Failure Modes and Effect Analysis of Steam Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٦٤ Al-khwarizmi Engineering Journal Al-Khwarizmi Engineering Journal, Vol.1, No.2,pp 64-85, (2005) Design of a Programmable System for Failure Modes and Effect Analysis of Steam-Power Plant Based on the Fault Tree Analysis Soroor K. Hussain Al-Khafaji Dr. Nihad M. A. Al-Rahman Mechanical Eng. Dept. / University of Technology Electrical Eng. Dept./ College of Engineering / University of Baghdad Dr. Zuhair I. Ahmad Al- Dauod Mechanical Eng. Dept. College of Engineering / University of Baghdad (Received 25 April 2005; accepted 2 October 2005) Abstract:- In this paper, the system of the power plant has been investigated as a special type of industrial systems, which has a significant role in improving societies since the electrical energy has entered all kinds of industries, and it is considered as the artery of modern life. The aim of this research is to construct a programming system, which could be used to identify the most important failure modes that are occur in a steam type of power plants. Also the effects and reasons of each failure mode could be analyzed through the usage of this programming system reaching to the basic events (main reasons) that causing each failure mode. The construction of this system for FMEA is depending on the logical relationships of the fault tree analysis for the systems that contained in the power station. The designing of such system could be used as an assistance tool for the specialist user (the power engineer) in identifying of all reasons and effects for any type of failures. So this is help to fastening the repairing operation of the identified failure mode to improve the efficiency of operating system as represented by the maintainability, which is a function of system reliability. The selection of the steam type of power generation systems for the application of this study, because this type is the most common type of Iraqi power plants. While such the designed system could be programmed to be use in another types of industrial systems. Keywords: Fault Tree, Reliability, Maintainability, Industrial Systems, Failure Mode and Effect Analysis, Diagnostic Expert System, Steam Power Plant 1. Introduction With the increasing of complexity degree for the industrial systems, there is an importunate need to the application of developed techniques in operating and maintaining of such systems. The failure modes and effect analysis (FMEA) is one of modern technique that is especially applied with complex systems to facilitate the identification process of the systems failure modes and to analyzing of their reasons and effects. The research deals with the power plant as a significance type of industrial systems. Where the reliability improvement of such systems has respective importance since the objective function of the power plant is to produce energy with reliable factors and available quality as planned as possible during the required period of time. Then the maintainability improvement has the main role for reliability enhancement, which is defined as “the probability that a failed component or system will Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٦٥ restore or repaired to a specified condition within a period of time when maintenance is performed in cordance with prescribed procedures.” (1) Although thermal generating facilities are aging, flexible operation in response to changes in the demand for electrical power is required. To extend the life and manage the operation and control activities of power generation unit, the information and network technologies have become their important role to ensure the safety functioning and control of the unit operation. Also, the focusing on the application of advanced preventive maintenance technology and scheduled inspections of the unit facilities such as the boiler, steam turbines, gas turbines, and other machinery used in thermal power generation, which were controlled by computerizing diagnostic systems. All of these facilities lead to strengthen preventive maintenance and increase the efficiency of the power unit production. 