This information on Simulation Modeling is designed to be read sequentially. You can, however, go directly to any of the following sections:
SIMULATION MODELING; an approach to facilities or operations planning that duplicates the business operation using a mathematical model with sufficient detail to truly duplicate its critical components and is used by the designer to evaluate design alternatives with much more detail in much less time with more accuracy.
Simulation modeling is a method of duplicating the operation of a process with a mathematical model. The model should be complex enough to include all of the true details of the process. The business analyst would define the equipment, specifications and rules for the process. The modeler would construct the model to duplicate the process. Together they would validate the model by ensuring the model produces known results under known conditions and produces known changes in output for small and known changes in the equipment. The business analyst now uses the model to experiment with alternate process configurations and operating rules using the model instead of the real process.
Facilities planning, debottlenecking, equipment sizing, expansions, storage sizing, and developing operating rules are all uses of these models. For designing new facilities it is essential and for changing present facilities it is far more convenient, faster and less expensive to experiment with the model than with the real process.
The kinds of processes that can be simulated include:
Detailed individual activities that can be simulated are:
The time period simulated would be long enough that typical operating situations are represented. The usual manual methods of analysing a plant configuration would never achieve the detailed features of a simulation model. The analyst can analyse many more alternatives, in more detail, with more information produced, and with more true interactions considered. Simulation modeling typically produces better designs at significantly lower costs.
Through the analysis of various cases, the best equipment configuration and operating strategy for different options can be compared and evaluated.
With today's simulation software, it is also possible to develop an animation of the process. While the key business decisions would be made using the results of long process simulations, the animation is useful for testing the model with operations and viewing the actual operation that would result from a particular case proposed.
These animations are a significant help in discussions with the plant staff. They help break down communication problems between the modeler and operations, and establish the credibility of the simulation by showing that the simulation does actually duplicate the detailed operation of the facility. The computer requirements to use these models and the animation are no more than a typical PC.
The power of the simulation model is its ability to handle the random events that occur in a typical process. Some of these include:
As an example, the following is a description of how the cycle of a truck might be handled in a mining simulation model (starting at the shovel):
Each of these activities could have a random component to it. The simulation system allows the modeler to easily include a variation in each of them, keep track of how long each activity is and move the truck to the appropriate place. Similar detail activity would be modeled for each of the pieces of equipment in the model. Thus the simulation model duplicates the mine operation minute by minute. When the model is run for long enough, the various combinations of events that can occur have occurred a typical number of time and the model has duplicated, in minutes, the details of a year's operation.
Reports from a simulation model can include equipment production, utilization, down time, idle time, a distribution of operating rates, production capabilities, where there is congestion in the mine, and detailed system changes over time. The following is an example from a 1 year mine simulation. Only the shovel and crusher data is shown along with the production restriction table.
PRODUCTION DETAILS EQUIPMENT TOTAL TONNES T/DAY T/OP HRS SHOVEL 1 24219494 66354.8 4499.4 SHOVEL 2 23467212 64293.7 4499.1 TOTAL SHOVELS 47686706 130648.5 4499.3 CRUSHER 1 18238122 49967.5 3101.7 CRUSHER 2 16722811 45815.9 2948.6 CRUSHER 3 11162899 30583.3 2656.8 TOTAL CRUSHERS 46123833 126366.7 2927.9 OPERATING SUMMARY OPERATING TOTAL MAINTENANCE UP IDLE EQUIPMENT HOURS UTIL HOURS UTIL HOURS SHOVEL 1 5382.8 0.614 1855.2 0.780 1522.0 SHOVEL 2 5216.0 0.595 1774.0 0.747 770.0 TOTAL SHOVELS 10598.7 0.605 3629.3 0.763 3292.0 CRUSHER 1 5880.0 0.671 2410.4 0.926 469.5 CRUSHER 2 5671.4 0.647 2298.1 0.878 2407.5 TOTAL CRUSHERS 15753.1 0.599 6859.4 0.811 3667.5 % RESTRICTIONS (BY TIME) SHOVELS 58.07 TRUCKS 0.05 CRUSHERS 31.10 CONVEYOR 10.78
The information on the restrictions in the process provides valuable information for debottlenecking studies.
The graph shows typical details that can be obtained from several case studies. They show the benefit of additional trucks for a 2 shovel mining system. A similar curve can be obtained for 1 and 3 shovels to determine the best equipment configuration.
Simulation modeling is a tool that will greatly enhance the ability of mining engineers, operations staff, and management to evaluate the impact of proposed changes to existing facilities or alternate designs for new facilities. More alternatives can be examined in more detail and with more accuracy. The increased detail and the equipment interactions that can now be considered usually result in significantly better designs with significant savings.
If you have analysed your production process and have developed a simulation model of it, you can use the model to help you determine the best areas to spent your time and resources to learn more about the process. In your process, your present work would have determined information on such things as maximum operating rates, vehicle travel times, processing times, and variations in maximum operating rates. All of these will have been determined to a particular level of accuracy. On which ones should you spend more time to improve the level of accuracy?
Use the simulation model to help answer this question. Run cases changing only the maximum operating rate for a piece of equipment. If the overall system measure of performance (total throughput?) varies little, then there is no need to spend more time improving the level of accuracy of this data. Do this for various performance data in the system and begin improvements on those data items that have the largest impact on the system performance.
