RBI Slides - Egypt Course Rev-3

 

RISK BASED INSPECTION

By PRAKASH JOSHI. INTEGRATED TRAINING

22-26 July 2006, Cairo. Egypt.

 

WHAT IS RBI ? • Traditional inspection methods : - Ge Gener nerall ally y time base based d - Ofte Often n unfocusse unfocussed d and indiscrim indiscriminat inate, e, - With little little relevance relevance to the actual actual risk of equipment. equipment.

• RBI is based on : - Ass Assessm essment ent of of RISK RISK level levels, s, - Prioritizin Prioritizing g the equipments based on risk levels - Focusing inspection program based based on risk levels.

 

WHY ADOPT RBI ? 1. RBI is based on RISK. 2. A relatively large percentage of the risk is associated with a small percentage of the equipments, 3. RBI permits the shift of inspection and maintenance resources to a higher level on the few high-risk items and to an appropriate level on several low risk items Thus,establish economic optimum levels of inspection .

 

WHAT IS “RISK” ? • Risk is the net result of: The Likelihood of Failure (LOF) and the Consequence of Failure (COF). Risk = Likelihood of failure x Its consequence Risk = LOF X COF • RBI is likely to reduce risk by : 1. Reducing LOF by Suitable inspection and, 2. Reducing COF by risk mitigation methods..

 

GRAPICHL DISPLAY OF RISK

 

GRAPHICAL DISPLAY OF RISK LEVELS

Highest Risk High Risk

5      D     Y 4      O     R      O     O      H      I      G3      L     E      E     T      K      I      A      L     C2

1

high Risk

Medium risk Low Risk 1

2

3

4

5

CONSEQUENCE CATEGORY

 

RISK ASSESSMENT • Risk assessments can be qualitative or quantitative. •  Assessm  Assessments ents combining combining features of both (i.e (i.e accuracy of quantitative and simplicity of qualitative are denoted as semi-quantitative. • Qualitativ Qualitative e answers are often sufficient to make major decisions • Qualitativ Qualitative e methods are cumbersome, time consuming consuming.. Semi-quantitative Semi-quanti tative results in reasonably accepted results with lesser efforts.

 

EQUAL RISK LINES

 

RISK ANALYSIS 1) Hazard Identificatio Identification n –

Study of Process, environment,

damage mechanism of each item 2) Likelihood Assessment – Assessment –

Inspection method, NDT Inspection Frequency

3) Consequence Assessment – Assessment – Type of product-flamma product-flammable ble or toxic, area affected etc. 4) Risk Risk Eval Evaluati uation on and and Reporti Reporting ng - Comb Combing ing LOF & COF COF 5) Mitigation and improvement improvement –  –  Appropriate & adequate adequate Inspection,Design improvement

 

BENEFITS OF RBI 1 - Opt Optimi imize ze ins inspec pectio tion n / mai mainte ntenan nance ce reso resourc urces es 2 - In Incre creas ase e av avai aila labi bilility ty ti time me of ce cert rtai ain n processes facilities 3 - Lon Longer ger ope operat ration ion of cer certai tain n equ equipm ipment ents s and and,, 4 - Main Mainta tain inin ing g the the same same lev level el of of risk risk for for the the whole plant

 

THE RBI ASSESSMENT (API 580) API RP 580 is intended to provide: provide: • Guidance on developing a Risk Based inspection (RBI) program in Hydrocar Hydrocarbon bon and Chemical process industries. • It details out: a. What is RBI b. What are the key elements of RBI c. How to implement a RBI program

 

THE RBI ASSESSMENT (API 580)…Contd. RP 580 is intended to supplement:  API 510: Pressure Vessel Vessel Inspection Inspection code,  API 570: Piping Inspection Inspection Code and  API 653: Tank Inspection code .

 

THE RBI ASSESSMENT (API 580)…Contd. The RBI assessment must systematically evaluate: • The probability of failure and • The associated consequence of failure.

The probability probability of failure failure assessment must be based based on all forms of deterioration that could be expected expected to affect the piece of equipment.

 

THE RBI ASSESSMENT (API 580)…Contd.

