Abstract:
Machine-implemented methods, systems, processing devices and machine-readable media are provided for simulating a mill reline, which involve collecting mill relining data and processing the relining data as simulation parameters using a mill relining model. The relining data generally include variables treated as discrete time/frequency distributions. Simulated events for the mill reline may be generated based on the relining data. Additional relining data relating to a specific existing site may be included as simulation parameters. The simulation may be used in determining an optimal work flow for carrying out the mill reline at a specific existing site, e.g., where time to carry out the mill reline is minimized. The simulation may also be employed for benchmarking. The additional relining data may be provided in video format, and analysis of the video format data may be undertaken, e.g., by an operator for refining and/or verifying the additional relining data, prior to utilizing the additional relining data as simulation parameters in the simulation model. The mill relining data may also include additional parameters, such as the size and quantity of the liners, the reline planning process and relining crew proficiency, the relining equipment and plant design surrounding the mill being relined, and the like.

Description:
TECHNICAL FIELD 
     This invention relates to a method and system for simulating a mill reline. In particular this invention is directed towards a method and system for simulating a mill reline using discrete event simulation software. 
     BACKGROUND 
     Hard rock grinding mills used in mineral processing utilize sacrificial segmented liners bolted to the internal casing of the mills which are regularly replaced during routine maintenance. Typically such mills may range in size from three meter to eleven meter diameter and are lined with replaceable heavy steel segments attached internally to the mill casing by through bolting. As the sacrificial liners wear, it becomes necessary to remove the bolts that held the sacrificial liner in place and reline the mill. In the last twenty-five years, considerable advances have been made to mechanize the mill relining process, including the use of liner bolt removal tools, an example of which is shown in WO 1997/026116 (Russell Mineral Equipment Pty Ltd) and mill relining machines an example of which is shown in Australian Patent No. 2005239667 (Russell Mineral Equipment Pty Ltd). 
     It has been identified that mill liner life dictates the ‘when’ of mineral concentrator maintenance shutdowns. Furthermore, the exchange of mill liners dictates the duration of each shutdown; the ‘how long’. In combination (the ‘when’ and the ‘how long’) dictate annual maintenance shutdown lost time and therefore the availability and the possible utilisation of the mineral concentrator plant. 
     Since all mineral ore of value must pass through the grinding mill, liner life and liner exchange rate can define the productive limits of the entire mine site. 
     The duration of a mill reline is the sum of thousands of discrete and interdependent activities. The choreographing of these activities occurs in an environment that is often noisy, full of other unrelated work and where the visibility of, and communication with, dependent activities is often obscured by the mill itself. Because of the complexity of the interplay between tasks and the difficulty of quantifying them the estimation of reline times has, in most cases, been reduced to assigning an average time per piece, based on historical data, to each type of liner and multiplying this by the number of pieces to be changed. 
     There are four major contributors to controlling the timing of mill relining shutdowns and the speed of liner exchange, these being the liners themselves (their size and quantity); the reline planning process and relining crew proficiency; relining equipment; and plant design surrounding the grinding mills. 
     The state of the art for estimating reline times is based on somebody familiar with mill relining estimating the time per type of liner and multiplying by the number of liners to be changed. Most if not all methods are spreadsheet based and are incapable of predicting the effects of small changes to the process. The cost for a mill to be shut down for relining is very high, and often is of the magnitude of hundreds of thousands of dollars per hour. 
     To date, the methods to estimate reline times have been quite crude, and do not provide mill owners, plant and machine designers and reline planners with the ability to maximize plant efficiency. 
     The ability of mill owners, plant and machine designers and reline planners to estimate re-line times is usually based on their own experience. The impediments they face to maximize reline times are the large number of variables, the low frequency of relines and the economic risk associated with some changes. Also their ability to maximize the efficiency of their plants suffers from the lack of opportunity to effectively benchmark current performance against best practice. 
