The hydraulic system plays an important role in supplying power and its transition to other working parts of a coal shearer machine. In this paper, the reliability of the hydraulic system of a drum shearer was analyze...The hydraulic system plays an important role in supplying power and its transition to other working parts of a coal shearer machine. In this paper, the reliability of the hydraulic system of a drum shearer was analyzed. A case study was done in the Tabas Coal Mine in Iran for failure data collection. The results of the statistical analysis show that the time between failures （TBF） data of this system followed the 3-parameters Weibull distribution. There is about a 54% chance that the hydraulic system of the drum shearer will not fail for the first 50 h of operation. The developed model shows that the reliability of the hydraulic system reduces to a zero value after approximately 1 650 hours of operation. The failure rate of this system decreases when time increases. Therefore, corrective maintenance （run-to-t^ailure） was selected as the best maintenance strategy for it.展开更多
The reliability and maintainability of electrical system of drum shearer at Parvade. 1 Coal Mine in central Iran was analyzed. The maintenance and failure data were collected during 19 months of shearer operation. Acc...The reliability and maintainability of electrical system of drum shearer at Parvade. 1 Coal Mine in central Iran was analyzed. The maintenance and failure data were collected during 19 months of shearer operation. According to trend and serial correlation tests, the data were independent and identically distributed （iid） and therefore the statistical techniques were used for modeling. The data analysis show that the time between failures （TBF） and time to repair （TTR） data obey the lognormal and Weibull 3 parameters distribution respectively. Reliability-based preventive maintenance time intervals for electrical system of the drum shearer were calculated with regard to reliability plot. The reliability-based maintenance intervals for 90%, 80%, 70% and 50% reliability level are respectively 9.91, 17.96, 27.56 and 56.1 h. Also the calculations show that time to repair （TTR） of this system varies in range 0.17-4 h with 1.002 h as mean time to repair （MTTR）. There is a 80% chance that the electrical system of shearer of Parvade. 1 mine repair will be accomplished within 1.45 h.展开更多
Negative pressure plays a very important role in compact spinning system.To know airflow field and its distribution is helpful to look into the condensing principle of fiber bundle.Therefore,computational fluid dynami...Negative pressure plays a very important role in compact spinning system.To know airflow field and its distribution is helpful to look into the condensing principle of fiber bundle.Therefore,computational fluid dynamics(CFD)software was used to simulate airflow field in this paper.Airflow velocity distributions both in different fiber layers and under different negative pressures were discussed.The results indicate that airflow velocity in upper layer of the fiber bundle is greater than that in lower layer.Airflow velocities in both X and Y axis directions have a positive correlation with negative pressure.It can provide a theoretical base to make high quality compact yarns in productive practice.展开更多
Taking simultaneous variations in both particle volume and density into account, the radial mixing and segregation of binary granular bed in a rotating drum half loaded were investigated by a 3D discrete element metho...Taking simultaneous variations in both particle volume and density into account, the radial mixing and segregation of binary granular bed in a rotating drum half loaded were investigated by a 3D discrete element method. Then, based on the competition theory of condensation and percolation, radial segregation due to differences in particle volume and/or density was analyzed. The results show that if either percolation effect induced by volume difference or condensation effect induced by density difference dominates in the active layer of moving bed, separation will occur. Controlling the volume ratio or density ratio of the two types of particles can achieve an equilibrium state between percolation and condensation, and then homogenous mixture can be obtained. When the percolation balances with the condensation, the relationship between volume ratioand density ratiopresents nearly a power function. Scaling up a rotating drum will not affect the mixing degree of the granular bed so long as the volume ratio and density ratio are predefined.展开更多
Complex segregation occurs in a binary particle system with differing particle sizes and densities,particularly when the larger particles are heavier(S–D system,i.e.,size minus density system).Predicting the segregat...Complex segregation occurs in a binary particle system with differing particle sizes and densities,particularly when the larger particles are heavier(S–D system,i.e.,size minus density system).Predicting the segregation pattern driven by multiple mechanisms simultaneously is often challenging.This study explores the segregation mechanisms in a quasi-2D circular drum containing a S–D system,realizing a transition between the S-core and Core-and-band patterns by adjusting the drum rotation speed.During the transition of the segregation pattern,only the S-core pattern chiefly driven by the percolation mechanism is initially observed.As the rotation speed increases,the buoyancy mechanism and particle diffusion gradually strengthen,jointly driving the formation of the Core-and-band pattern.A dimensionless strength ratio,λ=H/h,where H and h respectively represent the diffusion and buoyancy strengths at length scales,is introduced to elucidate this transition.The Core-and-band pattern emerges whenλreached 1.4.展开更多
As a by-product of steel enterprises,steel slag has a huge output and is rich in valuable minerals,but its comprehensive utilization rate is very low.The article mainly introduces the hot splashing method,hot sealing ...As a by-product of steel enterprises,steel slag has a huge output and is rich in valuable minerals,but its comprehensive utilization rate is very low.The article mainly introduces the hot splashing method,hot sealing method,and drum method for the treatment of steel slag outside the furnace,and compares and analyzes the advantages and disadvantages of the production operation process and steel slag treatment process.At the same time,it also introduces the residual slag+double slag process and gasification dephosphorization slag circulation steelmaking technology for steel slag treatment inside the furnace,providing direction for steel enterprises to clean and comprehensively utilize steel slag.展开更多
文摘The hydraulic system plays an important role in supplying power and its transition to other working parts of a coal shearer machine. In this paper, the reliability of the hydraulic system of a drum shearer was analyzed. A case study was done in the Tabas Coal Mine in Iran for failure data collection. The results of the statistical analysis show that the time between failures （TBF） data of this system followed the 3-parameters Weibull distribution. There is about a 54% chance that the hydraulic system of the drum shearer will not fail for the first 50 h of operation. The developed model shows that the reliability of the hydraulic system reduces to a zero value after approximately 1 650 hours of operation. The failure rate of this system decreases when time increases. Therefore, corrective maintenance （run-to-t^ailure） was selected as the best maintenance strategy for it.
