5231082
Description
Flashcards by Ben Jenner, updated more than 1 year ago
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Created by Ben Jenner
about 8 years ago
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| Question | Answer |
| Define Failure | Deviation from normal design intent or operating standard |
| Define Hazard | A situation with the potential to cause death, injury, damage, losses or liabilities |
| Define Accident | An unplanned, uncontrolled event giving rise to death, injury, ill health, damage or loss. |
| Define Consequences | An outcome resulting from an accident. |
| Define Severities | A measure of the consequence |
| =================================== HAZOP =================================== | =================================== HAZOP =================================== |
| Define Hazard Analsysis | The identification of events which lead to a hazard and an analysis of way in which these event could occur and how likely harmful effects are |
| What does HAZOP stand for? | Hazard and operability studies |
| What actually is Hazop? | The application of a formal, systematic, critical examination of the intentions of new facilities to assess the hazard potential of mal-operation of pieces of equipment and the consequential effects on the facility as a whole. |
| Aims of Hazop | Aims to stimulate the imagination of designers and operators in a systematic manner so that they can identify the causes of potential hazards in the design. |
| Who carries out a HAZOP? | A team of experts |
| Define Intention (Re. an item in hazop) | How the part is expected to function |
| Define deviations (Re. an item in hazop) | deviations from the design intention which are discovered by systematic application of the guide words. |
| Define causes (Re. an item in hazop) | reasons why deviations might occur. Causes can be classified as realistic or unrealistic. |
| What can we do with unrealistic causes | reject them |
| Define Consequences (Re. an item in hazop) | the results of the deviations. |
| What are the collums of a HAZOP table left to right | |
| meaning of guidewords? NO/NOT MORE THAN/ LESS THAN AS WELL AS PART OF REVERSE OTHER THAN | Parameter is zero increase of decrease in a parameter qualitative increase qualitative decrease opposite subsitution |
| Give some standard process parameters the guide words may describe | • Pressure • Temperature • Flow |
| Give some examples of HAZOP application areas | • chemical • oil and gas • pharmaceutical • food processing • UAVS • fork lift truck activities • nuclear |
| HAZOP limitations | - Cannot detect every weakness (e.g. layout problems) - Cannot make up for lack of knowledge - Assumes system constructed and operated as designed. |
| =================================== FMEA =================================== | =================================== FMEA =================================== |
| What does FMEA stand for? | Failure mode and effects analysis |
| What does FMECA stand for? | Failure Mode, Effects and Criticality Analysis |
| What does FMECA include that FMEA doesn't | classification of each potential failure effect according to its severity |
| State and describe the 2 types of FMEA | • Product - Analysis of product and how failures effect product operation • Process - Analysis of product manufacturing, maintenance and usage and effect on product operation |
| State and describe the 2 FMEA Approaches | • Functional - sub assemblies considered e.g. A valve control system • Hardware - each component considered e.g. Sensor, controller, valve. |
| What are the first 6 stages of FMEA? | 1. Define the system 2. Construct block diagrams 3. Record all assumptions made 4. Define failure modes of system 5. Define failure modes of components 6. Complete FMEA worksheets. |
| FMEA Stage 1. What must the definition of the system include. | • What the system comprises • Boundaries and interfaces • Function in all operation modes • Environment profile • System phases • System mission and objectives |
| FMEA Stage 2. Hierarchical diagrams | |
| FMEA Standard table | |
| What are the last 2 stages of FMEA? | 7. Review worksheets to determine reliability critical components 8. Make recommendations for design improvements and further work |
| What are the 4 severity classifications in FMECA | 1. Minor 2. Marginal 3. Critical 4. Catastrophic |
| What is the equations for criticality | Criticality = Frequency x Severity |
| What table heading must we ad to our FMEA table for FMECA? | Severity class and frequency |
| What is the equation for the critically number of a failure mode | Lambda 0 - failure mode rate t - mission or phase time |
| What is the equation for failure mode rate? | a - portion of failure in specified mode b - probabilities that effect will result lambda p - part failure rate |
| What does RPN stand for? | Risk priority number |
| What is the RPN equation? | RPN=occurrence x severity x detection when all are measure out of 10 |
| What is the equation for the criticality number of a part? | n - number of failure modes |
| FMEA Features (pro and cons) | + it is rigorous and systematic. - time consuming and expensive. - It does not consider the effects of multiple failures. |
| =================================== Fault Tree Analysis =================================== | =================================== Fault Tree Analysis =================================== |
| Name these gates | OR - 1 or more AND - all inputs k out of n (voting) - at least k of n Exclusive OR - one but not both |
| Name these gates | Inhibit - requires event and condition Priority AND - order left to right Not - Output if input event does not |
| Name these events | Intermediate - Event description Basic - Event for which data is available Undeveloped - system event 2 b developed conditional - condition of inhibit gate House - definitely occurring or not. e.g. maintence |
| Define cut set | A list of failure events such that if they occur then so does the top event. |
| Define minimal cut set | A cut set such that if any component failure event is removed the combination will no longer cause system failure |
| What is the distributive law of cut sets | (A + B) . (C + D) = A.C + A.D + B.C + B.D |
| What is the idempotent law of minimal cut sets | A + A = A (Removes repeated cut sets) A . A = A (Removes repeated event) |
| what is the absorption law of minimal cut sets | A + A . B = A (Removes redundant combinations) |
| What is order culling? (RE. minimal cut sets) | Produce cut sets or order k or less |
| What is probability culling? (RE. minimal cut sets) | Produce only cuts sets with probability of occurrence greater or equal to a specified value |
| What is frequency culling? (RE. minimal cut sets) | Produce only cuts with frequency of occurrence greater or equal to a specified value |
| How do you change a fault tree to a dual tree? | Switch AND gates to OR gates OR gates to AND gates Basic events to Complemented events |
| What is the dual tree equivalent of a minimal cut set? | A minimal path set which is a smallest number of things that need to be true for system to work |
| The downtime of a system or component depends on? | • Time taken to detect the failure • Time taken to repair the failure inc. - Diagnosis - Obtaining new parts - Intalling new parts • Time taken to test to check it works |
| Define reliability | Reliability, R(t), is the probability that the component/system works continuously over that time interval, t. |
| How do you determine unreliability, F(t)? | Unreliability = 1 - Reliability F(t) = 1 - R(t) |
| What are the 3 definitions of availability, A(t)? | 1) Probability that a component/system works on demand. 2) Probability that a component/system is working at time t. 3) Fraction of the total time that a system/ component can perform its required function. |
| How do you determine unavailability, Q(t) | Unavailability = 1 - Availability Q(t) = 1 - A(t) |
| for what type of components does: Availability = Reliability A(t) = R(t) | non-repairable components |
| What is the failure density function, f(t)? | f(t) = dF(t)/dt |
| What is the equation of the conditional failure rate (hazard rate), h(t) | h(t) = f(t) / (1 - F(t)) h(t) = f(t) / (R(t)) |
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