3.0 Best Practice - Corrosion Under Insulation
Short Description
Download 3.0 Best Practice - Corrosion Under Insulation...
Description
CHT INTEGRATED REFINERY BUSINESS IMPROVEMENT PROGRAM
HPCL Mumbai Corrosion Under Insulation
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
10/14/2011
CONFIDENTIAL
10/14/2011
1
2
1
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
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
CONFIDENTIAL
10/14/2011
3
CLADDING Role of Cladding and Vapour Barriers: Contain Isolation Material
Aluminised steel
To keep insulation dry.
Aluminium
Mechanical Protection
Stainless steel Polyester etc.
Mastics and sealants are used to close openings.
GRE wrap Tapes
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
CONFIDENTIAL
10/14/2011
4
2
DAMAGED CLADDING
Copyright of INSERT COMPANY NAME HERE
CONFIDENTIAL
10/14/2011
5
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
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
CONFIDENTIAL
Rockwool
Foam--glass Foam PU Foam
10/14/2011
6
3
MOIST INSULATION MATERIAL
Copyright of INSERT COMPANY NAME HERE
CONFIDENTIAL
10/14/2011
7
WATER SOURCES
1.
Condensation
2.
External
Steam discharge,
3.
Internal
Spillage
Rainfall
Damaged steam tracing
Deluge/sprinkler system, Drift from cooling towers
Copyright of INSERT COMPANY NAME HERE
CONFIDENTIAL
10/14/2011
8
4
WATER SOURCES
Copyright of INSERT COMPANY NAME HERE
CONFIDENTIAL
10/14/2011
9
TEMPERATURE Higher temperature: Increased corrosion rate High salt concentration
Lower temperature: •
Condensation
Reduced life coatings
Cyclic temperatures, Temperature gradients increase risk for Corrosion Under Insulation.
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
CONFIDENTIAL
10/14/2011
10
5
TEMPERATURE
Carbon Steel
Stainless steel:
-5 to 60°C Moderate 50-120°C
Stress Corrosion Cracking
Severe
120-150°C Moderate 150-250°C Cold spots >250°C No risk
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
150°C
no SCC
CONFIDENTIAL
10/14/2011
11
COATING STATUS, TYPE, APPLICATION, AGE Coating type Primer only Full coat
Application
Immersion coat
•
Surface preparation
•
Cold/Hot
•
Maintenance
•
No coating
Thermal Al spray
Coating life varies between 0 and 10 years (approx)
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
CONFIDENTIAL
10/14/2011
12
6
COATING STATUS
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
CONFIDENTIAL
10/14/2011
13
EQUIPMENT SHAPE: LINE SIZE, NOZZLE, ATTACHMENT Tees Valves
Difficult to seal
Instruments
Cold spots (Hot spots)
(Steam) Tracing Equipment Nozzles
Maintenance e.g. valves Water traps
Stiffeners
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
CONFIDENTIAL
10/14/2011
14
7
EQUIPMENT SHAPE
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
CONFIDENTIAL
10/14/2011
15
10/14/2011
16
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.
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
CONFIDENTIAL
8
CUI ASSESSMENT PROGRAMME Assessment of susceptibility to CUI Detection methods [and reliability] Determination of corrosion severity Criticality Repair procedures
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
CONFIDENTIAL
10/14/2011
17
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.
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
CONFIDENTIAL
10/14/2011
18
9
CUI INSPECTION GUIDELINE
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.
Copyright of INSERT COMPANY NAME HERE
CONFIDENTIAL
10/14/2011
19
STEP 1: CUI CRITICALITY RANKING
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.
Copyright of INSERT COMPANY NAME HERE
CONFIDENTIAL
10/14/2011
20
10
STEP 2: CUI INSPECTION PLAN
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.
Copyright of INSERT COMPANY NAME HERE
CONFIDENTIAL
10/14/2011
21
THE SCHEMATICALLY REPRESENTATION OF THE S-RBI PROCESS FOR CUI.
Susceptibility Susceptibility riticality CCriticality ating RRating C onsequence Consequence CConfidence onfidence Factor Factor
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
CONFIDENTIAL
IS0 IS1 IS1 IS2 IS2 Inspection Inspection IS3 IS3 Strategies Strategies IS4 IS4 IS5 IS5
10/14/2011
22
11
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.
Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
CONFIDENTIAL
10/14/2011
23
10/14/2011
24
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
CONFIDENTIAL
12
SUSCEPTIBILITY TO CUI FAILURE FOR CS/LOW ALLOY STEEL (2) 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
Conventional QA Paint protection; field welds at construction unpainted or unknown
Fiberglass, Cal Sil, Asbestos, Regular Perlite, Mineral/Rock Wool
3
-
5
−5 - 50 °C or 120 -150 °C
50 - 120 °C
* In cyclic service (or temporarily temperature changes), the range of the most critical temperature reached shall be taken. Copyright of Shell Global Solutions (Malaysia) Sdn Bhd
CONFIDENTIAL
10/14/2011
25
SUSCEPTIBILITY TO CUI FAILURE FOR CS/LOW ALLOY STEEL (3) Wall Thickness & Surface Features* ≥ 7.1 mm
4 – 7.1 mm or Surface at Location of Penetrations through Insulation ≤ 4 or Surface at Location of Reinforcement Rings & Other Water Traps
Internal corrosion / erosion rate** Negligible Low (or < 0.1 mm/yr)
Medium (or 0.1 - 0.4 mm/yr)
High (or > 0.4 mm/yr)
External coil / steam tracing
External environment
Points
Not present
inside building
0
rarely wetted High Integrity (150 °C or < 50 °C
Full QA paint protection
Low chloride insulation material (
View more...
Comments
