1. Donegani Anticorrosione S.r.l
RBI Methodology
Risk Based Inspection
API 580 – 581
Donegani Anticorrosione S.r.l

2. Donegani Anticorrosione S.r.l
Introduction
Although the term ‘RBI’ has been adopted relatively recently, the practice of planning plant inspection based on the risk of failure is not new. Most operators base the scope and depth of their inspection plans on the rate of in-service damage and the consequence of failure, within a traditional time-based inspection programme. (Same operators can rightly claim that their plant inspections have always been risk-based).
The term ‘RBI’ refers to a structured, team-based assessment process with the aim of targeting inspection by considering the Risk of Failure (RoF), which is a combination of the Likelihood of Failure (LoF) and Consequence of Failure (CoF).
Donegani Anticorrosione S.r.l

3. RBI – Risk Based Inspection
Is based on the norms API 581 & RP 580
Developed by API (American Petroleum Institute) in collaboration with:
- DOW
- SHELL
- FINA
- TEXACO
- EXXON
- ………….
Donegani Anticorrosione S.r.l

4. Objective of RBI Methodology
Increase safety
Increase the productivity of inspection
Decrease the losses of production
Reduce the direct costs of inspection
Change the frequencies of inspections in base to the risk
Prevent catastrophic damages
Donegani Anticorrosione S.r.l

5. Donegani Anticorrosione S.r.l
RISK
Definition of the Risk:
Risk (RoF) =
Likelihood of Failure (LoF) x
Consequence of Failure (CoF)
Donegani Anticorrosione S.r.l

6. Donegani Anticorrosione S.r.l
Risk Based Inspection
Consent of:
Define the critical state for every single ITEM
Create a priority for the Inspections basing on the critical state
Focus the attention on the expected damages
Donegani Anticorrosione S.r.l

7. Donegani Anticorrosione S.r.l
RBI Methodology
RBI Methodology developed by different companies, varied in the details, but it is founded however on fundamental step:
Background to RBI
Assessment Personnel
Damage Mechanism Assessment
Risk Assessment
Inspection Planning and Risk Mitigation
Updating RBI Assessment
Donegani Anticorrosione S.r.l

8. RBI Methodology Donegani Anticorrosione S.r.l Step 1.
Background to RBI
Step 2.
Assessment Personnel
Step 3.
Damage Mechanism Assessment
Step 4.1.
Likelihood of failure-LoF
Step 4.2.
Consequence of failure-CoF
Step 5.
Inspection Planning
Step 6.
Updating RBI Assessment
Step 4.3
Risk Assessment
Donegani Anticorrosione S.r.l

9. Donegani Anticorrosione S.r.l
Background to RBI
RBI study is designed around the systematic, inductive assessment process of identifying historical, active or potential damage mechanism in each equipment. The process is a ‘bottom up’ procedure where one damage mechanism id considered at a time. Once the feasible damage mechanisms have been identified, their probabilities (likelihood) of leading to component failure are determined and their effects on the components are recorder and analysed to yield a calculated failure consequence.
Donegani Anticorrosione S.r.l

10. Donegani Anticorrosione S.r.l
Assessment Personnel
All RBI systems have the following common
elements:
Assessment preparation
Information Gathering
Damage Mechanism Review
Risk Assessment
Inspection Plans
Inspection Review.
Donegani Anticorrosione S.r.l

11. Assessment preparation
Since RBI is a team-based approach, the first step in the introduction of an RBI programme is to identify and assemble a competent Study Team. The RBI team should include staff with knowledge of plant operation, process hazards, risk assessment and inspection techniques.
Donegani Anticorrosione S.r.l

12. Donegani Anticorrosione S.r.l
Typical RBI team
Inspection engineer(s);
Material and corrosion engineer(s);
Maintenance engineer(s);
Process engineer(s);
Operations engineer(s);
Safety engineer(s);
Team leader, typically a RBI specialist(s).
Donegani Anticorrosione S.r.l

13. Information Gathering
Are necessary the following information:
Operational manual
P&ID
Sketches of project of the equipment
Pipe class
Property of the fluids
Design and operating conditions
Special instructions and History inspection
……………
Donegani Anticorrosione S.r.l

14. Damage Mechanism Assessment
The Study Team will need to review the historical and generic date relevant to each item of equipment. This will include consideration of previous inspection reports (if available) to determine the known or expected damage mechanisms.
The review should consider damage mechanisms which may lead to failure, their expected rates of deterioration and the general location where damage may arise.
Wherever quantitative rates of damage are not available, an element of expert judgement will need to be exercised by the Study Team.
Donegani Anticorrosione S.r.l

15. Donegani Anticorrosione S.r.l
Risk Assessment
The failure likelihood and the failure consequence are calculated on the basis of quantitative Likelihood Factors (LF) and Consequence Factors (CF).
Donegani Anticorrosione S.r.l

