serious problem only gets worse. Even in the event of successfully inserting the Mill Relining Machine into the mill (scraping along the top of the ball charge) addition problems present: (i) inching the ball mill with the MRM still inside, risks majo
87、r MRM damage from torque and/or falling balls. Removing the MRM for each rotation increment is inconvenient. (ii) the ball charge height grows as worn liners are replaced with new liners. The extra volume of the new liners displace balls which further raise the ball charge level. Three solutions are
88、 possible and are offered for consideration and debate: Design the plant with the next size up (diameter) ball mill shell and run lower ball charges e.g. A full 24 diameter ball mill becomes an emptier 25 diameter ball mill. (Could mill manufacturers comment on the extra cost of a larger shell. Pres
89、umably motor size/power draw would be identical for both options) Run the ball charge down ie. stop ball addition 1-2 weeks before shutdown. RME understands this may not be acceptable for many plants due to reduced throughput/coarser grind issues. Develop a weird, upside-down Mill Relining Machine s
90、pecifically for full ball mills. The additional costs and unusual operating practices, when compared with the operational familiarity of mill Crushing and Grinding 2002 Conference Page 22 relining crews with conventional RME Seven (7) Axis liner placement Mill Relining Machines, make this solution u
91、nattractive. 4. LINER SUPPLIER The liner supply business is competitive, the pre-requisites being one or more foundries, exceptional quality assurance (casting design/manufacture) and cost effective delivery from manufacturing facilities to minesite. International sales are not uncommon but probably
92、 at a cost disadvantage to local suppliers. Only faultless quality can maintain market share and global sales. Mill downtime is so expensive that cheap liners rarely, if ever, save money. Taken to the extreme, a failure of a cheap liner can destroy a mill shell and perhaps destroy a single mill mine
93、s entire economic prospects. Short of catastrophic a mill shell or drive-line failure, the liner supplier is often at the centre of unscheduled mill downtime issues associated with reline problems (major time over-runs) and other causes of mill downtime. 4.1 Liner problems can include: 4.1.1 Deliver
94、y problems Not having liners on-site when the old ones are worn out, (i) risks the mill shell should grinding continue while the reline is postponed or (ii) causes crippling down time if the mill is stopped. This may be a late ordering problem, difficult supply route problems insufficient on-site st
95、ock for the remoteness of the site or manufacturing schedule problems. 4.1.2 Design and casting errors These can be minor and corrected on-site by arc-air gouging and/or grinding. One error (design, pattern, casting) means dozens of liners requiring adjustment. These liners have been cast from the h
96、ardest, toughest materials available and do not yield readily to on-site adjustment. Major errors eg. liners cast opposite hand are impossible to correct and are worse than non-delivery. No correct castings may exist anywhere in the world. This problem can only be avoided by quality assurance by the
97、 liner supplier at the minesite. 4.1.3 The odd bad liner (soft, porous, brittle) A single liner can fail unexpectedly, causing local mill shell erosion (minor to catastrophic). This is a foundry quality assurance issue. Crushing and Grinding 2002 Conference Page 23 4.1.4 A set of bad liners (soft, p
98、orous, brittle) All liners can fail unexpectedly or deliver shorter liner lives, can cause shell erosion (minor to catastrophic) or extended downtime while awaiting a replacement set. This is a foundry issue. 4.1.5 Mill Relining Machine interface errors (lifting lugs cast which do not fit MRMs grapp
99、le) This is a liner supplier and Mill Relining Equipment supplier quality assurance issue. RME (a) has produced standard interfaces (Please refer to Figure 4.1) and (b) provides liner/machine interface checking service, free with new Mill Relining Machine. Figure 4.1 An extract from RMEs standard ma
100、chine/liner interface documentation. 4.2 Liner development Liners serve two functions: Liners protect the mills structural shell from abrasion erosion i.e. liners are sacrificial and replaceable. Liners are the focus of increasing attention regarding mill power draw and grinding performance. Crushin
