Applications guide for determining the yield strength of in-service pipe by hardness evaluation : final report

136 Pages·2009·9.554 MB·English

by  Clark, Edward B., Amend, W. E

CRTD-Vol. 91

Applications Guide for Determining the
Yield Strength of In-Service Pipe by
Hardness Evaluation

Final Report

By
Edward B. Clark
Battelle’s Energy Systems

and

W. E. Amend
Structural Integrity Associates, Inc

Prepared for
American Society of Mechanical Engineers

ASME NEW YORK 2009
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Battelle Project No. N007044

ISBN: 978-0-7918-0291-5

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ACKNOWLEDGEMENTS

This report was prepared by Battelle Memorial Institute - Columbus under contract to the ASME
Gas Pipeline Safety Research Committee (GPSRC). The research would not have been possible
without tenacious effort by GPSRC and, most importantly, the support and input from the
following organizations:

Financial support from:
CenterPoint Energy Pipeline Services
Consolidated Edison
DTE Energy / MichCon
Dominion Gas
Pacific Gas & Electric
Southern California Gas Company
Southern Star Central Gas Pipeline
Southwest Gas Corp.
We-Energies

Steering Subcommittee, Applications Guide for Determining the Yield Strength of In-
Service Pipe by Evaluating Hardness:

Chair: Technical Coordinator:
Jon O. Loker, Consultant David Aguiar, Pacific Gas & Electric

GPSRC Members:
Robert C. Becken III, Energy Experts International
Richard Huriaux, U.S. DOT, PHMSA, Office of Pipeline Safety
Gopala Vinjamuri, Consultant (retired from DOT/OPS)
Dr. Michael Tinkleman, ASME

Sponsor Representatives on Committee:
David Aguiar, Pacific Gas & Electric
David E. Barkei, We-Energies
Gilbert K. Ching, Southern California Gas Company
Steve Frehse, Southwest Gas Corp.
Roy Hershberger, Southern Star Central Gas Pipeline
John A. Ludwigsen, Consolidated Edison
John D. Lueders, DTE Energy / MichCon
Brian Moidel, Dominion Gas
Andrew Pulsifer, CenterPoint Energy Pipeline Services

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Gas Pipeline Safety Research Committee (GPSRC):

F. Roy Fleet, Consultant – Chair
Jon Loker, Consultant – Vice Chair
Richard Huriaux, U.S. DOT, PHMSA, Office of Pipeline Safety – Secretary
Richard Arita, Pacific Gas & Electric
Nicholas Ashcraft, Kiefner and Associates
Robert C. Becken III, Energy Experts International
A. J. Del Buono, Steel Forgings Inc.
Raymond Lewis, H. Rosen USA
Danny A. Nichols, Energy Transfer Company
Eugene Palermo, Palermo Plastics Pipe Consulting
Robert Torbin, Cutting Edge Solutions, Inc.
Gopala Vinjamuri, Consultant

Added appreciation:
Special thanks to Steven P. Burnley, Columbia Gas Transmission Corporation, who initially
served as Technical Coordinator for the project, assisted in developing the project concept, and
provided an initial draft review.

