CORROSION ORROSION MONITORING ONITORING IN IN OIL IL &G &GAS AS INDUSTRY NDUSTRY IN IN OIL IL & G & GAS AS INDUSTRY NDUSTRY SEONYEOB LI GS ENGINEERING & CONSTRUCTION, CO., LTD. PLANT PROCESS ENGINEERING TEAM PLANT PROCESS ENGINEERING TEAM 21 JUNE 2012
Corrosion Monitoring in Plants. - Basic Theory, Specifications & Applications
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
PLANT PROCESS ENGINEERING TEAMPLANT PROCESS ENGINEERING TEAM21 JUNE 2012
CAUSES OF FAILURE IN REFINING & PETROCHEMICAL PLANTS IN JAPAN (2004)PETROCHEMICAL PLANTS IN JAPAN (2004)
“Comparing the 2004 survey results with data from a similar 1984 survey Source: R.D. Kane, Chemical Engineering, June 2007
Comparing the 2004 survey results with data from a similar 1984 survey shows the situation appears unchanged over the past 20 years.”
MATERIAL SELECTION - REALITY
Compromise between expensive CRA’s and less expensive, more available metal susceptible to corrosionsusceptible to corrosion.
Corrosion of CRA’s during upset conditions A more proactive (realtime) approach to corrosion mitigation is needed, e.g.,
corrosion monitoring
WHAT IS “CORROSION MONITORING”?
The practice carried out to assess and predict the The practice carried out to assess and predict the corrosion behavior in operating plant and equipment
DEVELOPMENT OF MONITORING PLAN
1. It shall be included in the detailed design stage of plant and facilities.
2. Corrosion Risk Assessment (system by system base)1) Process stream parameters1) Process stream parameters2) Specific corrosion mechanisms or modes of attack likely to occur3) Corrosion rate estimation4) Consequences of system failures
3 Development of corrosion monitoring plan3. Development of corrosion monitoring plan1) Monitoring system design including types, locations and orientation2) Prescribed monitoring frequency3) Monitoring procedures4) Allocation of responsibility
OBJECTIVES OF CORROSION
MONITORINGMONITORING
Diagnosis of corrosion problem Monitoring corrosion control methods Advanced warning of system upsets leading to corrosion damage Invoking process control Invoking process control Determination of inspection and/or maintenance schedules Estimating service life of equipmentg q p
CORROSION MONITORING SYSTEM DESIGN
Design process included the establishment of the type, location and orientation of devices and sampling ports in the facility.
PROBE LOCATION – GENERAL RULES
Positions where water will condense, pool or impinge. For long horizontal pipe runs, e.g., at the bottom of a pipeline In fluid streams with suspended solids, there is a risk of solids accumulating in the
access fitting located in positions between 3 and 9 O’clock, which cause probe sealing problemsproblems.
Positions of special sensitivity where turbulence, velocity mixing, temperature of H b f pH etc. may be of concern. Access fitting should be located a minimum distance of seven pipe diameters
downstream and a minimum of three pipe diameters upstream of any changes in flow caused by bends reducers valves orifice plates thermowells etccaused by bends, reducers, valves, orifice plates, thermowells, etc.
If access fittings are installed in pairs there should be a minimum distance of 1 m (3 ft) between each fitting.
If the monitoring devices are intrusive and comprise a probe and a coupon holder the If the monitoring devices are intrusive and comprise a probe and a coupon holder, the probe should be located in the upstream fitting to minimize turbulence around the second monitoring device.
PROBE LOCATION – GENERAL RULES
Positions where upsets may occur, i.e., after chemical injection, acid concentration or separation concentration or separation. Production chemicals, corrosion inhibitors, scale inhibitors, oxygen scavengers, etc. “Corrosion monitoring devices should be placed at a minimum of five pipe diameters
downstream of treatment chemical injection points ”downstream of treatment chemical injection points.
Positions where there are concentrations of corrosive species. Positions where abrupt changes occur such as plant metallurgy, process fluids, etc.
Positions where process stream change such as pressure, temperature, flow rate, etc.are prevalent.
