04_Practical Risk Assessment and Control, HAZOP, Fault tree analysis.pdf

The tree is structured so that the hazard appears at

This preview shows page 39 - 44 out of 44 pages.

The tree is structured so that the hazard appears at the top. It is then necessary to work downwards , firstly by identifying causes that directly contribute to this hazard. The same technique is applied to all these causes, breaking them down into sub-causes (or events) and repeated until the basic (or ‘root’) causes are identified. When all the causes and sub-causes have been identified, the next stage is to construct the fault tree . Fault Tree Analysis
Image of page 39

Subscribe to view the full document.

40 Deductive technique to identify combinations of events (causes) resulting in particular outcome (loss/accident) Combines hardware failures and human error in the same study Provides systematic basis for qualitative and quantitative measurement of risk Useful technique for accident investigation and analysis One of the most powerful risk management tools Fault Tree Analysis – Cont’d
Image of page 40
41 In designing the tree, a set of symbols, shown in the following table are used. Two logical operators, AND / OR gates are used to define the relationships between the events and branches of the tree. Symbol Designation Function EVENT / CAUSE Causes or events that can be developed further BASIC EVENT/CAUSE Basic or Root Causes or events that cannot be developed further UNDEVELOPED EVENT/CAUSE Causes are not developed due to lack of information or significance. AND gate Output event occurs only if all input events occur OR gate Output event occurs if any one of the input events occurs Fault Tree Analysis – Cont’d
Image of page 41

Subscribe to view the full document.

42 The ‘OR’ Gate ARRIVE LATE A OR WAKE UP LATE X DELAYED EN ROUTE Y INCORRECT TIME Z TOP EVENT (OUTPUT) INPUT EVENTS Event ‘A’ occurs if (at least) one of X OR Y OR Z occurs Fault Tree Analysis – Cont’d
Image of page 42
43 The ‘AND’ Gate AND FIRE A TOP EVENT (OUTPUT) INPUT EVENTS FLAMMABLE CONCENTRATION X IGNITION SOURCE Y & Event ‘A’ occurs if both X AND Y occur Fault Tree Analysis – Cont’d
Image of page 43

Subscribe to view the full document.

44 Example : Consider the lamp does not work in the simple circuit diagram shown below, plot the corresponding fault tree for the circuit. Lamp does not light No current through the lamp No power supply to the lamp Broken circuit No power feed Faulty Lamp No Power from battery No Power from unit Broken Circuit Defective switch Defective fuse The corresponding fault tree for the circuit, with the top event (or hazard) being the lamp not working is as follows: Fault Tree Analysis – Cont’d
Image of page 44
  • Winter '18
  • Ahmed Gawish
  • Root cause analysis, Safety engineering, HAZOP analysis

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern