api 580 - rbi table and info for cof assessing - 40 terms

8/16/2019 API 580 - RBI Table and Info for COF Assessing - 40 Terms

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RBI table and info for COF Assessing40 terms ! information on COF

1. Assessing Consequences of Failure

The consequence analysis in an RBI program is performed to providediscrimination between equipment items on the basis of the significance of apotential failure. The consequence analysis should be a repeatable, simplified,credible estimate of what might be expected to happen if a failure were tooccur in the equipment item being assessed.

2. COF analysis should be performed to estimate the consequences that occur due to afailure mode typically resulting from an identified damage mechanism(s) (see Section9). Consequence should typically be categorized as:

(a) safety and health impacts(b) environmental impacts

(c) economic impacts

3. In general, an RBI program will be managed by plant inspectors or inspectionengineers, who will normally manage risk by managing the what?

POF with inspection and maintenance planning.

4. They will not normally have much ability to modify the what?

Consequences of Failure. COF

5. Management and process safety personnel may desire to manage the consequence

side of the risk equation. How?

Numerous methods for modifying the COF are mentioned in Section 14. For allof these users, the consequence analysis is an aid in establishing a relative riskranking of equipment items. The consequence analysis should address allcredible failure modes to which the equipment item is susceptible.

6. Loss of Containment

The consequence of loss of containment is generally evaluated as loss of fluidto the external environment.

7. The consequence effects for loss of containment can be generally considered to bein the following categories:

(a) safety and health impact(b) environmental impact(c) production losses(d) maintenance and reconstruction costs


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8. Other Functional Failures Although RBI is mainly concerned with loss of containmentfailures, other functional failures could be included in an RBI study if a user desired.Other functional failures could include:

(a) functional or mechanical failure of internal components of pressurecontaining equipment (e.g. column trays, de- mister mats, coalescer

elements, distribution hardware, etc.);(b) heat exchanger tube failure(c) pressure-relief device failure(d) rotating equipment failure (e.g. seal leaks, impeller failures, etc.).

These other functional failures are usually covered within RCM programs andtherefore are not covered in detail in this document.

9. Types of Consequence Analysis

The following paragraphs discuss different approaches to the determination ofconsequences of failure. For the purposes of the discussion, these approaches

have been categorized as "qualitative" or "quantitative." However, it should berecognized that "qualitative" and "quantitative" are the end points of acontinuum rather than distinctive approaches.

10. Qualitative Consequences Analysis

A qualitative method involves identification of the units, systems or equipment,and the hazards present as a result of operating conditions and process fluids.On the basis of expert knowledge and experience, the consequences of failure(safety, health, environmental and financial impacts) can be estimatedseparately for each unit, system, equipment group or individual equipmentitem.

11. For a qualitative method, a consequences category

(such as "A" through "E" or "high," "medium," or "low") is typically assigned foreach unit, system, grouping or equipment item. It may be appropriate toassociate a numerical value, such as cost with each consequence category.

12. Quantitative Consequences Analysis

A quantitative method involves using a logic model depicting combinations ofevents to represent the effects of failure on people, property, the business andthe environment.


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13. Quantitative models usually contain one or more standard failure scenarios oroutcomes and calculate COF based on:

(a) type of process fluid in equipment(b) state of the process fluid inside the equipment (solid, liquid, or gas);(c) key properties of process fluid (molecular weight, boiling point, autoignition

temperature, ignition energy, density, flammability, toxicity, etc.);(d) process operating variables such as temperature and pressure;(e) mass of inventory available for release in the event of a leak;(f) failure mode and resulting leak size;(g) state of fluid after release in ambient conditions (solid, gas, or liquid).

14. Results of a quantitative analysis are usually?

Results of a quantitative analysis are usually numeric. Consequence categoriesmay be also used to organize more quantitatively-assessed consequences intomanageable groups.

15. Units of Measure in Consequence Analysis

Different types of consequences may be described best by different measures.The RBI analyst should consider the nature of the hazards present and selectappropriate units of measure. However, the analyst should bear in mind thatthe resultant consequences should be comparable, as much as possible, forsubsequent risk prioritization and inspection planning.

16. Safety consequences are often expressed as?

Safety consequences are often expressed as a numerical value or characterizedby a consequence category associated with the severity of potential injuries

that may result from an undesirable event.