Positions where from experience the highest corrosion rates would be expected.
LOCATIONS - GUIDELINES
NACE RP 0775“In lines handling wet gas water can accumulate at changes in the line elevation as depicted in Figure 8In lines handling wet gas, water can accumulate at changes in the line elevation as depicted in Figure 8.Corrosion may be accelerated where water has accumulated. Coupons in such systems must be locatedwhere they will be water‐wet to correlate with corroding areas. Coupons located in the vapor phasecould indicate only slight corrosion when water‐wet areas are corroding severely.”
The probe and coupon monitoring devices should be available without th d t h t d th f ilitthe need to shut down the facility. For systems of less than 10 bar(g) (150 psig), low pressure DN 25 (NPS 1)
access fittings can be employed. For high pressure systems, 10‐137 bar(g) (150‐2 000 psig) this shall be
achieved by the use of proprietary DN 50 (NPS 2) access fittings.
Selected location shall have adequate clearance for the operation of the Selected location shall have adequate clearance for the operation of the retrieval tool; otherwise, the access fitting is unusable.
CORROSION DATA QUALITY
Generally, the information from a single type of corrosion monitoring method should not be relied upon to provide a full understanding of the method should not be relied upon to provide a full understanding of the corrosion environment of interest.
For any monitoring program, control checks should be included to ensure reliability of the datareliability of the data. Duplicate devices Correlation with inspection results Comparison between direct and indirect monitoring data Correlating data with visual inspection results taken out of service
Validation If important damage mechanisms are transient, does the monitoring device
identify and/or record them? If timely awareness of excessive corrosion rates or excessive metal loss is
needed, is the monitoring device providing information in the right time scale? Is the monitoring system identifying the morphology of interest?
GENERAL GUIDE ON APPLICATION OF
CORROSION MONITORINGTECHNIQUES
eigh
tlos
s up
on
pro
bes
R pr
obes
ld Signa
ture
etho
d (FSM
)
ndMon
itorin
g vice
s
lvan
icpr
obes
drog
en pro
bes
tch
6 solved gas
ses
solved so
lids
cteria
onito
ring
We
cou
ER
LPR
Fie
Me
San
Dev
Gal
Hyd
pat
pH Dis
Dis
Bac
mo
Seawater injection and cooling system ○ ○5 ○4 ○ ○ ○ X ○ O2 ○ ○
Produced water treatment and injection systems ○ ○ ○ ○ ○ X ○ ○ O2, CO2, H2S ○ ○
Aquifer water ○ ○ ○1 ○ ○ X X ○ CO2, H2S ○ ○q ○ ○ ○1 ○ ○ ○ O2, 2 ○ ○
Effluent water ○ ○ ○ ○ X ○2 X ○ O2 ○ ○
Boiler feedwater and stream condensate ○ ○ ○ ○ X ○2 X ○ O2 ○ X
Multiphase flow with water ○ ○ ○3 ○ ○ ○2 ○ ○ X ○ ○
Unstabilized crude oil ○ ○ X ○ X X ○ X CO2, H2S X X
Hydrocarbon gas ○ ○ X ○ X X ○ X X X X
Fractionation units, CDU, and pipework ○ ○ X ○ X X ○ X O2 X X
FCCU reactor col mns ○ ○ X ○ X X ○ X X X XFCCU, reactor columns ○ ○ X ○ X X ○ X X X X
Solvent extraction units, amine/caustic treaters and piping ○ ○ X ○ X X X ○ O2 X X
Vacuum towers, regenerators, process units, and pipework ○ ○ X ○ X X X ○ O2 X Xp p
Storage vessels/tanks with separated water bottoms ○ ○ X ○ X X X ○ CO2, H2S X ○
○ : possible application, X: Not applicable, 1: Depends on water quality. Unsuitable if there is low ion content, strong scaling tendency, or other forms of electrode contamination are possible2: may be used if oxygen content are high, 3: only in water cuts above ca. 10%‐20%, 4: Depends on water quality. Unsuitable if there is biofliming tendency5: Intrusive probe preferred. Flush mounted probe unsuitable if there is biofilming tendency, 6: only in aqueous phase is present
On‐line pH or water analysisInternal hydrogen flux probes
Non‐intrusive
Ultrasonic testingRadiographyExternal hydrogen flux probesAnalysis of water samples obtained y pthrough an existing valveSurface patch hydrogen probes
*1To measure a direct result of corrosion.*2To measure an outcome of the corrosion process*3To require entry into the process stream
Of th t h i li t d b i ER d LPR f th f i d t i l i Of the techniques listed above, corrosion coupons, ER and LPR form the core of industrial corrosion monitoring systems.