16. Likelihood of Failure (LoF)
The answers to the LF questions are assigned a series of values and associated weighting and the combination of all these determines the Likelihood of Failure (LoF), derived for each equipment in turn.
The LoF formula is specifically of the following form:
LoF = LF2 Σ (LFi)
LF2 = Failure likelihood (within a given period of time)
LFi = represents several factors that are considered to
contribute to the overall Likelihood of Failure.
Donegani Anticorrosione S.r.l

17. Donegani Anticorrosione S.r.l
LFi Factors
LF1: Current condition
LF2: Failure likelihood
LF3: Inspection Effectiveness
LF4: Shutdown Frequency
LF5: Operational Stability
LF6: Operation in Relation to Design
LF7: Recurring Repairs
Donegani Anticorrosione S.r.l

18. Consequence of Failure (CoF)
The answers to the Consequence Factors (CF) questions are assigned a series of values and associated weightings and the combination of these results is the Consequence of Failure (CoF), derived for each item in turn.
The CoF formula is specifically of the following form:
CoF = (FM x CF1 x CF2) + (CF3 x CF6) +
CF4 + (CF5 x CF7) + CF8 + CF9
Donegani Anticorrosione S.r.l

19. Donegani Anticorrosione S.r.l
FM Factor
In addition to other consequence factors the consequence calculation also consider the failure mode of an assigned damage mechanism. Each damage mechanism knowledge base is assigned one of three failure modes, i.e. ‘Leakage’, ‘Leakage or Rupture’, ‘Rupture’.
Donegani Anticorrosione S.r.l

20. Donegani Anticorrosione S.r.l
CFi Factors
CF1: Product Loss
CF2: Pressure Factor
CF3: Explosion/Fire Damage Potential
CF4: Toxicity
CF5: Effect of Failure on Production
CF6: Location of Component
CF7: Time Taken to Rectify Failure
CF8: Threat Personnel/Environment
CF9: Engineered Safety Systems
Donegani Anticorrosione S.r.l

21. Donegani Anticorrosione S.r.l
Weight of Factors
Donegani Anticorrosione S.r.l

22. Donegani Anticorrosione S.r.l
Risk Matrix
The resultant Likelihood of Failure (LoF) is plotted on the vertical axis, and the Consequence of Failure (CoF) is plotted on the horizontal axis, as an assessment point on a dimensionless five-by-five Risk Plot. The Lof axis is grouped into five relative Likelihood Categories, ranging from 1 to 5 (approximately 10-2/yr to 10-7/yr), and the CoF axis is grouped into five relative Consequence Categories, ranging from A to E. In this way, the Risk of Failure (RoF) is considered to increase with increasing LoF and CoF.
Donegani Anticorrosione S.r.l

23. Donegani Anticorrosione S.r.l
Risk Matrix 5 4
Risk
Likelihood 3 2 1 A B C D E
Consequence
Donegani Anticorrosione S.r.l

24. Donegani Anticorrosione S.r.l
Inspection Planning
After the risk assessment, the Study Team develops action plan based on all of expected damage mechanisms. The inspection plane consider the inspection interval and the scope of inspection.
The proposed inspection plane are designed to provide an assurance that the ‘residual risk’ of the equipment is in accordance with the ‘ALARP’ principle, i.e. the aim of assessing and managing equipment is to reduce the RoF to As Low As is Reasonably Practicable (‘ALARP’).
Donegani Anticorrosione S.r.l

25. Donegani Anticorrosione S.r.l
Risk Mitigation
The RBI methodology systematically leads the Study Team through the process of risk mitigation, by considering several mitigation action. The impact of each mitigation action can be evaluated, for subsequent collective appraisal of the benefits of the proposed action, using the ALARP principle. An appropriate strategy to manage the integrity of each equipment is therefore developed.
Donegani Anticorrosione S.r.l

26. Updating RBI Assessment
RBI Study can be used to justify extending the periods between inspections. The RBI process relies on a feedback loop to update the inspection plan, such that it is relevant to the actual condition of the plan. The feedback stage provides continuing confidence that damage dose not exceed expectations and ensures that plan inspections take account of operational experience.
Once an inspection plan has been developed during a session, future inspection of the equipment should be carried out to confirm that damage rates are within expectations and to identify any unexpected damage. The inspection should be carried out by competent staff and the results recorded and re-evaluated.
Donegani Anticorrosione S.r.l

27. Donegani Anticorrosione S.r.l
FeedBack of the Study
Plant Operation
Plant Operation
Shutdown/
Inspection
Start RBI
Inspection Plan Rev.0
Inspection Reporting
Inspection Plan Rev.1
Maintenance Shutdown
Base RBI Assessments
Review RBI Assessments
Maintenance Shutdown
Donegani Anticorrosione S.r.l

28. Risk vs Time No Inspection Plan
180 months
120 months
60 months
Donegani Anticorrosione S.r.l

29. Risk vs Time With Inspection Plan
180 months
120 months
60 months
Donegani Anticorrosione S.r.l

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Donegani Anticorrosione S.r.l