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

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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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CONFIDENTIAL

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

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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

Rockwool

Foam

Foam--glass

glass

PU Foam

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MOIST INSULATION MATERIAL

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CONFIDENTIAL

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

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TEMPERATURE

Higher temperature:

Increased corrosion rate

High salt concentration

Reduced life coatings

Cyclic temperatures,

Temperature gradients

increase risk for Corrosion Under Insulation.

Lower temperature:

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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)

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COATING STATUS

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CONFIDENTIAL

EQUIPMENT SHAPE: LINE SIZE, NOZZLE, ATTACHMENT

Tees

Valves

Instruments

(Steam) Tracing

Equipment Nozzles

Stiffeners

Difficult to seal

Cold spots (Hot spots)

Maintenance e.g. valves

Water

traps

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EQUIPMENT SHAPE

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CONFIDENTIAL

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

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CONFIDENTIAL

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

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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

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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 F

ailure

is copied from the internal

corrosion failure.

The Criticality Matrix gives the

Criticality R

anking

for CUI.

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STEP 2: CUI INSPECTION PLAN

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1. Determine the

P

robability

based on the cumulative

score from the Susceptibility table.

2. Re-address the

C

riticality

based on this Probability

rating.

3. Determine the

Confidence R

ating

for CUI using the

dedicated Confidence Rating questionnaire.

4. Establish the

Inspection/Maintenance S

trategy

for CUI

based on the Criticality and Confidence Rating.

CONFIDENTIAL

THE SCHEMATICALLY REPRESENTATION OF THE S-RBI

PROCESS FOR CUI.

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 FAILURE

FOR 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.

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CONFIDENTIAL

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.

Operating

Temperature*

Initial coating

status

Insulation

type

Points

constantly >175 °C

or < −5 °C

Full QA paint

protection

-

0 150 - 175°C

Expanded Perlite, Foamglass,

Closed Cell Foam (right type)

1 −5 - 50 °C

or

120 -150 °C

Conventional

QA

Paint protection;

field welds

at construction

3 50 - 120 °C

unpainted

or

unknown

5 -Fiberglass, Cal Sil,

Asbestos, Regular Perlite,

Mineral/Rock Wool

-SUSCEPTIBILITY TO CUI FAILURE

FOR CS/LOW ALLOY STEEL (2)

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CONFIDENTIAL

Wall Thickness &

Surface Features*

_{corrosion / erosion}

Internal

rate**

External

coil / steam

tracing

External

environment

Points

-

_Negligible

Not present

_{inside building}

0 Low (or < 0.1 mm/yr)

_{(<10% of the time)}

rarely wetted

1 4 – 7.1 mm or

Surface at Location of

Penetrations

through Insulation

Medium (or 0.1 - 0.4 mm/yr)

Medium

_Integrity

Design

frequently

wetted

(~40% of the time)

3 ≤ 4 or

Surface at Location of

Reinforcement Rings

High (or > 0.4 mm/yr)

Low

Integrity

permanently

wetted (e.g.

cooling tower,

dripping water,

5 ≥ 7.1 mm

High Integrity Design

SUSCEPTIBILITY TO CUI FAILURE

FOR CS/LOW ALLOY STEEL (3)

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SUSCEPTIBILITY TO CUI FAILURE

FOR 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.

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CONFIDENTIAL

Operating

Temperature*

Initial

coating status

External coil /

steam tracing

External

environment

Points

Not present

0

2 120 - 150 °C

Medium

Integrity

Design

4 50 - 120 °C

Low

Integrity

Design

7 * In cyclic service (or temporarily temperature changes), the range of the most critical

temperature reached shall be taken.

Constantly

>150 °C

or < 50 °C

-Full QA paint

protection

Conventional QA paint Protection; field welds at construction

Unpainted

or

unknown

-Insulation type

Low chloride insulation material (<10ppm Cl-₎

-higher chloride insulation material (≥10ppm Cl-₎

-High

Integrity

Design

Inside building

Rarely wetted

(<10% of the time)

frequently

wetted

(~40% of the time)

Permanently wetted

(e.g. cooling tower,

dripping water,

condensation)

SUSCEPTIBILITY TO CUI FAILURE

FOR STAINLESS STEEL (2)

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MH = Medium High E = Extreme

H = High

M = Medium

L

= Low

N = Negligible

N

LL

M

H

MH

E

H

MH

M

LL

N

E

H

MH

LL

M L N H PR O BA BI LI TY C LA SS MULTIPLE FATALITIES EXT. DAMAGE ( >10M) NO/SLIGHT INJURY NO/SLIGHT DAMAGE (<10K) NO/SLIGHT EFFECT MINOR INJURY MINOR DAMAGE (10-100K) MINOR EFFECT MAJOR INJURY LOCAL DAMAGE (0.1-1M) LOCALISED EFFECT SINGLE FATALITY MAJOR DAMAGE (1-10M) MAJOR EFFECT MASSIVE EFFECT

HEALTH & SAFETY

ECONOMICS (USD)

ENVIRONMENT

C O N SE Q UE N C E CA TE G O RY

CONSEQUENCE CLASS

NEGLIGIBLE LOW MEDIUM HIGH EXTREME

TOTAL SCORE > 20 SUSCEPTIBILITY TO CUI FAILURE TOTAL SCORE 14 - 20 TOTAL SCORE 7 - 13 TOTAL SCORE 0 - 6

CUI RRM CRITICALITY CLASS

10/14/2011 29

CONFIDENTIAL

CUI CONFIDENCE QUESTIONS

Yes Intermediate No

+0.1

0 -0.1

+0.1

0 -0.1

+0.1

0

Cladding and insulation condition Cladding/insulation fully maintained: YES Cladding/insulation normal: Intermediate Cladding/insulation in poor condition: NO