Flush mounted monitoring device Simulation of processes that occur at the wall surface. Corrosion in low water cut situations (wet oil), water dropout (wet gas),
under‐deposit corrosion, and areas where water condenses. Susceptible to fouling (can be ignored in turbulence locations)
Intrusive probes Intrusive probes Overall corrosivity of streams rather than more specific environments Process upsets in a single phase, high wall shear stresses, “
worst case” situations For clean water steams Cannot be used in lines that are pigged, or must be drawn before pigging.p gg , p gg g
CORROSION (WEIGHT LOSS) COUPONS( )
The method involves exposing a specimen of material of interest (the coupon) to a process environment for a given duration, then removing the specimen for analysis. process environment for a given duration, then removing the specimen for analysis.
The basic measurement is weight loss; the weight loss taking place over the period of exposure being expressed as corrosion rate.
The simplicity of the measurement is such that the coupon technique forms the baseline method of measurement in many corrosion monitoring programs.
Typically, a 90‐day duration test (for pressure retrieval coupons), which gives basic corrosion rate measurements as a frequency of four times per year. NACE RP0497: a minimum exposure duration (h) = 50/[expected corrosion rate (mm/y)] Shutdowns or process interruption Shutdowns or process interruption
ASTM G58“C” Ring – ASTM G38C Ring ASTM G38
INHIBITOR COMPARISON
USING COUPONS (OIL WELL)USING COUPONS (OIL WELL)
FLOW
35 ppm 25 ppm
Oil Soluble Chemical
35 ppm
Water Soluble Chemical
CORROSION RATE
FROM COUPON DATAFROM COUPON DATA
Simplest and most reliable technique for corrosion rate determination is th W i ht L T h ithe Weight Loss Technique.
= Average corrosion penetration depth/time= (mass/density/surface area/time) (mass/density/surface area/time)
Common Corrosion Rate Units gmd: grams of metal loss per square meter per day (mdd) mm/y: average millimeters penetration per year mpy: average mils penetration per year 1 mil = 0 001 inch) mpy: average mils penetration per year, 1 mil 0.001 inch)
NACE RP 0775 -CORROSION RATES GUIDELINESCORROSION RATES GUIDELINES
lGeneral(mm/y)
Max. Pitting(mm/y)
CorrosionRating
< 0.025 < 0.13 Low
0.025 – 0.12 0.13 – 0.20 Moderate
0.13 – 0.25 0.21 – 0.38 High
> 0.25 > 0.38 Severe
CORROSION COUPONS
Advantages Disadvantages
Inexpensive, easily applied Corrosion rate averaged over exposure time
Coupon made of materials similar to pipe or vessel Corrosion rate calculation assumes uniform corrosion
Visual inspection identifies mode of corrosion attack Data generation slow (long exposure times)
Samples available for scale or surface deposit analysis
Requires insertion and retrieval under pressure or at a turnaround
Sources of microbiological data
Applicable to all environments
TYPICAL CORROSION MORPHOLOGY (SOIL)
Stray current corrosion
Corrosion in oxygen‐rich (aerobic) soil
Microbiologically influenced corrosion In anaerobic soil
25
EDS ANALYSIS OF CORROSION COUPON
3000
MIC2000
3000
O 부식생성물
Si
1000
FeCa
SAl
Inorganic corrosion
3000 0 1 2 30
일반부식생성물
Ca
Inorganic corrosion2000
Fe
O
0
1000Ca
SSi
0 1 2 3keV
AVERAGE CORROSION RATE VS. INSTANTANEOUS CORROSION RATEINSTANTANEOUS CORROSION RATE
TYPES OF PITTING (ASTM G46)( )
Ratio of maximum localized corrosion rate to general corrosion rate determined by mass g yloss (pitting factor) Pitting of SS Velocity‐accelerated corrosion
Percent of corrosion‐affected area on the coupon
ELECTRICAL RESISTANCE (ER) PROBE( )
Measures the change in electrical resistance of a corroding metal l t l ti t f di l t l d ithi th elements relative to a reference non‐corroding element sealed within the
probe body.
