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Dipresentasikan pada seminar Korosi Metalurgy & Material
Week 2011 :Permasalahan dan Penanggulangan Korosi pada Industri
Migas di Indonesia.Jakarta (Patra Jasa Office Tower), 13 14
Desember 2011
HOW TO HANDLE IT a sharing experience from PHEONWJ
Shared by : Ifan Rifandi
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Corrosion Under Insulation, How to handled it, a sharing
experience from PHEONWJ
Corrosion under insulation (CUI) is the corrosion of piping and
vessels that occurs beneath insulation as a result of water/
moisture penetration.
CUI is hidden under the insulation therefore CUI tends to remain
undetected until the insulation is removed for inspection or when
leaks occur.
CUI Incident Lesson learnt from Dow Chemical Plant
On March 13, 2008, at a Dows LHC plant, 8 schedule20, carbon
steel hydrocarbon line failed. The piping was a30 year old.The
material in the line was non-corrosive hydrocarboncracked gas (40%
ethylene). Due to the regenerationservice, the piping alternates
between three differentconditions, and the location of failure was
where operatingtemperatures cause frequent or continuous
condensationand re-evaporation of atmospheric moisture. (courtesy
of DowChemical)
Regeneration condition (4 bar, 220 C)On stream time: 20 days (30
bar, -17 C)Regeneration time: 24 hrs(220 C)Standby: 19 days
(ambient temperature)
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Corrosion Under Insulation, How to handled it, a sharing
experience from PHEONWJ
Equipment is insulated for any of the following reasons:1. Heat
conservation and/or freeze protection2. Condensation control3.
Sound control4. Personnel protection5. Fire protection.
Carbon steel corrodes, not because it is insulated, but because
it is contacted by aerated water/ moistureThree basic ingredients
must present to form CUI : Moisture Warm temperatures (CS = 4C
(25F) up to 175C (350F) or (SS = 50C (25F) up to 175C (350F)
Corrodent contaminant The two primary moisture/ water sources
involved in CUI of carbon steel are : Infiltration from external
source Condensation
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Corrosion Under Insulation, How to handled it, a sharing
experience from PHEONWJ
Contaminant in insulation system can be classed in two primary
classes. Contaminant external to the insulation materials
Contaminant leached from the insulation material
API 570 specifies :
Susceptible Temperature Ranges API 570 Piping Inspection Code,
Section 5.3.3.1 e, f & h:e. Carbon steel piping systems,
including those insulated for personnel
protection, operating between 25F250F (4C120C). CUI is
particularly aggressive where operating temperatures cause frequent
or continuous condensation and re-evaporation of atmospheric
moisture.
f. Carbon steel piping systems that normally operate in-service
above 250F (120C) but are in intermittent service.
h. Austenitic stainless steel piping systems operating between
150F400F (65C204C). (These systems are susceptible to chloride
stress corrosion
cracking.)
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Corrosion Under Insulation, How to handled it, a sharing
experience from PHEONWJ
Suspect Areas API 570 Piping Inspection Code, Section 5.3.3.2The
areas of piping systems listed in 5.3.3.1 may have specific
locations within them that are more susceptible to CUI, including
the following:a. All penetrations or breaches in the insulation
jacketing systems, such as: 1) Deadlegs
(vents, drains, and other similar items), 2) Pipe hangers and
other supports, 3) Valves and fittings (irregular insulation
surfaces), 4) Bolted-on pipe shoes and 5) Steam tracer tubing
penetrations.
b. Termination of insulation at flanges and other piping
components.c. Damaged or missing insulation jacketing.d. Insulation
jacketing seams located on the top of horizontal piping or
improperly lapped or
sealed insulation jacketing.e. Termination of insulation in a
vertical pipe.f. Caulking that has hardened, has separated, or is
missing.g. Bulges or staining of the insulation or jacketing system
or missing bands. (Bulges may
indicate corrosion product buildup.)h. Low points in piping
systems that have a known breach in the insulation system,
including
low points in long unsupported piping runs.i. Carbon or
low-alloy steel flanges, bolting, and other components under
insulation in high-
alloy piping systems.j. Locations where insulation plugs have
been removed to permit piping thickness
measurements on insulated piping should receive particular
attention. These plugs should be promptly replaced and sealed.
