NACE ECDA
Seminar
External corrosion
Direct Assessment
Seminar
A Spectra Energy Company
Houston 2009
NACE ECDA
Seminar
ECDA „ Clean‟ Data
&
D.E. Success Rate
NACE • ECDA Seminar Houston 2009
Agenda
• Union Gas (A Spectra Energy company)
• ECDA Step Overview
• Indirect Inspection - „Clean‟ Data
• Direct Examination „ Success‟
• Questions?
NACE • ECDA Seminar Houston 2009
NACE • ECDA Seminar Houston 2009
Union Gas Ltd.
• Transmission, Distribution, and Storage
• Transmission integrity program per Canadian Regulations
• Utilizes ILI and ECDA
• ECDA
– Started in 2004
– To date 34 pipelines (or partial pipelines)
and 142 DE (111 excavations)
NACE • ECDA Seminar Houston 2009
ECDA Steps Overview
• Pre-Assessment
• Indirect Inspection
• Direct Examination
• Post Assessment
Note:
– Excellence in Data
– Accountability Steps 1-4
NACE • ECDA Seminar Houston 2009
Indirect Inspection – „Clean Data‟
• Influence testing
• CIPS / DCVG (ACVG)
• AC Attenuation
• Soil Resistivity
• AC Voltage
NACE • ECDA Seminar Houston 2009
Indirect Inspection
Influence Testing
• Line needs to be „clean‟
• All influencing rectifiers are simultaneously
interrupted
• No dynamic stray currents (tellurics)
NACE • ECDA Seminar Houston 2009
Checking that the Line is “Clean”
• Record a waveform during the OFF cycle and search for single-phase and three-phase rectifiers fingerprints.
• Install recorders for tellurics
• Check for obvious “false OFF” potentials
• Assess the magnitude of lateral gradient in Off cycle
• Complete telluric compensation as required
NACE • ECDA Seminar Houston 2009
Waveform(As Captured by a Field Oscilloscope - OFF Cycle)
NACE • ECDA Seminar Houston 2009
Frequency Spectrum(As Displayed by the Instrument)
NACE • ECDA Seminar Houston 2009
Spectrum Analysis
DC Component – Matches survey value
60 Hz Component – Filtered by the survey equipment
1200
1620
270340
0
200
400
600
800
1000
1200
1400
1600
1800
DC 60 Hz 120 Hz 180 Hz
Frequency
Am
plit
ud
e (
mV
)
NACE • ECDA Seminar Houston 2009
Spectrum Analysis
120 Hz Component – Fingerprint of a single-phase rectifier left ON or out of sync. With a 270 mV value, the line is not “clean”.
1200
1620
270340
0
200
400
600
800
1000
1200
1400
1600
1800
DC 60 Hz 120 Hz 180 Hz
Frequency
Am
plit
ud
e (
mV
)
NACE • ECDA Seminar Houston 2009
Spectrum Analysis
180 Hz component - Fingerprint of a three-phase rectifier left
ON or out of sync and/or harmonics of 60 Hz. A 340mV
value versus 1620 mV 60 Hz is probably a harmonic.
1200
1620
270340
0
200
400
600
800
1000
1200
1400
1600
1800
DC 60 Hz 120 Hz 180 Hz
Frequency
Am
plit
ud
e (
mV
)
NACE • ECDA Seminar Houston 2009
TelluricsCIPS Data. As Measured.
-2500
-2000
-1500
-1000
-500
0
2000 2050 2100 2150 2200 2250 2300 2350 2400 2450 2500
Chainage (m)
Pote
ntial (m
V)
ON Potential OFF Potential -1000 mV Criterion
To T
B6
To T
B a
t R
d. 2
NACE • ECDA Seminar Houston 2009
TelluricsCIPS Data. Tellurically Compensated.-2500
-2000
-1500
-1000
-500
0
2000 2050 2100 2150 2200 2250 2300 2350 2400 2450 2500
Chainage (m)
Po
ten
tia
l (m
V)
ON Potential OFF Potential -1000 mV Criterion
To T
B6
To T
B a
t R
d. 2
NACE • ECDA Seminar Houston 2009
Interrupter Failure (Telluric Record at Remote TP)
-2000
-1800
-1600
-1400
-1200
-1000
-800
-600
-400
-200
0
0.65625 0.66125 0.66625 0.67125 0.67625
Time (GMT)
Po
ten
tia
l (m
V)
OFF Potential ON Potential
Problems During Indirect Inspections
NACE • ECDA Seminar Houston 2009
High Contact Resistance
( CIPS in Northern Ontario)-2500
-2000
-1500
-1000
-500
0
1740 1760 1780 1800 1820 1840 1860 1880 1900 1920
Chainage (m)
Po
ten
tia
l (m
V)
ON Potential OFF Potential -1000 mV Criterion
Severe CIPS Indication
Rock
Problems During Indirect Inspections
NACE • ECDA Seminar Houston 2009
When the contact resistance (Rc) is within the same range as
the internal resistance of the voltmeter (Rc), the measured
value would be only half of the real potential.
