【 Weak current College 】 FTA in fire safety management-Power By 【 China power house network 】

FTA is security systems engineering common a deductive reasoning method, this method sets the system which may occur to some accident and cause accidents of all kinds of reasons for the logical relationship between a known as accident tree tree diagram represents, through the fault tree of qualitative and quantitative analysis, identify the major causes of the accident, to determine the security solutions provide reliable basis in order to achieve the prediction and prevention of accidents. At present, the FTA has been removed from the aerospace, nuclear industry into general electric power, chemical industry, machinery, transport and other areas, it is possible to troubleshoot and analyze system weaknesses, guidance system safety operation to achieve optimum design of the system. However, in the current enterprise unit in particular fire safety key units daily security management, still more stuck in experience-oriented management phase, fire safety oversight of management and technological means to use, the lack of scientific and technological content, not the enterprise potential fire risk qualitative or quantitative. In this article, try the FTA on a large scale in Zhenjiang vinegar production enterprise of fire safety focus areas — acetic acid reactor units for fire and explosion risk analysis and targeted solutions and ideas.
　　
First, the fault tree analysis steps
　　
(A) the preparation phase: determine the analysis of systems and the analysis of the scope of the system; familiar with the system and gather system information and data collection, surveys and analysis system has been in accidents and the future possibility of accidents.
　　
(Ii) the preparation of the FTA: determine accident tree top events; investigation and top events of all-cause and impact analysis of the event; the symbol with a number of provisions in accordance with certain logical relationships, fault tree top events and attracted top event causes the event to draw into reflect causal arborescence.
　　
(Iii) accident tree qualitative analysis: follow the event tree, calculating accident tree minimal cut set or least path set, as well as the basic structure of the importance of the event, according to the results of qualitative analysis to determine the safety and security of accident prevention measures.
　　
(Iv) the fault tree analysis: according to the cause of the accident the basic event occurrence probability, calculation of accident tree top events of the probability that the calculation of basic importance of probability. According to the results of quantitative analysis as well as after the accident may cause harm to the system for risk analysis, to determine the safety input direction.
　　
(V) the fault tree analysis results summary and application: timely on fault tree analysis results evaluation, summary, recommendations for improvement, for system security assessment and security design.
　　
2. Select analysis of acetic acid reaction Kettle unit technical features
　　
The large-scale use of acetic acid production enterprise carbonylation of methanol to produce low-voltage process, carbon monoxide and methanol as raw material, in acetic acid reaction kettle in carbon monoxide and methanol by catalyst, catalyst role for low voltage auxiliary Carbonyl reaction of acetic acid, after separation, the distillation has finished the acetic acid.
　　
(A) response materials, fire and explosion hazards
　　
Carbon monoxide: general condition is a colorless, odorless, tasteless, toxic gas compounds, flash point is less than-50 ° c, relative air density 0.967, and mixed the lower explosive limit 12.5%, up to 74%.
　　
Methanol: a transparent, colorless, flammable liquid, toxic, slightly alcoholic flavour, flash point 12.22 ℃, spontaneous combustion point 47 ° c, relative density 0.7915, lower explosive limit is 6%, the limit is 36.5%.
　　
The data from the above list shows, carbon monoxide and methanol explosion range respectively 61.5 and 30.5, explosive range is very wide, explosion risk is very high, are inflammable and explosive substances is enormous, and become acetic acid production process in case of fire and explosion of major hazards.
　　
(Ii) acetic acid production technology unit of fire and explosion types
　　
Acetic acid production process is the main risk of fire and explosion, and the type of fire and explosion occurred mainly in the disclosure and out-of-two species of reactions.
　　
Disclosure-fire and explosion is the handling, storage or transportation of flammable substances in containers, machinery or equipment for any reason and to disclose to the combustible or combustion from outside into the device, after encountering the ignition source of the fire and explosion. Disclosure of the main reasons: equipment and materials performance, equipment defects, human factors, etc.
　　
Reaction out of fire and explosion is given acetate production process reaction heat faster than the speed, causing the system to cool the heat accumulation, temperature, speed of reaction, causing reaction product Flash cluster, with the result that reacting process out of control and cause a fire and explosion. The reaction of acetic acid in the production process, if the raw material feeding of multiple investing or too fast, the material is not pure, because of the violent reactions can be introduced, so that the reactor thermal doesn't bleed out. In acetic acid production technology, refrigeration equipment failure, failure of cold enough, mixer, mixing is not uniform and not full, is the main cause of thermal negative.
