Corrosion Under Insulation Inspection In Ammonia Urea Plant
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This document discusses corrosion under insulation (CUI) inspection planning for an ammonia and urea plant. It defines CUI and outlines the susceptible materials, temperature ranges, mechanisms, and locations. It provides details on organizing the inspection work, developing a schedule, selecting inspection types, and identifying at-risk equipment. Pipeline CUI is also addressed, highlighting common locations and examples found. The conclusion emphasizes the challenges of CUI detection and recommends design improvements and coatings to reduce corrosion risks over the long-term.
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Corrosion Under Insulation Inspection In Ammonia Urea Plant
- 1. Corrosion Under Insulation Inspection in Ammonia Urea Plant Work Preparation & Planning Khandaker Asirul Hoque Asirul.Hoque@outlook.com
- 2. Definition of CUI “Corrosion of piping, pressure vessels and structural components resulting from water or moisture trapped under insulation or fireproofing.” Affected Materials: Carbon steel, low alloy steels, 300 Series SS and duplex stainless steels. Ammonia jetty area pipeline CUI, 2009
- 3. Corrosion Under Insulation (CUI) As per Giel Notten, widely known corrosion expert “Corrosion Under Insulation (CUI) is the number-1 problem in Chemical Process plant after 20 years of operation” The plant is getting older and the insulation cover sheeting is deteriorating. Near lugs, attachments, instrumentation nozzles and inlet & outlet lines, the insulation cover sheeting is not properly installed. Rainwater can penetrate into the insulation and cause CUI.
- 4. Susceptible temperature range As per API 510- 9th Edition susceptable temperature range for CUI is • 10°F (–12°C) and 350°F (175°C) for carbon and low alloy steels 140ºF (60ºC) and 400ºF (205ºC) for austenitic stainless steels.
- 5. CUI Mechanism Corrosion Under Insulation caused by: Ingress of water through-insulation Water vapors condensation Corrosion promoted by: Trapping of water Elevated temperatures (around 100º C) Temperature gradient Temperature cycling (Intermediate Service) Absence or poor condition of coating Poor/broken insulation Marine Environment (Chloride Deposition) Ammonia jetty area pipeline CUI, 2009
- 6. Influence of relative Humidity on Atmospheric Corrosion of Carbon Steel
- 7. Susceptible Locations Insulation support or stiffening rings • Nozzles and man-ways CO2 absorber CUI near bottom skirt, 2010
- 8. Susceptible Locations Other penetrations, e.g. Ladder clips, pipe supports Damaged insulation areas
- 9. Susceptible Locations Un-insulated Lifting Lugs Near Bottom Drain Lines Saddle Support of Horizontal Heat Exchangers
- 10. Morphology of CUI After insulation is removed from carbon and low alloy steels, CUI damage often appears as loose, flaky scale covering the corroded component. In some localized cases, the corrosion can appear to be carbuncle type pitting Austenitic SS often shows Cl-SCC
- 11. Damage Mechanisms CUI Carbon Steel Uniform Corrosion & uniform wall loss Localized pitting (below painting) Stainless Steel Stress Corrosion Cracking
- 12. CUI Inspection: Work Organization Manager Inspection Supervisor from Production for permit and process related support (To be nominated for each plant) Visual Inspectors From Inspection Section Insulation Removal & Re-insulation work supervisor (To be nominated) Maintenance Support supervisor (To be nominated from each plant) Civil Supervisor For re-painting job (To be nominated) Operator from NH3/ Urea & Utility Plant Insulation Technician for Insulation removal Mechanical Technician for scaffolding, surface preparation for NDT Civil contactor for repainting Production Inspection Workshop Maintenance Civil
- 13. Work Organization (cont.) CUI inspection is a multi disciplinary work. Good communication & understanding is required between group members. Best time to execute such inspection is during plant shut down period and dry season. Insulation is hazardous material so proper safety supervision is also important.