     The present invention seeks to provide a method and system for simulating a mill reline that can ameliorate at least some of the disadvantages of the prior art. 
     SUMMARY OF INVENTION 
     According to a first aspect the present invention consists in a machine-implemented method for simulating a mill reline comprising: 
     collecting milling mill relining data from a plurality of mine sites and storing same in a database stored in at least one computer; 
     passing the relining data as simulation parameters to a mill relining model stored in the at least one computer or another computer connected thereto, in which at least some of said relining data are variables are treated as discrete time/frequency distributions; and simulating events for said mill reline based on said relining data. 
     Preferably additional relining data relating to a specific existing site is passed as simulation parameters to said mill relining model, and the simulation is for determining an optimal work flow for carrying out the mill reline at said specific existing site, where time to carry out said mill reline is minimized. 
     Preferably additional relining data relating to a specific existing site is passed as simulation parameters to said mill relining model, and the simulation is for benchmarking. 
     Preferably said at least some of said additional relining data is data initially provided in video format, and analysis of same is required by an operator for refining and/or verifying said additional relining data prior to same being passed as simulation parameters to said simulation model. 
     Preferably additional relining data relating to a proposed new site and/or mill design is passed as simulation parameters to said mill relining model, and the simulation is for determining an optimal work flow for carrying out the mill reline for said proposed new site and/or mill design. 
     Preferably mill relining data comprises the size and quantity of the liners, the reline planning process and relining crew proficiency, the relining equipment and plant design surrounding the mill being relined. 
     According to a second aspect the present invention consists in a processing device comprising: 
     at least one processor; 
     a memory including instructions for the processor: and 
     a bus for providing communication between the processor and the memory, the memory further comprising instructions for receiving mill relining data from a plurality of mine sites in which at least some of said relining data are variables treated as discrete time/frequency distributions, and simulating events in at least one mill reline based on said mill relining data. 
     According to a third aspect the present invention consists in a tangible, machine-readable medium having instructions for at least one processor recorded thereon, the medium comprising: instructions for receiving mill relining data from a plurality of mine sites, in which at least some of said relining data are variables treated as discrete time/frequency distributions; and instructions for simulating events in at least one mill reline based on said received reline data. 
     According to a fourth aspect the present invention consists in a system for simulating a mill reline on a web-based network, said system comprising: 
     (i) at least one computer operated on behalf of a simulation administrator for the purpose of maintaining a web-based mill reline simulation model using associated discrete event simulation software and a database for storing mill relining data in the form of variables treated as discrete time/frequency distributions, said web-based network comprising a website; 
     (ii) at least a second computer used by a first user to access said mill reline simulation model via an online account, and said website having a user web page associated with said first user; 
     wherein said user page is provided with a link to said database so that said user can add additional mill reline data to said database, and a link to said discrete event simulation software so that instructions may be provided to simulate at least one mill reline. 
     Preferably said additional relining data is data relating to a specific existing site, and the simulation is for determining an optimal work flow for carrying out the mill reline at said specific existing site, where time to carry out said mill reline is minimized. 
     Preferably said additional relining data is data relating to a specific existing site, and the simulation is for benchmarking. 
     Preferably said at least some of said additional relining data is data initially provided in video format, and analysis of same is required by an operator for refining and/or verifying said additional relining data prior to same being passed as simulation parameters to said simulation model. 