High Contact Resistance
V
c
meas
R
R
VV
1
Problems During Indirect Inspections
NACE • ECDA Seminar Houston 2009
The area was „surveyed‟ twice (once using a 1M spoiler) and
the “true potential” was calculated using simple math.
Double-reading Survey-2500
-2000
-1500
-1000
-500
0
1750 1770 1790 1810 1830 1850 1870 1890
Chainage (m)
Po
ten
tia
l (m
V)
True OFF Potential Measured OFF Potential -1000 mV Criterion
Real CIPS Indication
Problems During Indirect Inspections
NACE • ECDA Seminar Houston 2009
-1400
-1200
-1000
-800
-600
-400
-200
0
1000 1050 1100 1150 1200 1250 1300 1350 1400 1450 1500
Chainage (m)
Po
ten
tia
l (m
V)
-20
0
20
40
60
80
100
120
Gra
die
nt
(mV
)
ON Potential OFF Potential -1000 mV Criterion Lateral Gradient @ 3m
89.9
%IR
19.2
%IR
27.2
%IR
46.5
%IR
26.8
%IR 59.5
%iR
Low Shifts during DCVG Survey
(CIPS/DCVG in Northern Ontario)
Problems During Indirect Inspections
NACE • ECDA Seminar Houston 2009
To validate the calculated %IR, we measured both the
lateral gradient and the pipe-to-soil potential to
remote earth
Low Shifts during DCVG Survey
– Direct Measurements
RE
REOL
V
GIR%
Problems During Indirect Inspections
NACE • ECDA Seminar Houston 2009
95.0%
63.0%
89.9%
59.5%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
1101.6 1485.7Chainage (m)
%IR
Measured Calculated
The results show a very good match.
Low Shifts during DCVG Survey
– Validation Results
Problems During Indirect Inspections
NACE • ECDA Seminar Houston 2009
Extended Coating Damage at Chainage 1101.6
m.
Low Shifts during DCVG Survey
– DE Results (Photo)
Problems During Indirect Inspections
NACE • ECDA Seminar Houston 2009
Low Shifts during DCVG Survey
– DE Results (Coating Inspection
Map)
Problems During Indirect Inspections
FACTORY APPLIED
COAL TAR
Very Poor
Adhesion
12:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:00
11:00
1m
12:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:00
11:00
Ch. 1100.5m Ch. 1102.8m
FACTORY
APPLIED
COAL
TAR
N0m1.50.5
Disbonded Coating Unexcavated
LEGEND
Bare Pipe & Disbonbed Coating
BARE PIPE &
DISBONDED COATING
(SEE NOTE)
Note: Part of the disbonded coating came off during excavation. The entire coating was removed.
2m
Very
Poor
Adhesion
NACE • ECDA Seminar Houston 2009
AC Attenuation. Rate of Loss.
Coating Quality Under New Asphalt
(No Permission to Drill Holes)
0
100
200
300
400
500
600
700
800
900
1000
5550 5600 5650 5700 5750 5800 5850
Chainage (m)
Sig
nal (m
A)
DCVG Surveyed Area Asphalted Parking Lot
Rate of Loss: 10.74 dB/km Rate of Loss: 8.57 dB/km
Problems During Indirect Inspections
NACE • ECDA Seminar Houston 2009
Indirect Inspection• Criteria for identification of indications
• Criteria for classification of indications
• Prioritization
• Select D.E. sites
Direct Examination
Flag:
– How well we do on DE?
– Need to predict what we expected to find!
