Risk Analysis

Question 1

What are the three community risks?

Answer 1

Unavoidable, In Principle Avoidable, Avoidable

Question 2

Give an example of an unavoidable risk

Answer 2

Falling, Fire

Question 3

Give an example of an ‘In Principle’ Avoidable risk

Answer 3

Transport accident, Poison by medication

Question 4

Give an example of an avoidable risk

Answer 4

Drowning, Rock Climbing

Question 5

What is the formula for calculating risk?

Answer 5

Risk = consequence x frequency

Question 6

What does ALARP stand for?

Answer 6

As Low As Reasonably Practicable

Question 7

Name the three stages of an ALARP diagram

Answer 7

Unacceptable, ALARP or tolerable, acceptable

Question 8

What does HAZOP stand for?

Answer 8

Hazard and Operability Studies

Question 9

Define HAZOP

Answer 9

Applies a set of guidewords to determine consequences (more than, less than)

Question 10

What does FMEA stand for?

Answer 10

Failure Mode Effects Analysis

Question 11

Define FMEA

Answer 11

Step by step procedure for the evaluation of the severity of potential failure modes in a system

Question 12

Define reliability, R(t)

Answer 12

Probability system remains operating from time 0 to time t, given it was operating at time 0

Question 13

Define unreliability, F(t)

Answer 13

Probability system failed once or more from time 0 to time t, given it was operating at time 0

Question 14

R(t) + F(t) = ?

Answer 14

1

Question 15

Define availability, A(t)

Answer 15

Probability the system is operating at time t, given it was operating at time 0

Question 16

Define unavailability, Q(t)

Answer 16

Probability the system is not operating at time t, given it was operating at time 0

Question 17

A(t) + Q(t) = ?

Answer 17

1

Question 18

For a non repairable component, Q(t) = ?

Answer 18

F(t)

Question 19

On a bathtub curve the burn in period shows what in terms of failure?

Answer 19

A decrease in failure

Question 20

On a bathtub curve the useful life period shows what in terms of failure?

Answer 20

A constant failure

Question 21

On a bathtub curve the wear out period shows what in term of failure?

Answer 21

An increase in failure

Question 22

List the life cycle of a product?

Answer 22

Concept > design > manufacturing > operation > retirement

Question 23

Define risk identification

Answer 23

Find and describe risks

Question 24

Define risk analysis

Answer 24

Understand risks

Question 25

Define risk evaluation

Answer 25

Determine if risk is acceptable or tolerable

Question 26

What are the qualitative risk analysis methods?

Answer 26

Checklists, PHA, PFHA, Rapid Ranking, HAZAN/ID

Question 27

What does PHA stand for?

Answer 27

Preliminary Hazard Analysis

Question 28

What is PHA?

Answer 28

Tabular form and colour coding

Question 29

What does PFHA stand for?

Answer 29

Preliminary Functional Hazard Analysis

Question 30

What is PFHA?

Answer 30

Separates systems into functions

Question 31

What is Rapid Ranking?

Answer 31

List of risks according to severity and functions

Question 32

What does HAZAN/ID stand for?

Answer 32

Hazard Analysis/Identification

Question 33

Define failure

Answer 33

A deviation from normal intent

Question 34

Define hazard

Answer 34

Potential to cause damage

Question 35

Define accident

Answer 35

Unplanned event causing damage

Question 36

Define consequence

Answer 36

Outcome from accident

Question 37

Define severity

Answer 37

Measure of consequence

Question 38

Describe bow tie analysis

Answer 38

Like a spider diagram with tope evet in the middle, two threats on the left, two consequences on the right and a hazard in the top

Question 39

Define Design FMEA

Answer 39

Analysis of product and how failure modes affect the product operation

Question 40

Define Process FMEA

Answer 40

Analysis of process by which product is built, maintained and used. It examines how failures in manufacturing process can affect product operation

Question 41

Give an example of a functional approach (coarse-system breakdown)

Answer 41

Valve control system

Question 42

Give an example of a hardware approach (detailed system breakdown)

Answer 42

Valve, sensor, controller

Question 43

What is the FMEA procedure?

Answer 43

Define system > construct hierarchal breakdown and functional block diagrams > record assumptions > define system failure modes > list component failure modes > complete FMEA sheet > Determine reliability critical components

Question 44

List some failure mode examples

Answer 44

No feed to engines No feed to APU No feed to heat exchanger No fuel transfer

Question 45

List some component failure mode examples

Answer 45

Fails on Fails off Fails open Fails closed Fails high Fails low

Question 46

What does FMECA stand for?

Answer 46

Failure Modes Effects and Criticality Analysis

Question 47

How is a Risk Priority Number (RPN) calculated ?