2. The Method of Fault Tree Analysis “Fault tree analysis (FTA) is reliability/safety design analysis technique, which starts from consideration of system failure effects, referred to as Top Events. The analysis proceeds by determining how these can be caused by individual or combined lower level failures or events”. (1) By the FTA technique many events that interact to produce other events can be resulted using simple logical relationships such as (AND, OR,etc.), and these relationships permit a methodical building of a structure that represents complicated systems. When the tree structure has been established, subsequent analysis is deductive and takes two forms: (2) ◊ Qualitative analysis to reduce the tree to a logically equivalent form in terms of specific combinations of basic events (primary faults) sufficient to cause the undesired top event to occur. Each combination will be a “minimal cut set” of failure modes for the tree. (A minimal cut set is a set of events, which cannot be reduced in number, whose occurrence causes the top event). ◊ Quantitative analysis, which consists of transforming its established logical structure into an equivalent probability form and numerically calculating the probability of occurrence of the basic events. Standards symbols are used in constructing a FTA to describe events and logical connections, these symbols are shown in table-A. AND/OR gates are simply graphical symbols, which represent Boolean operation on the various events. The OR gate is equivalent to the Boolean symbol “+” and represent the union of the events attached to the gate. The AND gate is equivalent to the symbol “.” representing the intersection of events Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٦٦ Table-A: Standard Fault Tree Logic and Event Symbolism: (2) , (3) Event Representations Logic Operations The rectangle identifies an event that results from the combination of fault events through the input logic gate. AND gate describes the logical operation whereby the coexistence of all input events is required to produce the output event. The circle describes a basic fault event that requires no further development. OR gate defines the situation whereby the output event will exist if one or more of the input events exist. The triangles are used as a transfer symbols. A line from the apex of the triangle indicates a transfer in and a line from the side or bottom denotes a transfer out. INHIBIT gates describes a causal relationship between one fault and another. The input event directly produces the output event if the indicated conditional input defines a state of the system that permits the fault sequence to occur, and may be either normal to the system or result from failures. The diamond describes a fault event that is considered basic in a given fault tree. The possible causes of the event are not developed further because the event is of insufficient consequences or the necessary information is unavailable. The circle within the diamond indicates a sub-tree exists, but that sub-tree was evaluated separately and the quantitative results inserted as though a component. Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٦٧ 3. The Functional Description of Steam-Power Unit with the Application of Fault Tree Analysis Technique Through the studying of the operating nature of steam-power generation unit, one recognized that the unit operational system could be classified into three major operational subsystems. These subsystems are interconnected with each other in a specified manner to give the required output of the entire unit’s system, which is the planned capacity of electrical power. These major subsystems are the Mechanical, Electrical, and Control, and each one of them is consisting of a combination of components and subsystems, which are working dependently on each other to obtain the required function. In the following, a description to each one of the major subsystems is given. 3.1 The Mechanical System This system consists of the following major components: (4) ◊ The Boiler contains the furnace where burning fuel (oil, natural gas, and crude oil) and heats water to make steam. The boiler is the device meant for producing steam under pressure. ◊ The Super-heater is used to superheat the steam before passing through the boiler to the prime mover. ◊ Forced Draft Fans, for efficient combustion enough air has to be supplied. The chimney provides natural draught, and additional draught by forced draft (F.D.s) fans. ◊ The Economizer, where the gaseous products of combustion give most of their heat to the water in the tubes of the boiler and super- heater, and in order to make use of the remaining heat thereby heating the feed water in the economizer tubes. ◊ Air-Heaters arrangement used to provide initial heat to the air before it is admitted to the furnace. ◊ The Turbine changes steam’s heat energy into mechanical energy. Steam pushes blades rotating on a bar, causing it to spin at high speed. The generator changes the mechanical energy into electrical energy. The spinning bar of the