The conseque consequence nce of of failure failure asses assessment sment must address safety/health/environment aspects and/or Economic standpoint

 

PURPOSE AND SCOPE OF API 580  A successfully implemented RBI will throw up suggestions for: • Developi Developing ng the appropriate inspection strategy commensurate commensurat e with risk.

and/or,

• Risk mitigation and Risk-management

 

PURPOSE AND SCOPE OF API 580…Contd. By providing information on following: a. Ranking by risk of all the equipments b. An inspection plan to be employed, e.g: •

Inspection methods

•

Extent of inspection

•

Timing of inspection (insp.interval)

c. Suggestions of risk mitigation d. Expected levels of residual risk

 

RBI BENEFITS AND LIMITATIONS 1. Benefits: a. Overall reduction of risk of the plant and equipment b. Understanding / Acceptance of current risk c. RBI helps to identify equipments that may not require inspection or mitigation because of acceptable level of risk d. The inspection and maintenance activities can be more focused (towards risk) and also more cost effective.

 

RBI BENEFITS AND LIMITATIONS…Co LIMITATIONS…Contd. ntd. 2. Limitations: RBI does not compensate for: a. Inaccurate/ missing information b. Inadequate design or faulty installation c. Operations outside design limits d. Lack of the qualified persons or sound engineering judgments.

 

RBI BENEFITS AND LIMITATIONS…Co LIMITATIONS…Contd. ntd. 3. RBI as continuous improvement tool: •  As new data (inspection (inspection results) results) becomes available, available, reassessment reassessme nt of RBI program can be made with a refreshed view of risks. • It may identify shortcomings in effectivene effectiveness ss of presently available inspection methods. • RBI is expected to promote faster development of more appropriate inspection technologies. • Review of present but underutilized technologies, which may be more effective in risk assessment.

 

RBI BENEFITS AND LIMITATIONS…Co LIMITATIONS…Contd. ntd. 4. RBI as integrated Management tool: RBI is a risk assessment and risk-management tool. It produces inspection and maint. plans to achieve: •

Reliable and safe operation,

•

Cost effective inspection and

•

Longer process runs for uninterrupted productivity. productivity.

 

Scope of API 580 • RP 580 is specially targeted at the application of RBI in hydrocarbon and chemical process industry. •  API 580 is focused on mechanical integrity of pressure equipments and minimizing the risk of loss of containment due to deterioration.

 

Scope of API 580…Contd. • RBI complements (not replace): 

Process Hazard Analysis (PHA)



Hazardous operation (HAZOP)



Reliability centered Management (RCM)

Which focus on Design, Operation and Maintenance practices respectively.

 

was R B I deve devellop ope ed?  W hy was • All pressure equipment contain flaws Most flaws are innocuous - Don’t cause problems • Few flaws cause catastrophic failure Must find (inspect) those critical flaws in high risk service – service – Cost effectively • Typically 80% of the risk is associated with < 20% of the pressure equipment

 

Types of RBI Analysis • Leve Levell I - Qual Qualitativ itative e risk analys analysis, is, simple simple , brief brief  prioritization of equipment. equipment. • Le Leve vell II II - Se Semi mi--quantitative risk analysis, more detailed prioritization and planning. • Leve Levell III - Quan Quantitat titative ive risk risk analysis, analysis, in depth depth analysis

 

Types of RBI Analysis…Contd. Perform minimum level of analysis necessary to provide information adequate for decision making. • Detailed analysis, when not necessary, does not benefit the decision maker, but also inappropriately use resources .

 

Risk Assessments: API 580 and 581 •  A P I 580 : Recommended Practice that  describes all vital issues to be considered when implementing a RBI program . Used as the Standard guideline document for methods and requirements for RBI.

 

Risk Assessments: API 580 and 581…Contd. •  A P I 581 : Base Resource Document that describes specific step-by step RBI methodology for oil and gas plants. Used as working document. Contains detailed work-sheets, graphs, tables, and other data…all to be used by RBI task force for actual carrying out specific RBI implementations.

 

QUALITATIVE APPOACH to RBI It can be performed at following levels. •  An entire operating operating unit. • Major area or section of an operating unit. •  A system or major major equipment. equipment.