Answer 47

Severity x Likelihood of occurrence x Likelihood of detection

Question 48

What is on the horizontal axis of a criticality matrix?

Answer 48

Severity

Question 49

What is on the vertical axis of a criticality matrix?

Answer 49

Frequency

Question 50

How many severity levels are there?

Answer 50

4

Question 51

How many frequency/occurrence levels are there?

Answer 51

5

Question 52

What is the formula for criticality?

Answer 52

Criticality = Frequency x Severity

Question 53

What criticality number are deemed unacceptable?

Answer 53

12+

Question 54

What assumption is made for fault trees?

Answer 54

The events are independent

Question 55

List some typical top events

Answer 55

No fuel supply to engines Safety system unavailable Standby system unavailable Explosion Complete brake system failure Landing gear fails

Question 56

List some typical basic events

Answer 56

Pump fails to start Valve fails closed Piston stuck Operator fails to respond

Question 57

Define a cut set

Answer 57

A list of failure events such that if they occur then so does the top event

Question 58

Define a minimal cut set

Answer 58

A list of minimal, necessary and sufficient conditions for the occurrence of the top event

Question 59

Define a path set

Answer 59

A list of components such that if they all work then the system is also in a working state

Question 60

Define a minimal path set

Answer 60

If any item is removed, the system no longer functions

Question 61

Symbol for AND?

Answer 61

.

Question 62

Symbol for OR?

Answer 62

+

Question 63

Use the distributive law : (A+B).(C+D)

Answer 63

A.C + A.D + B.C + B.D

Question 64

Use the idempotent law : A+A

Answer 64

A

Question 65

Use the idempotent law : A.A

Answer 65

A

Question 66

Use the absorption law : A+A.B

Answer 66

A

Question 67

What is order culling?

Answer 67

Produce only those minimal cut sets which have k or less failure events

Question 68

What is probability culling?

Answer 68

Produce only those minimal cut sets which have probability of occurrence greater or equal to a specified cut off value

Question 69

What is frequency culling?

Answer 69

Produce only those minimal cut sets which have a frequency of occurrence greater or equal to a specified cut off value

Question 70

What is the symbol for failure rate?

Answer 70

λ

Question 71

What is the symbol for time of operation?

Answer 71

t

Question 72

What is the symbol for repair rate?

Answer 72

v or µ

Question 73

What is the symbol for inspection interval?

Answer 73

θ

Question 74

What is the symbol for mean time to repair?

Answer 74

T

Question 75

What is the formula for unscheduled maintenance when system is a steady state?

Answer 75

t -> θ Therefore formula: λ/(λ+v)

Question 76

What is a mutually exclusive event?

Answer 76

Events which cannot occur together

Question 77

Using the addition law: P(AuB)

Answer 77

P(A) + P(B) - P(AnB)

Question 78

Using the addition law : P(AuBuC)

Answer 78

P(A) + P(B) + P(C) - P(AnB) + P(AnC) + P(BnC) + P(AnBnC)

Question 79

Using the multiplication law : P(AnB)

Answer 79

P(A) x P(B)

Question 80

Using the multiplication law: P(AnBnC)

Answer 80

P(A) x P(B) x P(C)

Question 81

What are the features of a continuously operating system?

Answer 81

A system that can fail in any order Start point is system operating normally Success/Failure of each component is then considered

Question 82

What are the features of a system where the components are in standby mode?

Answer 82

Components operation can be dependent on success/failure of another component Start point (initiating event) is usually an unsatisfactory event Monitors all possible outcomes following an initiating event

Question 83

What does RBD stand for?

Answer 83

Reliability Block Diagrams

Question 84

What is a farmer curve (X axis?, Y axis?)

Answer 84

A graph with frequency on y axis and consequence on X axis. Above the line is considered unacceptable and below the line is considered acceptable

Question 85

What is the x and y axis of a bathtub curve?

Answer 85

X axis is the time and y axis is the hazard rate

Question 86

Why is the culling method used?

Answer 86

For if there are too many minimal cut sets, by culling, the most significant ones remain

Question 87

What assumption is made for fault trees?

Answer 87

The events are independent

Question 88

What is failure time?

Answer 88

The time between the occurrence of two failures

Question 89

What is lower bound?

Answer 89

First two terms in expression

Question 90

What is upper bound / rare event approximation?

Answer 90

First term in expression

Question 91

What is min cut set upper bound?

Answer 91

1 - (1-first terms)

Question 92

How do you calculate F(t)

Answer 92

number failed / total number

Question 93

How to calculate rate of something when given the mean?

Answer 93

rate = 1/mean

Question 94

Steady state formula for no repair?

Answer 94

1