turbine causes a huge magnet in the generator to rotate past copper bars producing electric current. ◊ The Condenser, where steam after expansion through the turbine goes through the condenser. The use of condenser improves the efficiency of power plant by decreasing the exhaust pressure of the steam below atmosphere. Another advantage of the condenser is that condensed steam can be recovered and this provides a source of good and pure feed water to the boiler. ◊ Circulating Water Pumps, to provide the required quantity of cooling water for condensing steam in the condenser. Where these pumps are normally installed on the source of water (river) to supply water throughout the year. ◊ The Hydraulic System, it is an important system that used for controlling the quantity of steam supplied to the turbine. This system used to supply the hydraulic oil with high pressure directly to an electric motor, which controls the automatic motion (open and closed) of the supplied steam valves to the turbine. ◊ The Serve Valve controls the quantity of hydraulic oil that pumped by the hydraulic pump. All failure modes of the mechanical system have been analyzed through the application of Fault Tree (FT) technique to describe the logical relationships among the failure events reached to the top event of this system, which is the turbine operating failure. The fault tree analysis of this system is shown in Fig. (1), where the failure symbols are explained in table-B. Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٦٨ 3.2 The Electrical System The electrical system of steam power unit is consists of the following major components: (5) ◊ Turbine-Generator Shaft, the turbine has single shaft with several stages (may be 17 stages), rotates with a velocity reaching to 3000 rpm, by input steam of temperature 4820C with pressure of 58 bar. The generator shaft is connected directly with turbine shaft so that it rotates with velocity of 3000 rpm and the generated voltage is usually 11kV. The generator is 3-phase AC. ◊ The 11kV Circuit Breaker (C.B), is designed to control the generated voltage of 11kV, which is supplied to the electrical system. ◊ 11/132kV Main Transformer, this transformer is used for the transformation from 11/132kV that supplied to the 132kV C.B when the generator is generating and vise versa when the generator is stopped. ◊ Rectifier, to convert the 125V A.C into 125V D.C that is required for the 125V D.C system to supply D.C voltage for some important equipment such as protection, control, and emergency oil pumps. ◊ 11/3.3kV Auxiliary Transformer, this transformer is used for the transformation from 11 to 3.3kV that required for operating of some auxiliary units (high & low voltage equipment). ◊ 3.3kV C.B, to control the power that fed to the 3.3kV Bus- Bar (B.B). ◊ 3.3kV B.B, to supply the required voltage for operating of high voltage motors in the system. ◊ 3.3/0.38kV Load Center Transformer, to obtain 0.38kV that is fed to the 0.38kV B.B. ◊ 0.38kV C.B, to control the power that is fed to the 0.38kV B.B. ◊ 0.38kV B.B, to supply the required voltage for operating the low voltage motors in the system. The failure modes of the electrical system have been analyzed with the application of the FT technique as described in Fig. (2), and the failure symbols are explained in table-C. 3.3 The Control System The control system of the steam power unit could be divided into three subsystems as follows: ◊ The Steam Turbine Control (STC) system, this part of control system is responsible for the speed and load of the turbine. The circuit board assemblies of this system contain the electronic printed- circuit boards (cards), which are provide the operational control and turbine-generator protective features in the system. The STC system consists of the following parts: a- Sp/Ov Sp/O Sp Board: it is sensitive to the speed of turbine through their probes, which are connected to the turbine. b- Interface and Set-point Select Boards: these boards are responsible for the setting sensitivity of the speed, load and load limiting. c- Dual Set-point Board: is used to give final signals for speed and load. d- Speed Summer Board: it takes the above signals as inputs and gives one signal as an output, which enters the Servo Amplifier Board. e- Ipl Summer Board: it is sensitive to the boiler pressure and gives signal that indicates the proper pressure. f- Servo Amplifier Board: used to control the operating activity of servomotor until executing the order. g- 3 kHz Board: it amplifies the signal coming from the Servo Valve to the Servo Amplifier Board. Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٦٩ Almost all types of faults, which occur in this part of control system, are the failures of cards for the above components due to the failure of the integrated circuits boards. Then, a trip signal are resulted from these failures such as the failure of Set-point Select Board, or the Dual Set-point Board, or the Servo Amplifier Board, or the 3kHz Board. And all of these trip signals lead to the failure of Servo valve. The Servo valve controls the output high-pressure hydraulic fluid flow in proportion to the magnitude and polarity of the input direct current command signals, which control the regulation valves to control the steam that goes to the turbine. ◊ Spec 200 control system, this system is used to control most of operating processes during the running of the power generation unit. This system consists of several important units or subsystems, which forming the basics of control functions, such as: a- Drum Level Control System, which control the normal level of water in the boiler drum. b- Airflow Control System, which controls the flow of air that is entering to the boiler for combustion process, through its control on the forced draft fans (FD fans). c- Oil Pressure Control System: this system controls the oil pressure, which is supplied to the boiler furnaces and required for combustion process. d- DA Level Control System, which controls the water level in DA drum and makes it in a normal level. ◊ Furnace Safety and Supervisory System, this system is known by the abbreviation (FSSS). It is responsible for the boiler running process and the boiler safety operation, through its controlling the fast closing valves for the fuel lines, which are supplied to the boiler. The running of any protection system of the unit is due to the resulted orders from this system. Since this system has several types of trip signals, so that if any of these signals results, the system will immediately emit a signal to the protection system of boiler to stop operating. Also any fault signal, which results from the electronic boards (cards) of this system, will lead to stopping the boiler. The faulty signals, which are produced from the FSSS, do comprise the following: a- Turbine trip signal. b- Flame failure trip signal. c- Loss of fuel trip signal. d- High furnace pressure trip signal. e- Loss of F.D fans trip signal. f- High or low level trip signal. g- Airflow low trip signal. h- Loss of 125V D.C trip signal. Fig. (3) shows the fault tree construction of components failure and the faulty signals for the three parts of control system, and the symbols of this figure are explained in table-D. The top events of the three systems (mechanical, electrical, & control) are related with each other in OR-gate leading to top event of whole unit system (unit shutdown). 4. The Designing of Knowledge- Based Representation for the Reasoning Programs of the Power Unit Fault Trees The state-space search is an important kind of control strategies that could be used to represent the level of procedural knowledge control. “State spaces can either be searched in a forward direction (or forward chaining) by starting at the initial states and applying the operators to find a Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٧٠ path to a goal state, or in a backward direction (or backward chaining) by starting with goal and applying the inverse of the operators to find a path to the initial state.” (6) The level of knowledge-based can be represented by some means such as the production rules, and the logical representations. “ The production rules are often simply called production. A production is a condition-action pair and defines a single chunk of problem- solving knowledge. The condition part of the rule is a pattern that determines when that rule may be applied to a problem instance. The action part defines the associated problem-solving step.”(6) Also the knowledge-based level can be represented in “first order predicate logic, if the formulas are suitably interpreted. The program may contain several different ways to establish predicate statements corresponding to the AND/OR graph. The solution of a problem is presented as a set of statements that are found by doing a depth-first search of the corresponding AND/OR graph until an instantiation of a set of assertions is found that provides a solution graph.” (7) To control the fault tree procedural knowledge, the state space search of forward direction (forward chaining) has been utilized at the level of knowledge control representation of the unit-systems fault trees. Then, the production of if-then rules based