220183537 Shell RBI Methodology

1© Shell Global SolutionsP-B-v1.1

Shell Global SolutionsShell Global Solutions

S-RBISHELL RISK-BASED INSPECTION

- THE METHODOLOGY -

Risk and Reliability Management

Presenter: Maarten FestenBUSINESS GROUP

MAINTENANCE, INSPECTION AND RELIABILITY ENGINEERING


S-RBI: SHELL RISK-BASED INSPECTION

• S-RBI Work flow

in the RRM software

• S-RBI methodology

part of RRM Manual, issued in 1999


S-RBI AS PART OF RISK ANDRELIABILITY MANAGEMENT (RRM)

methodologymethodologyandand

databaseRRMRRM

database

SS--RBIRBI SS--RCMRCM IPFIPF

SHELL RSHELL ReliabilityCCentered MMaintenance

IInstrumentedPProtective FFunctions

(safeguarding systems)


S-RBI PROCESS

ASSET INTEGRITYDATABASE

CORROSION LOOPDESCRIPTIONS

CRITICALITYASSESSMENT

CONFIDENCEASSESSMENT

INSPECTION/MONITORINGPLANNING

S-RB

I PA

CKA

GE

ANALYSIS/REVIEWFEEDBACK

TASK EXECUTION


THE ADVANTAGES OF SINGLE RRM DATABASE FOR RBI/RCM/IPF ANALYSES

• COMMON USE OF RESOURCE DATA

pick lists for e.g. equipment types, materials etc.

Consequence of Failure analysis/data

• STANDARD CRITICALITY DEFINITION

1 Criticality Matrix

in line with HSE standard (RAM, April 1999)

• TASKS FOR EACH ITEM DEFINED ON SAME CRITERIA

tasks can be compared & optimised


RBI STUDIES - RRM DATABASE

PREPARATION, WHERE POSSIBLE BEFORE THE STUDIES:

• Common part can be filled

or used from S-RCM or IPF, if already carried out

• Assets can be filled

or used from S-RCM or IPF, if already carried out

• Inspection information can be entered

“one liners”, giving relevant information only


RBI STUDY - TEAM SESSIONS

• Review plant data, former and future operating conditions (where applicable)

• Discuss materials selection and inspection experience

• Develop Corrosion Loops and Operating Windows

• Do criticality analysis

• List confidence rating

• Develop inspection/monitoring scope

mainly by inspection & corrosion members, team review


Shell Global SolutionsShell Global Solutions

S-RBI METHODOLOGY


SIMPLIFIED S-RBI FLOW CHART (1)

NO

YES

INTOLERABLE

RECTIFY

MediumHigh

ExtremeNegligible Low

Asset Integrity Database

Review operating conditionsand Materials Selection

Corrosion Loops

LoopCriticality

Assessment

LoopCriticalityNegligible

No inspectionReview only

RCM

EquipmentItem

ItemCriticality

Inspection/Monitoring

Interval & Scope

Analysis &Feedback

1

Inspection /Monitoring


CORROSION LOOPS

DIVIDE THE UNIT IN CORROSION LOOPS

• Discuss the process parameters

• Review materials applied

• Highlight inspection/degradation history

• Discuss Materials Engineering issues/experience (generic)

• Divide the unit in Corrosion Loops (colouring PFS schemes)


S-RBI IS BASED ON CORROSION LOOPS

CORROSION

WHAT TYPE OF DEGRADATION CAN OCCUR AND WHERE ?

MATERIAL+

ENVIRONMENT

WHICH (PROCESS) CONTROLSARE NEEDED ?


WHAT IS A “CORROSION LOOP”?

“A PRACTICAL WAY TO DESCRIBE, UNDERSTAND AND CHECK DEGRADATION MECHANISMS IN A UNIT”

• PART OF THE UNIT SUBJECTED TO:the same process conditionsthe same failure mechanismsthe same materials selectioncriteria

• ONE “OPERATING WINDOW”control of degradations viaprocess controlvalues agreed by team(boundary conditions for RBI)deviation should be reported

12-E-101

12-D

-101

12-G-101

12-K-1011st stage

12-E-102

to burn pit

Loop 1

Loop 2

Loop 3

CORROSION LOOP

• same process conditions• same degradation mechanisms


CORROSION LOOPS FOR A KERO HDT

Product toStripper

Sour Water

Recycle Hydrogen

Hydrogen from Platformer

To Fuel Gas systemCTW5Cr 0.5Mo

321 SSas sscs cs cs as

Feed fromCDU

R-1201

E-1202

ABCDEF

E-1201

CSCS

CSCS

1.25Cr 0.5Mo


EXPERIENCE WITH CORROSION LOOPS

• Applied in refineries, chemical plants and gasplants

• Good experience and part of S-RBI approach

• Useful to set operating windows

• Information on degradation mechanisms (and affected areas)

• Info on degradation available for all staff concerned with integrity!


CRITICALITY ASSESSMENTFOR THE CORROSION LOOP:• Stop if Negligible Criticality or Negligible Consequence of Failure

is obtained (no further analysis on item by item basis)these items are analysed by S-RCM to optimise maintenance plans and in a review scheme for RBI (checking if changes occurred)

FOR INDIVIDUAL ITEMS:• Carry out the criticality rating for each item

can be grouped for similar piping items into e.g. “LP piping”can be divided into 2 loops, e.g. “Column top”,and “Column bottom”


SIMPLIFIED S-RBI FLOW CHART (2)

NO

YES

INTOLERABLE

RECTIFY

MediumHigh

ExtremeNegligible Low

Asset Integrity Database

Review operating conditionsand Materials Selection

Corrosion Loops

LoopCriticality

Assessment

LoopCriticalityNegligible

No inspectionReview only

RCM

EquipmentItem

ItemCriticality

Inspection/Monitoring

Interval & Scope

Analysis &Feedback

1

Inspection /Monitoring

2


CRITICALITY MATRIX

HIGHNEGLIGIBLES-RBI LOW MED

IUMEXTENSIVE

NNNEGLI-GIBLE NN LL MM HH

NNLOW LL MM HH EELLMEDIUM MM HH EE XXLLHIGH HH EE XX XX

CONSEQUENCES

PRO

BA

BIL

ITY

NEGLIGIBLENEGLIGIBLENO INSPECTIONREVIEW ONLY

INTOLERABLEINTOLERABLE

LOWLOW MEDIUMMEDIUMHIGH CRITICALITYHIGH CRITICALITY

INSPECTION PLAN

RECTIFY

EXTREMEEXTREMECRITICALITYCRITICALITY

DETAILED ANALYSIS


SUSCEPTIBILITY TO FAILUREINSTEAD OF PROBABILITY• The Susceptibility to Failure (StF) is the worst case estimate for the

degradation under consideration, without corrective actions(no inspections, no monitoring).

• The StF will lead to the “Criticalty” of the items in combination with the Consequence of Failure (CoF).

• After implementation of monitoring & inspection, the remaining possibility that such a degradation leads to an incident is described as the Probability of Failure (PoF); together with CoF this describes the remaining “Risk” in operation.