- 14. Work Schedule Date April 2013 May 2013 June 2013 Job Tasks Week 1 Week 2 Week 3 Week 4 Week 1 Week 2 Week 3 Week 4 Week 1 Week 2 Study CUI as per API 510, 571 & RBI recommendation Preparation of CUI Job volume Assessment of material and Job by maintenance Inspection Checklist preparation CUI inspection work of Ammonia Plant Repainting and reinsulation job in Ammonia Plant CUI inspection work of Utility Plant Repainting and reinsulation job in Utility Plant CUI inspection work of Urea Plant Repainting and reinsulation job in Urea Plant Report Preparation Update information into RBI Software
- 15. Inspection Type Stainless Steel Uniform Oxidation &Thinning UltrasonicThickness Measurement (UT) Localized Metal Loss Pit Depth Measurement Carbon Steel Cl stress Corrosion Cracking Dye PenetrationTesting (DPT)
- 16. Ammonia Plant Equipment Sl Equipment Number Equipment Name Shell Material Probable CUI Locations 1 1-S-202 PROCESS CONDENSATE SEPARATOR Carbon Steel Bottom Skirt, Manhole, Lifting Lug 2 1-S-302 MIST SEPARATOR Carbon Steel Bottom Skirt, Manhole, Lugs 3 1-S-304 HOT CONDENSATE SEPARATOR Carbon Steel Bottom Skirt, Manhole, Lugs 4 1-S-412 INTER SEPARATOR FOR 1-K- 401 Carbon Steel Bottom Skirt, Ladder Supports, Lugs 5 1-S-502 Let DownVessel Carbon Steel Ladder, Manhole cover support 6 1-S-503 FlashVessel Carbon Steel Ladder, Level Gauge, Lugs 7 1-V-102 Blow DownVessel Carbon Steel Lugs, Manhole, Ladder supports
- 18. Ammonia Plant Equipment Sometimes insulation is used at locations where only personal protection (PP) is required.This increases the risk for CUI considerably.When installing personal protection instead of insulation, the structural integrity will be improved. 1-E-421 1st intercooler (air) no insulation required, only personal protection 1-E-504 NH3 water cooler no insulation required on inlet line (only PP). 1-E-510A/B NH3 condensers no insulation required, only personal protection 1-V-601 A/B Adsorber A & B
- 19. Utility Plant Equipment Sl Equipment Number Equipment Name Shell Material Probable CUI Locations 1 3-V-201 Continuous Blow Down Flash Tank Carbon Steel Near bottom support, flange connection 2 3-V-203 Drain Flash Tank Carbon Steel Near bottom support, flange connection 3 3-V-901 A Adsorber A Carbon Steel Around Insulation Support Ring, Lugs 4 3-V-901B Adsorber B Carbon Steel Around Insulation Support Ring, Lugs 5 3-S-901 MOISTURE SEPARATOR Carbon Steel Around Insulation Support Ring, nameplate 6 3-E-701 Mixing Station Heat Exchanger Carbon Steel Insulation support ring, nameplate, base 7 3-E-901 Air Cooler Carbon Steel Near nameplate & base 8 3-E-903 Regenaration Gas Heater Carbon Steel Near nameplate & base
- 21. Urea Plant Equipment Sl Equipment Number Equipment Name Shell Material Probable CUI Locations 1 2-V-903 Boiler Feed water Collecting Drum Carbon Steel Lifting lug- 2 nos & Ladder support 2 2-V-905 HP STEAM SATURATOR Carbon Steel Support- 2 nos & Level gauge support 3 2-E-303 LP CARBAMATE CONDENSER Stainless Steel Lifting lug- 2 nos., Bottom insulated part 4 2-E-202 HPCC Carbon Steel Saddle Support & inlet from 2-E-201 5 2-X-901 SteamVent Stack Carbon Steel Bottom Insulated part where damage occurred 6 2-E-803 A/B Hydrolizer Heat Exchanger Stainless Steel Partially remove insulation near saddle support and perform thickness monitoring 7 2-E-802 Desorber Heat Exchanger Stainless Steel Thickness check near saddle support and perform thickness monitoring
- 23. RBI Approach of Pipeline CUI Inspection
- 24. Critical Areas for Pipeline CUI
- 25. Common Locations of pipeline CUI 1. Pipes those are in intermittent service 2. Steam tracing pipe lines (sometimes in Urea plant SS pipe is steam traced by CS tracing line- Introduce risk of external Cl-SCC) 3.Termination of insulation in a vertical pipe. 4. Bulges or staining of the insulation or jacketing system or missing bands. 5. Low points in piping systems that have a known breach in the insulation system
- 26. Pipeline CUI Vertical run pipeline partially insulated are very prone for CUI at the lower portion of the pipe. Several Pipelines in Boil Off Gas and Ammonia Loading pump area were found continually wet and cold insulation lifetime exhausted. Immediate insulation replacement is recommended
- 28. Conclusion Atmospheric corrosion is a serious threat to the safe operation of older, petro-chemical process plant. CUI detection is a challenging job; it is highly unpredictable Reduce use of insulation as much as possible Avoid insulation where it is not a process requirements Design modification, apply suitable coating, surface preparation, use suitable aluminum cover sheet etc. Prepare painting surface and apply coating as per internationally acceptable codes & standard.
- 29. Q&A Session