First determine LOF within the Unit / Section / Equipment then the associated COF, COF, both of which are then combined to produce risk rating.

 

APPOACH – COF QUALITATIVE APPOACH – Six factors considered to assess Likelihood Category. • Equipment Factor (EF) – (EF) – 15 Points • Damage Factor (DF) – (DF) – 20 Points • Inspection Factor (IF) – (IF) – 15 Points (CCF) – 15 Points • Condition Factor (CCF) – • Process Factor (PF) – (PF) – 15 Points • Mech. Design Factor (MDF) – (MDF) – 15 Points

Sum of above six factors establishes overall Likelihood factor (Part A).

 

APPOACH – COF QUALITATIVE APPOACH – Major hazards or the consequences in Refinery & Petrochemical plants are: • Fire and Explosion (Part B) • Toxic Risk (Part C) Out of the above, (Part B & Part C), higher Level of consequence is taken as “Overall Consequence Category”.

 

Quantitative Approach Likelihood & consequence analysis gives the risk in quantified absolute figures i.e. • In US per year or  •  Area affected (Risk (Risk Area) in square square feet. The results are used to Develop Inspection programs to reduce Risk.

 

Quantitat Quanti tative ive App Approa roach ch - con contd. td. Likelihood Analysis works out failure frequency considering : • Generic Failure Frequency (Global) ( Global) • Equipment Modification factor (Equipment) • Management system evaluation factor (Plant)

 

Quantitat Quanti tative ive App Approa roach ch - con contd. td. Consequence Analysis considers : • Flammable consequences • Toxic consequences • Environmental consequences • Business interruption consequences

 

QUANTITATIVE RISK ASSESSMENTS Adjusted Failure frequency (AFF) is calculated by: AFF = GFF * FE * FM Where, GFF = The generic failure frequency. FE

= Equipment modification factor specific to the mechanical integrity of the equipment

FM =

Management factor, specific to the plant.

 

Likelihood Analysis 1. De Dete term rmin ine e Gen Gener eric ic Fa Faililur ure e Fre Freq. q. (D (Dat atab abas ase) e) 2. Eq Equi uipm pmen entt Mod Modif ific icat atio ion n fac facto torr con consi sist sts s of of : • •

Technical Module sub-factor  Universal sub-factor 

•

Mechanical sub-factor 

•

Process sub-factor 

3. Ma Mana nage geme ment nt Eva Evalu luat atio ion n fact factor or is is dete determ rmin ined ed fro from ma score out of 1000 points

 

QUANTITATIVE ANALYSIS Likelihood analysis is carried out to obtain Failure Frequency of equipment considering: • Generic Failure Frequency • Technical module based on •

Damage rate

•

Inspection effectiveness

• Univ Universal ersal - Factor Factors s applicable applicable to whole whole plant • Mechanical Mechanical –  – Factors applicable to equipment • Process – Process stability & safety • Management systems factor 

 

QUANTITATIVE RISK ASSESSMENTS…Contd. Equipment modification factors, (FE) considers: • Type and rate of damage expected (e.g. corrosion, cracking, property degradation) • Quality and scope of inspection program (e.g. frequency, methods, tools) • Maintenance and repair quality control program (e.g. control of workmanship)

 

QUANTITATIVE RISK ASSESSMENTS…Contd. • Design and construction standards utilized (e.g. active code, API codes) • Equipment and process histories (e.g. quality of inspection records) • Preventive maintenance programs (e.g. PSV servicing, insulation maintenance)

 

QUANTITATIVE RISK ASSESSMENTS…Contd. Equipment factor (FE) mainly depends on assessment of : 1). Potential damage mechanisms (e.g. localized corrosion or wet H2S cracking, cracking, SCC SCC etc.) and Damage rates (e.g. corrosion rates or cracking rates). 2). The effectiveness of the current inspection program in finding and monitoring the identified damage mechanisms.

 

Inspection effectiveness is rated as: • Highly Effective:

finds the damage nearly always.

• Usually Effective: finds the damage most of the time • Fairly Effective: finds damage about half of the time. • Poorly Effective – Effective – usually does not find the damage. • Ineffective Ineffective –  – does not find the damage.