     Preferably said additional relining data relates to a proposed new site and/or mill design, and the simulation is for determining an optimal work flow for carrying out the mill reline for said proposed new site and/or mill design. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagrammatic view of a system for simulating a mill reline conducted over web-based network. 
         FIG. 2  is flow diagram of the steps to simulate a mill reline using the system shown in  FIG. 1 . 
         FIG. 3 . is a schematic of a 3D mill set up model using the simulation software of the system shown in  FIG. 1 . 
         FIG. 4 . is a schematic of the mill reline simulation screen using the simulation software of the system shown in  FIG. 1 . 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  depicts a first embodiment of a system  100 , which allows for users on a web-based network over the Internet  50  to simulate a mill reline. 
     The simulation is for determining an “optimal work flow” for carrying out the mill reline. The term “optimal work flow” includes within its meaning the optimisation of tool configurations used for the mill reline, and optimisation of the mill parameters. 
     A plurality of users, five of which are shown in  FIG. 1  as users (with computer access)  1 ( a )- 1 ( c ) and  2 ( a )- 2 ( b ) are members of a web-based “simulation” network, administered by a website owner or alternatively a website administrator (not shown) on behalf of the owner, via at least a first computer  10 . 
     Users  1 ( a )- 1 ( c ) may be maintenance managers/engineers at mine sites, whilst user  2 ( a ) may be a plant designer, and user  2 ( b ) may be a mill manufacturing designer/engineer. 
     A simulation database  11  associated with simulation software (application)  12  reside on first computer  10  administered by the earlier mentioned administrator. 
     The users are able to access application  12 , via a website. A website page screen selection (not shown) allows users  1 ( a )- 1 ( c ) to register and then use the web-based simulation network by selecting various menus. Each user  1 ( a )- 1 ( c ),  2 ( a )- 2 ( b ) in a conventional way is able to register their details with the system. 
     A “mill reline raw data” database  21  with associated database software  22  resides on another computer  20  and is also administered by the earlier mentioned administrator. Database  21  contains a relational database of mill reline data, relating to particular mine sites. This data may for a particular mine site, include video captured recordings of actual relines, inventory of equipment and details of available personnel to carry out the reline. 
     “Raw data” provided to database  21  can be analysed and if suitable verified by the administrator for use as comparative/benchmarking purposes. “Verified data” can then be copied or transferred by the administrator from database  21  to database  11  associated with simulation software  12 . 
     Where “raw data” is provided by a user  1 ( a )-( c ) in video captured recordings to database  21 , it may require analysis by the administrator (or authorised operator) to refine and verify data prior to it being suitable for use in software  12 . 
     In use, a maintenance manager such as user  1 ( a ) may for example video record an actual “mill reline” as it is performed. The resultant video recording (not shown) along with other data may be provided by user  1 ( a ) over the Internet  50  to database  21 . The video recording may be analysed and refined for simulation purposes prior to being provided as “refined and verified data” to simulation database  11 . 
     This “refined and verified data” may then be used for simulation purposes. 
     Whilst maintenance managers (users  1 ( a )- 1 ( c )) may wish to run a simulation for benchmarking and/or optimization for existing mine sites, user (plant designer)  2 ( a ) or user (mill manufacturer)  2 ( b ) may wish to input proposed liner arrangement data and resources to simulate future reline scenarios for proposed new site and/or mill designs. 
       FIG. 2  depicts an example flow diagram of steps to simulate a mill reline as follows. 
     With reference to  FIG. 2 , user (maintenance manager)  1 ( a ), may for instance:
         input mill structure and site constraints as indicated at block  31     input proposed liner arrangement as indicated at block  32     input YES for “is this an existing site?” as indicated at decision block  33     input YES for “is this for benchmarking?” as indicated at decision block  34     select best practice variables from database  11  as indicated at block  37     Define reline scenario, includes tool inventory available, labour available, priorities and liner sequence as indicated at block  39     Run the simulation as indicated at predefined process block  40     If reline Duration is not acceptable, input NO at decision block  42     Analyze the output data and plan a revised scenario at  41  before returning to block  39     If reline Duration is acceptable, input YES at decision block  42     Finish analysis at block  43 .       

