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An approach to establishing manufacturing
process and vintage of line pipe using in-
situ nondestructive examination and
historical manufacturing data
Presented by Nathan Switzner
Authors: Nathan Switzner1, Peter Veloo2, Michael Rosenfeld1, Troy Rovella3, Jonathan Gibbs2
1RSI -Pipeline Solutions, New Albany, OH
2Pacific Gas and Electric Company, Walnut Creek, CA
3LineStar Services Inc, Houston, TX
1
Outline
•Motivation –Integrity management and US Federal Rules
•Background –Line-pipe manufacturing evolution and historical
data
•Enablers –In-situ non-destructive examination (NDE)
technologies
•Methodology –Align the NDE data with historical data and
documentation
•Case studies
•Concluding remarks
2
Motivation –Integrity Management
•For assets without traceable, verifiable, and complete (TVC)
records, the intent is to build a clearer picture of assets, like fitting
together the puzzle pieces:
•Basic measurements, like hardness, wall thickness, and outside
diameter, have limited utility.
•NDE data provide more information about composition, strength and
microstructure.
•Asset knowledge is further improved by comparing the data with
historical trends and documentation.
3
Motivation –US Federal Rules
•Populations
•Operators must “define separate populations of similar segments of
pipe for each combination of the following material properties and
attributes: Nominal wall thicknesses, grade, manufacturing
process,pipe manufacturing dates…” per (§192.607(e)(1)).
•Toughness
•One method given in §192.712(e)(2)(i)(A) is to use “Charpy v-notch
toughness values from comparable pipe with known properties of the
same vintage and from the same steel and pipe manufacturer.”
PHMSA’s Mega Rule drives development of methods to estimate
vintage and identify information about the manufacturing process.
4
Background –Line-pipe manufacturing trends
5
6
E. Clark, B. Leis, R. Eiber, “Integrity of Vintage Pipes”, INGAA, 2005
E. Clark, B. Leis, R. Eiber, “Integrity of Vintage Pipes”, INGAA, 2005 7
Methodology Concept
•A method to identify vintage and manufacturing process based on NDE
data can be conceived based on:
•Adequate historical data to facilitate trend identification
•Accurate and precise NDE estimates of:
•strength
•composition
•microstructure
8
•Historical laboratory data from ~1200 pipe segments from PG&E and
industry datasets were analyzed.
•Line pipe samples outside diameters ranged from 4-36”
•Data represent a wide variety of grades
•The distribution of grades and sizes in the historical database is an imperfect match to
the US distribution of grades and sizes.
•Remarkable trends were identified from the historical data.
•For brevity, we will only discuss the trends for:
•Yield strength
•Manganese and sulfur content
•Other strength and composition trends are provided in the associated paper, #9589.
9
Enablers –1. Identifying Trends in the Data
Enablers –1. Database of Historical Trends
•Data for yield strength from all steels
(without regard for grade) were binned
by decade of manufacture (+/- 1
decade for smoothing).
•Each vintage bin was plotted versus
average yield strength for that vintage.
•The purpose for plotting in this
manner is so that the vintage can be
estimated using an estimate of yield
strength from the in-situ test (IIT).
•Average yield strength has
increased steadily with time.
1900
1920
1940
1960
1980
2000
2020
25 50 75 100 125
Reported year of manufacture
Yield strength (ksi)
10
Enablers – 1. Database of Historical Trends
•To obtain a basic understanding of
the upper limits of line pipe strength,
̅+s and ̅+2s for each bin were
plotted (s is the standard deviation).
•The upper limit of yield strength
(̅+2s) has increased rapidly with time.
•The ̅-s and ̅-2s lines (lower
bounds) were not plotted because the
lower limit of strength has remained
relatively static over time. Grade B
has existed since the beginning of
API-5L. For this reason, ̅-s and ̅-2s
are not useful for identifying strength
trends.
