1、STP-PT-049INVESTIGATION OF TEMPERATURE DERATING FACTORS FOR HIGH-STRENGTH LINE PIPESTP-PT-049 INVESTIGATION OF TEMPERATURE DERATING FACTORS FOR HIGH-STRENGTH LINE PIPE Prepared by: Donovan A. Richie and M. J. Rosenfeld, PE Kiefner and Associates, Inc. Date of Issuance: September 28, 2012 This report
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9、LC Three Park Avenue, New York, NY 10016-5990 ISBN No. 978-0-7918-3426-8 Copyright 2012 by ASME Standards Technology, LLC All Rights Reserved Investigation of Temperature Derating Factors for High-Strength Line Pipe STP-PT-049 iii TABLE OF CONTENTS Foreword v Executive Summary vi 1 BACKGROUND, APPRO
10、ACH, AND FINDINGS 1 1.1 Introduction . 1 1.2 Background . 2 1.3 Technical Approach 3 1.4 Findings . 3 2 A REVIEW OF THE AVAILABLE DATA . 5 2.1 Introduction . 5 2.2 Study by Benfell, Morris and Barsanti 5 2.3 Study by Bredenbruch, Gehrmann, Schmidt, and Trger 8 2.4 Study by Gray 12 2.5 Other pipeline
11、 design standards 14 2.5.1 CSA Z662 . 14 2.5.2 AS 2885 15 2.5.3 ISO 13623 15 2.5.4 DNV-OS-F101 . 15 3 AN OVERVIEW OF THE STRENGTHENING MECHANISMS AND ROLLING PROCESSES OF HSLA STEELS FOR MODERN LINE PIPE 17 3.1 Introduction . 17 3.2 Strengthening Mechanisms . 17 3.3 Rolling Processes 17 4 AN ASSESSM
12、ENT OF THE AVAILABLE DATA 19 4.1 Introduction . 19 4.2 Variables Related to Pipe Manufacturing 19 4.3 Variables Related to the Tensile Test Procedure . 23 5 IMPLICATIONS OF THE AVAILABLE DATA FOR ASME CODES 25 5.1 Other ASME codes affected 25 5.2 Possible B31.8 Code Committee Response . 26 6 RECOMME
13、NDATIONS FOR ADDITIONAL TENSILE TESTING 28 References 30 Acknowledgements 31 Abbreviations, Acronyms and Variables 32 LIST OF TABLES Table 1Effect of Elevated Temperature on the Microstructure in X60 Line Pipe 8 Table 2Plate Rolling Processes and Microstructures in X52-X120 Line Pipe . 20 Table 3Pip
14、e Forming and Seam Welding Methods for X52-X120 Line Pipe 20 STP-PT-049 Investigation of Temperature Derating Factors for High-Strength Line Pipe iv Table 4Alloying Approaches and Microstructures in X52-X120 Line Pipe . 21 Table 5Variables Related to Pipe Manufacturing in Each Study 22 Table 6Variab
15、les Related to the Tensile Test Procedures in Each Study . 24 Table 7Pipe Manufacturing Variables to Include in a Future Test Program 28 Table 8Tensile Test Procedures for a Future Test Program 28 LIST OF FIGURES Figure 1Transverse Yield Strength in X52-X70 Line Pipe as a Function of Temperature . 1
16、 Figure 2Longitudinal Yield Strength in X60-X70 Line Pipe Steel . 6 Figure 3Derating Factors for Transverse Yield Strength in X52-X70 Line Pipe Steel 7 Figure 4Derating Factors for Longitudinal Yield Strength of X60-X70 Line Pipe Steels 7 Figure 5Longitudinal Yield Strength of X70 Line Pipe 9 Figure
17、 6Longitudinal Yield Strength of X60 Line Pipe 9 Figure 7Longitudinal Yield Strength of X65 Line Pipe 10 Figure 8Derating Factors for Longitudinal Yield Strength of X70 Line Pipe 11 Figure 9Derating Factors for Longitudinal Yield Strength of X60 Line Pipe 11 Figure 10Derating Factors for Longitudina
18、l Yield Strength of X65 Line Pipe 12 Figure 11Yield Strength of ASTM A841, Grade F Plate Steel . 13 Figure 12Derating factors of ASTM A841, Grade F Plate Steel 14 Investigation of Temperature Derating Factors for High-Strength Line Pipe STP-PT-049 v FOREWORD This report reviews the ASME derating fac
19、tors, identifies the range of line pipe steel grades that may be affected and the potential impacts to ASME pipeline and piping design standards, and makes recommendations for further study or experimental investigation as necessary. Established in 1880, the American Society of Mechanical Engineers
20、(ASME) is a professional not-for-profit organization with more than 127,000 members promoting the art, science and practice of mechanical and multidisciplinary engineering and allied sciences. ASME develops codes and standards that enhance public safety, and provides lifelong learning and technical
21、exchange opportunities benefiting the engineering and technology community. Visit www.asme.org for more information. The ASME Standards Technology, LLC (ASME ST-LLC) is a not-for-profit Limited Liability Company, with ASME as the sole member, formed in 2004 to carry out work related to newly commerc
