3.0 Best Practice - Corrosion Under Insulation

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Copyright of Shell Global Solutions (Malaysia) Sdn Bhd

CHT INTEGRATED REFINERY BUSINESS IMPROVEMENT PROGRAM

HPCL Mumbai

Corrosion Under Insulation

10/14/2011 1

Copyright of Shell Global Solutions (Malaysia) Sdn Bhd 210/14/2011CONFIDENTIAL

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FACTORS CONTRIBUTING TO CORROSION UNDER INSULATION

Cladding and insulation condition

Insulation type

Water source

� External environment

� Presence of steam tracing

Temperature

Coating status, surface preparation, lifetime, coating type

Equipment shape: line size, nozzle, attachment

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CLADDING

Role of Cladding and Vapour Barriers:

Contain Isolation Material

To keep insulation dry.

Mechanical Protection

Mastics and sealants are used to close openings.

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Aluminised steel

Aluminium

Stainless steel

Polyester etc.

GRE wrap

Tapes

CONFIDENTIAL

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Copyright of INSERT COMPANY NAME HERE

DAMAGED CLADDING



INSULATION MATERIAL

Water leachable salt content.

� chlorides, sulphate, acidic materials in fire retardants

Water retention, permeability, wettability.

Insulation foams that react with water to form acids

�

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RockwoolRockwool

FoamFoam--glassglass

PU FoamPU Foam

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MOIST INSULATION MATERIAL



WATER SOURCES

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1. Condensation

2. External

3. Internal

Damaged steam tracing

Rainfall

Steam discharge,

Spillage

Deluge/sprinkler system,

Drift from cooling towers

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WATER SOURCES



TEMPERATURE

Higher temperature:

Increased corrosion rate

High salt concentration

Reduced life coatings

1010/14/2011

Cyclic temperatures, Temperature gradients

increase risk for Corrosion Under Insulation.

Lower temperature:

• Condensation

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TEMPERATURE

Carbon Steel

-5 to 60°C Moderate

50-120°C Severe

120-150°C Moderate

150-250°C Cold spots

>250°C No risk

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Stainless steel:Stress Corrosion

Cracking

<50°C no SCC

50-120°C High

120-150°C Moderate

>150°C no SCC

CONFIDENTIAL


COATING STATUS, TYPE, APPLICATION, AGE

Coating type

� Primer only

� Full coat

� Immersion coat

� Thermal Al spray

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Application

• Surface preparation

• Cold/Hot

• Maintenance

• No coating

Coating life varies between 0 and 10 years (approx)

CONFIDENTIAL

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COATING STATUS



EQUIPMENT SHAPE: LINE SIZE, NOZZLE, ATTACHMENT

Tees

Valves

Instruments

(Steam) Tracing

Equipment Nozzles

Stiffeners

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Difficult to seal

Cold spots (Hot spots)

Maintenance e.g. valves

Watertraps

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EQUIPMENT SHAPE



CORROSION UNDER INSULATION

Prevention and mitigation of CUI is largely

a maintenance issue, whereby the corrosion is prevented

in case the insulation and underlying coating is

maintained where and when needed.

If no maintenance is executed, the coating and insulation

will deteriorate and corrosion will start.

The actual need for insulation has always to be challenged.


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CUI ASSESSMENT PROGRAMME

Assessment of susceptibility to CUI

Detection methods [and reliability]

Determination of corrosion severity

Criticality

Repair procedures



CUI INSPECTION GUIDELINE

The CUI Inspection Guideline is used during the S-RBI process to

determine the Criticality Class, the Confidence Rating and the

corresponding Inspection/Maintenance Strategy for Corrosion Under

Insulation.


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CUI INSPECTION GUIDELINE

1910/14/2011

THE CUI INSPECTION GUIDELINE CONSISTS OF TWO STEPS:

Step 1: A criticality ranking requiring limited input data.

Step 2: A detailed assessment and inspection plan for the high ranking items.

CONFIDENTIAL


STEP 1: CUI CRITICALITY RANKING

2010/14/2011

The Susceptibility to CUI is determined with the dedicated questions in the Criticality Matrix for CUI.

This provides a worst case assessment.

The Consequence of Failure is copied from the internal corrosion failure.

The Criticality Matrix gives the Criticality Ranking for CUI.