     Where a maintenance manager  1 ( a ) is instead not doing it for benchmarking, then at block  34  he would answer NO, and instead have to provide a video of an “actual mill reline” as indicated at block  36 . The earlier mentioned administrator (or personnel acting on behalf of the administrator) could then analyse the video and extract the data necessary to input at block  38 . The maintenance manager  1 ( a ) could then run through the steps shown at blocks  39 - 43  of  FIG. 2 . 
     Where a plant designer  2 ( a ) or mill manufacturing engineer  2 ( b ) were wishing to simulate a proposed mill reline, they would take the following steps.
         input “proposed” mill structure and site constraints as indicated at block  31     input proposed liner arrangement as indicated at block  32     Select variables from database  11  to estimate performance as indicated at decision block  35     Define proposed reline scenario, includes tool inventory available, labour available, priorities and liner sequence as indicated at block  39     Run the simulation as indicated at predefined process block  40     If reline Duration is not acceptable, input NO at decision block  42     Analyze the output data and plan a revised proposed scenario at  41  before returning to block  39     If reline Duration is acceptable, input YES at decision block  42     Finish analysis at block  43 .       

     In the abovementioned embodiment, databases  11  and  21  are shown as separate databases, but they could in another embodiment be a single database of data. 
     In the abovementioned embodiment, user  1 ( a ) may record a video of an actual mill reline to capture data. However it should be understood that instead of recording a video of an actual mill reline, user  1 ( a ) could have a “time and motion study” conducted on an actual mill reline to collect similar data. This “time and motion study” could be conducted by a consultant or contractor, preferably associated with or certified by the abovementioned administrator. 
     An explanation of how simulation software (application)  12  has been developed and used in system  100  is as follows. 
     There are four major contributors to controlling the timing of mill relining shutdowns and the speed of liner exchange, these being:
         the liners themselves (their size and quantity);   the reline planning process and relining crew proficiency;   relining equipment; and   plant design surrounding the grinding mills.       

     Simulation software  12  includes “discrete event software” is used to model complex process flow where the interplay of operations or part/labour flows cannot be predicted using analytic methods and where the only other alternative to modelling is trying out the changes on a live system. 
     In order to provide a simulation of a mill reline model, we started with four separate mining sites which use RUSSELL 8™ or RUSSELL TWIN 8™ mill mining machines. These four mining sites were initially studied to collate identifying major variables related to equipment used. These major variables are shown in Table 1. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Major Variables 
               
             
          
           
               
                 Variable 
                 Tool 
                 Parameters affecting variable 
               
               
                   
               
               
                 Fastener Removal 
                   
                   
               
               
                 Nut Resistance 
                 Rattle gun 
                 Rattle gun relative effectiveness × standardised 
               
               
                   
                   
                 nut resistance distribution 
               
               
                 High torque tool 
                 High torque tool 
                 Unique to tool - independent of nut resistance 
               
               
                 Oxy acetylene Torch 
                 Oxy acetylene torch 
                 Bolt diameter/operator skill - independent of nut 
               
               
                   
                   
                 resistance 
               
               
                 Washer removal 
                 Pry bar/specialised tool 
                 Unique to tool/washer combination 
               
               
                 Bolt resistance 
                 THUNDERBOLT ™ 
                 Hammer relative effectiveness × standardised bolt 
               
               
                   
                 Hammer 
                 resistance 
               
               
                 Time between bolts 
                 THUNDERBOLT ™ 
                 A function of suspension method and operator 
               
               
                   
                 Hammer 
                 skill 
               
               
                 Time lost on bolts 
                 THUNDERBOLT ™ 
                 A function of guidance method 
               
               
                   
                 Hammer 
                   
               
               
                 Lost time due to 
                 Platform - manual or 
                 A function of platform type 
               
               
                 platform movement 
                 powered 
                   
               
               
                 Liner Removal 
                   
                   
               
               
                 Liner resistance 
                 THUNDERBOLT ™ 
                 THUNDERBOLT relative effectiveness × liner 
               
               
                   
                 Hammer 
                 resistance × liner mass scaling factor 
               
               
                 Stuck liner time 
                 Mill Relining Machine 
                 Applies to liners not removed using 
               
               
                   
                   
                 THUNDERBOLT hammers and is unique to each 
               
               
                   
                   
                 liner 
               
               
                 Liner turning 
                 Mill Relining Machine 
                 Applies to any liner needing machine intervention 
               
               
                   
                   
                 prior to slinging - a user specified ratio 
               
               
                 Slinging time 
                 Sling/O-ZONE ™ Tool 
                 Varies with tool 
               
               
                 Machine travel time 
                 Mill Relining Machine 
                 Varies with liner position in Mill 
               
               
                 Liner Cart loading 
                 Sling/O-ZONE ™ Tool 
                 Varies with suspension method and operator skill 
               
               
                 Liner Release 
                 Sling/O-ZONE ™ Tool 
                 Varies with suspension method and operator skill 
               
               
                 Liner Cart Turning 
                 Liner Cart 
                 A function of liner mass 
               
               
                 Liner Placement 
                   
                   
               
               
                 Liner pick up 
                 Grapple Tool 
                 Operator skill and tool type 
               
               
                 Liner positioning 
                 Mill Relining Machine 
                 Operator skill 
               
               
                 Liner Securing and 
                 Grapple Tool 
                 Tool type 
               
               
                 release 
                   
                   
               
               
                 Fork Lift Loading 
                 Fork Lift 
                 Operator skill 
               
               
                 and Unloading 
               
               
                   
               
             
          
         
       
     
     In order to be effective as a simulation model it should be able to easily change and analyse the effects on reline time of something as small as:
         the speed of the liner cart;   the size of, or distance to, the liner lay down area;   the size, type, priority or number of any tool in any particular work zone;   whether the liner cart is loaded from the rear or the side.       