22、ialized technology. The ASME ST-LLC mission includes meeting the needs of industry and government by providing new standards-related products and services, which advance the application of emerging and newly commercialized science and technology and providing the research and technology development
23、needed to establish and maintain the technical relevance of codes and standards. Visit www.stllc.asme.org for more information. STP-PT-049 Investigation of Temperature Derating Factors for High-Strength Line Pipe vi EXECUTIVE SUMMARY The current ASME B31.8 code gives no derating of line pipe steels
24、for temperatures below 250F. For pipeline steels in the Grade X60-X70 range, data show that a reduction of the yield strength may be exhibited at temperatures below 250F in some cases. Some pipeline design standards developed for other countries (e.g., Norway, Netherlands, and Australia) already app
25、ly derating factors at temperatures well below 250F. Thus, the ASME derating factors appeared to be in need of review. This report reviews the available information, identifies the range of line pipe steel grades that may be affected, identifies the potential impacts to ASME pipeline and piping desi
26、gn standards, and makes recommendations for further study or experimental investigation as necessary. A review of data suggests that (a) there is a high likelihood of some decrease in the actual yield strength of high-strength low-alloy grades of line pipe in current usage at temperatures between 75
27、F and 250F; (b) against a limited set of data the current Code derating factors appear to be adequate, provided room temperature yield strength is at least 5% above specified minimum levels; (c) there are insufficient data to recommend a change in the Code at this time; (d) there are insufficient da
28、ta to determine whether the present Code derating factor is adequate for all variables of alloy design and steel processing used with current grades of high strength pipe; and (e) further investigation by testing a broader sample base is needed to adequately address these issues. Investigation of Te
29、mperature Derating Factors for High-Strength Line Pipe STP-PT-049 1 1 BACKGROUND, APPROACH, AND FINDINGS 1.1 Introduction The current ASME B31.8 standard (“the Code”) requires no derating of line pipe steels for temperatures below 250F. For pipeline steels in the Grade X60-X70 range, data show that
30、a reduction of the yield strength may be exhibited at temperatures below 250 F in some cases. For example, Figure 1 presents a reduction in measured yield strength with increasing temperature above 50C (122F) in high strength line pipe observed by one manufacturer. Some pipeline design standards dev
31、eloped for other countries (e.g., Norway, Netherlands, and Australia) already apply derating factors at temperatures well below 250F. Thus, the ASME derating factors are in need of review. Figure 1Transverse Yield Strength in X52-X70 Line Pipe as a Function of Temperature 1 The goal of this project
32、is to develop an understanding of available information, identify the range of line pipe steel grades that may be affected, identify the potential impacts to ASME pipeline and piping design standards, and make recommendations for further study or experimental investigation as necessary. STP-PT-049 I
33、nvestigation of Temperature Derating Factors for High-Strength Line Pipe 2 1.2 Background Design of pipe for internal pressure in accordance with ASME B31.8 is based on SMYS via the Steel Pipe Design Formula given in Paragraph 841.1.1 as: Equation 1Steel Pipe Design Formula The variables are as defi
34、ned under Abbreviations, Acronyms and Variables at the end of this report. Of concern is the temperature derating factor, T, which is specified in Table 841.1.8-1. Factor T has a value of 1.000 for temperatures of 250 F or less, and decreases linearly to a value of 0.867 as temperature increases to
35、450 F as listed below: Temperature, F (C) Factor T 250 (121) or less 1.000 300 (149) 0.967 350 (177) 0.933 400 (204) 0.900 450 (232) 0.867 The temperatures in C units are rounded by ASME to the nearest whole degree. Interpolation of the derating factor for intermediate temperatures is permitted. The