1900
1920
1940
1960
1980
2000
2020
25 50 75 100 125
Reported year of manufacture
Yield strength (ksi)
+s
+2s
11
s =
Where:
s = sample standard deviation
= the number of observations
= ith observed value
= mean of observed values
Enablers – 1. Database of Historical Trends
•Manganese content in line pipe
steels appears to have increased
generally with time, since the
increase of manganese is based
on steel suppliers trying to improve
strength and toughness.
•In the past 80 years, average
manganese has doubled from ~0.6
wt% to ~1.2 wt%.
•For manganese it makes sense
to include a lower bound (̅-2s)
because the content is approx.
normally distributed 1900
1920
1940
1960
1980
2000
2020
00.5 11.5 2
Reported year of manufacture
Manganese (wt%)
-2s
-s
+s
+2s
12
s = standard deviation
Enablers – 1. Database of Historical Trends
•Sulfur content in steels has
decreased with time because
sulfur has long been recognized
as a tramp element and a
detriment to toughness.
•Since sulfur is a tramp
element, the distribution was not
a normal distribution. The
distribution had a longer tail at
higher values. Thus a log-
normal distribution was used to
obtain the standard deviation
trendlines. 1900
1920
1940
1960
1980
2000
2020
0.001 0.01 0.1
Reported year of manufacture
Sulfur (wt%)
-s
+s
+2s
-2s
13
s = standard deviation
Enablers – 1. Database of Historical Trends
•Technology advances in de-
sulfurization enabled reduction
of sulfur to obtain high
toughness steels.
•Over the last 100 years,
average sulfur in line-pipe steel
has dropped an order of
magnitude from ~0.023 to
~0.002, making the sulfur
content a very useful element
for estimating vintage. 1900
1920
1940
1960
1980
2000
2020
0.001 0.01 0.1
Reported year of manufacture
Sulfur (wt%)
-s
+s
+2s
-2s
14
s = standard deviation
•Instrumented Indentation Testing (IIT)
•J. Kornuta et al, “Uncertainty Quantification of Nondestructive Techniques to Verify Pipeline Material Strength”, IPC2018
•J. Kornuta et al, “An Evaluation of Instrumented Indentation Testing to Estimate Yield and Tensile Strength”, PPIM2019
•N. Switzner et al, “Influence of line-pipe steel microstructure on NDE yield strength predictive capabilities”, PPIM2020
•J. Kornuta et al, “Automated error identification during nondestructive testing of pipelines for strength”, IPC2020.
Indenter
Enablers – 2. NDE Strength Estimation
15
Enablers – 3. NDE Compositional Data
16
•M. Louie et al., “Nondestructive Testing of Pipeline Materials:
Analysis of Chemical Composition from Metal Filings,’ PPIM2019.
•N. Switzner et al., “Nondestructive Testing of Pipeline Materials:
Further Evaluation of Portable OES, XRF, LIBS, and Filings to
Estimate Chemical Composition,” PPIM2020.
•PG&E has tested several NDE
composition technologies.
•Accurate, reliable technologies
have been identified and
validated that enable the use of
NDE compositional data for
vintage estimation.
Example validation plot of filings data versus
laboratory data for manganese
0
0.5
1
1.5
2
00.5 11.5 2
Filings (wt %)
Lab OES (wt %)
Manganese
Enablers –4. NDE Microstructure Replication
•Microstructure helps establish manufacturing process.
17
25 µm 25 µm
Ferrite
Ferrite
Second phase
25 µm
“Normalized”
•Large ferrite grains.
•Large amount of dark phase
(pearlite).
Pearlite
Ferrite
“Quenched and tempered”
•Small, jagged ferrite grains.
•No dark phase.
“Thermo-mechanical
controlled processed”
•Fine ferrite grains.
•Small amount of dark
phase.