LAL
R
ER PROBE TYPES (CORROSOMETER®)( )
Velocity shield
ER PROBE
TRADEOFF BETWEEN SENSITIVITY AND
SENSOR LIFE IN COMMERCIAL ER PROBESENSOR LIFE IN COMMERCIAL ER PROBE
Wire type: loss of a quarter of thickness
Other types: loss of a half of thickness
ER PROBE
Recommended measurement interval
ER PROBE
Advantages Disadvantages
Direct measurement of metal loss Sensitive to thermal change
Will work in most environments: does not require continuous aqueous phase(suitable for multiphase non aqueous environments)
Corrosion rate calculated as uniform corrosion. No information on localized corrosion
(suitable for multiphase, non‐aqueous environments)
Quicker response than corrosion coupons Manual readings subject to signal noise (probe connections)
Continuously logged probes give high quality data Crevice corrosion can occur on poorly constructed Continuously logged probes give high quality data (logging rate as low as 5 min)(trends and changes in corrosion activity)
Crevice corrosion can occur on poorly constructed flush‐type probes
Meter output is in cumulative metal loss. Slope of Requires insertion and retrieval under pressure data needed to calculated corrosion rate which can have safety implications
High sensitivity type probe is available.(Takreer RRE #2)
Requires several days to determine a reliable corrosion rate trend
N di l t b d Ad l ff t d b d ti lfid fil Non‐corroding elements can be used as pure erosion monitor.
Adversely affected by conductive sulfide film corrosion products where H2S is present
APPLICATIONS OF ER PROBE
Oil and gas production Gas sweetening, storage, and transportation systems Refineries and petrochemical plants Inhibitor evaluation/optimization programs Inhibitor evaluation/optimization programs Power plants—for cooling water, feedwater, and scrubber systems. In
bag houses and stacks for special function such as dew point alarming in flue gas systems
Chemical processes Cathodically protected systems Cathodically protected systems Air‐cleaning systems in control rooms Paper mills or other plants with a volatile inherently corrosive process p p y p
Corrosion in an electrochemical process that can be monitored by i t ti l & t th t h t i th i measuring potential & current that characterize the corrosion process.
CORROSION RATES AND POLARIZATION
POTENTIODYNAMIC POLARIZATION CURVE
LINEAR POLARIZATION RESISTANCE (LPR) METHOD
Within ~10mV more noble or active than the Ecorr,, i is a linear function of the electrode potential.
iapp = |ia‐ic| = f(E)E
E
pp
E = Eapp ‐ Ecorr
= alog ia/io,M ‐ alog icorr/io,M= a log ia/icorr l
Ecorr
Eappic ia
= a/2.303 ln ia/icorr
ia = icorr e2.303E/a
io,a log i
Similarly, ic = icorr e‐2.303E/c
o,a g
iapp = ia ‐ ic = icorr (e2.303E/a – e‐2.303E/c )= icorr (2.303E/a + 2.303E/c)
= 2.303icorrE(a + c)/ac = icorrE/BS G i Stern Geary equation
assuming that a = c = 0.12R = E/i = B/i = 0.026/iRp E/iapp B/icorr 0.026/icorr
Rp: polarization resistance.
