corrosion under insulation inspection in ammonia urea plant
TRANSCRIPT
Corrosion Under Insulation
Inspection in Ammonia
Urea Plant
Work Preparation & Planning
KhandakerAsirul Hoque
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
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.
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.
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
Influence of relative Humidity on Atmospheric
Corrosion of Carbon Steel
Susceptible Locations� Insulation support or stiffening rings
• Nozzles and man-ways
CO2 absorber
CUI near
bottom skirt,
2010
Susceptible Locations� Other penetrations, e.g. Ladder clips, pipe supports
� Damaged insulation areas
Susceptible Locations
� Un-insulated Lifting Lugs
� Near Bottom Drain Lines
� Saddle Support of
Horizontal Heat Exchangers
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
Damage Mechanisms
CUI
Carbon Steel
Uniform Corrosion &
uniform wall loss
Localized pitting
(below painting)
Stainless Steel
Stress Corrosion Cracking
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
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.
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
Inspection Type
Stainless Steel
Uniform Oxidation & ThinningUltrasonic Thickness
Measurement (UT)
Localized Metal Loss Pit Depth Measurement
Carbon Steel
Cl stress Corrosion Cracking Dye Penetration Testing (DPT)
Ammonia Plant EquipmentSl 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 Down Vessel Carbon Steel Ladder, Manhole
cover support
6 1-S-503 Flash Vessel Carbon Steel Ladder, Level
Gauge, Lugs
7 1-V-102 Blow Down Vessel Carbon Steel Lugs, Manhole,
Ladder supports
Ammonia Plant Equipment
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
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
Utility Plant Equipment
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 Steam Vent 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
Urea Plant Equipment
RBI Approach of Pipeline CUI Inspection
Critical Areas for Pipeline CUI
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
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
Pipeline CUI
� 4”-LA-60007-A2-C55
� 4”-LA-60020-A2-C55
12”-GA-60009-A2-C55
To 6-K-201 B inlet line
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.
Q&A Session