101、g and Grinding 2002 Conference Page 24 It is worth mentioning the improved understanding of mill operation through computer modelling of charge behaviour and the (sometimes related) move to fewer, heavier liners. Concurrently, RME has developed the worn liner removal, new liner placement Mill Relini
102、ng System which has permitted the move to much larger liners. The current worlds-largest-liner is PT Freeport, Indonesias 8340 lb feed end liners used in their 34 SAG mill. RME is currently building a 10,000 lb capacity Mill Relining Machine for Kennecott, USA. Mr. Dale Coray of Freeport believes th
103、e final limit will be around 13,000 lb, nearly 6000 kg for 34 to 40 SAG mills. There are three interface points between liner supplier and Mill Relining Equipment supplier (RME): Maximum liner weight must not exceed the Project MRMs Safe Working Load (SWL). RME provides guidance with Mill Relining M
104、achines specification (including recommended SWL) at the Request for Quotation stage and, where possible, provides an MRM with a capacity margin to accommodate future liner development. Maximum liner dimensions must fit the available area for liner access into the mill. Please refer to back Figure 2
105、.11. The lifting lugs casting into the liners must fit with RMEs Hydraulic Pinning Tool. Please refer back to Figure 4.1. RME enjoys excellent working relationships with all quality liner suppliers, worldwide. For new machine supply, RME usually reviews the liner drawings (to ensure a machine/liner
106、correct interface) as part of the machine supply contract. 5. PLANT OPERATING PERSONNEL Grinding plant operators inherit the Owners decisions, the Project Managers plant design, the cheapest acceptable mill, the cheapest acceptable liners and perhaps some mill relining equipment. The plant operators
107、 also inherit a new ore-body and an operating budget. Despite all the above limitations, the single greatest characteristic a Plant Operating group can possess is the desire to be world class. Some of the problems faced, and their effect upon mill relining, are described in detail. 5.1 Operating cir
108、cumstances which lead to difficult mill relines A common and nasty scenario sees a new, open-cut ore-body, of variable hardness, being processed through a fixed-speed SAG mill. During periods of soft ore, the operational choices are to (i) increase throughput (which overloads all downsteam processes
109、) or (ii) hold throughput and hammer the mill liners with balls cascading into the shell liners, beyond the toe of the charge. Crushing and Grinding 2002 Conference Page 25 In the extreme, the ductile flow of the hammered liners actually spring the mill shell. Arc air gouging such liners is accompan
110、ied by sudden, loud reports as the mill returns to its (hopefully) original shape. This uncontrollable operating scenario illustrates the consequences of the Project Owners decision to order a fixed speed mill (perhaps constrained by capital) and the effects of SAG ball strike beyond the toe of the
111、charge. Under optimum circumstances, Plant Operators will be presented with a mature and consistent ore body and have at their disposal a variable-speed mill. Grinding performance can be optimised by aids such as mill microphones which halt mill speed increases just short of ball strike. This delive
112、rs maximum throughput, maximum grinding performance and easily replaced liners (not hammered into a single mass). Conscientious operators, and their careful mill control, hold the key to quick, safe SAG mill relines. AG mills and ball mills are obviously less sensitive to indifferent operation. Oper
113、ators also carry the following mill relining responsibilities: 5.2 Liner monitoring Monitoring of liner wear and other failure modes eg. early detection of liner cracking 5.3 Liner re-ordering Timely ordering of re-placement liners taking into consideration the logistical problems of a remote site a
114、nd the possibility of liner problems. 5.4 Liner development Liner development for wear and power draw in conjunction with liner suppliers and perhaps third party consultants. 5.5 Shutdown spacing Shutdown timing and duration (not too soon and definitely not too late). 5.6 Shutdown organisation Whole
115、 shutdown organization * * Shutdown organization responsibilities depend upon the individual plants organizational structure. For the purposes of this paper, I have assumed the maintenance staff are within the overall operational management structure. Crushing and Grinding 2002 Conference Page 26 5.