The PoF must be As Low As Reasonably Possible (ALARP) and not exceed “Low” in general, and

“Negligible” where the CoF is Medium, High or Extreme


CRITICALITY RATING

• Determine the Susceptibility to Failure (StF)

• Determine the Consequence of Failure (CoF)

• Combination of StF and CoF yields the Criticality

CRITICALITY = potential riskwithout preventive measures or corrections


RBI CRITICALITY MATRIX (1)

N LL MM

E

H

XEH

HMM

MMLL

LL

N

N

XXEHLL3

2

1

4

PRO

BABI

LITY

CLA

SS

MULTIPLEFATALITIES

EXTENSIVEDAMAGE >10M

SLIGHT INJURY

SLIGHT DAMAGE<10K

SLIGHT EFFECT

MINOR INJURY

MINOR DAMAGE10-100K

MINOR EFFECT

MAJOR INJURY

LOCAL DAMAGE0.1-1M

LOCAL EFFECT

SINGLE FATALITY

MAJOR DAMAGE1-10M

MAJOR EFFECT MASSIVE EFFECT

HEALTH & SAFETY

ECONOMICS (USD)

ENVIRONMENTCON

SEQ

UEN

CECA

TEG

ORY

CONSEQUENCE CLASS NEGLIGIBLE1

LOW2

MEDIUM3

HIGH4

EXTREME5

NEGLIGIBLE

LOW

MEDIUM

HIGH

SUSCEPTIBILITY TO FAILURE RRM CRITICALITY CLASS

X = Intolerable E = ExtremeH = High M = MediumL = Low N = Negligible


RBI CRITICALITY MATRIX (2)

N LL MM

E

H

XEH

HMM

MMLL

LL

N

N

XXEHLL3

2

1

4

PRO

BABI

LITY

CLA

SS

MULTIPLEFATALITIES


SLIGHT INJURY

SLIGHT DAMAGE<10K

SLIGHT EFFECT

MINOR INJURY

MINOR DAMAGE10-100K

MINOR EFFECT

MAJOR INJURY

LOCAL DAMAGE0.1-1M

LOCAL EFFECT

SINGLE FATALITY

MAJOR DAMAGE1-10M


HEALTH & SAFETY

ECONOMICS (USD)

ENVIRONMENTCON

SEQ

UEN

CECA

TEG

ORY


LOW2

MEDIUM3

HIGH4

EXTREME5

NEGLIGIBLE

LOW

MEDIUM

HIGH


NORMAL DESIGN CASE

NEGLIGIBLE OR LOW SUSCEPTIBILITY TO FAILURE

NOTE: Medium or High StF can occure.g. as a result of changed operating conditions


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SUSCEPTIBILITY TO FAILURE ASSESSMENT


SUSCEPTIBILITY TO FAILURE (STF) (1)

• Determine potential degradation mechanisms for the Loop.

• For those degradation mechanisms, identify the StF per item.

for each item since there can be differences in temperature etc..

• For each item, analyse the different degradation mechanisms separately since they may result in different failure modes.

Different inspection techniques/intervals may be required.

Monitoring scheme to be indicated for non-age realateddegradations.



• The failure mode will influence the Consequence of Failure and therefore the Criticality.

The “item criticality” will be the highest rating of all failuremodes.



• AGE RELATED DEGRADATIONStime factor (very) important in relation to degradationdegradations can be foreseen/predicted and controlled

– general corrosion (thinning)– creep

part of normal design criteria, basis for “design life”

• NON-AGE RELATED DEGRADATIONStime factor not important in relation to degradationdegradations can be fast often related to plant upsets

– e.g. stress corrosion cracking due to Cl or caustic– brittle failure ⇒ not acceptable, not in normal designs;

special precautions/controls needed


FAILURE MODES

Time

Time

Tim

AGE-RELATED NON-AGE-RELATED

4

5

6

1

2

3

Time

Time

Time

Time

Time

PoF

PoF

PoF

PoF

PoF

PoF

⇒ internal/external corrosion⇒ creep

Random failures

Failures are mostlyrandom with only afew early-life failures

More failures occurshortly after installation,repair or overhaul

Time

PoF

?

SCC due to a Process upset


SUSCEPTIBILITY OF FAILURESUSCEPTIBILITY OF FAILURE

DEGRADATION MODULESDEGRADATION MODULES

failure characteristic:non age-related

THINNING

- CRACKING- H-ATTACK- MECHANICALCREEP

determinefailure characteristic

failure characteristic:age-related

determine susceptibilitybased on the ratio:

actual corrosion rate/design corrosion rate

determine Susceptibilitybased on

API Technical ModulesFitness for Service study

determine susceptibilitybased on the

operating conditions


StF - AGE-RELATED DEGRADATIONS1 Internal Corrosion The actual corrosion rate is very high (e.g. > 4 × CRd) H

General and/or localised The actual corrosion rate is high (e.g. 1 - 4 × CRd) M

The actual corrosion rate is acceptable/low (e.g. 0.5 - 1.0 × CRd) L

The actual corrosion rate is very low (e.g. < 0.5 × CRd) N

2 External Corrosion Severe external corrosion ( e.g. 60 -120 °C with high humidity and/orspray, condense, cycling conditions, damaged insulation)

H

Corrosion underinsulation

Serious external corrosion , (e.g. -5 to 60 °C or 120 - 150 °C andhumid climate, damaged insulation)

M

Minor external corrosion under normal operating conditions(0.05mm/yr) L

No foreseeable external corrosion (not insulated or >150 °C) N

3 Creep Operation in the creep range, risk of major upsets which must bequantified in terms of remnant life

H

Operation in the creep range, risk of minor upsets which must bequantified in terms of remnant life

M

Operation in the creep range at or below design conditions L

No foreseeable operation in the creep range N


SUSCEPTIBILITY TO FAILURE INTERNAL CORROSIONgeneral & localized corrosion

0.5 - 1 x design CR

< 0.5 x design CR

Corrosion Rating for Susceptibility to Failure

RRM MATRIX

H igh

M edium

L ow

N egligible

> 4 x design CR

>1 - 4 x design CR


StF - NON AGE-RELATED DEGRADATIONS (1)

4 Fatigue - Thermal Cyclic temperature range or delta T of two process streams greater than 250 °C H

Cyclic temperature range or delta T of two process streams between 150 and 250 °C

M

Cyclic temperature range or delta T of two process streams between 100 and 150 °C

L

All other lines or equipment N

5 Fatigue - Vibrations Vibrating in zone 1, or nominal pipe diameter less than 50 mm and in zone 2 and 3

H

Vibrating in zone 2, or nominal pipe diameter between 50 and 100 mm and in zone3

M

Vibrating in zone 3 L

No foreseeable fatigue due to vibration (zone 4 or no vibrations N

6 Stress Corrosion Cracking High susceptibility H

External or internal Medium susceptibility M

Low susceptibility L

Not susceptible N


CAUSTIC CRACKING MODULEAPI 581 and degradation library

Start

Plot Point on NACECaustic SodaService Graph

Medium Susceptibility

Yes

No

No

Yes

Yes

Yes

No

TemperatureNaOHConcentration

Heattraced?

No

Medium Susceptibility

Not Susceptible

Yes

Steamedout?

No

Heattraced?

No

Not Susceptible

Yes

Yes

High SusceptibilityNo

H

NaOHconc<5%wt?

Plots inArea “A”?

StressRelieved?

NaOHconc<5%wt?

Steamedout?

Yes

No

M

ML

Low Susceptibility

N



NAR 7 Low Temp. Embrittlement Operating or upsets outside the limits of DEP 30.10.02.31Gen.

H

(No cat. M)

Operating or upsets within the limits of DEP 30.10.02.31Gen.

