9 - Assessing Probability of Failure

Question 1

Introduction to Probability Analysis:

The probability analysis in an RBI program is performed to estimate the probability of a specific adverse consequence resulting from ,,,,,that occurs due to damage mechanism(s)

Answer 1

a loss of containment

Question 2

Introduction to Probability Analysis:

,,,,,,,analysis should be credible, repeatable, and documented.

Answer 2

Probability

Question 3

Units of Measure in the POF Analysis:

POF is typically expressed in terms of ,,,,

Answer 3

frequency

Question 4

Units of Measure in the POF Analysis:

Frequency is expressed as a ,,,,,, occurring during a specific timeframe

Answer 4

number of events

Question 5

Units of Measure in the POF Analysis:

For probability analysis, the timeframe is typically expressed as a ,,,,, and the frequency is expressed as ,,,,

Answer 5

fixed interval (e.g. one year)
events per interval (e.g. 0.0002 failures per year).

Question 6

Units of Measure in the POF Analysis:

The timeframe may also be expressed as ,,,,,, and the frequency would be ,,,,,

Answer 6

an occasion (e.g. one run length)
events per occasion (e.g. 0.03 failures per run).

Question 7

Units of Measure in the POF Analysis:

For a qualitative analysis, the POF may be categorized as ,,,,

Answer 7

high, medium, and low, or one through five

Question 8

Units of Measure in the POF Analysis:

Three Levels of POF,,,,,

Answer 8

Low ( < 0.0001 )
Medium ( 0.0001 to 0.001 )
High ( > 0.01 )

Question 9

Units of Measure in the POF Analysis:

Six Levels of POF,,,,,

Answer 9

Remote ( < 0.00001 )
Very Low ( 0.00001 to 0.0001 )
Low  ( 0.0001 to 0.001 )
Moderate  ( 0.001 to 0.01 )
High  ( 0.01 to 0.1 )
Very High ( > 0.1 )

Question 10

Types of Probability Analysis:

Probability Analysis have been categorized as ,,,,,, or ,,,,

Answer 10

“qualitative”

“quantitative.”

Question 11

Types of Probability Analysis:

it should be recognized that “qualitative” and “quantitative” are the end points of a continuum rather than ,,,,

Answer 11

distinctive approaches

Question 12

Types of Probability Analysis:

Most probability assessments use a ,,,,, of qualitative and quantitative approaches

Answer 12

blend

Question 13

Quantitative POF Analysis:

There are several approaches to a quantitative probability analysis. One example is to take a probabilistic approach where ,,,,,, or ,,,,,,are used to calculate a POF

Answer 13

specific failure data

expert solicitations

Question 14

Quantitative POF Analysis:

probability may be expressed as a ,,,,,, rather than a single deterministic value.

Answer 14

distribution or range

Question 15

Quantitative POF Analysis:

Another approach is used when inaccurate or insufficient failure data exists on the specific item of interest. In this case, ,,,, or ,,,,, data is used

Answer 15

general industry, company,

manufacturer failure

Question 16

Determination of POF:

Regardless of whether a more qualitative or a quantitative analysis is used, the POF is determined by two main considerations, as follows

Answer 16

• Damage mechanisms and rates of the equipment item’s resulting from its operating environment (internal and external).
• Effectiveness of the inspection program to identify and monitor the damage mechanisms so that the equipment can be repaired or replaced prior to failure

Question 17

Determine the Deterioration Susceptibility and Rate:

Combinations of process conditions and existing materials of construction for each equipment item shall be evaluated to identify ,,,,, and ,,,,,,damage mechanisms

Answer 17

active

credible

Question 18

Determine the Deterioration Susceptibility and Rate:

One method of determining these mechanisms and susceptibility is to group components that have the ,,,,,, and ,,,,

Answer 18

• same material of construction

- are exposed to the same internal and external environment

Question 19

Determine the Deterioration Susceptibility and Rate:

Inspection results from one item in the group can be related to the ,,,,

Answer 19

other equipment in the group

Question 20

Determine the Deterioration Susceptibility and Rate:

Susceptibility is often designated as ,,,,,, or ,,,, based on the environmental conditions and material of
construction combination

Answer 20

high, medium,

low

Question 21

Determine the Deterioration Susceptibility and Rate:

Sources of deterioration rate information include,,,

Answer 21

a) published data and unpublished company data,
b) laboratory testing,
c) in situ testing and in-service monitoring,
d) experience with similar equipment,
e) previous inspection data

Question 22

Determine the Deterioration Susceptibility and Rate:

The best information will come from ,,,,, where the conditions that led to the observed deterioration
rate could realistically be expected to occur in the equipment under consideration

Answer 22

operating experiences

Question 23

Determine the Effectiveness of Past Inspections:

After the likely damage mechanisms have been identified, ,,,,, shall be evaluated to determine the effectiveness in finding the identified mechanisms

Answer 23

the inspections

Question 24

Determine the Effectiveness of Past Inspections:

Reduction in uncertainty of the damage state of a component is a function of the effectiveness
of ,,,,

Answer 24

the inspection

Question 25

Determine the Effectiveness of Past Inspections:

effectiveness of inspections is determined for each type of damage mechanism and is a function of the ,,,,, and the ,,,,,, (reference API 581 Part 2, Annex 2.C for
informative examples of inspection effectiveness)

Answer 25

type of technique used

extent of coverage