on the AND/OR graph have been used to represent the knowledge-based system. Figures (5, 6, & 7) show the state spaces search to identify the top events from the procedural knowledge-based representation of mechanical, electrical, and control systems fault trees, respectively. The set of production rules of isolating the mechanical system failure causes reaching to the system top event (MF1) that could inferred from Fig. (5), would be represented as follows: 3MF10MF9MF8MF7MF6MF5MF4MF ⇒∨∨∨∨∨∨ 11MF15MF14MF13MF12MF ⇒∨∨∨ 19MF21MF20MF ⇒∨ (1) 16MF19MF18MF17MF ⇒∨∨ 1MF16MF11MF3MF2MF ⇒∨∨∨ where the symbol ∨ means OR . From Fig. (6), the inferred set of production rules to isolate the electrical system failure causes reaching to the top event (EF1) would be represented as follows: 4EF8EF7EF6EF5EF ⇒∨∨∨ 9EF11EF10EF ⇒∨ 12EF14EF13EF ⇒∨ 9.12EF12EF9EF ⇒∧ (2) 2EF9.12EF4EF3EF ⇒∨∨ 17EF19EF18EF ⇒∨ 15EF17EF16EF ⇒∨ 1EF51EF2EF ⇒∧ where the symbol ∧ means AND. And the set of production rules, which inferred from Fig. (7) to isolate the control system failure causes reaching to the top event (CF1) would be represented as follows: Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٧١ 2CF8CF7CF6CF5CF ⇒∨∨∨ 3CF16CF15CF14CF13CF12CF11CF10CF9CF ⇒∨∨∨∨∨∨∨ (3) 4CF20CF19CF18CF17CF ⇒∨∨∨ 1CF4CF3CF2CF ⇒∨∨ The three systems top events (MF1, EF1, & CF1) are connected with each other reaching to the whole unit-system top event (UF) through the production rule as represented by: UF1CF1EF1MF ⇒∨∨ (4) Function (4) could be deduced from the knowledge-based representation of the unit-system fault tree as that shown in Fig. (8). 5. The Programmable System that Designed for the Failure Mode and Effect Analysis “The failure mode and effect analysis (FMEA) can be described as a systematic way of identifying failure modes of a system, item or function, and evaluating the effects of the failure modes on the higher level. The objective of FMEA is to determine the causes for the failure modes and what could be done to eliminate or reduce the chance of failure. This technique is an effective way to identify component failures or system malfunctions, and to document the system under consideration.”(8) The programmable system is designed to be used as an expert system to help the specialist user (power plant engineers) in identifying the failure modes and to analyze their reasons and effects on whole unit system. The designed system consists of a set of programs, and all are written in Matlab programming system. In the following a brief explanation for some of the designed programs with their flowcharts: q The first program is known by “RCS” since it works as a reasoning control structure for the unit-system fault trees to cognizing the failure causes and the effect analysis for whole system of the steam-power unit reaching the unit-system top event the (Unit Shutdown). Fig. (9) shows the flow chart of this program. q The second program is denoted by “FTREE”, which is specialized in explaining the logical relationships among the failure modes for the whole unit-system as described in the fault tree diagrams. Also the running of this program gives the minimal cut sets of failure events, where such events should given more attention since the occurrence of any one of the will leading to the failure of whole system (Top Event). Fig. (10) shows the flow chart of this program. q “DBp” denotes another program that is contained in the programming system and it is designed to be use as an input-output database program. This program contains all the necessary input database (failure & repair rates) that is required to quantify the reliability and availability of all individual components or events of the unit-system fault trees. Then, the output results of this program could be used as an output database that is required for other analytical programs of the system. The analytical procedures of this program are out the range of this research. q Another sets of programs are designed in a systematic way such as the backward chaining of the unit-system fault trees that is beginning from higher level (top event) reaching to lower level (primary events). The running of these programs is appeared in a shape of windows, which are controlled by different types of pushbuttons. All these windows are set in the programming system that is specialized to perform the function of FMEA of the steam-power plant. Some of the system windows of the failure mode analysis for the steam- power plant are shown in Figs. (11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, & 22). Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٧٢ 6. Discussion and Conclusion v For complex type of industrial systems such as the power plant, the Fault Tree Analysis (FTA) has a respective importance in recognizing all types of failure modes, which affect their performance efficiency, and deducing the reasons of system malfunctions. v The effectiveness of the designed programmable system for FMEA is mainly depending on the precision of knowledge, which were obtained from the expertise of operating staff in the power plant. Therefore, there is substantial need to involve a large number of experts (engineers and specialists) who are operating in the different departments of the power plant as consultants in constructing the knowledge-based system of the FMEA programming system. v The knowledge of the designed programmable system could be modified to be applied in other types of complex industrial systems to identify their failure modes and analyzing their reasons and effects to improve the maintenance activities and then enhancing the reliability of the system performance. v The FMEA may be considered as a reasoning technique of a diagnostic expert system. This technique describes the logical relationships among the failure events of the system fault tree. v The Matlab programming system could be considered as an effective tool in designing such programming systems to solve the different types of industrial engineering problems, since it has the ability of programming with both of linguistic and analytic statements. 7. Suggestion for Future Work v The designed programmable system of this work could be developed to be working on line with systems of the power plant. Such development requires the connection of the systems and components with appropriate sensors for sensing any error that might occur in the operating systems of the power plant, then converting them into signals to be translated into commands in a central control unit. Such control unit should comprise computers network that is programmed on the FMEA programming system to have the ability of translating of the error commands into failure modes, and to analyze the reasons and all possible effects of each failure mode. v The programmable system is designed specifically for the failure modes analysis of the steam type power units, and could be developed to cover other types of thermal power units depending on the extension of the constructed knowledge-based system. Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٧٣ Fig. (1) The Fault Tree Construction of Mechanical System Failure Modes MF1 (Turbine Operating Failure) MF16 MF 17 MF 18 MF19 MF 21 MF 20 MF11 MF 12 MF 13 MF 14 MF 15 MF 2 MF 3 MF 4 MF 5 MF 6 MF 7 MF 8 MF 9 MF 10 Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٧٤ Table-B: Symbols explanation of failure modes or events of the mechanical system fault tree of Fig. (1): Event Symbol Explanation Event Symbol Explanation MF1 Mechanical System Top Event (Turbine Operating Failure) MF12 Air Removal Pumps Failure MF2 Boiler Feed Water Pumps Failures MF13 Circulating Water Pumps Failure MF3 Boiler Failure MF14 Condenser Tubes Dirty MF4 Loss of Air Combustion Fans MF15 Condensate Water Pumps Failure MF5 Max. or Min. Water Level MF16 Hydraulic System Failure MF6 Boiler Tubes Leakage MF17 Hydraulic Oil Pressure Pumps Failure MF7 Heavy Oil Control Valve Failure MF18 Oil Level Low MF8 Air Combustion Register System Failure MF19 Servo Valve Failure MF9 Rotating Air Heater Failure MF20 Servo Valve Filter Dirty MF10 Heavy Oil Pressure Pumps Failure MF21 Hydraulic Oil Control Valve Closed MF11 Condenser Failure Fig. (2) The Fault Tree Construction of Electrical System Failure Modes EF 16 EF 18 EF 19 EF 3 EF 4 EF 5 EF 6 EF 7 EF 8 EF 9 EF 12 EF 10 EF 11 EF 13 EF 14 EF 15 EF 2 EF 17 EF 1 (No Power Generation) Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٧٥ Table-B: Symbols explanation of the failure modes or events of the electrical system fault tree of Fig. (2): Event Symbol Explanation Event Symbol Explanation EF1 Electrical System Failure (Top Event) EF11 Trip of Differential Relay 1 EF2 The Generator Stop of Power Generation EF12 Auxiliary TRR Failure EF3 Stator Earth Fault EF13 Trip of Differential Relay 2 EF4 Loss of Excitation EF14 Auxiliary TRR Earth Fault EF5 Rotor Failure EF15 132 kV C.B Failure EF6 Excitation C.B Failure EF16 Failure in Pressure of Gas “SF6” EF7 Rectifier Failure EF17 Air Compressor Unit Failure EF8 Carbon Brushes Failure EF18 Leakage in the Compressor Unit Pipes EF9 Main TRR Failure EF19 Compressor Failure EF10 Main TRR Earth Fault Figure (3) The Fault Tree of Control System Failure Modes CF 1 (Control System Failure) CF 