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STEP 2: CUI INSPECTION PLAN

2110/14/2011

1. Determine the Probability based on the cumulative score from the Susceptibility table.

2. Re-address the Criticality based on this Probability rating.

3. Determine the Confidence Rating for CUI using the dedicated Confidence Rating questionnaire.

4. Establish the Inspection/Maintenance Strategy for CUI based on the Criticality and Confidence Rating.

CONFIDENTIAL


THE SCHEMATICALLY REPRESENTATION OF THE S-RBI PROCESS FOR CUI.

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Susceptibility

Consequence

Confidence

Factor

Inspection

Strategies

Criticality

Rating

IS1

IS2

IS3

IS4

IS5

Susceptibility

Consequence

Confidence

Factor

Inspection

Strategies

Criticality

Rating

IS1

IS2

IS3

IS4

IS5

IS1

IS2

IS3

IS4

IS5

IS0

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SUSCEPTIBILITY TO CUI FAILUREFOR CS/LOW ALLOY STEEL (1)

DETERMINE THE PROBABILITY SCORE BY ADDING POINTS FROM THE

INDIVIDUAL COLUMNS IN THE TABLE (NEXT SLIDES).

NOTE:

Remember to challenge the requirement for insulation - it may be

possible to permanently remove it.

For Personal Protection perforated sheeting is preferred.



CUI PREVENTION

Only insulate where necessary

Use screens for personnel protection

Use insulating coatings

Use waterproof cladding (plastics, laminates)

Use immersion coating or TSA

Use non-contacting insulation


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* In cyclic service (or temporarily temperature changes), the range of the most critical temperature reached shall be taken.

OperatingTemperature*

Initial coatingstatus

Insulationtype

Points

constantly >175 °Cor < −5 °C

Full QA paintprotection

- 0

150 - 175°C Expanded Perlite, Foamglass, Closed Cell Foam (right type)

1

−5 - 50 °Cor

120 -150 °C

Conventional QA

Paint protection; field welds

at construction

3

50 - 120 °Cunpainted

orunknown

5-

Fiberglass, Cal Sil,Asbestos, Regular Perlite, Mineral/Rock Wool

-




* The most susceptible area of the equipment determines the rating.**Can be taken from RBI study for internal corrosion.

Wall Thickness &Surface Features*

Internalcorrosion / erosion

rate**

Externalcoil / steamtracing

Externalenvironment

Points

-Negligible

Not present inside building 0

Low (or < 0.1 mm/yr)rarely wetted

(<10% of the time)1

4 – 7.1 mm or Surface at Location of

Penetrationsthrough Insulation

Medium (or 0.1 - 0.4 mm/yr)Medium IntegrityDesign

frequentlywetted

(~40% of the time)3

≤ 4 orSurface at Location ofReinforcement Rings& Other Water Traps

High (or > 0.4 mm/yr)Low

IntegrityDesign

permanentlywetted (e.g.cooling tower,dripping water,condensation)

5

≥ 7.1 mmHigh Integrity Design



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SUSCEPTIBILITY TO CUI FAILUREFOR STAINLESS STEEL (1)

DETERMINE THE PROBABILITY SCORE BY ADDING POINTS

FROM THE INDIVIDUAL COLUMNS IN THE TABLE (NEXT SLIDES).

NOTE:

Remember to challenge the requirement for insulation - it may be

possible to permanently remove it.

For Personal Protection use perforated sheeting.



OperatingTemperature*

Initialcoating status

External coil /steam tracing

Externalenvironment

Points

Not present 0

2

120 - 150 °C Medium IntegrityDesign

4

50 - 120 °C

LowIntegrityDesign

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* In cyclic service (or temporarily temperature changes), the range of the most criticaltemperature reached shall be taken.

Constantly>150 °C

or < 50 °C

-

Full QA paintprotection

Conventional QA paintProtection;field welds

at construction

Unpaintedor

unknown

-

Insulation type

Low chlorideinsulationmaterial

(<10ppm Cl-)

-

higher chlorideinsulationmaterial

(≥10ppm Cl-)

-

High IntegrityDesign

Inside building

Rarely wetted(<10% of the time)

frequentlywetted

(~40% of the time)

Permanently wetted (e.g. cooling tower,dripping water,condensation)

SUSCEPTIBILITY TO CUI FAILUREFOR STAINLESS STEEL (2)


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MH= Medium High E = ExtremeH = High M = MediumL = Low N = Negligible

N LL MM

H

MH

E

HMH

MHMM

MMLL

LL

N

N

EEHMHLL

M

L

N

H

PROBA

BILITY C

LASS

MULTIPLEFATALITIES

EXT. DAMAGE( >10M)