L

Not susceptible under any foreseeable conditions N

NAR 8 High Temp. Embrittlement Operating in the embrittlement range and no S/Dprecautions

H

Design or upsets in the embrittlement range and no S/Dprecautions

M

Design and operation below the embrittlement range or S/Dprecautions

L

Not susceptible under any foreseeable conditions N



NAR 9 High TemperatureHydrogen Attack

Operating/upset conditions above the Nelson curve limit(API 941)

H

Operating conditions between the Nelson curve limitand 20 °C below (API 941)

M

Operating conditions are 20 - 50 °C belowthe Nelson curve limit (API 941)

L

Operating conditions are > 50 °C below the Nelson curvelimit (API 941) or Material is not susceptibleunder any foreseeable conditions

N

NAR 10 Erosion Flow velocity is much higher than design and/or much largeramounts of solids/droplets present

H

(non protected system) Flow velocity is higher than design, and/or solids/dropletshigher than design

M

Flow velocity is per design or less, solids/droplets loading asper design or less

L

No foreseeable occurrence of erosion N


StF - DEGRADATION MODULESfor further information

• Based on the API BRD 581 Technical Modules

modified where required to reflect SIOP experience

• 15 Modules available for all major degradation mechanisms (and more under development)

general corrosion – acids– water– etc.

CUI, H2S, H2 attack, SCC, etc.



CONSEQUENCE OF FAILURE (CoF) ASSESSMENT


CONSEQUENCE OF FAILURE ASSESSMENT

• PURPOSE IS TO ESTIMATE CONSEQUENCE CLASS (1 OUT OF 5)

• THREE LEVELS OF ASSESSMENT ARE AVAILABLE

1 Direct selection (using Risk Assessment Matrix - RAM)

2 “Simple” questionnaire using RAM descriptions,but split over important aspects of each category

3 “Detailed” questionnaire, using relevant processand equipment data

• USE TOP-DOWN APPROACH

Use 3 to set the levels for the loop, for main items


DIRECT ASSESSMENT OFCONSEQUENCE OF FAILURE

>10 M$SUBSTANTIAL/TOTAL LOSS OF

OPERATION

MULTIPLEFATALITIES

MASSIVE EFFECTSEVERE DAMAGE

NUISANCE INLARGE AREA

1 - 10 M$PARTIAL

OPERATIONLOSS (2 WEEKS)

SINGLE FATALITYINCLUDING

PERMANENT TOTAL DISABILITY

MAJOR EFFECTEXTENSIVE

RESTAURATIONREQUIRED

0.1 - 1 M$PARTIAL

SHUTDOWNCAN BE RESTARTED

MAJOR INJURYINCLUDINGPERMANENT

PARTIAL DISABILITY

LOCALISED EFFECTAFFECTING

NEIGHBOURHOOD

10 - 100 k$BRIEF DISRUPTION

MINOR INJURYLOST TIMEINCLUDED

MAXIMUM 1 WEEK

MINOR EFFECTCONTAMINATION,NO PERMANENT

EFFECT

<10 k$NO DISRUPTION

NO/SLIGHT INJURYFIRST AID/MEDICAL

TREATMENT

NO/SLIGHT EFFECTLOCAL DAMAGEWITHIN FENCE

ECONOMICS

HEALTH& SAFETY

ENVIRONMENT

EXTENSIVEHIGHNEGLIGIBLE LOW MEDIUM

MAXIMUM CLASS IS GOVERNING


ECONOMICS

• PRODUCTION LOSS

deferred income (no or downgraded product)

product wasted (flared or spilled)

• REPAIR COSTS

repair/re-install item

fixed contractor costs (lump sum)

• LABOUR


DIRECT ASSESSMENT OFECONOMIC CONSEQUENCES

Class Potential Impact Description

N Slight damage< 10 kUSD

No disruption to operation

L Minor damage10-100 kUSD

Brief disruption

M Local damage0.1-1 MUSD

Partial shutdown that can berestarted

H Major damage1 - 10 MUSD

Partial operation loss (2 weeksshutdown)

E Extensive damage> 10 MUSD

Substantial or total loss ofoperation

definitions as given in the HSE RAM


ECONOMIC CONSEQUENCESsimple questionnaire

1

2

3

6

COSTELEMENT

Production loss k

Repair costs k

Labour k

Total k

Economic consequence class: N


PRODUCTION LOSS EQUATIONProduction lossesDown time 6 hr = 100 kUSD

Reduced throughput 5 hr @ 20 % = 50 kUSD

Miscellaneous = 30 kUSD

Total production losses 180 kUSD

Repair costsMaterials / Equipment = 10 kUSD

Fixed contractor costs = 4 kUSD

Miscellaneous = 0 kUSD

Total repair costs 14 kUSD

LabourCraftsmen 5 hr = 300 USD

Operator 4 min = 7.2 USD

Staff 1 hr = 80 USD

Contractor 2 hr = 100 USD

Total labour 0.487 kUSD

Total economic consequence 194.487 kUSD

Economic consequence class M


STAGGERED PRODUCTION LOSS EQUITION

0

20

40

60

80

100

0 5 10 15Time [h]

Loss

[kU

SD]

PLE example:0 - 2 h: 2 kUSD/h2 - 8 h: 4 kUSD/h> 8h : 8 kUSD/h

t1 t2

22

88

In software 2 and 8 should be entered asthe inputs with the loss value up to that limit

5 periodscan bedefined


HEALTH AND SAFETY• Three health and safety effects are considered:

1 Thermal effect (fire) 2 Blast and fragment (explosion)3 Toxic effect

– which can be reduced by mitigation

• Maximum of three minus mitigation is overallHealth and Safety class

• “Simple” questionnaire connects the degree of hazard toHealth and Safety descriptions

e.g. medium fire which could cause minor injuries


HSE RAM DEFINITIONSTable 3-2 Health/Safety consequence definitions as given in the HSE RAMdocument

Class Potential Impact Description

N No/Slight injury First aid case and medical treatment case. Not affectingwork performance or causing disability.

L Minor injury Lost time injury. Affecting work performance, such asrestriction to activities or a need to take a few days to fullyrecover (maximum one week).

M Major injury Including permanent partial disability. Affecting workperformance in the longer term, such as prolonged absencefrom work. Irreversible health damage without loss of life,e.g. noise induced hearing loss, chronic back injuries.

H Single fatality Also includes the possibility of multiple fatalities (maximum3) in close succession due to the incident, e.g. explosion.

E Multiple fatalities May include 4 fatalities in close succession due to theincident, or multiple fatalities (4 or more) each at differentpoints and/or with different activities.


HEALTH & SAFETYsimple questionnaire (1)

CONSEQUENCECLASS

CONSEQUENCE DESCRIPTION

FIREFailure mode leads to:

1 N No fire or fire which could only cause slight injuries (no LTI)2 L Fire which could cause minor injuries (LTI)3 M Fire which could cause major injuries (LTI> 1 week and/or partial disability)4 H Fire causing up to a single fatality or permanent total disability

EXPLOSIONFailure mode leads to:

1 N No explosion but just a flash fire which could only cause slight injuries (first aid)2 L No explosion but a flash fire which could cause minor injuries (LTI)3 M Explosion or flash fire which could cause major injuries (LTI>1week and/or

partial disability)4 H Explosion or flash fire which could cause a single fatality or permanent total

disability5 E Explosion which could cause multiple fatalities


HEALTH & SAFETYsimple questionnaire (2)

CONSEQUENCECLASS

CONSEQUENCE DESCRIPTION

TOXICFailure mode leads to:

1 N No or very small toxic release which could cause only slight injuries (first aid)2 L Small toxic release which could cause minor injuries (LTI)3 M Medium toxic release which could cause major injuries (LTI>1week and/or

partial disability)4 H Large toxic release which could cause a single fatality or permanent total

di bilit5 E Very large toxic release which could cause multiple fatalities

MITIGATIONExposure near failure location and possibility to avert danger of hazardousevent could reduce possible H/S consequence class by:

0 No means or only marginally-1 One class-2 Two classes


HEALTH & SAFETYdetailed questionnaire

Table 3-4 Common consequence matrix

4 N H E E

quantity 3 N M H E

2 N L M H

1 N N L M

1 2 3 4

property

flammability

quantityreleased

For fires

Consequenceof FailureNegligible toExtreme


HEALTH AND SAFETYfire• Two parameters are used to estimate fire consequence:

Flammability

– NFPA (National Fire Protection Association) flammability index, 0 ≤ Nf ≤ 4 and temperature

Released quantity (instantaneous/per hour/inventory)

– three levels: < 500 kg, 0.5 - 5 ton, and > 5 ton

• Matrix to determine fire class (Max H)


FIREdetailed H & S questionnaire

Nf Products

0 Sulphur Diox ide, SodiumChloride

1 Sulphur, Am m onia

2 Diesel Fuel, Fuel O il 1 to 6

3 Gasoline, Naphtha, EthylAlcohol, Petroleum Crude

4 Hydrogen, Methane,Hydrogen Sulphide

Table 3-6 Fire safety questionnaire

Flammability

1 Not flammable (Nf < 2) or lowflammability (Nf >1 and Tproduct < Tflash)

2 Medium flammability(Nf > 1 and Tflash < Tproduct < Tauto ign)

3 High flammability(Nf > 1 and Tproduct > Tauto ign)

Released quantity(instantaneous or per hour or inventory)

1 < 500 kg

2 0.5-5 ton

3 > 5 ton

released 3 N M H

quantity 2 N L M

1 N N L

1 2 3

flammability


RELEASE OF LIQUID THROUGH A HOLE

1

10

1 10 100pressure [barg]

hole

dia

met

er [m

m]

505005000

5 mm

advised as theaverage case, results

in released Q=2

kg/h


HEALTH AND SAFETYexplosions

TWO EXPLOSION/IMPACT RISKS ARE CONSIDERED:1 Vapour Cloud Explosions (VCE)

VCE possibility (flammable cloud and congested area)released vapour mass (instantaneous, per hour)matrix to determine VCE class

2 Other impact/high pressure riskshigh pressure equipmentfailure causing flying debris

⇒ MAXIMUM OF THE TWO IS EXPLOSION CLASS (MAX E)


EXPLOSIONdetailed H & S questionnaire Table 3-7 VCE consequence questionnaire

VCE possibility

1 None; no release of anexplosive cloud

2 Low; release of an explosivecloud in an open area

3 Medium; release of an explosivecloud in a medium congestedarea (some obstacles present)

4 High; release of an explosivecloud in a heavily congestedarea (many obstacles present)

Released vapour mass(instantaneous or per hour)

1 < 50 kg

2 50 - 500 kg

3 0.5 - 5 ton

4 > 5 ton

released 4 N H E E

vapour 3 N M H E

mass 2 N L M H

1 N N L M

1 2 3 4

VCE possibility


RELEASE OF GASthrough a 3 mm hole C1-C2 and H2

10

100

1000

0 50 100 150 200 250Pressure [bara]

Rel

ease

rate

[kg/

h]

C1-C2 (@ 50 C)H2 (@ 50 C)


RELEASE OF LPG THROUGH A 3 MM HOLE

0

500

1000

1500

2000

2500

0 50 100 150 200 250Pressure [bara]

Rel

ease

d qu

antit

y [k

g/h]

C3 @ 50 CC3 @ 100 CC4 @ 50 CC4 @ 100 C


EXPLOSION & HPdetailed H & S questionnaire

Table 3-8 Other explosion and high pressure equipment consequence questionnaire

N no gas present or p*V<5 bar m3

L gas present and 5 ≤ p*V ≤ 50 bar m3

M gas present and 50 < p*V < 500 bar m3

H gas present and p*V>500 bar m3 or failure causing some flying debris (solid particles)

E failure causing major flying debris (solid particles)


HIGH PRESSURE CONSEQUENCE OF GAS PIPES

0.1

1

10

1 10 100pressure [barg]

pipe

dia

met

er [m

]

550500

P x Vbar m3


HEALTH AND SAFETYtoxic effects

TWO PARAMETERS DETERMINE TOXIC CONSEQUENCE:Toxicity

– NFPA “health” index, 0 ≤ Nh ≤ 4 Concentration

– four levels: < 1000 ppm, …, > 10%

⇒ MATRIX TO DETERMINE TOXIC CLASS (MAX E)


Table 3-9 Toxicity index, Nh, examples

Nh Products

0 Diesel

1 Butane, Gasoline

2 CO, benzene,Ethylene Oxide

3 H2S, chlorine, Ammonia,Sulphuric Acid, Phenol

4 Hydrogen Fluoride (HF),Hydrogen Cyanide

Table 3-10 Toxic consequence questionnaire

Toxicity

1 Not toxic (Nh≤1) or low toxicity(Nh≤3 and conc. < 100 ppm).

2 Medium toxicity (Nh=2)

3 High toxicity (Nh=3)

4 Extreme toxicity (Nh>3)

4 N H E E

Concentration (in ppm or % volume) Concentration 3 N M H E

1 < 1000 ppm 2 N L M H

2 < 10 000 ppm (or < 1%) 1 N N L M

3 1-10 % 1 2 3 4

4 > 10 % Toxicity

TOXIC RELEASESdetailed H & S questionnaire


HEALTH AND SAFETYmitigation

TWO FACTORS DETERMINE MITIGATION:

1 Exposure

Frequency of and exposure time in hazardous zone

2 Possibility to avert the hazardous situation

Depends on: rate of development, ease of recognition, avoidance of exposure, use of ppe, experience.

⇒ MATRIX TO DETERMINE OVERALL REDUCTION(0, 1 or 2 classes)


MITIGATIONdetailed H & S questionnaire

Possibility 3 -1 0 0

to avert 2 -1 -1 0

danger 1 -2 -1 -1

1 2 3

Exposure

Table 3-11 Mitigation questionnaire

Exposure

1 Very rare(less than 10 man-minutes per day)

2 Occasionally(less than 6 man-hours per day)

3 Frequently to continuously(more than 6 man-hours per day)

Possibility to avert danger

1 In almost all circumstances

2 In some circumstances(more than 25% of cases)

3 Not (or hardly possible)


ENVIRONMENT

TWO EFFECTS ARE CONSIDERED:

1 Liquid spills (max E)toxicityReleased quantity (or inventory)location (within / outside fence)surface (possibility to reach surface and/or ground water

2 Gas emissions (max M)Type (volume and how harmful)Effects (complaints)

⇒ MAXIMUM OF TWO IS ENVIRONMENT CLASS


ENVIRONMENTALsimple questionnaire

Table 3-13 Simple environment questionnaire

Severityrating

Consequence description

Liquid spillsFailure mode leads to a liquid spill with:

1 N No or negligible environmental damage2 L Minor environmental damage3 M Localised environmental damage4 H Major environmental damage5 E Massive environmental damage

Gas emissionFailure mode leads to:

1 N No or small harmful release2 L Small harmful release leading to many complaints or large3 M Large harmful release leading to many complaints


ENVIRONMENTALdetailed questionnaire

Table 3-14 Liquid spills questionnaire

Environmental toxicity

1 Not harmful to environment (e.g.water)

2 Harmful but not toxic(e.g. most alkanes)

3 Harmful and toxic(e.g. drins)

4 N H E

Released quantity ( or inventory) 3 N M H

1 < 500 kg Quantity 2 N L M

2 0.5 - 5 ton 1 N N L

3 5 - 50 ton 1 2 3

4 > 50 ton Toxicity

Location0 Contamination remains inside fence1 (Part of) contamination is outside fence

Surface of spill0 No chance that spilled liquids will reach

outside fence surface or ground water1 There is a possibility that spilled liquids will

reach outside fence surface or ground water


ENVIRONMENTALdetailed questionnaire

Table 3-15 Gas emission questionnaire

Type of release3 large (> 1000 normal m3 ) and harmful2 small and harmful1 other

Effect1 No or few complaints2 Many complaints or is to be reported to the Authorities.