TYPICAL POLARIZATION RESISTANCE PLOT
FARADAY’S LAW AND CORROSION RATES
MF
Qm
WhereQ = charge (C) = I∙t
nF
g ( )F = Faraday’s constant (96,500 C/eq.)n = number of equivalents (moles of electrons) transferred per mol of metalm = mass of metal corroded (g)m = mass of metal corroded (g)M = molecular (atomic) weight of metal (g/mole)
C i R ( / ) (8 6 4 ) / (A D T)Corrosion Rate (mm/y) = (8.76104 ∙ m) / (A ∙ D ∙ T)
WhereA = Coupon surface area (cm2)D = Material density (g/cm3)T = Time of exposure (hours)p ( )
LPR PROBE
• Gives instantaneous corrosion ratesrates
• Only used in conductive, aqueous solutionsaqueous solutions
• Based on the current flow between two or more electrodesbetween two or more electrodes
• Requires the surface to become polarized and current resistance polarized and current resistance is measured.
• Sometimes probe has a • Sometimes probe has a reference electrode as well.
LPR PROBE – OPERATING RANGE
Close Spaced 3 electrode probes
APPLICATION OF LPR PROBE
Water systems Condensing water systems Oil systems with high water contents
LPR PROBE WITH REMOTE MONITORING
Honeywell’s SmartCET® uses a sensor for background l h l d l helectrochemical noise (EN) to detect pitting along with
LPR probe.
LPR PROBE
Advantages Disadvantages
Rapid measurement of corrosivity General corrosion rates indicative of trend rather than absolute
Sensitive to any process changes: flow,pressure, temperature, etc.
Continuous water phase requiredpressure, temperature, etc.
Probes are susceptible to fouling by deposits or hydrocarbon phase.
Measures the current flowing between two dissimilar metal electrodes through a zero resistance ammeter (ZRA).
The magnitude of the current and its direction gives an indication of the corrosivity of the fluid and which material is anodic or cathodic.
Customarily, a pair of steel and brass Sensitive to DO
DO monitoring in East Texas Water Injection StationWater Injection Station
DIRECT NON-INTRUSIVE TECHNIQUES
Field signature method (FSM)
NDT methods NDT methods
RT IMAGE - EXAMPLE
54
INDIRECT ON-LINE TECHNIQUES
Hydrogen monitoring Acoustic solid particle detectors Water chemistry parameters Process parameters Process parameters
HYDROGEN FLUX MONITORING
Hydrogen‐related problems Blistering HIC SOHIC SSC
Hydrogen probe to monitor hydrogen absorption by steel I i (fi b ) P d i Intrusive (finger probes) – Pressure detection Non‐intrusive – electrochemical probe
Water chemistry parameters Dissolved solids analysis (API RP 45) Dissolved solids analysis (API RP 45) Metal ion corrosion analysis (NACE RP0192 – iron count analysis) Dissolved gas analysis
At sites of condensation of acidic chloride in the distillate drum boot and the ejector inter‐condenser collector drum.
Areas susceptible to naphthenic acid corrosion (NAC, 500‐700F) such as VDU preheater, shell and trays of tower transfer line column side stripper gas oil circuitstower, transfer line, column side stripper, gas oil circuits.
In regions of condensation found inside of the column. High sulfur corrosion (bottom)
High temperature cylindrical element probes of the retractable types High temperature cylindrical element probes of the retractable types
CORROSION MONITORING IN FCCU
Reactor & regenerator g High temperature (900‐1200oF) Not by probes, but by UT or visual inspection
Corrosion probes Fractionator overhead system side stripper Fractionator overhead system, side stripper Effluent piping of the compressor after coolers
CORROSION MONITORING IN CLER UNIT
Chemical Test CN‐ and SCN‐ content in wastewater stream pH (high pressure condensate) for water wash control
Corrosion probes Condenser/cooler bunldes (high pH corrosion of Cu alloys) Condenser/cooler bunldes (high pH corrosion of Cu alloys) Heat exchanger effluents in gas compression system Debutanizer overhead system, etc.