116、7 RMEs Mill Reline Director software as a shutdown planning aid For over a decade, RME has focused on reducing the time taken to reline a mill, the only confined, in-series, shutdown activity i.e. the only shutdown activity which cannot be accelerated by adding more personnel. This halving of mill r
117、elining downtime has been achieved by providing the limited crew numbers with powerful technologies. However, halving traditional, mill-relining downtime will win no overall gain in annual plant utilisation unless plant operating and plant maintenance personnel arrange for sufficient resources to ac
118、hieve all other plant repairs within the (now reduced) mill relining period. This means predicting the mill relining time accurately and organizing enough other resources (for other, non-relining shutdown work) to match that reline time. To assist in mill relining time prediction (and therefore whol
119、e shutdown duration production), RME is developing Mill Reline Director Software. RMEs Mill Reline Director Software will aid mill relining duration predication. From this prediction the whole plant shutdown can be arranged including the provision of sufficient resources to complete all other (non-r
120、elining) shutdown activities within the (now reduced) mill reline period. As of October 2002, the prototype Mill Reline Director software package is now complete such that an RME programmer can commence in-field trials. Various Plant Operators will be approached for program trials in the near future
121、. There is no interference with the relining process for such trials. 6. PLANT MAINTENANCE PERSONNEL Maintenance staffs core responsibility is to optimise the life of every item of equipment in order to eliminate unscheduled (breakdown) time. Large, modern grinding mill availabilities in excess of 9
122、6% are being achieved thanks to the combined efforts of the mill manufacturers, plant maintenance personnel and the Mill Relining Team detailed in this paper. It is the responsibility of the maintenance group to ensure that every other piece of equipment in the plant can equal or exceed this remarka
123、ble performance. Focusing on the mills and the mill relines, Plant Maintenance Personnel responsibilities are: QA of new lines, linerbolts, rubber etc (well before the reline) Maintenance and repair of mill relining equipment either directly or using RMEs factory technicians Provision of mill relini
124、ng crew either from in-house personnel or, increasingly, from specialist contractors Provision of auxiliary equipment e.g. forklifts Fitting of inching drive equipment (geared mills) Crushing and Grinding 2002 Conference Page 27 7. MILL RELINING CREW Before the arrival of RMEs Mill Relining System,
125、the pre-requisite for mill relining crew membership was physical strength and stamina. RMEs goal of halving mill downtime via mechanisation has seen the emergence of a different type of mill relining crew member. The more advanced mill relining crews now include equipment operators/technology users.
126、 These advanced mill reline crew members are quite different from the characters still required for manual mill relining, generally on smaller mills. Mill Relining Crews can be in-house staff, specialist contract reliners or a combination of both where supervision may be provided by specialist contr
127、actors while the balance of the crew consist of in-house staff or other local labour. Supervision of the mill relining crew is the key to fast, safe mill relines, all other factors being equal. RME has observed world-best-practice performances from in-house staff, from contracted specialists and fro
128、m combined groups. Some sites, regardless of the mill relining crew makeup, achieve unbelievable times. Other sites are relatively slow. The significant difference is the organisational talent of the crew supervisors. 7.1 RMEs Mill Reline Director software - as a Mill Relining Crew aid In response t
129、o this observation, RME is developing the Mill Reline Director Software, previously mentioned under 5.7 above. This software contains all the site-specific constraints, the liners to be replaced etc. and produces an overall program with short term (hour by hour) milestone targets. This detailed mile
130、stone program provides the organisational skills of the best reliners for every relining crew. 7.2 Mill Relining Crews RME Mill Relining System users The Mill Relining Crew are the users of RMEs worn liner removal , new liner placement Mill Relining System. Since the mill is a confined space, provid