Type of 3 L MRelease 2 N L

1 N N

1 2Effect


DETERMINATION OF THECONSEQUENCE OF FAILURE - Summary

• DIRECT

• SIMPLE QUESTIONNAIRE

compliant with HSE descriptions

• DETAILED QUESTIONNAIRE

provide guidance and consistency

useful if limited HSE experience is available

mechanistic ⇒ keep thinking

seek specialist advice in cases of doubt or high criticality


DETERMINE INSPECTION SCOPEDETERMINE FAILURE

CHARACTERISTIC

FAILURE CHARACTERISTIC:

AGE-RELATEDFAILURE CHARACTERISTIC:

NON AGE-RELATED

- CRACKING- H-ATTACK

- MECHANICALCREEP

MONITORING= TABLE

MAX. INSP. INTERVAL= RL X INTERVAL FACTOR

Determine Susceptibilitybased on the ratio: Actual corrosion

rate/design corrosion rate

Determine Susceptibilitybased on API Technical

Modules Fitness for Service study

Determine Susceptibilitybased on the

operating conditions

THINNING StFHMLN

CoFEHMLN

CRITICALITY

CONFIDENCERATING

ADVISED METHODS AS PER DEGRADATION MODULE,EXTENT PER CRITICALITY LEVEL

ADVISED MONITORING BASED ON DEGRADATION MODULE,EXTENT PER CRITICALITY LEVEL


CONFIDENCE RATING

• INDICATOR FOR CONFIDENCE IN FORECAST OF DEGRADATION

• RATING - very low to very high – REFLECTS:stability/predictability of degradationnumber and quality of previous inspectionsprocess stability

⇒ BETTER CONFIDENCE YIELDS LONGER INSPECTION INTERVALS


CALCULATION OF INSPECTION INTERVALfor age-related degradations

consequence of failure(questionnaire)

susceptibility tofailure (questionnaire)

- inspection records- experience- judgement

matrix

CONFIDENCERATING

matrix

CRITICALITY

corrosion allowancecorrosion rate

REMNANT LIFE Xmultiply

INTERVAL FACTOR

MAXIMUM INSPECTIONINTERVAL (in years)

MAXIMUM INSPECTIONINTERVAL (in years)


AGE-RELATED DEGRADATION - inspection interval factor function of Criticality and Confidence Rating

Criticality Interval FactorE 0.2H 0.3M 0.4L 0.5N 0.6

Confidence Rating Adjustment factorVH - Very high + 0.2H - High + 0.1M - Medium 0L - Low -0.1VL - Very Low -0.2

Description ScoreYES Int. NO

Degradation mechanism is stable and properly controlled + 0.1 0 -0.1Multiple reliable inspections have been carried out + 0.1 0 -0.1Relevant process parameters are reliably monitored + 0.1 0 0

Inspection Interval Factor forMedium Confidence Rating

add orsubtract

add/subtractto/fromMEDIUMSCORE

Adjustment of interval factorbased on Confidence Rating

Scoring points for adjustment factor withmedium confidence as starting point. Maximum adjustment +/- 0.2


INTERVAL FACTORSfor age-related degradations

CONFIDENCE RATING

CRITICALITY Very Low Low Medium High Very High

E

H

M

L

N (review only)

0 0.1 0.2 0.3 0.4

0.1 0.2 0.3 0.4 0.5

0.2 0.3 0.4 0.5 0.6

0.3 0.4 0.5 0.6 0.7

0.4 0.5 0.6 0.7 0.8


MAXIMUM INSPECTION INTERVAL

XX

LIFETIME IN YEARS

INSPECTIONS

X

WALLTHICKNESS

MINIMUM ALLOWABLE THICKNESSt (min)

t new REMNANT LIFE

MAXIMUM INSPECTIONINTERVAL


INSPECTION COVERAGE (PERCENTAGE)age-related degradation

CONFIDENCE RATINGCRITICALITY VERY LOW LOW MEDIUM HIGH VERY HIGH

REDESIGNINTOLERABLE80-100%EXTREME

25-100%HIGH5-25%MEDIUM

5-25%LOWNEGLIGIBLE 0-5%

SELECTION OF PROPER NDT-TECHNIQUEVIA SHELL NDT HANDBOOK


MONITORING SCHEMEfor non age-related degradations

consequence of failure(questionnaire)

susceptibilityto failure (questionnaire)

ACCEPTABLE?

IMPLEMENTMONITORING– PROCESS

MONITORING– OPPORTUNITY

INSPECTIONS

YESmatrix

NOREDESIGN– PROCES DESIGN– MECHANICAL DESIGN

matrix

CONFIDENCERATINGCRITICALITY


N LL MM

E

H

XEH

HMM

MMLL

LL

N

N

XXEHLL3

2

1

4

PRO

BABI

LITY

CLA

SS

MULTIPLEFATALITIES

EXT. DAMAGE>10M

SLIGHT INJURY

SLIGHT DAMAGE<10K

SLIGHTEFFECT

MINOR INJURY

MINOR DAMAGE10-100K

MINOREFFECT

MAYOR INJURY

LOCAL DAMAGE0.1-1M

LOCALISEDEFFECT

SINGLE FATALITY

MAYOR DAMAGE1-10M

MAYOREFFECT

MASSIVEEFFECT

HEALTH & SAFETY

ECONOMICS (USD)

ENVIRONMENTCON

SEQ

UEN

CECA

TEG

ORY


LOW2

MEDIUM3

HIGH4

EXTREME5

NEGL.

LOW

MEDIUM

HIGH

RBIStF RRM CRITICALITY CLASSRRM CRITICALITY CLASSIPF

DR

> 20 y

4 - 20 y

0.5 - 4 y

0 - 0.5 y

RCMETBF

> 20 y

4 - 20 y

0.5 - 4 y

0 - 0.5 y NOT acceptable for non age-relateddegradation mechanismsAdditional

processmonitoringNOT required

RRM CRITICALITY MATRIXfor non age-related degradation

STF (RBI): Susceptibility to FailureDR (IPF): Demand RateETBF (RCM): Estimated Time Between Failures



CONFIDENCE RATING non-age related degradation

Confidence Rating Adjustment factorVH - Very high + 0.2H - High + 0.1M - Medium 0L - Low -0.1VL - Very Low -0.2

Description Score

YES Int. NO

Degradation mechanism can be easily controlled + 0.1 0 - 0.1

Relevant proc. parameters are reliably monitored + 0.1 0 - 0.1

Reliable inspections were carried out + 0.1 0 0


MONITORING AND INSPECTION PLANfor non age-related degradationsMONITORING AND INSPECTION PLANfor non age-related degradations

CONFIDENCE RATINGCRITICALITY VERY LOW LOW MEDIUM HIGH VERY HIGH

NO INSPECTION/PROCESS MONITORING REQUIRED

IMPROVE MONITORING

MONITORING AND OPPORTUNITY INSPECTION

DESIGN AND/OR PROCESS CHANGE REQUIRED

INTOLERABLE

EXTREME

HIGH

MEDIUM

LOWNEGLIGIBLE


PROCESS MONITORINGnon-age related degradations

• Parameters to be monitored, as described in the operating window.