2 CF 5 CF 6 CF 7 CF 8 CF 4 CF 17 CF 18 CF 19 CF 20 CF 3 CF 9 CF 10 CF 11 CF 13 CF 16 CF 14 CF 15 CF 12 Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٧٦ Table-C: Symbols explanation for the failure modes or events of the control system fault tree of Fig. (3): Event Symbol Explanation Event Symbol Explanation CF1 Control System Failure (Top Event) CF11 Loss of Fuel Trip Signal CF2 STC System Failure CF12 High Furnace Pressure Trip Signal CF3 FSSS Failure CF13 Loss of FD Fan Trip Signal CF4 Spec.200 System Failure CF14 High & Low Drum Level Trip Signal CF5 Setpoint Select Board Failure CF15 Low Air Flow Trip Signal CF6 Dual Setpoint Board Failure CF16 Loss of 125V DC Trip Signal CF7 Servo Amplifier Board Failure CF17 Drum Level Control System Failure CF8 3 kHz Board Failure CF18 Air Flow Control System Failure CF9 Turbine Trip Signal CF19 Oil Pressure Control System Failure CF10 Flame Trip Signal CF20 DA Level Control System Failure Figure (4) Unit System Fault Tree MF1 MF3 MF16 MF2 MF19 MF11 MF4 MF10 MF18 MF5 MF8 MF12 MF6 MF7 MF20 MF9 MF21 MF17 MF13 MF14 MF15 Fig. (5) The State Space Search to Identify the Top Event from the Knowledge-Based Representation of the Mechanical System Fault Tree UF (Unit Shutdown) MF 1 CF 1 EF 1 Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٧٧ EF1 EF15 EF2 EF 9.12 EF3 EF4 EF16 EF17 EF5 EF6 EF7 EF12 EF9 EF18 EF19 EF13 EF14 EF12 EF11 Fig. (6) The State Space Search to Identify the Top Event from the Knowledge-Based Representation of the Electrical System Fault Tree CF1 CF4 CF2 CF5 CF3 CF20 CF6 CF19 CF7 CF8 CF18 CF17 CF9 CF15 CF16 CF12 CF14 CF10 CF11 CF13 Fig. (7) The State Space Search to Identify the Top Event from the Knowledge Based Representation of the Control System Fault Tree UF MF1 EF1 CF1 Figure (8) The Knowledge Based Representation of the Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٧٨ Unit System Fault Tree A = 1, B = 0 Yes disp('UF occured due to the events: MF or EF or CF') UF=B disp('UF=N O') End IF UF = A Else MF=B E Else disp('UF is due to: EF OR CF' ) Input MF Start IF MF=A disp('MF = O C' ) disp('MF =N O') IF EF=A disp('EF = O C' ) C Else disp('EF=N O') E Input EF EF=B C Input CF disp('CF = OC' ) CF=B End Else IF CF=A disp(' CF = N O' ) End O C = Event Occurred ; N O = Event Not Occurred ; MF = Mech. Syst. Failure; EF = Electrical Sys. Failure ; CF = Control Sys. Failure Figure (9) The Flow Chart of “ RCS” Program Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٧٩ Start disp('N=1=MFT'), disp('N=2=EFT'), disp('N=3=CFT') Input N IF N=1 N=2 E N=3 C disp('MF=1=O, MF=0=N O') ElseifElse MF19=MF20+MF21 MF16=MF17+MF18+MF19 Input MF12=1 or 0: Input MF13=1 or0 1 Print MF19 Print MF16 Yes Input MF20=1 or0 : Input MF21=1 or 0 Input MF17=1 or 0 : Input MF18=1 or 0 1 Input MF14=1 or 0 : Input MF15=1 or 0 MF11=MF12+MF13+MF14+MF15 MF3=MF4+MF5+MF6+MF6+MF7+MF8+MF9+MF10 Input MF2=1 or 0 2 Print MF11 Print MF3 Input MF4=1 or 0 : Input MF5=1 or 0 : Input MF6=1 or 0 : Input MF7=1 or 0 : Input MF8=1 or 0 : Input MF9=1 or 0 : Input MF10=1 or 0 MF1=MF2+MF3+MF11+MF16 Print MF1 MF1=0 disp('TEMFT=O') disp('TEMFT=N O') Else Yes IF MF1=1 TEMFT = Top Event of Mech. Sys. F T ; O = Occurred ; N O = Not Occurred Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٨٠ 2 d i s p (' M C S M F T ') In p u t M F 1 = 1 o r 0 : In p u t E F 1 = 1 o r 0 : In p u t C F 1 =1 o r 0 T E = M F 1 + E F 1 + C F 1 IF T E = 1 d is p (' U T E = O ') T E = 0 d is p ('U T E = N O ') E n d P ri n t T E E l s e Y e s d i s p (' E F = 1 = O , E F = 0 = N O ' ) In p u t E F 1 0 = 1 o r 0 : In p u t E F 1 1 =1 o r 0 E F 9 = E F 1 0 + E F 1 1 P rin t E F 9 E F 1 2 = E F 1 3 + E F 1 4 P r in t E F 1 2 E F 4 =E F 5 + E F 6 + E F 7 + E F 8 P rin t E F 4 In p u t E F 1 3 = 1 o r 0 : In p u t E F 1 4 = 1 o r 0 E i n p u t E F 5 = 1 o r 0 : In p u t E F 6 = 1 o r 0 : In p u t E F 7 = 1 o r 0 : In p u t E F 8 = 1 o r 0 In p u t E F 3 =1 o r 0 E F 2 =E F 3 + E F 4 + E F 9 * E F 1 2 P rin t E F 2 3 MCSMFT = Minimal Cut Set of Mech. Sys. FT ; UTE = Unit Top Event Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٨١ 3 Input EF18=1 or 0 : Input EF19=1 or 0 : EF17=EF18+EF19 Input EF16=1 or 0 EF15=EF16+EF17 Print EF17 Print EF15 Print EF1 EF1=0 disp('TEEFT=N O') EF1=EF2*EF15 IF EF1=1 Else Yes disp('TEEFT= O') disp('MCSEFT') Input MF1=1 or 0: Input EF1=1 or 0: Input CF1=1 or 0 TE=MF1+EF1+CF1 4 4 Print TE disp('UTE=N O') IF TE=1 TE=0 disp('UTE= O') End Else Yes C disp('CF1=1=O, CF1=0=N O') Input CF5=1 or 0: Input CF6=1 or 0: Input CF7=1 or 0: Input CF8=1 or 0 CF2=CF5+CF6+CF7+CF8 Print CF2 Input CF9+1 or 0 :Input CF10=1 or 0: Input CF11=1 or 0: Input CF11=1 or 