Research On Reliability Of Mechanical Smoke Exhaust System In Buildings

Studies have shown that more than 50% of the total number of people died from high-temperature smoke in the fire.Mechanical smoke exhaust system can play a key role in removing smoke and heat generated by fire in case of fire,so as to effectively delay and prevent fire roar,improve the living environment of the fire site,and increase valuable time for site personnel to escape and professional fire brigade to extinguish fire.It is one of the most important systems in fire system equipment.In recent years,new building appearance,internal structure,construction technology,construction raw materials and new products and new equipment with various functions have been widely used in the construction of buildings,such as high-span atrium,indoor commercial pedestrian street,large commercial shopping complex,high-automatic unmanned elevated warehouse,tall space air bearing membrane buildings,etc.in case of indoor fire in buildings with complex functions and conditions,The complex flow and rapid growth of fire smoke will make the effectiveness and reliability of the mechanical smoke exhaust system set in accordance with the relevant national specifications seriously uncertain.Therefore,it is an essential and important link to comprehensively carry out the reliability research of the building mechanical smoke exhaust system.Recently,some organizations and individuals have realized the importance of the reliability research of fire safety system,and have carried out the reliability research of some fire safety systems,but most of them focus on the reliability research of the whole fire system,such as the analysis of the whole fire system based on the failure of Mechanical smoke exhaust system.There are some defects in the fine level of analysis and research.According to the demand of building development trend and some characteristics of relevant research at present,this topic will carry out the reliability research of building mechanical smoke exhaust system based on fault tree theory by comprehensively analyzing the composition of mechanical smoke exhaust system and various influencing factors of actual operation.The main research contents are as follows:（1）Investigate and analyze various elements that constitute and affect the reliability of building mechanical smoke exhaust system,draw a perfect fault tree of mechanical smoke exhaust system according to its logical relationship,and establish a fault tree reliability research system.Take "failure of fire mechanical smoke exhaust system" as the top-level event,involving 7 categories and 41 basic events.（2）The qualitative analysis and quantitative calculation of mechanical smoke exhaust system in fire are carried out according to the fault tree theory,and the factors and events affecting the reliability of mechanical smoke exhaust system are selected according to the structural importance and probability importance of basic events.The results show that the failure probability of mechanical smoke exhaust system under steady-state conditions is41.94%.The probability importance of basic events is divided into three categories,among which class I basic events include "double power switch fault","main circuit breaker fault","main circuit thermal relay fault","main circuit contactor fault","main circuit control relay fault","loose and falling off of short pipe connecting screw","damage caused by external force of short pipe environment" and "fan coupling device fault".（3）Based on the results of reliability analysis,the methods to improve the reliability of mechanical smoke exhaust system are analyzed and summarized from seven aspects: "smoke retaining vertical wall","smoke exhaust fan","fire damper","smoke exhaust outlet","air duct regulating valve","smoke exhaust air duct and hose","fan power supply and control".（4）Systematically form the reliability evaluation form of the whole life cycle of mechanical smoke exhaust system from product manufacturing,design,construction to maintenance,and establish the reliability evaluation framework of mechanical smoke exhaust system.