131、ing extra personnel could have no effect on the overall mill relining downtime. Only the provision of technologies to the existing mill relining crew has provided the necessary power and empowerment. 7.3 THUNDERBOLT empowerment A single RME THUNDERBOLTTHUNDERBOLT 1500 recoilless hydraulic hammer del
132、ivers much greater blows at much greater rates when compared with the strongest man and Crushing and Grinding 2002 Conference Page 28 his sledge hammer. Also, the THUNDERBOLTTHUNDERBOLT never tires. One THUNDERBOLTTHUNDERBOLT 1500 hammer provides impulse energy delivery rates equal to over 100 stron
133、g men. Please refer to Figure 7.1. Figure 7.1 Another happy THUNDERBOLTTHUNDERBOLT crew. 7.4 Mill Relining Machine empowerment A mill liner, suspended by a three (3) axis crane style mill liner handler, must be manhandled into position. Few liners hang at the correct orientation to the mill shell. F
134、itting the liner to the mill shell requires raising the liners centre of gravity. For liners of 1000kg, this becomes increasingly difficult. For liners, over 1500kg it is impossible. RMEs Seven (7) axis Liner Placement Mill Relining Machine has permitted todays application of 3800kg/8360lb liners an
135、d will permit the use of 6000kg/13,200lb liners in the future. RME research and development has refined the Seven (7) Axis Liner Placement Mill Relining Machine such that a broad range of personnel skill levels can control placement of very heavy liners with millimetre accuracy. Please refer to Figu
136、re 7.2 Crushing and Grinding 2002 Conference Page 29 Figure 7.2 A typical RME Mill Relining Machine placing 1500kg liners. The human face of the benefits of RMEs Mill Relining Systems sees individual crew members going home on day 4 after three or four 12 hour shifts involving technology operation a
137、nd little in the way of hard physical work. In contrast, manual methods see crew members still forced to deliver intense physical effort for yet another 12 hours shift on day 6 or 7. These exhausted crews have an increased exposure to accidents. RME would to take this opportunity to thank all those
138、Mill Relining Crews who, while initially sceptical of the new technologies, have been willing to give it a go and are now rewarded with the fastest and safest reline in the world. 8. THE MILL RELINING SYSTEM SUPPLIER RME, the Mill Relining Equipment Suppler, interfaces with all other mill relining t
139、eam players, hence our interest. RMEs responsibilities are: 8.1 RMEs responsibilities to the Project Owner RME has a responsibility to the industry (Project Owners) to maximise the annual utilisation of grinding plant in order to maximise rate of return on investment and long term project profitabil
140、ity. RMEs roles are (i) to develop and supply equipment with the potentional to provide the fastest and safest relines in the world and (ii) do all within our power to see that equipment applied effectively to achieve the fastest and safest reline in the world. The rate of return on investment for a
141、 RME Mill Relining System lies in the range of one reline event to, occasionally, one full year (3-5 relines). RMEs travelling, onsite technical support services provide equipment maintenance and on-going training. Crushing and Grinding 2002 Conference Page 30 8.2 RMEs responsibilities to the Projec
142、t Manager RME must win a competitive bid process for equipment supply. RMEs Mill Relining System is the clear technological leader and may also be a little more expensive. It is RMEs responsibility to make clear the performance advantages of our Mill Relining System where the entire cost of a system
143、 will be repaid (in increased plant utilisation) at an astonishing rate: typically between one use (one reline) and one year (3-5 relines). The cost differential between RMEs Mill Relining System and other mill liner handlers is insignificant when compared with the performance differential, the long
144、evity differential and the long term technical support differential. RMEs Mill Relining System, properly maintained, is a life-of-plant solution. RME must also ensure free-flow of information relating to interfaces between plant and mill design and RMEs Mill Relining System. Each Mill Relining Syste
145、m solution is unique for each different application. 8.3 RMEs responsibilities to the Mill Supplier RME must work with the Mill Suppliers to optimize mill relining performance for our mutual customer, the Project Owner. Large, clear-mill-entry diameters, are necessary for large liners and correspond