• Frequency to be described/agreed.

• Deviations measured (outside monitoring scheme) shall be discussed in the team and actions reported;changes via Plant Change procedure if needed.

• Revise inspection plans if needed.


INSPECTION/MONITORING TIMING?

• AGE-RELATED DEGRADATIONS - INSPECTIONS

Calculate Remnant Life

Apply Interval Factor: Max. inspection interval

– based on Confidence and Criticality Rating

• NON AGE-RELATED DEGRADATIONS - MONITORING

Apply table to check if monitoring is required/acceptable:

– monitoring scheme (+ opportunity inspections)

Based on Confidence and Criticality Rating


CRITICALITYMATRIX

negligiblecriticality

intolerablecriticality

LOW/MEDIUM/HIGH& EXTREME CRITICALITY

‘no’ inspection rectify

INSPECTION/MONITORING TASKS

INFORMATION FROMDEGRADATIONMODULES OR

NDT HANDBOOK

CONFIDENCE RATING

NON-AGE RELATED DEGRADATIONS

INSPECTION INTERVAL

NON-INTRUSIVE/INTRUSIVE

PROCESS MONITORINGAND OPPORTUNITY INSPECTION

REMNANT LIFE

CONFIDENCE RATING

AGE RELATED DEGRADATIONS

RECTIFY IFREQUIRED

INSPECTION TASKS



BACK-UPSLIDES


NDT TECHNIQUES - see NDT Handbook• INTERNAL WALL THINNING

internal corrosion UT, RT, MFL, LRUT, PETerosion UT, RT, MFL, LRUT, PETcavitation UT, RT, MFL, LRUT, PETweld corrosion UT, RT

• EXTERNAL WALL THINNINGexternal corrosion VTcorrosion under insulation VT,RT,TT,RTR, PET

• CRACKINGfatigue UT, PT, MT, ET, TOFD, AETstress corrosion cracking UT, PT, MT, ET, TOFD, AETwet hydrogen cracking UT, PT, MT, ET, TOFD, AET

• OTHERcreep DM, R, PT, MT, UThot hydrogen damage MT, R, UThigh temperature embrittlement MT, R, UT


FEEDBACK/REVIEW• VALIDATION AND UPDATING

OF THE PLANT INTEGRITY DATABASE:after each maintenance and inspection shutdownat the implementation of plantchangesat deviations of operating conditions

• YEARLY REVIEW BY RBI-TEAM TO ESTABLISH:actual condition and fitness for purposedegradation mechanism and -rateconfidence rating

• UPDATE INSPECTION PLAN, IF REQUIRED


RBI METHODOLOGY• REVIEW THE OPERATING CONDITIONS OF THE PLANT

past/present/future operating conditionsprocess monitoringmain changes from design

• REVIEW MATERIALS OF CONSTRUCTIONcheck materials vs process conditions

• DEFINE CORROSION LOOPSsimilar process conditions/materials/degradations

• DO THE S-RBI STUDY FOR EACH CORROSION LOOP (following slide)

• INTEGRATE RESULTS IN AN OVERALL WORK-PLANNING


S-RBI STUDY FOR A CORROSION LOOP• Define the Corrosion Loop• Describe process conditions• Establish the “Operating Window”• List Items in the loop

materials and corrosion allowances (design)• Agree Potential Degradation Mechanisms for the loop• Review inspection history - corrosion rates• Give a Confidence Rating for each item and degradation• Do the criticality rating per Degradation Mechanism• Establish remnant life & max. inspection interval OR

monitoring scheme • Define scope of inspections / monitoring

⇒ next stage - DEVELOP DETAILED INSPECTION PLANS


DEGRADATION MECHANISMS

• Internal corrosion (general)Sulphur, TAN, Acids, H2S

• External corrosionCUI, ESCC

• Creep• Stress Corrosion Cracking• Embrittlement• Fatigue - thermal• Fatigue - mechanical• Erosion• Hydrogen attack

AGE - RELATED DEGRADATIONS

NON AGE - RELATED DEGRADATIONS


AGE-RELATED DEGRADATIONS VSNON AGE-RELATED DEGRADATIONS (1)

AGE-RELATED

Deg

rada

tion

Time


AGE-RELATED DEGRADATIONS VSNON AGE-RELATED DEGRADATIONS (2)

AGE-RELATED

NON AGE-RELATEDE.G. SCC

Deg

rada

tion

Time


A

C

B

CAUSTIC SODA SERVICE DIAGRAM

Concentration NaOH, % weight

Tem

pera

ture

(C)


Table S1-2A Environmental Severity - SSC H2S CONTENT OF WATER (mg/kg)

pH of water Cyanide content (mg/kg)

< 50 50 to 1000 > 1000

SEVERITY CATEGORY

< 4.0 (Note 1) Moderate High High

4.0 to 5.4 (Note 1) Low Moderate High

5.5 to 7.5 (Note 1) Low Low Moderate

7.6 to 7.9 < 50 Low Moderate High

7.6 to 7.9 ≥ 50 Moderate High High

≥ 8.0 < 20 Low Moderate High

≥ 8.0 ≥ 20 Moderate High High

NOTE 1. HCN level is not significant at pH 7.5 and below.

SUSCEPTIBILITY TO FAILURE BY SSC

Table S1-3 Susceptibility to SSCAs-welded PWHT

Environmental Max Vickers Hardness(1) Max Vickers Hardness(1)

Severity < 248 248-290 > 290 < 248 248-290 > 290

High Low Medium High Not Low Medium

Moderate Low Medium High Not Not Low

Low Low Low Medium Not Not Not(1) Actually tested as Vickers or converted from portable techniques, e.g. Equotip, Microdur etc.


FATIGUE MONITORING (PROPOSAL)monitoring/inspection interval(s) FATIGUE MONITORING (PROPOSAL)monitoring/inspection interval(s)

NO INSPECTIONS

CONFIDENCE RATINGVERY LOW LOW MEDIUM HIGH VERY HIGHCRITICALITY

EXTREME

HIGH

MEDIUM

LOW

1 DAY 3 DAYS

1 WEEK 1 MONTH

2 MONTHS

NEGLIGIBLE

INTOLERABLE SEE NOTE

NOTE:Where Fatigue could lead to X = INTOLERABLE criticality,a full supporting system shall be designed and maintained;for criticality E, a similar approach is usually followed.


RRM CRITICALITY MATRIX

N LL MM

E

H

XEH

HMM

MMLL

LL

N

N

XXEHLL3

2

1

4

PRO

BABI

LITY

CLA

SS

MULTIPLEFATALITIES

EXT. DAMAGE>10M

SLIGHT INJURY

SLIGHT DAMAGE<10K

SLIGHTEFFECT

MINOR INJURY

MINOR DAMAGE10-100K

MINOREFFECT

MAYOR INJURY

LOCAL DAMAGE0.1-1M

LOCALISEDEFFECT

SINGLE FATALITY

MAYOR DAMAGE1-10M

MAYOREFFECT

MASSIVEEFFECT

HEALTH & SAFETY

ECONOMICS (USD)

ENVIRONMENTCON

SEQ

UEN

CECA

TEG

ORY


LOW2

MEDIUM3

HIGH4

EXTREME5

NEGL.