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Table of Contents
Page
1. Introduction............................................................................................................................1
2. Scope......................................................................................................................................3
3. Hardness Testing Background...............................................................................................4
3.1 General Hardness Testing Background........................................................................4
3.2. Hardness Relationships to Strength...............................................................................5
4. Field Hardness Tester Types, Attributes, Application Criteria and Codes............................6
4.1 Field Hardness Tester Types........................................................................................6
4.2 General Hardness Tester Attributes..............................................................................8
4.3 Specific Application Criteria......................................................................................14
4.4 Codes/Standards.........................................................................................................19
5. Pre-Assessment....................................................................................................................19
6. Pre-Assessment Data Evaluation.........................................................................................22
7. Hardness Tester Selection....................................................................................................27
8. Procedure Qualification and Documentation.......................................................................31
8.1 Procedure Contents.....................................................................................................31
8.2 Procedure Qualification Record (PQR)......................................................................34
9. Project Staff/Test Technician Qualification Requirements..................................................34
9.1 Required Skills............................................................................................................34
9.2 Qualification Criteria..................................................................................................35
9.3 Federal Regulations - Qualification of Pipeline Personnel.........................................38
9.4 Personnel Safety Considerations and Requirements..................................................38
10. Pipe Sample Size and Lower Bound Hardness Statistical Estimates...................................38
10.1 Introduction.................................................................................................................38
10.2 Background.................................................................................................................39
10.3 Pipe Sample Size Determinations...............................................................................42
10.4 Example Calculations.................................................................................................43
10.5 Additional Considerations..........................................................................................45
11. Hardness Test Locations on Pipe Lengths...........................................................................45
11.1 Pipe Manufacturing Aspects.......................................................................................45
11.2 Pipe Surface Access....................................................................................................46
11.3 Test Location Proximity to Pipe Long Seams............................................................46
11.4 Proximity to Girth Welds, Repair Welds, Arc Burns, and Open Ends.......................47
11.5 Proximity to Mechanical Damage, Corrosion, and Pipe Surface Imperfections........47
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11.6 Test Temperature Considerations...............................................................................47
11.7 Vibration.....................................................................................................................47
11.8 Magnetic Fields..........................................................................................................48
12. Pipe Surface Preparation......................................................................................................48
12.1 Extent of Prepared Pipe Surface Area........................................................................48
12.2 Rough and Final Preparation......................................................................................48
12.7 Steel Surface Conditions and Required Metal Removal Depth..................................51
13. Testing Calibration, In-Process Evaluation, and Uncertainty..............................................51
13.1 Hardness Test Uncertainty..........................................................................................51
13.2 Hardness Calibration Blocks......................................................................................53
13.3 Verification and Calibration Checks..........................................................................54
13.5 Calibration Frequency................................................................................................55
13.6 In-Process Test Evaluations........................................................................................56
14. Field Hardness Data Evaluations.........................................................................................57
14.1 Test Plan Contents......................................................................................................57
14.2 Field Hardness Testing Data Sheet.............................................................................58
14.3 In-Process Evaluation of Hardness Test Results........................................................58
15. Hardness Conversion to Yield Strength...............................................................................59
15.1 Conversion Methods...................................................................................................59
15.2 Hardness-Yield Strength Conversion Example..........................................................61
16. Hardness Conversion Validation..........................................................................................63
17. DOT/State Special Permit (Waiver) Petition Requirements................................................64
17.1 Federal Special Permit................................................................................................64
17.2 State Special Permit....................................................................................................66
REFERENCES..............................................................................................................................67
APPENDIX A Yield Strength from Hardness – Additional Background.................................A-1
APPENDIX B Field Hardness Tester -- Detailed Information...................................................B-1
APPENDIX C Selected Industry Codes/Standards....................................................................C-1
APPENDIX D Hardness Test Locations Within a Pipe Length................................................D-1
APPENDIX E Hardness Test Procedure Qualification Record (PQR).....................................E-1
APPENDIX F Hardness Test Technician Qualification Record (TQR)....................................F-1
APPENDIX G Statistical Methods Background........................................................................G-1
APPENDIX H Field Hardness Testing Data Sheet...................................................................H-1
APPENDIX I Effect of Pipe Pressure on Rebound Hardness Tester Results..............................I-1
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APPENDIX J Surface Roughness Considerations......................................................................J-1

List of Tables

Table 1. Hardness Tester Load Range Categories.........................................................................6
Table 2. Field Hardness Tester General Attributes(17-29)..............................................................11
Table 3. Comparative Selection Guide(17-31)................................................................................15
Table 4. Hardness Tester Type - Minimum Pipe Wall Thicknesses............................................17
Table 5. Common ASTM Hardness Testing Standards...............................................................19
Table 6. Pre-Assessment Data Elements.....................................................................................20
Table 7. Equation 5 Subtraction Factor for α = 0.1, 0.05, and 0.01 with α* = 0.001, 0.01, and
0.05................................................................................................................................................42
Table 8. Hardness-Yield Strength Proportion and Confidence Levels (Reproduced from
Reference 1, Table A.3.8).............................................................................................................61
Table 9. Example of Hardness Test Conversion Table (Reproduced from Reference 1, Table
A.3.8)............................................................................................................................................61
Table 10. Hypothetical UCI Hardness Test Data Output as HRB...............................................62

List of Figures

Figure 1. Hardness Testing Process Flow Diagram.......................................................................2
Figure 2. Field Hardness Testing Methods....................................................................................7
Figure 3. Pre-Assessment Evaluation Process for Establishing a Uniform Sampling Lot..........24
Figure 4. Hardness Test Evaluation Block (not to scale).............................................................27
Figure 5. Hardness Tester Selection Flow Diagram....................................................................30
Figure 6. Normal Probability Density Distribution with a Cutoff at -2.......................................40
Figure 7. Subtraction Factor vs. Sample Size [α= 0.05 and 0.01 (95% and 99%confidence
bounds), α* = 0.001].....................................................................................................................43
Figure 8. Abrasive Disks Used for Pipe Surface Preparation......................................................50
Figure 9. Uncertainty Coverage Factor vs. Degrees of Freedom................................................53
Figure 10. Alternative Calibration of Leeb Rebound and UCI Testers.......................................55
Figure 11. Asymmetric Shape UCI Indentations.........................................................................56
Figure 12. Symmetric Shape UCI Indentation.............................................................................56
Figure 13. Leeb Rebound and UCI Indentations.........................................................................57
Figure 14. Leeb Hardness Wall Thickness Correction Factor.....................................................59
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8/01/11
Errata Sheet 8-1-2011--- Applications Guide