 

QUANTITATIVE RISK ASSESSMENTS…Contd. Management factor (FM) considers managemen managementt issues affecting the plant integrity like:

• Maintenance procedures and training • Process safety information • Management of change procedures and practices • Operating procedures • Process hazards analysis

 

Consequence Overview 1. Estimate Release ra rates 2. Determine type of release •

Instantaneous

•

Continuous

3. Dete Determ rmin ine e typ type e of of dis dispe pers rsio ion n / dam damag age. e. 4. Es Esti tima mate te imp impac actt of mit mitig igat atio ion n syst system ems s 5. Estimate consequences

 

CONSEQUENCE ASSESSMENT 1)

Severity and extent of potential damage depends on the size of the leak or rupture and the likelihood of a release being instantaneous or continuous for a period of time

2)

For flammable events, four events are calculated for hole sizes: ¼", 1”, 4” and full rupture.

 

CONSEQUENCE ASSESSMENT…Contd. 3)

Calculations are made to determine if the release is likely to result in •

vapor cloud explosion,

•

a flash fire,

• •

a jet fire, a liquid pool fire,

•

or safe dispersion (no ignition).

 

Consequence Analysis 1.

Dete De term rmin ine e Re Repr pres esen enttat ativ ive e fl flui uid d

2.

Sele Se lect ct se sett of of hol hole e siz sizes es (s (sim imul ulat atio ion n of of lea leak) k)

3.

Fluid available for release

4.

Release rates

5.

Type of release

6.

Final phase of fluid

7.

Post leak response

8.

Consequences of Release

 

RISK ANALYSIS RISKS = Cs X Fs Where, s= Failure Scenario Anticipated (Hole Size) CS = Consequence for Each Failure Scenario FS = Frequency Anticipated for Each Scenario The frequency for each scenario (FS) is calculated using the Adjusted Failure Frequency (AFF).

 

RISK ANALYSIS…Contd. Then the risk for each piece of equipment is the summation of all the risk calculations for each of four hole sizes: RISKEQUIP = Σs RISKs Where, RISKs = Risk for Each Scenario (1/4", 1", 4", and rupture cases) RISKEQUIP = Total Risk for Each scenario of Equipment

 

RISK ANALYSIS…Contd. The units of risk are expressed in terms of: • Potential damaged area /year for flammable and toxic events, or • Potential dollars lost/year for business interruption or • Major environmental damage. This would also need consideration of the local statutory laws and resulting liability the owner has to incur towards the compensation /penalty.

 

SEMI-QUANTITATIVE RBI • This shortened process (Level II) is an 80/20 version of Level III analysis. and is expected to produce 80% of the results with 20% of the effort. • It retains all of the vital aspects of risk analysis utilized in Level III analysis, but makes numerous simplifications significantly reducing the time and effort to collect data and to conduct an RBI .

 

Semi-quantitative Approach • It is scaled down approach from Quantitative approach. It considers considers the effect effect of the vital factors ignoring the trivial ones. • It thus results in most of the benefits of Quantitative but does not require much input. • The results is plotted on 5 X 5 risk matrix as in qualitative approach.

 

SEMI-QUANTITATIVE QUANTITATIVE RBI…Contd. SEMI• Likelihood of failure is based solely upon the assessment of potential damage mechanisms and the effectiveness of the inspection program  All other aspects of process process safety management and mechanical integrity programs included in Level III analysis are deleted for the simplified Level II analysis.

 

Likelihood Analysis • It only considers Technical Module sub factor to determine likelihood category • TMSF (around 1000) usually for outweighs all other factors (usually less than 10) • Other factors tend to be similar across the plant and do not provide discriminations between equipments • Likelih Likelihood ood category ( 1 to 5 ) is therefore decided based on TMSF only.

 

Consequence Analysis It consists of : • Simplifi Simplified ed approach for estimating inventory amounts • Consequence area is calculated for each hole size • Likelihood Likelihood weighted average area is worked out to determine consequence consequence category (A-E) • Risk matrix matrix ( 5 X 5 ) is then constructed constructed for analysis and assessment purpose.