　　
Third, the application fault tree on acetic acid reaction Kettle unit of fire and explosion hazard analysis
　　
(A) preparing the fault tree
　　
According to the above disclosure-fire and explosion, reaction out of control-type fire-explosion both fire and explosion accident reason analysis, combined with the large enterprise producing acetate acetic acid reaction Kettle specific production process unit, prepared the acetic acid reaction Kettle element fire and explosion tree, resulting in acetic acid reactor units of fire and explosion of the top events of the underlying cause of the event: negative X1: cooling; X2: feed too much too fast; X3: over-temperature; X4: overpressure; X5: Agent overdose; X6: raw materials with liquid; X7: equipment and materials performanceDrop; X8: equipment defects; X9: human factors; X10: open fire; X11: high temperature; X12: electrostatic sparks; electrical sparks X13:; X14: striking sparks; X15: lightning sparks; X16: up to explosion limits.
　　
(B) to strike a minimal cut set
　　
According to the underlying cause of the incident on the accident at the top of the tree of the event and how they relate to each other, using mathematical methods to express it, and then use the simplified method of Boolean algebra for the fault tree of minimal cut set.
　　
T=G1+G2=(X1*G3)+(G4*G5*X16)
=X1*(X2+X3+X4+X5+X6)+(X7+X8+X9)*(X10+X11+X12+X13+X14+X15)*X16
=X1X2+X1X3+X1X4+X1X5+X1X6+X7X10X16+X7X11X16+X7X12X16+X7X13X16+X7X14X16+X7X15X16+X8X10X16+X8X11X16+X8X12X16+X8X13X16+X8X14X16+X8X15X16+X9X10X16+X9X11X16+X9X12X16+X9X13X16+X9X14X16+X9X15X16
　　
The calculated minimum cut set {X1, X2}, {X1, X3}, {X1, X4}, {X1, X5}, {X1, X6}, {X7, X10, X16}, {X7, X11, X16}, {X7, X12, X16}, {X7, X13, X16}, {X7, X14, X16}, {X7, X15, X16}, {X8, X10, X16}, {X8, X11, X16}, {X8, X12, X16}, {X8, X13, X16}, {X8, X14, X16}, {X8, X15, X16}, {X9, X10, X16}, {X9, X11, X16}, {X9, X12, X16}, {X9, X13, X16}, {X9, X14, X16}, {X9, X15, X16}, for a total of 23.
　　
(3) calculation of acetic acid reaction Kettle unit the underlying cause of the event importance of structure
　　
According to the basic structure of the event importance calculation formula, you can get the following result:
　　
IΦ(1)=1-（1-1/2）5=0.969
IΦ(2)=IΦ(3)=IΦ(4)=IΦ(5)=IΦ（6）=1-（1-1/2）=0.5
IΦ（7）=IΦ（8）=IΦ（9）=1-（1-1/4）6=0.822
IΦ（10）=IΦ（11）=IΦ（12）=IΦ（13）=IΦ（14）=
IΦ（15）=1-(1-1/4）3=0.578
IΦ（16）=1-（1-1/4）18=0.994
　　
Therefore, the structure of the underlying cause of the event importance order as I Φ (16) > I Φ (1) > I Φ (7) = I (8) = Φ
IΦ（9）>IΦ（10）=IΦ（11）=IΦ（12）=IΦ（13）=IΦ（14）=
IΦ（15）>IΦ（2）=IΦ（3）=IΦ（4）=IΦ（5）=IΦ（6）
　　
(Iv) the prevention of acetic acid reactor units of fire and explosion accidents targeted strategies and ideas
　　
From the above analysis we can see: acetic acid reaction Kettle unit production process may cause fire and explosion occurred in the way of 23, a large number, indicating that the system of fire and explosion hazards is large, the difficulty of preventing accidents is also larger. Among the many basic cause events, reactor fuel material disclosure and air mixture reaches the explosion limits, the adverse reaction Kettle cooling are the two most important factors, followed by the equipment and materials performance degradation, equipment defects, as well as other human factors lead to combustible material disclosure. The open fire, heat, electric spark, electric spark, striking Sparks, lightning Sparks, etc cause event is at the third level of impact factors, compared to the above events, feed too much too quickly, over temperature, pressure, catalyst of excessive, raw materials with liquid and other factors were relegated among the last. In order to effectively prevent acetic acid reaction Kettle unit production process fire explosion, you must pair reactor combustible leaks and air mixture reaches the explosion limits, reactor cooling adversely the two most important factors to give priority to security control, and in accordance with the underlying cause of the events on the top level of the event in order to strengthen the control size, no gaps. At the same time, should be as comprehensive security measures to prevent high efficient and intensive acetic acid production process of fire and explosion accidents.