Multiple reliable inspections for CUI have been carried out* Frequent inspection and selective delagging, followed by appropriate remedial action: YES

Inspection irregular/not to standard: Intermediate No proper inspections: NO

-0.1

CONFIDENCE RATING FOR CUI

Monitoring CUI promoting conditions

The presence of ALL possible CUI promoting conditions (see susceptibility categories) has been established and quantified: YES

The operating temperature is monitored and constantly in identified range AND the coating condition is known/established: Intermediate

The operating temperature is not established AND/OR the coating condition is not known/established: NO

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COATING/PAINT PROTECTION CREDIT

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Coverage and Quality of Applied Coating/Paint

_protection

Years of

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 STEEL

DETERMINING INSPECTION/MAINTENANCE STRATEGIES

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_{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

VERY LOW LOW MEDIUM HIGH VERY HIGH

CRITICALITY

MEDIUM

LOW

STRATEGY 3

NEGLIGIBLE

(review only)

STRATEGY

0 _STRATEGY

1 _STRATEGY

2 _STRATEGY

3 _STRATEGY

4 _NO

INSPECTIONS

_{CONFIDENCE RATING}

VERY LOW LOW MEDIUM HIGH VERY HIGH

CRITICALITY

MEDIUM

LOW

STRATEGY 2

STRATEGY 3

NEGLIGIBLE

(review only)

NO INSPECTIONS

STRATEGY 1

CONFIDENCE RATING

VERY LOW LOW MEDIUM HIGH VERY HIGH

CRITICALITY

MEDIUM

LOW

STRATEGY 3

NEGLIGIBLE

(review only)

STRATEGY 0

STRATEGY 1

STRATEGY 2

STRATEGY 3

STRATEGY 4

NO INSPECTIONS

CONFIDENTIAL

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CUI INSPECTION/MAINTENANCE STRATEGIES

CS/LOW ALLOY STEEL STRATEGY 0

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Initial Action*

Initial

Resul

t

1

st

_Following

Action*

Furthe

r

Results

2

nd

_{Following Action*}

Reduce Criticality !

Analyse in detail

Consider 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 STRATEGIES

CS/LOW ALLOY STEEL STRATEGY 1

Initial Action

Initial

_Result**

1

st

_{Following Action}

Further

_Results*

*

2

nd

_{Following Action}

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

⇒_{within 1 year*} Piping & equipment nozzles ≤≤≤≤ 8": 100% delagging:

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

Significan t CUI found Delag 100%: ⇒within 6 months More significant

CUI found Repair & paint;

repeat Initial Action: ⇒_{every 3 years*} No more significant CUI found No significan t CUI found

100% delagging of ALL wet and susceptible areas:

⇒within 3 years

Significant CUI found

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

⇒every 3 years* No

significant CUI found

Adjust confidence rating with +0.1; repeat Initial Action:

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CUI INSPECTION/MAINTENANCE STRATEGIES

CS/LOW ALLOY STEEL STRATEGY 2

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Initial Action

Initial

_Result**

1

st

_{Following Action}

Further

_Results*

*

2

nd

_{Following Action}

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

⇒_{every 6 years*} Piping & equipment nozzles ≤≤≤≤ 8": 100% delagging of ALL possible wet and susceptible areas : ⇒every 6 years* Significan t CUI found Delag 100%: ⇒within 1 year More significant

CUI found Repair & paint;

repeat Initial Action: ⇒_{every 6 years*} No more significant CUI found No significan t CUI found

Delag more selective areas: ⇒within 1 year

Significant CUI found

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

⇒every 6 years* No

significant 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 STEEL

DETERMINING INSPECTION/MAINTENANCE STRATEGIES

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CONFIDENCE RATING

VERY LOW

LOW

MEDIUM

HIGH

VERY HIGH

CRITICALITY

HIGH

MEDIUM HIGH

MEDIUM

LOW

STRATEGY 2

NEGLIGIBLE

(review only)

EXTREME

NO INSPECTIONS

STRATEGY 1

CONFIDENCE RATING

VERY LOW

LOW

MEDIUM

HIGH

VERY HIGH

CRITICALITY

MEDIUM

LOW

NEGLIGIBLE

(review only)

STRATEGY 0

STRATEGY 1

STRATEGY 2

NO INSPECTIONS

CONFIDENCE RATING

VERY LOW

LOW

MEDIUM

HIGH

VERY HIGH

CRITICALITY

MEDIUM

LOW

STRATEGY 2

NEGLIGIBLE

(review only)

NO INSPECTIONS

STRATEGY 1

CONFIDENCE RATING

VERY LOW

LOW

MEDIUM

HIGH

VERY HIGH

CRITICALITY

MEDIUM

LOW

NEGLIGIBLE

(review only)

STRATEGY 0

STRATEGY 1

STRATEGY 2

NO INSPECTIONS

CONFIDENTIAL

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CUI INSPECTION/MAINTENANCE STRATEGIES

STAINLESS STEEL STRATEGY 0

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Initial Action*

Initial

Resul

t

1

st

_Following

Action*

Furthe

r

Results

2

nd

_{Following Action*}

Reduce Criticality !

Analyse in detail

Consider 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 STRATEGIES

STAINLESS STEEL STRATEGY 1

Initial Action

Initial

_Result

1

st

_{Following Action}

Further

Results

2

nd

Following Action

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

More cracking

found Repair & paint;

repeat Initial Action: ⇒_{every 5 years*} No more cracking found No cracking 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*} No

cracking found

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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

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CONFIDENTIAL

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