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Monitoring corrosion protection of pipelines utilizing the main
survey techniques
By
Dr. S. Leeds
DC Voltage Gradient Technology & Supply Ltd (DCVG Ltd).
E-mail: dcvg@dcvg.com
©
Electrochem 2019
DCVG Ltd
For Corrosion To Take Place You Need The Following ALL Present At
Same Time:
➢ An anode area where corrosion occurs.
➢ A cathode area for counter electrode reactions.
➢ A driving force between anode and cathode.
➢ Anode and cathode area must be electrically
interconnected (through the pipe)
➢ Anode and cathode must be in same electrolyte
(moist soil).
Corrosion is Electrochemical by Nature➢ REMOVE ANY ONE AND CORROSION STOPS.
DCVG Ltd
Corrosion Mitigation
➢We use Coatings to separate Pipe Anode andCathode areas from the moist soil.
➢We use Coatings to physically isolate PipeAnode and Cathode areas from each other.
➢We use CP to change the driving forcebetween Pipe Anode and Cathode areas.
DCVG Ltd
To Mitigate Corrosion and to Maintain Pipeline Integrity You Need to Ensure
a Good Coating and Effective CP
But
What Happens if You Don’t get a Good Balance between Good Coating and
Effective CP?
DCVG Ltd
Brown/Red Corrosion
Product Indicates Poor
CP.
Pin Hole Corrosion
– Metal Loss
Root Damage to Coating. Root Vegetation Seeks Water in
CoatingBlistering - Main Line Flake
Shield Coated PipelineDCVG Ltd
Monitoring Pipelines To determine Corrosion Protection
DCVG Ltd
The Properties of a Coating Fault and their Priority.PROPERTY PRIORITY METHOD
Location 1 GPS
Fault Cathodic Current 2 DCVG
Fault Anodic Current 3 DCVG
Net Current Flow NACE Criterion 4 DCVG
DC Interference 5 CIPS / DCVG
Soil Resistivity 6 EM Technique
OFF Potential NACE Criterion 7 CIPS
Soil pH 8 pH meter
Fault Severity 9 DCVG
AC Interference 10 AC Voltmeter
ON Potential NACE Criterion 11 CIPS
Type of Soil/Bacteria 12 Analysis
Fault Size 13 Excavation/Visual
Origin of Fault 14 Excavation/Visual
Type of Coating 15 Records
Field Joint Coating 16 Records
Overall Density of Faults 17 DCVG/GPS
Closeness to Another Fault 18 DCVG/GPS
Age of Coating 19 RecordsDCVG Ltd
Data Compiled From Survey Techniques
DCVG CIPS SOIL
RESISTIVITY
% IR ON Potential Soil Resistivity
Corrosion Status OFF Potential Change in Soil Type
Current Demand Large Coating Fault
Location
Moisture Content
Shape & Orientation Effective range of
CP
Average Soil pH
Effective Range of
Rectifier
Weak Areas of CP Presence of Rock or
Stones
% Efficiency of
Casings, Foreign
Structures, etc
Interference
Effects
Location of Coating
Faults
Attenuation of CP Soil Composition
Voltage VariationsDCVG Ltd
DC VOLTAGE GRADIENT BURIED PIPELINE COATING FAULT SURVEYS -
DCVG
DCVG Ltd
10
+ TRANSFORMER
RECTIFIER UNIT
GROUND BED
Current Flow Through the
Soil to Coating Fault
Generates a Voltage Gradient
INTERRUPTER
Gradient Forming and
Dissipating as CP switched
ON/OFF by Interrupter, 0.45
Sec ON, 0.8 Sec OFF
+-
RED
BLACK
DCVG Ltd
% IR Severity Rating:
Severity
%IR
Visual size Action required
0 to 15 Small Repair Unlikely
16 to 35 Medium Consider Repair
36 to 70 Medium / Large Consider Early Repair
71 to 100 Large Immediate Excavation for
Investigation.
Corrosion Characterisation of a
Coating Fault:Interpretation Shorthand
Representation
Corrosion Status
Cathodic / Nil (CPON/CP OFF) Protected CP On or Off
Cathodic / Cathodic (CPON/CP OFF) Protected CP On or Off
Cathodic / Anodic (CPON/CP OFF) Protected CP On Unprotected
CP Off
anodic / anodic (CPON/CP OFF) Unprotected CP On or Off
Epicenter to remote earth (RE)% IR Severity =
Calculated MV to remote earth (RE)X 100
% IR =
OL/RE
P/REX 100
DCVG Ltd
86 graph
Pipeline from 0 to 174 311 feet. Texas USA
Fault Severity v Distance
Cultivated
Uncultivated
Fa
ult
Se
ve
rity
%IR
Distance (m)
The Soil pH has an Effecton the Corrosion Statusof Pipe buried beneath
DCVG Ltd
DCVG DATA
Typical Fault Severity
Distribution
Nu
mb
er
of
Fa
ult
s
Fault Severity %IR
SMALL
MEDIUM
LARGE
DCVG Ltd
Examples of GPS
Locations Using Google
Earth
DCVG Ltd
Example of Coating Defects
2cm x 5 cm 2.5 metres deep
Excavator Damage
New Pipeline.
Failure mechanism: Scrape from a Excavator as a result of mechanical damage.
Crown Cracking of Coal TarCoatings has long sausageshaped voltage gradient iso-potential plot
DCVG Ltd
Examples of GPS
Locations Using Google
Earth
Coating
Fault
DCVG Ltd
Examples of GPS
Locations Using Google
Earth
Coating
Fault
Remote Control DCVG
DCVG Ltd
Close Interval Pipe-To-Soil Potential
Surveys - CIPS / CIS
Monitoring the Pipeline CP Potentials.
