Reliability Analysis Of Medium Speed Coal Mill Hydraulic Systembased On Bayesian Network

Medium speed coal mill is the main equipment of coal pulverizing system of thermal power plant. Along with the development of the industry, existing medium speed coal mill is difficult to meet the requirement of industry output of large capacity units. In this paper, according to production needs a new type of MPS235 medium speed mill hydraulic system is designed, but its working environment is bad and easy to cause trouble, hydraulic system’s reliability is analyzed by common cause failure of the bayesian network analysis method and continuous time of the bayesian network analysis method, and provide the basis for the improvement of its reliability.First, a new type of medium speed coal mill hydraulic system is designed. The use of proportional variable loading technology reduces the system energy consumption and improves grinding efficiency, the use of accumulator reduces body vibration, the use of dual pump reduces the system energy consumption, the use of automatic oil supply device prevents the system supply shortage. At the same time, the main components of the system is designed and selected.Secondly, because the traditional bayesian network analysis method is difficult to analyze the correlated failure between the elements. Common cause failure of bayesian network analysis method is researched and for the first time used in the reliability analysis of the hydraulic system. The leaf node failure rate and the root node probability important degree, key important degree, posterior probability and reliability index are put forward under the condition of common cause failure. Medium speed coal mill hydraulic system reliability analysis is carried out by using beta factor common cause failure model of bayesian network analysis method, the hidden trouble of the system and the weak link are found out.Then, due to the medium speed coal mill hydraulic system has dynamic timing characteristics, the static bayesian network analysis method is difficult to accurately assess the reliability of the system dynamic process. The fuzzy uncertainty analysis method based on continuous time bayesian network reliability is researched. The methed can be used to establish the dynamic characteristics of node failure and solve the system’s reliability index of dynamic failure. And the common cause failure model is introduced into the reliability calculation of dynamic bayesian network, considering the fuzzy uncertainty, dynamic failure and common cause failure conditions, the reliability of medium speed coal mill hydraulic system is analyzed.Finally, according to the result of reliability analysis, the proportional relief valve which is the highest failure rate part in the hydraulic system is carried out an experiment research. By adding a transition board increases back pressure and reduces vibration, improving exhaust device makes it exhaust more quickly.The improvements of the valve not only improve its stability, and improve medium speed coal mill hydraulic system’s stability, which has certain practical significance.