LOW

MEDIUM

HIGH

RBIStF RRM CRITICALITY CLASSRRM CRITICALITY CLASSIPF

DR

> 20 y

4 - 20 y

0.5 - 4 y

0 - 0.5 y

RCMETBF

> 20 y

4 - 20 y

0.5 - 4 y

0 - 0.5 y

STF (RBI): Susceptibility to FailureDR (IPF): Demand RateETBF (RCM): Estimated Time Between Failures



0.10

1.00

10.00

100.00

1,000.00

1 10 100 1000

Vibration Frequency, Hz

Vib

ratio

n A

mpl

itude

, mils

pea

k to

pea

k

Danger

Correction

Marginal

Design

Threshold of perception

SEVERITY OF VIBRATIONZONE 1

ZONE 4

23

ALLOWABLE PIPING VIBRATION LEVELS


S-RBI AS PART OF RRMmain changes

• CONSEQUENCE OF FAILURE new questionnaire, identical for S-RBI, S-RCM and IPF

• SUSCEPTIBILITY TO FAILUREnew questionnaire

• AGE AND NON-AGE RELATED DEGRADATIONSdifferent approach

• TECHNICAL MODULESgive guidance to StF ratings

• CONFIDENCE RATING• INTERVAL FACTORS


StF - CORROSION RATESdesign life 20 years

CA 1mm CA 3mm

CR CR

4 H >0.2 >0.6

3 M >0.05 - 0.2 >0.15 - 0.6

2 L 0.02 - 0.05 0.07 - 0.15

1 N <0.02 <0.07


CORROSION ALLOWANCESspecial cases

• STAINLESS STEEL AND ALLOYSno corrosion allowance in designs

– use tolerances, +/–12.5% (FFP can give actual value)– or take an arbitrary small value, e.g. 0.5 mm– also take a worst case CR, e.g. 0.01 mm/yr– that results in 50 years initial lifetime

• HEAT EXCHANGER TUBESwall thickness is CA50% for inside, 50% for outside, if leaks are acceptedsometimes users want e.g. 0.5 mm minimum for pressure containment.higher minimum thickness can be agreed.


HEAT EXCHANGER DEFINITIONS

Shell side Tube side

Shell (Sh)

Tube outside (To)

Head (He)

Tubeinside(Ti)


SUB TAGS & TAG GROUPS

SUB - TAGS

C-20124”P10023117X

4” P1005 3117Y

“WET PIPING”tags P1002, P1003

16” P1004 3117YC-201 TOP

“DRY OH PIPING”Tags P1004, P1005, P1006

TAG GROUPSC-201 Bottom

12” P1003 3117X


FAILURE

• TERMINATION OF THE ABILITY OFAN ITEM TO PERFORM A REQUIRED FUNCTION:

corrosion allowance lost(after FFP) below minimum required thicknessleak to outside (or internal)crack detected (beyond tolerable)deformation (beyond tolerable)extreme case: rupture

– brittle or ductile

• NORMAL DESIGNS - “LEAK BEFORE BREAK”:warns and allows to avoid hazards


PLANTSrisk and reliability - mechanical

PLANT DEGRADATIONS INSPECTION MAINTENANCE

visualultrasonicX-rayinfraredmagnetic part.dye penetranteddy current

pHtemperaturechloride level

corrosiongeneral- pitting- Stress CCmechanical- fracture- fatigue- etc.

repairreplace

preventiveorbreak down

timing ofinspection/monitoring tasks

processconditions

+

DESIGNPER CODEpressure/

temperature

materials


FAILURE CLASSIFICATION

CORROSION STRESS

SURFACE GRANULARINTER/TRANS

LOCALISEDCORROSION

GENERALCORROSION

NON-FLUCTUATING FLUCTUATING

OVERLOAD TEMPERATUREEFFECTS

BRITTLEFRACTURE

LOW HIGH

CREEPRUPTURE

THERMALFATIGUE

DUCTILEFRACTURE

THERMAL

MECHANICAL

HYDRAULIC

CAVITATIONerosion

FATIGUEWEAR

CORROSIONFATIGUE

STRESSCORROSIONCRACKING

HYDROGENEMBRITTLEMENT

OGBR MHR

- pitting- crevice- galvanic- fretting- velocity

(erosion)


S-RBI RELATED TOOLS

Maintenanceand Inspection

Database

Electronic Drawings(VISIO)

TrendingSoftware

S-RBI ANALYSIS

S-RBI (RRM)Software

S-RBI (RRM)Manual

MEP/Corrosion ControlManual

Statistical Recipe Book

DegradationLibrary

NDTHandbook

FFPHandbook


S-RBI IN COMPARISON WITH API STANDARDS (1) API 510 Pressure Vessel Inspection codeAPI 570 Piping Inspection codeAPI RP 580 Risk Based Inspection DRAFT

S-RBI FULLY IN LINE WITH API REQUIREMENTS

• involve various part of organisation• incorporate likelihood and consequence of failure• include HSE consequences• assess all potential degradation mechanisms• evaluate effectiveness of inspection methods• re-assessment after process change• consider design relative to operating conditions• RBI assessment should be properly documented


S-RBI IN COMPARISON WITH API STANDARDS (2)

ADDITIONAL ADVANTAGES OF S-RBI• team effort is pre-requisite• approach is very practical, easy to apply and transparent• auditable consideration to assure integrity and define inspection plan• corrosion loop concept streamlines the analysis and adds clarity• linked to Corrosion Control Manual• definition of (integrity) operating window• comprehensive but concise report• enhanced synergy of S-RBI with S-RCM and IPF under RRM• S-RBI based on long lasting experience and applied within Shell

worldwide


WALL THICKNESS UT MEASUREMENTS

POOR QUALITY+/– 1 mm

GOOD QUALITY+/– 0.5 mm

109 11

High quality UT measurements canobtain +/– 0.3 mm

109 11


DEFECT SIZES UPON FAILURE• Standard hole size 3 mm for gas and 3 - 5 mm for liquids for

normal degradations leading to pitting and small holes;these sizes are detected rather quickly and precautionswill be in hand if sizes are larger:

– depressurization– evacuation– firefighting etc.

• A 1 inch hole for degradations leading to large area thinning, e.g. ammonium chloride salt attack.

• Ruptures are considered if embrittlement is encountered or large scale Stress Corrosion Cracking could occur.

• Local standards/philosophies can overrule these sizes.


TAG NUMBERS

ADVISED DETAILS:

• PIPING (max 25 characters)sizeline code 8 PL1010 CS HI INSPmaterialinsulation codeauthority code (if applicable)

• EQUIPMENTTAG numberinsulation code V-1101 CI INSPauthority code E-302 TS Ti HI INSP


STANDARDIZED CORROSION RATES (CR)CARBON STEEL • If no corrosion detected after about 10 years:

Assume detection limit of 0.5 mm, corrosion rate must be lower than 0.05 mm/yrUse this value as worst case CR until better information is available

STAINLESS STEEL• If no corrosion detected after about 10 years

Assume detection limit of 0.1 mm, corrosion rate must be lower than 0.01 mm/yr (after VT) or 0.03 mm/yr (if UT, good quality)Use this value as worst case CR until better information is available


STRESS CORROSION CRACKING

START

Is the material ofconstruction austenitic

stainless steel?