146、ingly large MRMs. Large bearings are also expensive. RME and the mill manufacturer must understand each others constraints. Liner-knock-out holes may mean extra expense, or may simply mean the use of now redundant liner bolt holes made available in a standard drilling pattern thanks to fewer and lar
147、ger liners. 8.4 RMEs responsibilities to the Liner Supplier RME must work the Liner Supplier to ensure a perfect interface between the MRM and each individual liner casting. A standard machine/liner interface on every liner means a single engagement tool on the MRM. Changing mill engagement tools th
148、roughout the reline is deemed unacceptable by mill relining crews. 8.5 RMEs responsibilities to the Plant Operating Personnel RMEs responsibilities to the Plant Operating Personnel are not dissimilar to our responsibilities to the Project Owner. Plant Operating Personnel are the onsite representativ
149、es for the Owner, charged with the responsibility of maximising the Owners return on investment. Crushing and Grinding 2002 Conference Page 31 8.6 RMEs responsibilities to the Plant Maintenance Personnel RME must provide reliable equipment which does not fail mid-reline. RME does provide quality, re
150、liable equipment which can be maintained by factory-trained, travelling technicians at each minesite. RME must also ensure the highest standards of spare parts supply and on-going technical support. 8.7 RMEs responsibilities to the Mill Relining Crew RMEs responsibility to the Mill Relining Crew is
151、to provide empowering technologies which are reliable, safe and easy to use. 8.8 RMEs responsibilities to ourselves the Mill Relining Equipment Supplier RMEs responsibility to ourselves is to retain the same intensity of focus, with respect to achieving worlds best practise mill relining outcomes fo
152、r all our customers. Retaining focus through ongoing research and development (often in response to constructive advice from other Team Players), consistent quality and reliable after-sales service will ensure the popularity of RMEs Mill Relining System. 8.9 The perfect grinding plant optimised for
153、mill relining SAG mill and ball mill diameters do not exceed the ratio of 36:20. A ratio of 40:20 is not possible. A ratio of is 36:24 easier than 36:20 etc. This SAG mill/Ball mill diameter ratio allows a single machine to service both the SAG and the Ball mills. Ball mill clear entry diameter (wit
154、h trunnion liner annulus only removed) is sufficient for SAG mill/Mill Relining Machine/liner weight. The current standard for 32 diameter SAG mill is 3500 kg/7700 lb. For example, a minimum clear entry diameter for a combination 32/20 SAG/Ball mill Relining Machine of 3500kg SWL would be around 185
155、0mm, assuming the physical size of the liner was not to great. Larger feed end liners and grates may require (say) 2150mm. Identical mill Floor to mill Axis Heights for all mills. This allows a simple, single- height MRM to service all mills. Platforms (re-moveable) are provided to optimise working
156、height relative to SAG/AG and Ball mills. The high mill style eliminate lift-in/lift-out floor sections for mill bearing maintenance and permits the Mill Relining Machine hard-points to be placed close to the mill entries. Mill Shells are provided with large diameter liner knock-out holes for all li
157、ners. Mill design and adjacent plant design provides clear, strike lines for THUNDERBOLTTHUNDERBOLT 1500 recoilless hammer. THUNDERBOLTTHUNDERBOLT/Thunderstrike twin-tube Monorails are provided for SAG/AG mill Feed End, SAG/AG mill Shell and Ball mill (Feed end, Shell, Discharge End Circumferential)
158、. THUNDERBOLTTHUNDERBOLT telescoping jibs are provided for SAG/AG discharge end. Crushing and Grinding 2002 Conference Page 32 FOOTNOTE: About RME RME is more than an equipment manufacturer. RME combines the attributes of an Engineering Research and Development Laboratory, an Engineering Design Cons
159、ultancy and Engineering Manufacturing Company complete with global after-sales support. In combination, RME provides a complete, vertically integrated unit capable of undertaking all aspects of product development from the first idea through development and production, to on-site maintenance. More s
160、ignificantly, RME sets and achieves goals. In the early 1990s RME set about to halve traditional mill relining downtime. By 2001, many world famous sites such as Freeport, Escondida, users of RMEs Mill Relining System, were not only achieving but exceeding RMEs ambitious goals of a decade before. RMEs Mill Relining System provided the key to unlock mill downtime. One of RMEs current goals is to see the proven performance and benefits of our Mill Relining System achieved at every significant grinding plant.