 

RBI BASED INSPECTION PROGRAM • RBI gives, the prioritized risk ranking (combined likelihood and consequence of failure), • It also contains a prioritized list of equipment by likelihood of failure only and consequence of failure only. • This allows the user to focus on the specific issues that drive up total risk,

 

RBI BASED INSPECTION PROGRAM …Contd. • It helps to understand whether the total risk is driven primarily by likelihood of failure or primarily by consequence of failure. • It therefore clearly shows up the such aspects which needs to be addressed ( dealt with) for reducing the risk.

 

RBI Based Inspection Program It addresses two issues : • Develop inspection program and appropriate technique relevant to type of damage • Optimize inspection program commensurate with risk, i.e. decrease in inspection activity if no gain in risk reduction results in high level of inspection

 

RISK REDUCTION THROUGH INSPECTION • Having calculated a total risk for each piece of equipment, the next step is to decide what to do with the risk-prioritized list of equipment. • One of important potential risk reduction efforts is inspection and testing (I&T) program. Once we know what our highest priority pressure equipment, we will be able to determine very specifically where I&T efforts should be focused to reduce total risk.

 

RISK REDUCTION THROUGH INSPECTION –

contd. Inspection influences risk by reducing probability of failure considering 4 factors : • Damage mechanism active in the system and type of damage it can cause • Rate of damage progression • Selecting appropriate technique to detect damage (Inspection Effectivenes Effectiveness) s) • Tolerance of equipment to type of damage

 

RISK REDUCTION THROUGH INSPECTION –

contd. Inspection strategy should be developed considering : • What damage to look for (Service condition) • Where to look for it (Location of inspection) • How to look for damage ( Type of NDT) • When to look (Frequency)

 

INSPECTION STRATEGY BASED ON RBI • First, of all, the frequency of inspection can be adjusted. • The methods and tools for I&T can be changed. • The scope, quality, and extent of the inspection and data taking can be adjusted. • More global I&T techniques (like AE and thermography) can be applied, when appropriate.

 

INSPECTION STRATEGY BASED ON RBI…Contd. • More on-stream inspections can be utilized to assess damage occurring while in-service. • Inspections can be more focused at areas of expected damage. • Where appropriate, more sophisticated tools and techniques can be used to find and characterize localized damage and cracking.

 

INSPECTION STRATEGY BASED ON RBI…Contd. • The proposed changes in inspection activity are then planned into upcoming scheduled inspection, (turnaround planning,) • Once the inspections are conducted, results analyzed, higher risk equipment on the list might have dropped in risk ranking appreciably, as a result of having received more inspection and maintenance attention during turnaround.

 

INSPECTION STRATEGY BASED ON RBI…Contd. • This may require another reprioritizing of equipments (though at reduced risk levels) thus continuing the cycle of Continuous improvement • Overall, one can reduce not only the potential for injury, capital asset loss, and production losses, but you may be able to accomplish that with fewer inspection resources.

 

RISK REDUCTION THROUGH INSPECTION In short, The RBI throws-up:  A prioritization prioritization ranking of each each piece of equipment equipment for deciding three different levels of inspection activity: 1. A reduced but adequate inspection plan 2. Continuation of current actual level of inspection, and 3. Increased but optimized level of inspection

 

INSPECTION PROGRAM OPTIMIZATION • RBI analysis could be an effort to optimize the inspection program, by obtaining the lowest risk at at the lowest cost. cost. • Thus, a company may shift its limited inspection resources away from low risk equipment (which may be over-inspected)) towards the higher risk equipment (that over-inspected may be under-inspec under-inspected). ted). • The iso-risk lines help to clearly differentiate higher risk equipment from lower risk equipment.

 

INSPECTION PROGRAM OPTIMIZATION…Contd. • The management can focus inspection and/or mitigation resources on equipment items that are above a maximum acceptable risk level and bring them within acceptable risk. Thus the total risk is minimized. • The changes in risk can bring about changes in planned inspection strategy eliminating redundant inspections and inspection costs as to resources earlier costs will be reduced. Thus total risk is decreasing and inspection costs are also decreasing. decreasing.