17. An approach for assigning monetary values to safety and health consequences isincluded in?

API 581

18. Units of Measure in Consequence Analysis Cost?

Cost is commonly used as an indicator of potential consequences.Consequences may be expressed in relative monetary units (e.g. dollars) to themaximum extent practical with an understanding that the numbers are

typically not absolute. For example, low, moderate and high categories couldbe assigned values of $100,000, $1,000,000 and $10,000,000 respectively. Thiswill permit adding the different consequences of a single event and facilitatecomparisons of risk from one process unit to another. Potential injuries andfatalities may be considered separately, with a maximum acceptableprobability of occurrence assigned.


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19. It is possible, although not always credible, to assign costs to almost any type ofconsequence. Typical consequences that can be expressed in "cost" include:

(a) production loss due to rate reduction or downtime,(b) deployment of emergency response equipment and personnel,(c) lost product from a release,

(d) degradation of product quality(e) replacement or repair of damaged equipment(f) property damage offsite,(g) spill/release cleanup onsite or offsite,(h) business interruption costs (lost profits),(i) loss of market share,(j) injuries or fatalities,(k) land reclamation(l) litigation,(m) fines,(n) goodwill.

20. Cost generally requires fairly detailed information to fully assess. It is possible,although not always practical, to assign a monetary value to almost any type ofconsequence.

The cost associated with most of the consequences listed above can becalculated using standard methods. Information such as product value, capacity,equipment costs, repair costs, personnel resources, and environmental damagemay be difficult to derive, and the manpower required to perform a completefinancial-based consequence analysis may be limited depending on thecomplexity of the relationship of failure to lost opportunity cost. However,expressing consequences in monetary units has the advantage of permitting adirect comparison of the various categories of consequences on a common basis.

Therefore, it is often better to provide approximations or "best estimates" thanto use only verbal descriptions

21. Instead of determining point values or unique ranges of economic loss for eachconsequence scenario, consequences may be placed into categories that have pre-defined ranges.

The ranges may be adjusted for the unit or plant to be considered. For example,$10,000,000 may be a catastrophic loss for a small company, but a largecompany may consider only losses greater than $1,000,000,000 to becatastrophic.

22. In a Six Level Table Catastrophic Category 1

Economic Loss Range = >$100,000,000

23. In a Six Level Table Major Category 2

Economic Loss Range = > $10,000,000 < $100,000,000


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24. In a Six Level Table Serious Category 3

Economic Loss Range = > $1,000,000 < $10,000,000

25. In a Six Level Table Significant Category 4

Economic Loss Range = > $100,000 < $1,000,000

26. In a Six Level Table Minor Category 5

Economic Loss Range = > $10,000 < $100,000

27. In a Six Level Table Insignificant Category 6

Economic Loss Range =


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32. Three Level Safety, Health and Environmental Consequence Categories High

Safety Consequence = Fatality or injury with permanent disabilityHealth Consequence = Long-term health effectsEnvironmental Consequence = Major offsite response and cleanup

33. Three Level Safety, Health and Environmental Consequence Categories Moderate

Safety Consequence = Lost time injury with full recovery expected HealthConsequence = Short-term health effect with full recovery expectedEnvironmental Consequence = Minor offsite, but possible major

34. Three Level Safety, Health and Environmental Consequence Categories Low

Safety Consequence = First aid only injuryHealth Consequence = Minimal health impactEnvironmental Consequence = Minor on-site response

35. Six Level Safety, Health and Environmental Consequence Categories Category I

Catastrophic= Large number of fatalities, and/or major long-termenvironmental impact

36. Six Level Safety, Health and Environmental Consequence Categories Category II

Major = A few fatalities, and/or major short-term environmental impact

37. Six Level Safety, Health and Environmental Consequence Categories Category III

Serious = Serious injuries, and/or significant environmental impact

38. Six Level Safety, Health and Environmental Consequence Categories Category IV

Significant = Minor injuries, and/or short-term environmental impact

39. Six Level Safety, Health and Environmental Consequence Categories Category V

Minor = First aid injuries only, and/or minimal environmental impact

40. Six Level Safety, Health and Environmental Consequence Categories Category VI

Insignificant = No significant consequence

api 580 - rbi table and info for cof assessing - 40 terms

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