0: Input CF12=1 or 0 : InputCF13=1 or 0: Input CF14=1 or0 : Input CF15=1 or 0: Input CF16=1 or 0 5 5 CF3=CF9+CF10+CF11+CF12 +CF13+VF14+CF15+CF16 Print CF3 Input CF17=1 or 0: Input CF18=1 or 0; Input CF19=1 or 0: Input CF20=1 or 0 CF4=CF17+CF18+CF19+CF20 Print CF4 CF1=CF2*CF3*CF4 Print CF1 IF CF1=1 CF1=0 disp('TECFT= N O') disp('MCSCFT') 6 6 Else TE=MF1+EF1+CF1 Print TE IF TE=1 TE=0 disp('UTE=N O') disp('UTE= O') End Input MF1+1 or 0: Input EF1=1 or 0: Input CF1=1 or 0 Else Yes disp('TECFT= O') Yes MCSEFT = Minimal Cut Set of Elect. Sys. F T ; MCSCFT = M. C. S of Cont. Sys. FT TEEFT, TECFT = Top Event of Elect. & Cont. Systems. F T respectively Fig. (10) The Flow Chart of “FTREE” Program Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٨٢ Fig. (12) The Second Window of the System for Basic Failure Mode Identification Fig. (13) The Basic Definition Window Mechanical System Failure Mode Fig. (11) Introduction Window of the Designed system Fig. (14) The Basic Definition Window of Electrical System Failure Mode Fig. (15) The Basic Definition Window of Control System Failure Mode Fig. (16) Main Reasons Window for the Mechanical System Top Event Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٨٣ Fig. (19) The Main Three Reasons Window for the control System Failure Fig. (20) The First Reason Window of the Spec.200 System Failure Fig. (21) The First Reason Window of the STC System Failure Fig. (22) The First Reason Window of the FSSS Failure Fig. (17) The Main Two Reasons Window of Electrical System Failure Fig. (18) The Main Reasons Window of Generator Failure Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٨٤ References: 1. O’Connor P D. T., Newton D., & Bromely R., “Practical Reliability Engineering”, 4th ed., John Wiley & Sons. Ltd., 2002. 2. U.S Nuclear Regulatory Commission, “Fault Tree- Appendix II to Reactor Safety Study”, Wash-1400 (NUREG- 75/014), October 1975. 3. McCormick N. J., “Reliability and Risk Analysis-Methods and Nuclear Power Applications”, Academic Press, Inc., 1981. 4. Morse F. T., “Power Plant Engineering”, Litton Educational Publishing, Inc., Affiliated East- West Press PVT LTD, 1978. 5. Soni M. L., Gupta P. V., & Bhatnagar U.S., “A Course in Electrical Power”, Dhanpat Rai & Sons, Delhi, 1986. 6. Luger G. F., “Artificial Intelligence and Design of Expert Systems”, The Benjamin/Cummings Publishing Company, Inc., 1998. 7. Jackso P., “Introduction to Expert Systems”, 3rd ed., Addison Wesely Lonman Ltd., 1999. 8. Pentti H., & Atte H., “Failure Mode and Effects Analysis of Software- Based Automation Systems”, (VTT Industrial Systems), STUK- YTO-TR 190, www.stuk.fi, Finland, August 2002. 9. Assaf T., & Dugan J.B., “Automatic Generation of Diagnostic Expert Systems from Fault Trees”, University of Virginia, 2003 RM. 10. Kmenta S., & Ishii K., “Advanced FMEA Using Behavior Modeling for Concurrent Design of Products and Controls”, ASME Design Engineering Technical Conferences, Sept. 13-16, 1998, Atlanta, GA. 11. Konar A., “Artificial Intelligence and Soft Computing Behavioral and Cognition Modeling of Human Brain”, CRC Press, Inc., 2000. 12. Ohman B., “Failure Mode Analysis Using Multilevel Flow Models”, European Union Control Association (EUCA), Karlsruche, Germany, 1999. http://www.stuk.fi Soroor K. Hussain Al-Khafaji /Al-khwarizmi Engineering Journal ,Vol.1, No. 2,PP 64-85 (2005) ٨٥ الفشل وتحليل التأثيرات لمحطة بخارية لتوليد الطاقة الكهربائية اعتمادا تصميم نظام مبرمج لتمييز أنماط على انشاء شجرة تحليل الخطأ زهير عيسى احمد داود.نهاد عبد الرحمن د.سرور خضر حسين الخفاجي د.د كلية اهلندسة/كلية اهلندسة قسم اهلندسة امليكانيكية/اهلندسة الكهربائية قسم قسم اهلندسة امليكانيكية جامعة بغداد جامعة بغداد اجلامعة التكنولوجية : الخالصة الرئيسة التي يمكن أن تحدث فـي ) العطالت(م مبرمج يمكن أن يستخدم في تمييز أنماط الفشل يهدف البحث الى إنشاء نظا كما ومن خالل استخدام هذا البرنامج يمكن تحليل التأثيرات واألسباب لكل نـوع مـن . هربائيةمحطة بخارية لتوليد الطاقة الك .أنواع العطالت وصوال الى ما يعرف باألحداث األساسية المسببة للعطل دا ، وذلك اعتمـا (FMEA)لقد تم إنشاء هذا النظام الخاص بعملية تمييز أنماط العطالت وتحليل أسبابها أي ما يعرف بـ . الخاصة بكل نظام من األنظمة المكونة لمحطة توليد الطاقة (FT- analysis) على إنشاء شجرة تحليل الخطأ ان تصميم مثل هذا النظام المبرمج يمكن أن يستخدم من قبل مهندسي الطاقة في المحطة كوسيلة مساعدة في تسهيل عملية النظام الشامل لوحدة إنتاج الطاقة وهذا يساعد على اإلسراع فـي عمليـة تمييز نوع العطل مع تحليل أسبابه وتأثيراته على تشخيص العطالت وإصالحها وبالتالي تحسين كفاءة عمل المنظومة من خالل تطوير قابلية صيانة أنظمتها والتي تعتبر دالة من . ن تطبيقه في أنظمة صناعية أخرىومن خالل التعديل في برمجة المعرفة الخاصة بهذا النظام يمك. دوال موثوقية األداء