Determine theseverity index for

each potentialmechanism

Have youdetected SCC in this

or similar serviceequipment?

Do you know thecause of SCC?

Increase thesusceptibility for

that mechanism tohigh

Increase susceptibilityfor all potential

mechanisms to high

No problem

No

Determine maximumseverity index

Is the material ofconstruction carbon or

low alloy steel?

Yes

No

NoYesYes Yes

Screen for Caustic, Amine,SSC, HIC/SOHIC,

Carbonate Cracking

Screen for PTA,Cl-SCC

No

Determine susceptibility foreach potential SCC

mechanism for austeniticStainless Steels

Determine susceptibilityfor each potential SCC

mechanism for Carbon andLow Alloy steels


MAXIMUM INSPECTION INTERVAL

X

MIN. ALLOWABLE THICKNESSt(min)

t new

LIFETIME IN YEARS

Inspections

X

NLMH

20

40

< 5 ~ 5 -10

N to H CriticalityVL to VH Confidence0.1 - 0.8 Int. Factor

L to E (X) CriticalityVL to VH Confidence0.0 - 0.7 Int. Factor

StF

thic

knes

s

design life


EFFECT OF MONITORING/INSPECTION AND/OR MITIGATIONEFFECT OF MONITORING/INSPECTION AND/OR MITIGATION

REMAINING RISK = CRITICALITY - “PREVENTIVE MEASURES”

Prob

abili

ty

LOW RISK

HIGH RISK

Criticality

monitoring/inspectioneffect

Define inspection tasksto get lowest possible riskConsequence


“REMAINING” RISK TO BEAS LOW AS REASONABLY POSSIBLE (ALARP)

Prob

abili

ty

LOW RISK

Criticality

HIGH RISK

(ALARP)

1. Inspection interval and coverage- based on Criticality andConfidence Rating

2. Type of Inspection(s)- based on failure mode(s)

3. Location(s) to inspect- for each failure mode

4. Process Monitoring- where applicable (operating window)

Consequence


FAILURE MODE & CONSEQUENCES

Consequence of Failureworst case & if flammable contents

Typical defect:w

Degradationw

Failure modew

Pitting Small leak Leak, no significant damage Hole, 3-5 mm dia Small fire System Inventory(Big fire or explosion)

Embrittlement Fracture Big fire or explosion System Inventory

Caustic cracking Cracks Leaks Hole, 3-5 mm dia SCC

General corrosion Leak Fire, small explosion Hole, 3-5 mm dia Rupture Big fire or explosion System Inventory

To avoid long discussions, general worst case failure modes are taken as default starting point(modified if required, after discussions)


YEARS TO MEASURE CORROSION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0.02

0.04

0.06

0.08

0.10

0.12

0.14

Corrosion Rate, mm/yr

Mea

sure

men

t Tol

eran

ce +

/–, m

m

?

20 years

10 years

3 years


COST REDUCTIONS

• By risk reduction• By longer inspection intervals• By lower inspection cost

N LL MM

E

H

X

EH

HMM

MMLL

LL

N

N

XXEHLL

3

2

1

4

PRO

BABI

LITY

CLA

SS

MULTIPLEFATALITIES


SLIGHT INJURY

SLIGHT DAMAGE<10K

SLIGHT EFFECT

MINOR INJURY

MINOR DAMAGE10-100K

MINOR EFFECT

MAJOR INJURY

LOCAL DAMAGE0.1-1M

LOCAL EFFECT

SINGLE FATALITY

MAJOR DAMAGE1-10M


HEALTH & SAFETY

ECONOMICS (USD)

ENVIRONMENTCON

SEQ

UEN

CECA

TEG

ORY


LOW2

MEDIUM3

HIGH4

EXTREME5

NEGLIGIBLE

LOW

MEDIUM

HIGH


Risk reduction- count total if new plant- count difference if existing plant

= Freq. Reduction x CoF

from 0.1 * 5 MM to 0.001 * 5 MM⇒ reduction = 495. 000/yr

1.00.10.010.001


FAILURE MODEWall thinning- minor loss, < 0.2 x wt- medium loss, < 0.5 x wt- serious loss, > 0.5 x wt- general or localised

Hole- small hole, < 5 mm dia- large hole, > 5 mm dia- very large hole, > 25 mm dia

Cracking- small crack, < 5 mm- medium size crack, < 25 mm- large crack, > 25 mm- through-the-wall

Rupture

DEGRADATION MECHANISM- General corrosion

- Erosion

- Hot H2-attack

- Pitting corrosion

- Fatigue

- Creep

- Stress Corrosion Cracking

- Embrittlement

DEGRADATIONS AND FAILURE MODES


PROBABILITY OF FINDING LOCALIZED CORROSIONvia Spot Thickness measurements - with replacementPROBABILITY OF FINDING LOCALIZED CORROSIONvia Spot Thickness measurements - with replacement

4020 60 80 1000

5

10

15

Num

ber

of th

ickn

ess

read

ings

Probability of finding localized corrosion (%)

1% area

2%

5%

10%

25%

50%

75%

90%


0

40

80

120

160

0.00 0.10 0.20

Proportion corroded

General corrosion on surface area200

50 8090 95 98% Confidence

Sam

ple

size

STATISTICAL SAMPLING


PIPING REJECTION THICKNESSES (1)

• Piping classes have 1 or 3 mm Corrosion Allowance (CA):11010 has 1 mm CA for 150 lbs conditions11030 has 3 mm CA for 150 lbs conditions

• Pressures and temperatures are often significantly below the design conditions of the piping classes.

• Therefore EXTRA CA is often available.• Determine the minimum required wall thickness by:

spreadsheettableminimum thickness for mechanical stability


PIPING REJECTION THICKNESSES (2)

corrosion

- Available schedule/thickness- CA, Corrosion Allowance- Plate/Pipe tolerance- DT, Design Thickness

- TminMinimum Allowable Thickness

- Tminfor single pit


PIPING REJECTION THICKNESSES (3)PIPING REJECTION THICKNESSES (3)

corrosion wall thickness reduction

Residual wall thickness

Residual Corrosion Allowance

Fitness for Purpose (FFP) extra CAstudy

TminDESIGN

Localized pitting (FFP or Code)


HEAT EXCHANGER TUBE - CA ?

• Internal (tube side) corrosion ?

• External (shell side) corrosion ?

• Corrosion Allowance CA ? External corrosion

CA = wt ?50/50 Int./Ext.

WT

Internal corrosion


MINIMUM REQUIRED WALL THICKNESSmax. 250°CPipe size

1) B31.3 calculation, CS A106 Bor API 5L-B

2) Max. pipe span as per memo (check), filled with water and weight in the middle

3) Full vacuum4) NOT valid where additional stresses from

expansion etc. occur

DN 25 DN50 DN80 DN100 DN150 DN200 DN250 DN300 DN350

5 barg

10

15 2mm

20 4mm

25 4mm 4mm 5mm

30 3mm 4mm 5mm 5mm

40 4mm 5mm 6mm 7mm

50 4mm 5mm 6mm 8mm 9mm

60 5mm 6mm 8mm 9mm 10mm

75 4mm 6mm 8mm 9mm 11mm 12mm

100 4mm 5mm 8mm 10mm 12mm 14mm 16mm

125 4mm 5mm 7mm 9mm 12mm 15mm 18mm 20mm

Pres

sure


NDT MEASUREMENTS - PLUGS

plug

Documents

220183537 Shell RBI Methodology