NACE • ECDA Seminar Houston 2009
DC Voltage
Gradient
Indication
Close Interval
Potential Survey
Indication
DC Interference (DCI)
SV MD MN NI
5 6 7 8
DCVG-SV
CIPS-SV 1 I I I I
CIPS-MD 2 I S S S
CIPS-MN 3 I S S S
DCVG-MD
CIPS-SV 4 I I I S
CIPS-MD 5 I S S S
CIPS-MN 6 I S M M
Prioritization Table Sample
NACE • ECDA Seminar Houston 2009
Prioritization Table (Cont‟d)
DC Voltage
Gradient
Indication
Close Interval
Potential Survey
Indication
DC Interference (DCI)
SV MD MN NI
5 6 7 8
DCVG-BT
CIPS-SV 10 I S S S
CIPS-MD 11 I S M M
CIPS-MN 12 I S M N
DCVG-NI
CIPS-SV 13 I* N N N
CIPS-MD 14 I* N N N
CIPS-MN 15 I* N N N
* Consider excavating a short section of line under severe risk of
external corrosion, even if DCVG indications were not found.
NACE • ECDA Seminar Houston 2009
Direct Examination Success
• Expectation of findings from the predictions
(for each DE)
• Actual findings from each DE excavation
• Compared the predictions to the actual
findings
NACE • ECDA Seminar Houston 2009
Direct Examination - Prediction
Coating Condition and Metal Loss
(Only two areas to predict)
• Relatively simple, straight forward
statements in ECDA reports
• Variety of terms used in the reports to
describe the severity of each area on 122
„recommended‟ sites
NACE • ECDA Seminar Houston 2009
Direct Examination - Findings
Coating Condition and Metal Loss
• Detailed findings documented by
measurements & photos for each area in the
reports
• Again a variety of descriptive terms used
NACE • ECDA Seminar Houston 2009
Direct Examination - Comparison
Coating Condition and Metal Loss
• Categorized and scaled the descriptive
terms used from both coatings and metal
loss
• Done for both predictions and findings
• Made relative evaluations within and
between all categorizations
NACE • ECDA Seminar Houston 2009
Small holidays / minor holidays
DE Descriptor Expectation FindingSuccess
Rate
DE#2. 8" Augusta Lateral
Ch. 4504.70 m- Minor holidays - Four very small holidays (jeep indications) (two pinholes, 0.5x0.1cm, 0.2cm diameter) 90
DE#2
Ch. 1009.40 m- Minor holidays
- Eight very small holidays (jeep indications) (two 0.3cm, 0.4cm, 0.8cm, 1cm
diameters; 0.4x0.2cm, 1.0x0.5cm, 1.3x0.5cm)
- Some of the jeep indications appeared fresh and may be the result of probing the line
during excavation 100
- Five of the jeep indications were on the longitudinal weld
DE#5
Ch. 3896.40 m- Small holidays
- One small holiday (5cm diameter) and nine very small holidays (jeep indications) (0.1
to 0.5cm diameter dents, 0.5x0.1cm scratch) 100
DE#4
Ch. 1454.90 m
(Validation with indication)
- Minor holidays- Five "minor" coating holidays (3cm, 4cm, and three 5cm diameters) in field applied
Denso tape, 20-30% damaged100
DE#1
Ch. 256.60 m- Minor holidays
- Eight very small holidays (jeep indications) covered by calcareous deposits (3cm,
6cm, 6cm, 10cm, 10cm, 15cm diameters; 10x3cm, 30x20cm)
- Extent of coating damage could not be measured due to adherent calcareous
coverage
100
- Spot of poor adhesion (1-2cm dia.) was found at jeep indication with largest deposit
NACE • ECDA Seminar Houston 2009
Direct Examination - Comparison
For each Direct Examination
• Compared coating expectation to finding
• Compared metal loss expectation to finding
• „Scored‟ the comparison by %
• Averaged the two % comparison
NACE • ECDA Seminar Houston 2009
Direct Examination - Results
Prediction vs. Finding
• 4 years (2004, 2005, 2006, 2007)
• 27 pipelines
• 122 DE (some validation)
• Approx 4 DE = n/a
• Overall success rate of 95%
NACE • ECDA Seminar Houston 2009
Questions?
• Questions?