Closed network queue model of underground coal mining production, failure, and repair
Underground coal mining systems production, failure, and repair cycles were mathematically modeled as a closed network of two queues in series, in order to understand better the technological constraints on availability of current underground mining systems and to develop guidelines for estimating the availability of advanced mining systems and their associated needs for spares as well as production and maintenance personnel. Sensitivity analysis of the model produces four major conclusions: (1) The mean availability of a section has a theoretical limit of rho/(1 + rho), where rho is defined to be the ''maintainability ratio'' of Mean Time Between Failures (MTBF) to Mean Time to Repair (MTTR). Moreover, this theoretical limit will be achieved only when there are so many production and repair crews that sections never need to wait for either. (2) Given a value for the maintainability ratio representative of current operating experience, section availability exhibits steep improvement in response to small improvements in the maintainability ratio. Hence big payoffs can be expected from concentrating efforts upon developing ways to increase the time between failures and/or decrease the time to repair failures. (3) The number of production crews should be 0.85 to 1.00 times the number of sections, and the number of repair crews should exceed the quotient of the number of production crews divided by the maintainability ratio, rho, and (4) the sensitivity of production at the mine mouth to the availability of any link in the haulage system is exactly equal to the quantity of coal that that link is expected to receive from all sections and haulage links feeding into it, times the availability of all haulage links between it and the mine mouth.
- Research Organization:
- California Institute of Technology (CalTech), Pasadena, CA (United States). Jet Propulsion Lab. (JPL)
- DOE Contract Number:
- ET-76-I-01-9036
- OSTI ID:
- 6232564
- Report Number(s):
- FE-9036-2
- Country of Publication:
- United States
- Language:
- English
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