NO/SLIGHTINJURY

NO/SLIGHTDAMAGE (<10K)

NO/SLIGHTEFFECT

MINOR INJURY

MINOR DAMAGE(10-100K)

MINOREFFECT

MAJOR INJURY

LOCAL DAMAGE(0.1-1M)

LOCALISEDEFFECT

SINGLE FATALITY

MAJOR DAMAGE(1-10M)

MAJOREFFECT

MASSIVEEFFECT

HEALTH & SAFETY

ECONOMICS (USD)

ENVIRONMENTCONSEQUEN

CE

CATEGORY

CONSEQUENCE CLASS NEGLIGIBLE LOW MEDIUM HIGH EXTREME

TOTAL SCORE > 20

SUSCEPTIBILITY TOCUI FAILURE

TOTAL SCORE 14 - 20

TOTAL SCORE 7 - 13

TOTAL SCORE 0 - 6

CUI RRM CRITICALITY CLASS

10/14/2011 29CONFIDENTIAL


For Confidence Rating add scores; minimum: -0.2, maximum: +0.2Confidence Rating: -0.2 = very low, - 0.1 = low, 0 = medium, +0.1 = high, +0.2 = very high*In case of new equipment or piping, a 0 (zero) score shall be given for this aspect

CUI CONFIDENCE QUESTIONS Yes Intermediate No

+0.1 0 -0.1

+0.1 0 -0.1

+0.1 0

Cladding and insulation conditionCladding/insulation fully maintained: YESCladding/insulation normal: IntermediateCladding/insulation in poor condition: NO

Multiple reliable inspections for CUI have been carried out*Frequent inspection and selective delagging, followed by appropriateremedial action: YESInspection irregular/not to standard: IntermediateNo proper inspections: NO

-0.1

CONFIDENCE RATING FOR CUI

Monitoring CUI promoting conditionsThe presence of ALL possible CUI promoting conditions (see susceptibility categories) has been established and quantified: YESThe operating temperature is monitored and constantly in identified range AND the coating condition is known/established: IntermediateThe operating temperature is not established AND/OR the coatingcondition is not known/established: NO


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COATING/PAINT PROTECTION CREDIT

3110/14/2011

Coverage and Quality of Applied Coating/PaintYears of protection

100% coverage (including field welds);according to the appropriate engineering standards

8

100% coverage (including field welds);not completely in accordance with the appropriate engineering standards

4

No 100% coverage or unknown;poor or unknown quality

0

CONFIDENTIAL


CUI MONITORING CS/LOW ALLOY STEELDETERMINING INSPECTION/MAINTENANCE STRATEGIES

3210/14/2011

CONFIDENCE RATING

VERY LOW LOW MEDIUM HIGH VERY HIGH CRITICALITY

HIGH

MEDIUM HIGH

MEDIUM

LOW

STRATEGY 2 STRATEGY 3

NEGLIGIBLE (review only)

EXTREME

NO INSPECTIONS

STRATEGY 1

CONFIDENCE RATING


MEDIUM

LOW

STRATEGY 3


STRATEGY 0 STRATEGY

1 STRATEGY 2 STRATEGY

3 STRATEGY 4 NO

INSPECTIONS

CONFIDENCE RATING


MEDIUM

LOW

STRATEGY 2 STRATEGY 3


NO INSPECTIONS

STRATEGY 1

CONFIDENCE RATING


MEDIUM

LOW

STRATEGY 3


STRATEGY 0

STRATEGY 1

STRATEGY 2

STRATEGY 3

STRATEGY 4

NO INSPECTIONS

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CUI INSPECTION/MAINTENANCE STRATEGIESCS/LOW ALLOY STEEL STRATEGY 0

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Initial Action*Initial Result

1st Following Action*

Further Results

2nd Following Action*

Reduce Criticality !

Analyse in detailConsider corrective action

Meanwhile follow strategy 1

- - - -

* Recommended maximum timing; an analysis should be performed to determine if the work should be completed within a shorter time frame.