•N. Switzner et al, “Influence of line-pipe steel microstructure on NDE yield strength predictive capabilities”, PPIM2020
Two Case Studies: NDE Data Collection
Case Study 1 NDE Data Case Study 2 NDE Data
•Reportedly installed in 1952
•YS: 43 ksi (avg of 6 IIT estimates)
•Mn: 0.5 wt% (avg of 3 lab AA
measurements of filings)
•S: 0.026 wt% (avg of 3 lab combustion
measurements of filings)
•Microstructure replica
•Reportedly installed in 1951
•YS: 75 ksi (avg of 7 IIT estimates)
•Mn: 1.28 wt% (avg of 3 lab AA
measurements of filings)
•S: 0.005 wt% (avg of 3 lab combustion
measurements of filings)
•Microstructure replica
18
Two Case Studies: IIT Yield Strength Estimate
•For Case Study 1 the IIT
yield strength estimate was
low, but reasonable for 1950s
line pipe.
•For Case Study 2 the IIT
yield strength estimate was
quite high for 1950s line pipe.
1900
1920
1940
1960
1980
2000
2020
25 50 75 100 125
Reported year of manufacture
Yield strength (ksi) 19
Case
Study 1Case
Study 2
1900
1920
1940
1960
1980
2000
2020
00.5 11.5 2
Reported year of manufacture
Manganese (wt%)
Two Case Studies: Manganese
•For Case Study 1 the filings
result for manganese was
low, but reasonable for 1950s
line pipe.
•For Case Study 2 the filings
result for manganese was
quite high for 1950s line pipe.
20
Case
Study 1Case
Study 2
1900
1920
1940
1960
1980
2000
2020
0.001 0.01 0.1
Reported year of manufacture
Sulfur (wt%)
Two Case Studies: Sulfur
•For Case Study 1 the filings
estimate for sulfur met the
expectation for 1950s line
pipe.
•For Case Study 2 the filings
estimate for sulfur was quite
low for 1950s line pipe.
•This low sulfur content is
unlikely based on the poor
sulfur removal capabilities
prior to the 1990s.
21
Case
Study 1
Case
Study 2
Two Case Studies: Microstructure
Case Study 1Case Study 2
•Evidence of 1950s vintage
manufacturing:
•Ferrite and pearlite constituents
•Relatively large grains
•Relatively large amount of pearlite
•Visible pearlite lamellae indicating
slow cooling
•Evidence of manufacturing later
than the 1950s:
•Relatively fine grains
•Unresolvable pearlite lamellae
possibly indicating modern
accelerated cooling processes. 22
Two Case Studies: Discussion
•We have examined the yield strength, manganese, sulfur, and
microstructure results for Case Study 1 and 2.
•Case Study 1 meets expectations for 1950s steel line pipe.
•Case Study 2 appears to be a more modern steel line pipe.
•All the strength, composition and microstructure data were
brought into consideration for suggestion of a new vintage, but
the additional data will not be discussed here for brevity.
•The data were used to suggest an updated vintage of the year
2000.
23
Two Case Studies: Discussion
The suggestion of the year 2000 rather than 1951 for the Case 2 steel line
pipe vintage results in better alignment of the NDE results with expected
values.
1900
1920
1940
1960
1980
2000
2020
25 50 75 100 125
Reported year of manufacture
Yield strength (ksi) 00.5 11.5 2
Manganese (wt%) 0.001 0.01 0.1
Sulfur (wt%) 24
Case
Study 1
Case
Study 2
Case
Study 1
Case
Study 2
Case
Study 1
Case
Study 2
Concluding remarks
•A method to confirm steel line pipe vintage or suggest a new vintage was
explained and demonstrated.
•Crucial aspects of the method include a detailed understanding of historical
line pipe manufacturing processes and an extensive database of historical
strength and composition data.
•For vintage confirmation using NDE data, the NDE data collection methods
must be validated against destructive laboratory data to ensure accuracy.
•Future work will include:
•Expanding the database to include microstructure evaluation data (grain size and
pearlite fraction) and validation of the NDE methods for microstructure.
•Introduction of algorithms to estimate vintage and improve the certainty of the vintage
confirmation and suggestion process
25
Please send comments or questions to nswitzner@rsi-ps.com.
Thank you!