     Furthermore, analysis of significant elements are as follows:
         using a Single or Twin Mill Relining Machine;   changing the number of liners in the mill; or,   installing an elevating platform;   the number of personnel on dayshift or nightshift.       

     All variables are treated as discrete time/frequency distributions; five discrete intervals are used for each variable. The time measurement of the operations associated with each variable are grouped or averaged together into five logical time intervals and a count of the number of occurrences at that time entered in the frequency column. 
     The use of distributions rather than overall average times is essential to the accuracy of simulation software. For example if the time taken for a mill relining machine to retrieve a worn liner is represented by the distribution in Table 2 (shown below) and the time taken for the liner cart to return to pick up the liner is represented in Table 3 (shown below), if overall average times (75 sec for the machine and 74 sec for the liner cart) were used, it appears that the machine never waits for the liner cart. However it is obvious from the tables that (using this fictitious data) the machine may wait at times up to 250−30=220 seconds for the liner cart. The total time the machine waits depends on the order in which the variables are combined. A random number stream is used to select the time assigned to an event based on its relative frequency in the appropriate variable. This type of relationship is repeated throughout the reline thousands of times and illustrates why a simulation such as this is necessary to provide sensible real world results. It should be noted that the distributions in Tables 2 and 3 are for illustration purposes only. In the actual simulation each of these actual activities is the result of the combination of many variables. 
     
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Liner Retrieval Distribution 
               
             
          
           
               
                   
                 Time (Seconds) 
                 Relative Frequency 
               
               
                   
               
             
          
           
               
                   
                 30 
                 5 
               
               
                   
                 45 
                 15 
               
               
                   
                 60 
                 30 
               
               
                   
                 120 
                 10 
               
               
                   
                 300 
                 3 
               
               
                   
                 Average time 
                 75 Sec 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Liner Cart Return Distribution 
               
             
          
           
               
                   
                 Time (Seconds) 
                 Relative Frequency 
               
               
                   
               
             
          
           
               
                   
                 20 
                 2 
               
               
                   
                 30 
                 6 
               
               
                   
                 50 
                 25 
               
               
                   
                 100 
                 10 
               
               
                   
                 250 
                 4 
               
               
                   
                 Average Time 
                 74 Sec 
               
               
                   
               
             
          
         
       
     
     The data populating each variable is determined from video recordings of actual relines at each of the separate mining sites, Whilst even based on a small set of data of say only four mine sites, the method of simulating a mill reline is possible, a larger data set is required for simulations to be statistically accurate. 
     The relative effectiveness of various tools, for example the time difference between a THUNDERBOLT™ 1500 and a THUNDERBOLT™ 750 Hammer removing the same liner bolt, needed to be considered. To allow one variable to be used by different sized hammers a theoretical relative effectiveness index was calculated. This will be validated in the future via experiment. Similar experiments will be required for comparing rattle guns and suspension methods. 
     The modelling process begins by specifying the geometry of the mill and its surroundings and defining the shape and location of each liner and fastener. A 3D model is generated progressively as data is entered; this provides visual validation of the progress and accuracy of construction. The area around the mill is divided into six independent work zones two each on the feed end, discharge end and shell. The floor levels in each zone are entered and also the height that is accessible at each zone. The charge level and access height inside the mill are also specified. These inputs result in transparent surfaces at the heights specified and are provided as visual prompts to the operator when planning a reline scenario.  FIG. 3  shows a fully populated 3D model of the outside of a mill  55 , whilst  FIG. 4  shows an “animation screen” (or web page)  60  for the simulation in which the “six work zones” surrounding the mill are schematically depicted. 
     The variables appropriate to each liner and fastener are then assigned. The user selects these from the data set that is most appropriate to the liner/fastener element being defined. If the simulation relates to an existing mill these variables can be sourced from data gathered during previous relines. If it is a new mill the data selected can be sourced from the nearest geometric and operational match. It is anticipated that over time database  11  will become comprehensive, covering a wide range of mills and operating parameters, including a greater variety of tools used in mill relining. In the future a data set will evolve in database  11  that captures the current best practice time and frequency distributions may be constructed to allow mill owners to “benchmark” the relative performance of their relines. 
     Once the mill is constructed and populated with liners and fasteners any number of reline scenarios can be defined, run and analysed as discussed below. 
     Using the same 3D model constructed during mill setup, the operator is able to rotate the mill to its starting angle and select liners for removal in this position. Any fasteners associated with the liner are automatically selected at the same time. As liners to be removed are selected, they are identified by a change in colour. The transparent surfaces representing the floor and reach height provide a guide as to which liners are accessible. This data is captured via a check box and then the liners that are to be replaced before inching are selected in the same way. The mill is then rotated to the next position and the liners for removal and replacement are selected. This process is repeated until the full reline is specified. 
     Bolt Removal and Liner Knock in Phase 
     Each of the six external work zones is programmed to operate independently and can be configured with any tool combination. 
     Tools that can be specified in each zone include any combination or quantity of:
         THUNDERBOLT™ Hammers or sledge hammers;   rattle guns (range of sizes);   high torque tools (torque multipliers);   washer removal tools;   T-MAG™ hammer moil guides;   elevating platforms;   manual platforms;   jib or monorail tool suspension;   Oxy acetylene torches (this equipment is shared between zones).       