Several types of removable plugs are commercially available that
permit inspection and identification of inspection points for
future reference.
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Corrosion Under Insulation, How to handled it, a sharing
experience from PHEONWJ
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Corrosion Under Insulation, How to handled it, a sharing
experience from PHEONWJ
How to handle it
1. RBI approach Risk study/ identification Risk Mapping
Inspection prioritization Etc.
2. Process requirement approach Aging facilities Re-engineering
study of existing & future process requirement Issue
recommendation Prepare facility change permit (FCP)
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Corrosion Under Insulation, How to handled it, a sharing
experience from PHEONWJ
Define ProgramStation Name - CUI Risk Reduction program
Socialization(site owner, executor, inspection, HSE, etc.)
Engineering Study & Recommendation
MOC Documention (FCP)
Execution
Prepare Work pack
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Insulated pipe inspection without insulation removal
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Insulated pipe inspection without insulation removal
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Work package
1. Engineering Recommendation2. Material Selection (Hot &
Anti sweat Insulation, Cage material,
Coating material, etc.)3. Cage & Insulation Installation
Design4. Application Procedure5. Potential Hazard / Risk
Assessment6. Data Sheet
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Work package
Material Selection (Insulation Specification)
Insulationmaterial
Compressive strength range [kPa (lb/in2)]
Other significant properties Comments
Calcium silicate 410 1 700 (60 250)@ 5% deformation
Able to absorb up to 400 times its own weight of water.High-pH
extracts, but aggressive to steel when wet.
Suitable only for plant operating consistently at high
temperatures > 100C (212F).
Glass fibre 3,4 17 (0,5 2,4)@ 10% deformation
Able to transmit moisture.Chemically inert.
Will support corrosion on unprotected steel.
Mineral fibree.g. Rockwool
69 - 410 (10 60)@ 5% deformation
Non water repellent grades able to transmit (wick)
moisture.Chemically inert.
Even water-repellent grades support corrosion on unprotected
steel.
Organic foams- Polyurethane- Polyisocyanurate- Phenolic
69 - 480 (10 70)@ 10% deformation
(*See footnote)
Able to absorb and transmit water, particularly when damaged.Low
pH and halide extracts possible at elevated temperatures.
Not recommended for equipment operating at temperatures above
ambient.
Cellular glasse.g. foam glass
340 1 600 (50 230) Non absorbent provided it remains intact.May
release acidic species (CO2, H2S) if cells are broken.
Stable over a wide operating temperature range.High compressive
strength gives good integrity.
Flexible elastomeric foams
280 (40)@ 10% deformation
100% closed cell.Low water absorption (about 1%).Non aggressive
to steel.
Upper temperature limit 105 to 150C (220 to 300F), depending
upon specific product. Need to allow for circumferential thermal
expansion.
*Note: organic foams are anisotropic with the compressive
strength parallel to the foam, about twice that perpendicular to
it.
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Cellular Glass
b. Anti sweat insulation material Safety / health friendly
Chemically inert Physically robust Easy to be applied Market
availability
Work package
Calcium Silicate
a. Hot insulation material Safety / health friendly Chemically
inert Physically robust Easy to be applied Market availability
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c. Coating material Safety / health friendly Anti corrosion
coating Easy to be applied Market availability
Can be applied without plant S/D
Work package
Epoxy Phenolic (< 150 oC)
Epoxy Novolac (< 250 oC) Inorganic Zinc + Silicon-Aluminium
(
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d. Cage material
Work package
Corrosion resistant Physically robust Easy to be applied Market
availability
304 SS perforated plate
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Work package
Application Procedure Insulation removal procedure New
insulation installation procedure Emergency/ temporary piping
repair procedure Coating application procedure Cage installation
procedure Etc.
