RBI (Risk Based Inspection)
THE CONOCOPHILLIPS HUMBER REFINERY ON 16 APRIL 2001
Definition of Risk •
Risk is danger d anger and undesirable event represent for People , Environment and Economic assets. assets.
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Risk In Risk Based Inspection, risk is defined as the product prod uct of two t wo separate terms – the Likelihood that a failure will occur and the Consequence of a failure
Risk Risk = Probability Probability of Failure x Consequ Consequences ences of Failure Failure •
Failure mode,
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Material/Environment;
Degradation ; type & rate,.... •
Damage tolerance
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Personnel
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Environment
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Economic
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Quality
What is Risk Management ? •
Risk management is a process to identify , measure (quantify) and then develop plans to maintain risks at on acceptable level.
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It is a well known known fact that , in general 80% of the failures occur in 20% of the equipment.
Risk-Based Inspection API AP581 A risk assessment assessment and management manag ement process that is focused on loss of containment of pressurized pressuriz ed equipment in processing processing facilities, due to material deteriorat deterioration ion.. These These risks are managed manag ed primarily primari ly through throu gh equipm e quipment ent inspection
Scope of API RP 580 •
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Equipment Cov Covered ered –
Pressure Vessels - All pressure containing components.
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Process Piping - Pipe and piping components.
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Storage Tanks - Atmospheric and pressurized.
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Rotating Equipment - Pressure containing c ontaining components.
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Boilers and Heaters - Pressurized components.
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Heat exchangers (shells, floating heads, channels, chann els, and bundles).
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Pressure-relief Pressure-relie f devices. devices.
Not covered –
Electrical Electri cal systems systems
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Instrument and an d control cont rol systems systems
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structural systems, systems,
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machinery components (except pump and compressor casings).
What is RBI ? (Risk Based Inspection) •
Risk Based Inspection is a dynamic , Systematic tool for priora p rioratising tising inspection inspection according to the potential pote ntial risk assoc a ssociated iated with specific equipmen eq uipment. t.
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RBI systematical systematical evaluated evaluated both the probability of failure and the associated consequence of failure.. failure
Management of Risk using RBI
Risk Plot
The Principles of RBI •
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It formalises a common-sense approach It considers the Consequences and Likelihood of failure
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Identifies the highest-risk equipment
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Quantifies Quantifies the risk ris k
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Reflects the risk in the written scheme of examination
Benefits of RBI program •
The basic benefits of a RBI program are :
It provides the th e capability to define and measure risk
It allows management management to review safety in and integrated , cost cos t -effective manner
Systematically reduces reduces the likelihood of failures by making better use of the inspection in spection resources
Improves Improves the th e reliability of plant equipment equipment
RBI Process Probability of Failure Data and Information
Risk Ranking
Inspection Plan
Mitigation (if any)
Collection Consequence of Failure
Risk Assessment Process
Reanalysis
Establish RBI Team
Planning the Risk Analysis
Collect data
Probability of Failure
Consequence of Failiure
Identify Damage Mechanism
Determine the Damage Mode (Option)
Determine credible failure mode(s)
Identify credible consequence scenarios
Determine the probability of each consequence scenario
Determine the probability of failure
Risk Analysis Process
Determine the risk
Develop and inspection plan
Develop Mitigation (if any)
Type of RBI Assessment
Qualitative : provides a broad-based risk assessment of and operating unit or a part of an operating unit ,required less detail information about the facility. In this assessment using engineering judgment and experience for the analysis of probability probabilit y and consequences of failure
Quantitative : Provides risk values for each equipment item and pipe segment in a operating unit , required comprehensive comprehens ive detail information informatio n about the facility and equipment. In this assessment using logic models , likelihood and probability probab ility data to calculate the risk of failure
Semi-qualitative : Some were between either approach.
Assessing Probability of Failure
Terms Damage (or deterioration) d eterioration) Mechanism Mechanism A process that induces micro micro and/or macro material material changes over over time that tha t are harmful to the material condition or mechanical properties. pro perties. Damage mechanisms are usually incremental, cumulative, and, in some instances, unrecoverable. Common damage mechanisms include corrosion, stress corrosion cracking, crack ing, creep, erosion, fatigue, fracture, and an d thermal aging .
Damage (or deterioration) mode The physic physical al manifestation manifestation of damage (e.g. ( e.g. wall thinning, pitting, cracking, cracking, rupture ).
Failure mode The manner of failure. For RBI, the failure of concern is loss of containment of pressurized pressurized equipment items. Examples of failure modes are small hole, crack, and rupture.
Probability of Failure
Assessing Consequ Consequences ences of Failure Failure •
Safety and health health impacts impact s
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Envir Environment onmental al impacts
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Economic impacts
Risk Ranking
Inspection and Maintenance Planning
Inspection Inspecti on and Maintenance Maintenance Planning
RBI Assessment to Inspection Program
Other Mitigation Plan •
Equipment Equipment Replacement and Repair
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Fitness-for-Ser Fitness -for-Service vice Assessment Assessment
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Equipment Equipment Modification, Redesign, and Rerating Re rating
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Emergency Emergency Isolation Isola tion
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Modify Process
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Reduce Inventory
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Etc.
Difference Between RBI & Others Inspection Philosophes
RBI & RCM - RBI is used for static for static equipment, equipment, where the main failure is loss of containment or structural damage. damage . Usually there are a few failure modes only, only, e.g. corrosion, erosion etc.
- RCM is suitable when there are many failure modes and consequences. consequences. It usually applies to complex machinery such as Pumps, compressors, alternators etc. V.Narayan (Vee) Lead Author, 100 Years of Maintenance: Maintenance: Practical Pr actical Lessons Les sons from Three Lifetimes, Industrial Industr ial Press P ress.NY .NY ISBN-13: 9780831133238 Author, Effective Maintenance Management: Risk and Reliability Strategies for Optimiz ing Performance, Perform ance, Second Edition, Edition, 2011, Industrial Press NY ISBN-13: 978-0-8311-3444-0 978-0-8311-3444-0