36、 factor T first appeared in the pressure design formula in the 1955 Edition of ASA B31.1.8. The values for T were the same as that which appears in the Code today. The T factor has its origins in the first edition of B31.8 in 1952 as a separate book publication of Section 8 of the ASA B31.1 Code for
37、 Pressure Piping. (Prior to this edition, different services e.g. power piping, refineries, oil pipelines, and gas pipelines were covered by their own chapters within a B31.1 published as a single volume.) The T factor was not in the 1952 pressure design formula however the allowable stresses for de
38、sign were listed for all pipe grades in a table contained in section 827. The allowable stress for temperatures up to 100 F was 60% of the SMYS at room temperature, and at a temperature of 450 F was 86.7% of the allowable stress for temperatures below 100 F. A footnote instructed the user to linearl
39、y interpolate to determine the allowable stress at service temperatures between 100 F and 450 F. It is noted that in going from the 1952 to the 1955 editions of B31.8, the room temperature allowable stress was extended from 100 F to 250 F. These derating factors were almost certainly derived from te
40、nsile tests at elevated temperatures that had been performed on carbon steel pipe samples to support the allowable stresses specified in other service chapters of the ASA B31.1 Code (e.g. for refineries and power plants). The allowable stresses for various grades of carbon steel pipe in the 1942 ASA
41、 B31.1 (in which all services appear together in one volume) for power plant piping shows that the room temperature design stress was maintained up to a temperature of 150 F, but at a temperature of 450 F the allowable design stress was between 85% and 88% of the allowable stress for 150 F. This bra
42、ckets the 86.7% factor adopted by B31.8. Also, the allowable stresses at 250 F were only 4% to 5% below the allowable stress for 150 F. This may have provided the justification for extending the room temperature rating all the way to 250 F in B31.8. The listed grades of carbon steel pipe were typica
43、lly A106, A53, or API 5L Grades A, B, and C, or similar, having yield strengths between 30 ksi and 45 ksi. It is not uncommon for these grades of material to exhibit room temperature yield strength considerably greater than specified minimum properties, even in pipe contemporary for that time. A 4%
44、to 5% decrease in actual strength at a temperature of 250 F relative to that at 100 F or 150 F might have been considered tolerable. Investigation of Temperature Derating Factors for High-Strength Line Pipe STP-PT-049 3 The present derating factor appears to have its origins in an early Code era, an
45、d is almost certainly associated with the observed characteristics of hot-finished plain carbon steel or C-Mn steel pipe of low to intermediate strength. These early pipe varieties are sufficiently different from modern HSLA pipe in terms of strengthening mechanisms that there can be some doubt that
46、 factors derived from them are applicable to the more modern grades. 1.3 Technical Approach The project was divided into three phases. Phase 1 entailed collecting and evaluating available mechanical properties data for line pipe steel grades X60 through X100 at temperatures ranging from 100 F to 500
47、 F. This range of pipe grades covers most modern line pipe steels that are in use today. We have excluded X52 and lower-strength grades for two reasons. One is that in order to make the low to moderate strength grades of pipe including X52, it is unnecessary to resort to the microalloy additions and
48、 control-rolled thermomechanical processing of the cast slab that is typically used to manufacture grades X60 and greater. Secondly, X42 and X52 pipe often is manufactured concurrently with materials identified as Grade B on which the temperature derating factors are thought to be based and for whic
49、h the current factors are thought to be appropriate. It was recommended that the temperature range for investigation be extended to 500 F, which is beyond the maximum temperature of 450 F within the scope of B31.8. This was intended to encompass temperatures at which fusion-bonded epoxy (FBE) coatings are applied to line pipe. Mechanical properties may (or may not) change after exposure to the temperatures the pipe experiences when FBE coatings are applied, as a