     The number of reline personnel available is entered and can be varied from day to night shift. Tools are only active if sufficient labour is available, so labour control is important. The operator can assign priorities to the feed, shell and discharge work zones and specify the preferred number of operators for each stage of nut, washer, bolt and liner removal. Labour is then allocated according to zone priority and stage. Each operation commences after the preceding operation is complete or after a user specified number of nuts or washers is removed. If T-MAG™ hammer moil guides are used washers need not be removed. If high torque tools are specified these will be used to remove nuts that the rattle gun cannot. If high torque tools are not specified seized nuts are removed using the oxy acetylene torch. 
     Liner knock in will be carried out by the largest hammer specified for the zone where possible. 
     Liner Removal/Replacement 
     Liner removal commences once liner knock in is complete. RUSSELL™ Single or Twin mill relining machines can be specified for the scenario along with the variables that define their behaviour. 
     There is a great deal of flexibility around the set up of the storage yard, liner lay down area, number and method of operation of forklifts and travelling distances. The method of operation of the liner cart/s can also be easily configured. 
     Set up times are allocated for the relining machine between the various reline phases. The number of personnel working on the mill charge is specified. They commence by placing slings on accessible liners using O-ZONE™ liner lifting tools or chains and hooks if O-ZONE™ tools are not specified. Walk time between liners and tool specific slinging times dictate how long this task takes. The relining machine operator randomly selects liners and the program uses different variables depending on whether the liner must be dislodged from the mill, turned on the charge or can be removed immediately. 
     The next phase of the reline, liner placement, commences once all liners specified for the current mill position are removed. Because the RUSSELL TWIN™ machines are completely independent, there is an option in the program to allow either of the twin machines to commence placing liners before the other machine has completed removal. Liner placement is largely dictated by the type of liner being placed and the placement variables specified during mill set up. 
     Running the Scenario 
     The program, as it executes the scenario, creates an animation of the reline. This is a very useful tool as it provides visual verification that everything is interacting as expected. The speed of the animation can be varied however it does significantly slow the program down. Once satisfied that the scenario is running correctly, the animation can be turned off allowing fast computation. As the reline runs data relating to the timing of every function is collated and stored in the program. Various reports are generated that reveal the performance of the reline. Bottlenecks and areas that require focus are also highlighted. 
     The Importance of Labor 
     As previously indicated, the assignment and control of labor is critical in replicating the real world situation and predicting the duration of relines. The software  12  is written so that an analyst (user) can prioritize zones and assign desired team sizes to each zone for each phase of fastener and liner removal. The total number of personnel available for both night and day shifts and the maximum number in any one zone are specified for each simulation. As the software (application)  12  runs it assigns labor to the high priority zones to satisfy the demand and the desired team size for the task being undertaken. If there is insufficient labor to satisfy the requirements of all zones those with a lower priority must wait until labor becomes free. 
     The software (application)  12  is written to reflect the four major phases of a reline:
         Knock in
           Nut removal   Washer removal   Bolt removal   Liner knock in   
           Liner Removal   Liner Installation   Mill Inching       

     The terms “comprising” and “including” (and their grammatical variations) as used herein are used in inclusive sense and not in the exclusive sense of “consisting only of”.