A Methodology to Determine the Grade for a Vintage Gas Transmission Pipe

Abstract

This presentation is an interim brief about a multi-year effort to develop a non-destructive methodology to establish or confirm the grade of pipe in natural gas transmission assets. This project aligns with the Pipeline and Hazardous Materials Safety Administration's (PHMSA) proposed requirements to verify material properties for pipe without records. Programs were established for laboratory testing and non-destructive examination technologies to estimate strength and quantify vintage pipe chemical composition. The goal is to utilize non-destructive methods to determine a pipe grade using machine learning algorithms, probabilistic analysis and extensive reference data sets. This paper discusses the details of the program.

Full text

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A Methodology to Determine the Grade
for a Vintage Gas Transmission Pipe
Nathan Switzner1, Peter Veloo1, Bill Amend2,
Melissa Gould2, Michael Rosenfeld3, Jing Ma3,
Troy Rovella4
1Exponent, 2DNV GL, 3Kiefner, 4Pacific Gas and Electric

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Pacific Gas and Electric Company (PG&E)
One of the largest gas and electric
utilities in the US
~20,000 employees
~70,000 square mile service
territory
Pipeline assets
~7,000 miles transmission
32”-42”
~40,000 miles distribution
Gas transmission facilities
9 compression and processing
~400 regulating and metering
3 terminals

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PG&E Asset Installation Years

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US Hazardous Materials Pipeline Age
Demographics
Source: JF Kiefner, MJ Rosenfeld, The Role of Pipeline Age in Pipeline Safety,
INGAA Foundation Final Report No. 2012.04

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Federal Regulations Governing Natural Gas
Transport
Pipeline and Hazardous
Materials Safety
Administration (PHMSA)
proposed federal
regulations updates
Verification of material
properties
Pipe without material
documentation records
Verification of Maximum
Allowable Operating
Pressure (MAOP)
Pipe without records of an
initial life (post installation)
hydrostatic pressure test

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Modeling Risk and Prioritization
Hydrotest
Remaining In-Service Life (Years)
Probability of Failure
Rebuild/Replace Schedule
Hydrotest Pressure
Operating Pressure
Probability of Failure
Material Properties:
Pipe Grade,
Toughness, Fatigue

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Material Properties
Material Properties
Grade (UTS, YS)
Toughness
Fatigue Properties
Locations
Pipe body
Long seam & HAZ
Girth weld & HAZ

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Feasibility of Vintage and Grade Estimation
Processing
Chemical Composition
Microstructure
Strength
Toughness

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Composition as a Marker of Vintage
Sulfur Content Weight %
Year of Manufacture
API 5L and 5LX
PSL1
PSL2
Source: Keifner database

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Composition as a Marker of Grade
Manganese
Cumulative Probability
Source: M. Rosenfeld, J. Ma, T. Rovella, P. Veloo, “Going from in-situ nondestructive testing to a probabilistic
MAOP”, The 30th International Pipeline Pigging and Integrity Management Conference, 2018

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Toughness as a Marker of Grade
Cumulative Probability
Source: M. Rosenfeld, J. Ma, T. Rovella, P. Veloo, “Going from in-situ nondestructive testing to a probabilistic
MAOP”, The 30th International Pipeline Pigging and Integrity Management Conference, 2018

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Grade Estimation Inputs and Algorithms
Trial 1 Trial 2 Trial 3 Trial 4
%C %C %C %C
%Mn %Mn %Mn %Mn
UTS %S %S %S
YS UTS %P %Si
YS UTS UTS
YS YS
Trial 5Trial 6Trial 7Trial 8
%C %C %C %C
%Cu %Cu %Cr %Cr
%Mn %Mn %Cu %Cu
%P %P %Mn %Mn
%S %S %P %Mo
%Si %Si %S %P
UTS Vintage %Si %S
YS UTS Vintage %Si
YS UTS Vintage
YS UTS
YS
Error in Grade Estimation
Certainty of Match (%)
Example Evaluation of the Outputs for Various Algorithms
Example Input Data Sets
Lower Grade Estimated Higher Grade Estimated

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Determination of Material Properties

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Case Study: Seamless Pipe (Grade B, 1952)

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Case Study: Seamless Pipe (Grade B, 1952)
Tensile
Instrumented Indentation Testing
Hardness (HRB)
74.4
Charpy est. upper shelf energy
18.0 (ft-lb)
YS,0.2(ksi) UTS(ksi) n
43.8 67.0 0.14
Composition (wt%)
YS,0.2(ksi) UTS(ksi) n Elong(%)
41.9 67.2 0.19 33.1
CMn Si S P Nb V
0.25 0.51 0.06 0.025 0.009 N/A <0.01
Ti Cr Ni Mo Cu Al B
N/A 0.11 0.03 <0.01 0.03 N/A <.001

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Concluding Remarks
Changes in federal regulations will require
verification of pipeline properties
A risk-based, fracture-mechanics prioritization
model has been developed
Multiple markers and algorithms have been tested
to estimate grade
A variety of nondestructive examination
technologies can be used to generate grade
estimation inputs