DCVG Ltd
Satellite
Synchronised
with Interrupters
Typical
CIPS
Equipment
CIPS Data
Logger
Pipe
Locator
Satellite
Aerial
Trailing
30swg
Wire
Typical CIPS
Equipment
DCVG Ltd
OFF
Cathodic Spike
Anodic Spike
IR
Error
Polarised Potential
ON
Time
Po
ten
tia
l
ON
SPIKE ERRORS WHEN
SWITCHING
RECTIFIER ON/OFF
OFF MeasurementON Measurement
DCVG Ltd
Distance
NO SYNCHRONISATION OF DATA
LOGGER WITH INTERRUPTERSP
ipe t
o S
oil P
ote
nti
al
0
200
400
600
800
1000
1200
1400
0 100 200 300 400 500 600 700 800 900 1000
Distance (Metres)
Pip
e-t
o-S
oil
Po
ten
tial
(-m
V)
Casing
RiverCrossing
TYPICAL SYNCHRONISED
CIPS SURVEY DATA
DCVG Ltd
Defe
cts
epic
entr
e p
ote
ntials
(-m
V)
Exponentially Corrected Fault Epicentre Potentials
Distance (ft)
DCVG Ltd
Lateral/Trailing CIPS➢Close Interval Pipe-to-soil Potential Survey with Additional Reference
Electrode at 90o or trailing behind.
DCVG Ltd
-1500
-1000
-500
0
500
1000
1500
2000
2500
3000
0 100 200 300 400 500 600 700CIP
S &
Late
ral
Po
ten
tials
mV
Distance Metres
Figure J: Section 1 . ON/OFF Close Interval Potential Survey and Lateral Gradients.
Rectifier
Lateral CIPS
LHS
Lateral CIPS
RHSCoating Faults
CIPS ON
CIPS OFF
Rock Layer?
Anodic Area
Pipe-To-Soil Potentials vs Lateral Gradients
DCVG Ltd
CIPS
DCVG
Pipe Locator
One Pass Two Surveys
DCVG Ltd
ELECTROMAGNETIC SOIL RESISTIVITY
To Determine Right of Way Soil Corrosivity.
An important input of where to digThis technique which has been used for +30 years. Speeds of 15 Km/day
achievable with readings at one metre spacing.
DCVG Ltd
HEADING FROM CORPUS CHRISTIE TO VICTORIA TX
TIDAL MUD FLATS
0
10
20
30
40
50
60
70
80
90
100
51500 51700 51900 52100 52300 52500 52700 52900 53100
DISTANCE (m)
ME
TA
L L
OS
S D
EP
TH
(%
WA
LL
TH
ICK
NE
SS
)
0
100
200
300
400
500
600
700
800
900
1000
SO
IL R
ES
IST
IVIT
Y (
Oh
m.c
m)
ML DEPTH %
SOIL RESISTIVITY
Corrosive
Highly Corrosive
Corrosion Classification of Soils
Soil
Classification
Resistivity
(ohm.cm)
Highly
Corrosive
< 500
Corrosive 500 – 1000
Moderately
Corrosive
1000 – 5000
Lightly
Corrosive
5000 –
10,000
Non Corrosive > 10,000
pH Characteristics:
DCVG Ltd
Portable Electrochemical Noise Measurement Device -
ProCoMeter➢ Non destructive technique so ideal for site use or continuous monitoring of
corrosion behaviour.
➢ Predicting types of corrosion under coating such as pitting, crevice corrosion.
➢ Identify areas of poor coating hence potential locations for corrosion.
➢ No activation signal is required thus non intrusive. It uses the natural occurringpotential and current fluctuation under-film corrosion.
➢ Real time monitoring.
➢ Analysis of electrochemical noise involves calculating the noise resistance(Rn).
➢ Rate the protective nature of coatings according to the noise resistance criteriabased on The Bacon Smith and Rugg criteria :>1E8ohms.cm2: Good coating,1E6-1E8ohms.cm2:fair coating and <1E6ohms.cm2 poor coating.
DCVG Ltd
Portable Electrochemical Noise Measurement Device -
ProCoMeter
➢ Example of one of the 5 modes – Basic No Connection To Substrate (BNCS)
- No contact is made to coated metal sample to carry out measurements.
Substrate
Coating Probes
WE1
WE2
REF
To ProCoMeter
2 Sets of 512 simultaneouscurrent & Voltagemeasurements recorded,one every 0.5 seconds.Each set saved. It alsostarts with a 30sec pause atthe beginning (settling step)and between each 2 sets.DCVG Ltd
Portable Electrochemical Noise
Measurement Device - ProCoMeter
Museum Artefacts
Off Shore
Platforms
Aircraft
Monuments
Storage Tanks
Water Pipelines
Ships
New
Coatings
Bridges
Rebar in ConcreteTesting Inhibitors
Oil and Gas Pipelines
DCVG Ltd
Conclusion
©
➢ Monitoring corrosion protection of pipelines or any other infrastructure
needs to be non destructive but still gather information about the
important properties that can be obtained at coating faults, where
corrosion is most likely to occur.
➢ Need to consider both the properties of the coating and the interaction of
the coating with the local environment.
➢ Need to combine information gathered about the condition of the
cathodic protection system along with the coating system to understand
the full extent of corrosion control.
DCVG Ltd
Thank You.
©DCVG Ltd
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