Risk AssessmentData sheet & MSDS material
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PHEONWJ Sharing - CUI risk reduction program
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PHEONWJ Sharing - CUI risk reduction program
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PHEONWJ Sharing - CUI risk reduction program
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PHEONWJ Sharing - CUI risk reduction program
Survey (Validation, Cost Estimation, BOM)
Execution
Provision Material (Coating, Insulation, Cage,
Emergency Repair, Etc.)
Assign SPA & appoint Executor Party
Fabrication
Scaffolding Installation& Insulation Removal
WT Inspection & temporary repair (if any)
Surface Preparation & Coating Application
Re-InsulationCage Installation
Final Report
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PHEONWJ Sharing - CUI risk reduction program
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PHEONWJ Sharing - CUI risk reduction program
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PHEONWJ Sharing - CUI risk reduction program
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Insulated pipe inspection without insulation removal
1. Infrared Thermal Gram2. Profile radiography3. Real Time
Radiography or Lixi4. Neutron Backscatter5. Ultrasonic Teletest6.
Acoustic Emission7. Pulsed Eddy Current (Incotest)
Infrared detect damp spot in the insulation, because usually
temperature difference between dry insulation and wet insulation
are detectable.Corrosion is possible occurred beneath the wet
insulation.
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Insulated pipe inspection without insulation removal
Exposures is done in a small section of the pipe. A comparator
blocksuch as a Ricki T is used to calculate the blowout factor for
the exposure inorder to calculate the remaining wall thickness of
the pipe.
Profile radiography is an effective evaluation method, but
radiation safety can be a real concern that nobody can work within
the area while the inspection is underway. This can result in
downtime and personnel scheduling conflicts.
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Insulated pipe inspection without insulation removal
The real time device has a source and image intensifier/
detector connected to a C-arm. Fluoroscopy provides a clear view of
pipe outside diameter through the insulation, producing silhouette
of the pipe outside diameter on a TV type monitor.
There are two type device, one using a X-ray source and another
using a radioactive source. Each has its own advantage and
disadvantage, however X-ray type deliver better resolution.
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Insulated pipe inspection without insulation removal
The Neutron Backscatter Technique works due to the principles of
the interaction of neutrons with matter. The radioactive source
emits fast neutrons with high energies which are difficult to
detect. These fast neutrons interact with matter to become slow or
thermal neutrons. Thermal neutrons are most likely to interact with
atoms of a similar size to the neutron itself. Hydrogen is the atom
closest in size and mass to the neutron and therefore accounts for
the majority of the collisions that reduce the fast neutrons to
thermal neutrons. When a fast neutron collides with a hydrogen atom
it releases energy and becomes a slow or thermal neutron. The
thermal neutrons are scattered in all directions but have a short
travel path. Some of these thermal neutrons are scattered back
towards the scanning head and these are the neutrons counted by the
detector
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Insulated pipe inspection without insulation removal
Ultrasonic Teletest (known as the Teletest Focus) is developed
by TWI. It is used Guided Wave Ultrasonic (GWU) technology.These
inspections are carried out using multi-mode (flexural and
torsional)wave focusing approach. This technique provides 100%
inspection coverage and has the ability to inspect inaccessible
areas such as clamps, pipe elbow and cased or buried
pipes.Originally developed for the inspection of corrosion under
insulation, the Teletest Focus is suited for application to
pipelines and process pipe work, including road crossings, bridge
piers and hardly accessible pipe work generally.
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Insulated pipe inspection without insulation removal
Acoustic emission monitoring is the analysis of the ultrasonic
waves generatedby dynamic events, such as deformation and cracking,
occurring in thematerial under investigation. Thus, stress
corrosion cracking, hydrogenembrittlement and corrosion fatigue can
be detected. However, acousticemission cannot indicate the size of
a defect, only whether a defect is growingor not.
A typical AE system setup.
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Insulated pipe inspection without insulation removal
Incotest is Pulsed Eddy Current licensed by Shell Global
Solutions. A currentpulse is sent through a coil. When the current
is interrupted, eddy currents aregenerated in the material, which
will decay in time. Measuring the rate ofdecay of the eddy currents
will determine the wall thickness. High wallthickness will result
in a slower decay. The description of the equipment isshown in
Attachment Q.