文摘The reliability and maintainability of electrical system of drum shearer at Parvade. 1 Coal Mine in central Iran was analyzed. The maintenance and failure data were collected during 19 months of shearer operation. According to trend and serial correlation tests, the data were independent and identically distributed （iid） and therefore the statistical techniques were used for modeling. The data analysis show that the time between failures （TBF） and time to repair （TTR） data obey the lognormal and Weibull 3 parameters distribution respectively. Reliability-based preventive maintenance time intervals for electrical system of the drum shearer were calculated with regard to reliability plot. The reliability-based maintenance intervals for 90%, 80%, 70% and 50% reliability level are respectively 9.91, 17.96, 27.56 and 56.1 h. Also the calculations show that time to repair （TTR） of this system varies in range 0.17-4 h with 1.002 h as mean time to repair （MTTR）. There is a 80% chance that the electrical system of shearer of Parvade. 1 mine repair will be accomplished within 1.45 h.
基金Key Project in National Science & Technology Pillar Program,China(No.2007BAE41B04)
文摘Negative pressure plays a very important role in compact spinning system.To know airflow field and its distribution is helpful to look into the condensing principle of fiber bundle.Therefore,computational fluid dynamics(CFD)software was used to simulate airflow field in this paper.Airflow velocity distributions both in different fiber layers and under different negative pressures were discussed.The results indicate that airflow velocity in upper layer of the fiber bundle is greater than that in lower layer.Airflow velocities in both X and Y axis directions have a positive correlation with negative pressure.It can provide a theoretical base to make high quality compact yarns in productive practice.
基金Projects(5137424151275531)supported by the National Natural Science Foundation of ChinaProject(CX2014B059)supported by the Innovation Foundation for Postgraduate of Hunan Province,China
文摘Taking simultaneous variations in both particle volume and density into account, the radial mixing and segregation of binary granular bed in a rotating drum half loaded were investigated by a 3D discrete element method. Then, based on the competition theory of condensation and percolation, radial segregation due to differences in particle volume and/or density was analyzed. The results show that if either percolation effect induced by volume difference or condensation effect induced by density difference dominates in the active layer of moving bed, separation will occur. Controlling the volume ratio or density ratio of the two types of particles can achieve an equilibrium state between percolation and condensation, and then homogenous mixture can be obtained. When the percolation balances with the condensation, the relationship between volume ratioand density ratiopresents nearly a power function. Scaling up a rotating drum will not affect the mixing degree of the granular bed so long as the volume ratio and density ratio are predefined.
基金supported by Qingdao National Laboratory for Marine Science and Technology(grant No.2015ASKJ01)National Natural Science Foundation of China(grant Nos.12072200,12372384)Program of Shanghai Academic Research Leader(grant No.23XD1421400).
文摘Complex segregation occurs in a binary particle system with differing particle sizes and densities,particularly when the larger particles are heavier(S–D system,i.e.,size minus density system).Predicting the segregation pattern driven by multiple mechanisms simultaneously is often challenging.This study explores the segregation mechanisms in a quasi-2D circular drum containing a S–D system,realizing a transition between the S-core and Core-and-band patterns by adjusting the drum rotation speed.During the transition of the segregation pattern,only the S-core pattern chiefly driven by the percolation mechanism is initially observed.As the rotation speed increases,the buoyancy mechanism and particle diffusion gradually strengthen,jointly driving the formation of the Core-and-band pattern.A dimensionless strength ratio,λ=H/h,where H and h respectively represent the diffusion and buoyancy strengths at length scales,is introduced to elucidate this transition.The Core-and-band pattern emerges whenλreached 1.4.
文摘As a by-product of steel enterprises,steel slag has a huge output and is rich in valuable minerals,but its comprehensive utilization rate is very low.The article mainly introduces the hot splashing method,hot sealing method,and drum method for the treatment of steel slag outside the furnace,and compares and analyzes the advantages and disadvantages of the production operation process and steel slag treatment process.At the same time,it also introduces the residual slag+double slag process and gasification dephosphorization slag circulation steelmaking technology for steel slag treatment inside the furnace,providing direction for steel enterprises to clean and comprehensively utilize steel slag.