Gone are the days when large project decisions are based on a point estimate of its rate of return. Simulation modeling can help you estimate not only the expected project rate of return but also the potential variation (risk) in it. There is a large difference between a project with an expected rate of return of 25% with a 95% confidence interval of 10%-35% and one with the same expected rate of return but a 95% confidence interval of 19%-28%.
The first approach is to run the simulation of the final project case 10-20 times varying only the random number seeds. The resulting variation in the project performance will contribute to the confidence interval for the project rate of return. Our paper Mine Design Using Simulations describes how to quantify this variability.
The next approach is to run cases with different data (knowing their likelihoods). For example, your best estimate of the demand for a product would be used in the base case. Then, with estimates of the likelihood of lower or larger demands, run cases with these different demands to see the systems changes. These also provide input to the determination of the confidence interval for the rate of return for the project.
D.W. Ellis & Associates Ltd. offers a complete consulting service in Risk Management. Please follow this link to learn more about risk management and risk models.
D.W. Ellis & Associates Ltd., with 32 years of experience, offers a complete consulting service in the Management Sciences. For our clients, this means being close to your business, knowing your business, and unmatched responsiveness and costs. We have worked with many large and small Alberta and national companies to simulate various aspects of their business.
We have developed many modules that handle typical operating situations. These Simulation Modules made our model development time faster and more accurate.
Our services revolve around 4 main phases of model development:
This short study (1-3 weeks) allows the client to obtain a detailed look at what the model will be able to do, the costs and the timing.
This phase requires significant time on the client's part. The client must provide us with details of his business situation. Together we develop the level of detail to be modeled, the extent of the process to be modeled, and the format of the input data and reports produced.
The client's decision to continue is required at this point.
D.W. Ellis & Associates Ltd. will be responsible for this phase. The client will be provided with intermediate results so progress can be monitored and changes can be made as they are required.
This phase is usually very short. The model is transferred to the client's computer and tested. As only PC's are involved, there are typically few complications.
Although the client will be involved as the model is designed and developed, additional training on the use of the model will be included in the plan. The client will have been involved with the details of the input data and the reports produced. An organized approach to data collection, case analysis and the intepretation of the data will be covered.
The client must select a typical period of historical time, and collect the data for this time period, and the model is run. Its results are compared to the known results for this period. The model and the data are adjusted to obtain a very close fit between the model results and the known results. The model is now ready for extensive case studies.
This 1/2 day course includes an introduction to Simulation, the importance of including variability in the model, the concept of randomness, the client's role in the model development, an implementation plan, a modeling process, down time data analysis, typical uses and results, time and effort required to develop a model, and an animation. This course is recommended for management, professional, technical and office staff seeking a first look at Simulation Modeling.
More detail is available.
We would be pleased to arrange a demonstration of an animation of a process simulated. Several examples are currently available;
It is difficuly to assess the impact of other's actions on complicated business operations. Simulation modeling is a way to duplicate a business's operation under 'before' and 'after' conditions to determine the impact of the change.
Follow this link to see more about this concept.
Industries with whom D.W. Ellis and Associates Ltd. has consulted concerning facilities or operations modeling:
This model duplicates a shovel loading a truck to detemine the compatibility of the two. The relative sizes of the shovel dipper and truck load along with the strategy for loading the truck determine the efficiency of the shovel, efficiency of the truck, and the overall process efficiency.
This model is available for use now. It is Windows based, easy to use, and comes with a test file.
More detail and example screens are are available.
Please read our paper Mine Design Using Simulations. It is a mining application but the concepts of facility planning with the help of simulation models is valid for any industry. It is about 120K including 15 charts and graphs.
A large amount of our mine simulation experience is with the tarsands mining. We currently have 5 models in use in the tarsands. Over the past 15 years, we have developed 5 major mine and process simulations for Syncrude Canada Ltd. The most recent is a complete process simulation from the shovels to the upgrader. We have recently completed a simulation model for Albian Sands Energy Inc. (Shell) again modeling the process from the shovels to the upgrader in Edmonton. The two mayor companies mining the tarsands in northern Alberta are Suncor Energy Inc. and Syncrude Canada Ltd.
The first developments in the tar sands used drag lines and bucklet wheels for the mining parts of their operations. They were followed or replaced by shovel truck operations. All used some form of a process that used hot water or steam to separate the bitumen from the sand.
More recent new processes are using steam assisted gravity drainage to produce the bitumen. There is no longer any mining. Wells are paired; one to inject steam and another to extract the bitumen. Both are put in parallel to the ground and the second is below the first. The injected steam heats the bitumen while it is in the ground and it drains downward where it is pumped to the surface.
It is particularly suited for bitumen that has a large amount of overburden.
D.W. Ellis & Associates Ltd. has developed a sample simulation model of this process. It is based on our experience with the heavy oil industry and previous tar sands simulation models. Please have a look. It is intended to demonstrate that simulation modeling can be useful for the development of a SAGD process as well as a mining based process.
D.W. Ellis & Associates Ltd. is a management consulting firm specializing in the management sciences. With 32 years of industry experience in management science, David Ellis has a very good mix of academic knowledge of simulation and practical experience using simulation modeling. He has developed over 30 significant simulation models for various business situations. These include a gas collection system, open pit mining based on shovels and trucks and bucketwheels, oil and gas plant production, steel production, manufacturing and assembly production, water line breaks, computer scheduling, refinery/pipeline system, inventory management, and risk analysis.
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