CONFIDENTIAL



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Initial ActionInitial Result**

1st Following ActionFurther Results**

2nd Following Action

Equipment shell& nozzles/piping ≥≥≥≥ 8":100% NDE combined with 100% delagging of ALL possible wet and susceptible areas:

⇒ within 1 year*

Piping & equipmentnozzles ≤≤≤≤ 8":100% delagging:

⇒ within 1 year*(proceed according to column "Further Results")

Significant

CUI found

Delag 100%:⇒ within 6 months

MoresignificantCUI found Repair & paint;

repeat Initial Action:⇒ every 3 years*No more

significant

CUI found

Nosignifican

t

CUI found

100% delagging of ALL wet and susceptible areas:

⇒ within 3 years

SignificantCUI found

100% delagging within 6 months; repair & paint; repeat Initial Action:

⇒ every 3 years*

Nosignificant

CUI found

Adjust confidence rating with +0.1; repeat Initial Action:

⇒ within 3 years

* 50% of coating/paint protection credit can be applied, Inspection interval starting at the moment the coating/paint protection has ended ** ”Significant CUI” means corrosion damage that requires remedial action.

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3510/14/2011

Initial ActionInitial Result**

1st Following ActionFurther Results**


Equipment shell& nozzles/piping ≥≥≥≥ 8": 100% NDE combined with selective delagging of possible wet and susceptible areas:

⇒ every 6 years*

Piping & equipmentnozzles ≤≤≤≤ 8": 100% delagging of ALL possible wet and susceptible areas :

⇒ every 6 years*

Significant

CUI found

Delag 100%:⇒ within 1 year

MoresignificantCUI found Repair & paint;


significant

CUI found

Nosignifican

t

CUI found

Delag more selective areas:⇒ within 1 year

SignificantCUI found

100% delagging within 1 year; repair & paint; repeat Initial Action:

⇒ every 6 years*

Nosignificant

CUI found


⇒ within 6 years

* Inspection interval starting at the moment the coating/paint protection has ended** ”Significant CUI” means corrosion damage that requires remedial action.

CONFIDENTIAL


CUI MONITORING FOR STAINLESS STEELDETERMINING INSPECTION/MAINTENANCE STRATEGIES

3610/14/2011

CONFIDENCE RATING


HIGH

MEDIUM HIGH

MEDIUM

LOW

STRATEGY 2

NEGLIGIBLE

(review only)

EXTREME

NO INSPECTIONS

STRATEGY 1

CONFIDENCE RATING


MEDIUM

LOW

NEGLIGIBLE

(review only)

STRATEGY 0

STRATEGY 1

STRATEGY 2

NO INSPECTIONS

CONFIDENCE RATING


MEDIUM

LOW

STRATEGY 2

NEGLIGIBLE

(review only)

NO INSPECTIONS

STRATEGY 1

CONFIDENCE RATING


MEDIUM

LOW

NEGLIGIBLE

(review only)

STRATEGY 0

STRATEGY 1

STRATEGY 2

NO INSPECTIONS

CONFIDENTIAL

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CUI INSPECTION/MAINTENANCE STRATEGIESSTAINLESS STEEL STRATEGY 0

3710/14/2011

Initial Action*Initial Result

1st Following Action*

Further Results

2nd Following Action*

Reduce Criticality !

Analyse in detailConsider corrective action

Meanwhile follow strategy 1

- - - -

* Recommended maximum timing; an analysis should be performed to determine if the work should be completed within a shorter time frame.

CONFIDENTIAL


CUI INSPECTION/MAINTENANCE STRATEGIESSTAINLESS STEEL STRATEGY 1

3810/14/2011

Initial ActionInitial Result

1st Following ActionFurther Results


100% delagging of ALL possible wet and susceptible areas;check coating and perform Eddy Current testing:

⇒ within 3 months*

Cracking found

Delag 100%;check coating and perform DPI:

⇒ within 3 months

Morecracking found Repair & paint;


cracking found

Nocracking found

100% delagging of ALL wet and susceptible areas;check coating and perform DPI:

⇒ within 2 years

Cracking found

100% delagging within 3 months; repair & paint; repeat Initial Action:

⇒ every 5 years*

Nocracking found


⇒ within 3 years

* 50% of coating/paint protection credit can be applied, Inspection interval starting at the moment the coating/paint protection has ended . CONFIDENTIAL

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CUI PREVENTION

Only insulate where necessary

Use screens for personnel protection

Use insulating coatings

Use waterproof cladding (plastics, laminates)

Use immersion coating or TSA

Use non-contacting insulation


Copyright of Shell Global Solutions (Malaysia) Sdn Bhd 4010/14/2011

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Documents

3.0 Best Practice - Corrosion Under Insulation