Hydrogen monitoring Probe Sour water lines Different elevation of the absorber/stripper tower Different elevation of the absorber/stripper tower Vapor/liquid interface area of the high‐pressure separator drum
HIGH PRESSURE ACCESS FITTING FOR A
RETRIEVABLE PROBERETRIEVABLE PROBE
COUPON INSTALLATION INTO HIGH
PRESSURE LINEPRESSURE LINE
67
CORROSION MONITORING SYSTEMS
Use of Portable CorrosometerTM Instrument f M i C i f Sh ll id f H t E hfor Measuring Corrosion of Shell-side of Heat Exchanger
ON-LINE THICKNESS MEASUREMENTS
Source: Hydrocarbon Processing, March 2012, pp.35-37
ASSESSMENT OF CORROSION INHIBITOR
PERFORMANCE FOR MEG REBOILERPERFORMANCE FOR MEG REBOILER
Temp. : 140oC
0.3250.3500.3750.400
solution : EG + inhibitor
Ar blowing (+ NaCl 16%) Air blowing (+ NaCl 16%)Ar blowing
0.2250.2500.2750.300
EG:waterr
g Air blowing
0 1000.1250.1500.1750.200
EG:water
60:40
78:22m
m/y
r
0.0000.0250.0500.0750.100
22 24 26 28 30 32 34 36 38 40 42
water %
LPR (CASE STUDY – HONEYWELL)( ) River Water Analysis
Chemical Treatment Program
Cycled Water Analysis
LPR (CASE STUDY – HONEYWELL)( )
LPR (CASE STUDY – HONEYWELL)( )
LPR (CASE STUDY – HONEYWELL)( )
EXAMPLE – EFFECT OF UNSTABLE OPERATION
Source: N.P. Hilton, Hydrocarbon Processing, March 2012, 49.
ON-LINE MONITORING
MONITORING STRATEGY
CORROSION AS A PROCESS CONTROL VARIABLE!
REFERENCES
1) R.D. Kane, Chemical Engineering, June 2007, 34.2) Coursebook for Corrosion Control in the Refining Industry, NACE International, July 2011.) S f C i C i J C i C f C i i J J S i f C i E i i (JSCE) 3) Survey of Corrosion Cost in Japan, Committee on Cost of Corrosion in Japan, Japan Society of Corrosion Engineering (JSCE),
March 2001.4) Alabama Specialty Products, www.metalsamples.com.5) NACE RP0775, Preparation, Installation, Analysis, and Interpretation of Corrosion Coupons in Oilfield Operations, 2005.6) NACE RP0497, Field Corrosion Evaluation Using Metallic Test Specimens, 2004.7) ASTM G4 “Standard Guide for Conducting Corrosion Coupon Tests in Feld Applications”8) ASTM G46 “Standard Guide for Examination and Evaluation of Pitting Corrosion”9) ASTM G102 “Standard Practice for Calculation of Corrosion Rates and Related Information from Electrochemical
Measurements.” 10) Coursebook for Corrosion Basics, NACE International, Jan 2003.11) P.R. Roberge, Handbook of Corrosion Engineering, McGraw‐Hill, 2000.12) P.A. Schweitzer, Corrosion of Linings and Coatings – Cathodic and Inhibitor Protection and Corrosion Monitoring, CRC Press,
2007. 1) NACE Publication 3T199 “Techniques for Monitoring Corrosion and Related Parameters in Field Applications,” NACE
International, 1999.2) NACE Publication 3D170 ““Electrical and Electrochemical Methods for Determining Corrosion Rates,” NACE International13) Application Note AN 107, Corrosion Monitoring in Crude Unit Distillation Columns, Rohrback Cosasco Systems, Inc., April 1990.14) J. Gutzeit, Crude Unit Corrosion Guide – A Complete How‐To Manual, PCC, 2004.15) Application Note AN 109, Corrosion Monitoring in Fluid Catalytic Crackers (FCC), Rohrback Cosasco Systems, Inc., April 1990.16) K. Wold and R. Stoen, Monitoring Internal Corrosion in Pipelins, ASTME India Oil & Gas Pipeline Conference, GOA, February ) , g p , p , , y
2011.17) Operating Manual for Model CET5000, Series SmartCET Corrosion Monitoring Transmitter, Honeywell, July 2006.18) P. Collins, Hydrocarbon Processing, March 2012, 35.19) Guidance on Practice for Corrosion Monitoring, Engineering Technical Practices GP 06‐70, BP Group, 2005.