Reference: “Applications Guide for Determining the Yield Strength of In-Service Pipe
by Hardness Evaluation,” ASME Publication CRTD-91 (2009)

The following corrections or editorial refinements are outlined as applicable to the
original publication (page numbers are those related to the printed document):

Section 5
• Ref page 20, last paragraph before Table 6: The 1st sentence is editorially
adjusted as shown below in order to directly synchronize with the categories in
Table 6:
Table 6 contains data elements organized into several categories including Pipe-Related,
- Construction/Maintenance-Related, Operational Data, and Corrosion-Related records.

Section 10.3
• Ref page 42, text after formula (8): “Values for α = 0.1, 0.05, and 0.01 with α* =
0.001, 0.01, and 0.05 for a range of sample sizes (N) have been calculated and
shown in Table 7.”
• Ref page 42, title for Table 7 following the above text as subject to the same
correction: 
   “Table 7. Equation 5 Subtraction Factor for α = 0.1, 0.05, and 0.01 with α* = 0.001,
0.01, and 0.05”
• Ref page 43, top line of text: “The data shown in Table 1 7 for α = 0.05 and
0.01(95% and 99% confidence bounds) with α* = 0.001 are plotted in Figure 7.”

Section 14
• Ref page 59, 2nd par, 1st line: The adjusted hardness item E6 in Section F in the
data collection form….

Appendix G
• Ref page G-6, text after formula (G-8): “Subtraction Factor values for α = 0.1,
0.05, and 0.01 for a range of sample sizes (N) have been calculated and shown
in Table G-1.” 
• Ref page G-7, title for Table G-1 following the above text as subject to the same
correction: 
   “Table G-1. Equation G-8 Subtraction Factor for α = 0.1, 0.05, and 0.01 with α* =
0.001, 0.01, and 0.05”

Errata #80291E
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1. INTRODUCTION
Situations arise where pipe tensile properties may not be sufficiently documented to satisfy
regulatory requirements thus requiring an additional effort to obtain the data. This more often
occurs in the case of older pipelines where records necessary to document the pipe properties
may have been misplaced over time or may even be non-existent for very old pipelines.

In such cases, the operator currently has two methods available according to the requirements of
Appendix B of 49 CFR Part 192. One method is to adopt the 24,000 psi yield strength and base
the pipeline MAOP on that value. The second method is to implement the provisions that permit
yield strength to be determined by tensile testing according to the prescribed criteria. Adopting a
maximum allowable operating pressure (MAOP) based on an assumed 24,000 psi yield strength
has some immediate utility but often results in reduced pipeline throughput. Otherwise, tensile
test coupon removal requires removing the pipeline from service. Neither of these alternatives is
an optimal solution when additional pipe yield strength documentation of an operating pipeline is
required. Additional methods, preferably non-destructive, are needed to provide a reliable
assessment of pipeline yield strength without the need for destructive test methods.

This Guide describes a complete process for conducting field hardness testing to estimate the
yield strength of pipeline steels1. The process is non-destructive so it is suitable for in-situ testing
on operating pipelines, at pipe storage facilities, or various other locations. It also allows for
process variations that are suitable for application in different situations and conditions that may
be encountered on a pipeline right-of-way and elsewhere. Field hardness testing is not a “one
size fits all” methodology where a single hardness testing methodology is suitable for application
in all situations that can be encountered.

In order to establish that hardness testing is a feasible method and optimize the test methods for
each application, the process begins with data collection and pre-assessment to determine if
hardness testing can be effectively applied to the pipe population being considered. It then
continues with hardness tester selection, pipe sampling methods, testing criteria operation, and
correlations necessary to establish a technically defensible pipe yield strength estimate. Proven
statistical methods are incorporated throughout the process from pipe sample size selection
through hardness correlation with yield strength. Since a process is described, it is strongly
recommended that the user should complete all of the steps as described to assure that a credible
yield strength estimate is obtained.

Figure 1 is a flow diagram the outlines the process steps with the applicable Section(s) of this
Guide also referenced in each. References to supplementary information contained in relevant
Appendices are also included in Figure 1 that contains additional guidance applicable to the
indicated process step.

1 Only the estimated pipe yield strength can be determined by this process. The grade is established by the pipe
tensile testing and mill hydrostatic test.
1
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Figure 1. Hardness Testing Process Flow Diagram

The process described in this guide has been designed to be used in conjunction with a report on
a previous project conducted by Battelle(1) in 1999 that established a statistically based
relationship between yield strength and the hardness of steel pipe. The results of this project led
2
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