Effective December 6, 2006, this report has been made publicly available in accordance with Section 734.3(b)(3) and published in accordance with Section 734.7 of the U.S Export Administration Regulations As a result of this publication, this report is subject to only copyright protection and does not require any license agreement from EPRI This notice supersedes the export control restrictions and any proprietary licensed material notices embedded in the document prior to publication RRAC – Guidelines for Repair of Socket Welds Chamfered Socket Joint Configuration for Enhanced High Cycle Fatigue Resistance 1012060 RRAC – Guidelines for Repair of Socket Welds Chamfered Socket Joint Configuration for Enhanced High Cycle Fatigue Resistance 1012060 Technical Update, November 2005 EPRI Project Manager G Frederick ELECTRIC POWER RESEARCH INSTITUTE 3420 Hillview Avenue, Palo Alto, California 94304-1395 ▪ PO Box 10412, Palo Alto, California 94303-0813 ▪ USA 800.313.3774 ▪ 650.855.2121 ▪ askepri@epri.com ▪ www.epri.com DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITIES THIS DOCUMENT WAS PREPARED BY THE ORGANIZATION(S) NAMED BELOW AS AN ACCOUNT OF WORK SPONSORED OR COSPONSORED BY THE ELECTRIC POWER RESEARCH INSTITUTE, INC (EPRI) NEITHER EPRI, ANY MEMBER OF EPRI, ANY COSPONSOR, THE ORGANIZATION(S) BELOW, NOR ANY PERSON ACTING ON BEHALF OF ANY OF THEM: (A) MAKES ANY WARRANTY OR REPRESENTATION WHATSOEVER, EXPRESS OR IMPLIED, (I) WITH RESPECT TO THE USE OF ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS DOCUMENT, INCLUDING MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, OR (II) THAT SUCH USE DOES NOT INFRINGE ON OR INTERFERE WITH PRIVATELY OWNED RIGHTS, INCLUDING ANY PARTY'S INTELLECTUAL PROPERTY, OR (III) THAT THIS DOCUMENT IS SUITABLE TO ANY PARTICULAR USER'S CIRCUMSTANCE; OR (B) ASSUMES RESPONSIBILITY FOR ANY DAMAGES OR OTHER LIABILITY WHATSOEVER (INCLUDING ANY CONSEQUENTIAL DAMAGES, EVEN IF EPRI OR ANY EPRI REPRESENTATIVE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES) RESULTING FROM YOUR SELECTION OR USE OF THIS DOCUMENT OR ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS DOCUMENT ORGANIZATION(S) THAT PREPARED THIS DOCUMENT Electric Power Research Institute (EPRI) Pacific Gas and Electric This is an EPRI Technical Update report A Technical Update report is intended as an informal report of continuing research, a meeting, or a topical study It is not a final EPRI technical report NOTE For further information about EPRI, call the EPRI Customer Assistance Center at 800.313.3774 or e-mail askepri@epri.com Electric Power Research Institute and EPRI are registered service marks of the Electric Power Research Institute, Inc Copyright © 2005 Electric Power Research Institute, Inc All rights reserved CITATIONS This document was prepared by Electric Power Research Institute (EPRI) Repair and Replacement Application Center (RRAC) 1300 W.T Harris Blvd Charlotte, NC 28262 Principal Investigator G Frederick Pacific Gas and Electric 3400 Crow Canyon Road San Ramon, CA 94583 Principal Investigator J Schletz This document describes research sponsored by EPRI This publication is a corporate document that should be cited in the literature in the following manner: RRAC – Guidelines for Repair of Socket Welds, Chamfered Socket Joint Configuration for Enhanced High Cycle Fatigue Resistance EPRI, Palo Alto, CA: 2005 1012060 iii ABSTRACT Socket weld failures are typically the result high cycle fatigue amplified by substandard quality of the root weld The root weld is required to assure good fusion between the pipe section and the fitting, but often associated with root anomalies that have the appearance of cracks In an effort to improve the root quality and eliminate crack initiation sites, a chamfered fitting was fabricated and tested under typical high cycle fatigue conditions The chamfered fitting also offers an increase in the effective weld throat of a standard socket weld (fillet weld) A test matrix was established to evaluate the root weld quality achieved with various welding processes and joint configurations In addition to the weldability tests, Shaker table tests were conducted to evaluate the high cycle fatigue resistance of the chamfered configurations in relation to standard socket welded configurations Chamfered socket welds were fabricated with specific joint geometries including J-groove and vgroove configurations The joint configurations were achieved by chamfering the socket welding fitting with no modification to the pipe section The mockups were evaluated to establish weldability of the modified joint configuration with common welding processes used for socket weld applications Welding was limited to SMAW and manual GTAW processes The weld specimens were metallographically evaluated to verify the condition of the root weld Each configuration was cross sectioned at various radial gap dimensions ranging from to 100% to evaluate welding processes and configurations The weldability was based on accessibility to the root with the welding process, slag entrapment, and arc stability and weld fusion between the pipe section and the socket-welding fitting Socket weld mockups were fabricated with optimal chamfer configurations for each welding process for Shaker table tests Preliminary results have shown the chamfer can enhance the fatigue life for standard Code socket welds Weldability test have provided guidance for welding process selection and chamfer geometries that are favorable for improved root welds v CONTENTS INTRODUCTION 1-1 1.1 Test Matrix 1-1 WELDABILITY EVALUATIONS 2-1 2.1 Modified Socket Weld Joint Configurations 2-1 2.2 Observation on Weldability 2-5 METALLOGRAPHIC EVALUATION 3-1 3.1 Weld Cross Section Evaluations 3-1 3.1.1 J-groove Chamfer Configurations 3-1 3.1.2 Beveled Chamfer Configurations 3-3 3.2 General Observations 3-6 HIGH CYCLE FATIGUE EVALUATIONS 4-1 vii Table 3-1 Evaluation criteria for J-groove chamfer prep for 2-in SS and CS Socket-Welding Fittings Chamfer Configuration 3/16 in radius by 3/16in deep chamfer 3/16 in radius by 1/8-in deep chamfer Material Location Voids at root Acceptable Chamfer fill ratio Acceptable Penetration into pipe and fitting SS radial gap of of of SS 50% radial gap of of of SS 100% radial gap of of 3 of CS radial gap of 4 of of CS 50% radial gap of 8 of of CS 100% radial gap of 4 of of SS radial gap of 4 of 4 of SS 50% radial gap of 8 of 8 of SS 100% radial gap of 3 of 3 of CS radial gap of 4 of of CS 50% radial gap of 8 of of CS 100% radial gap of 4 of 4 of 3-2 Figure 3-1 3/16 in radius chamfers at 50% radial gap with acceptable root welds 1/8-in deep (left) and 3/16in deep chamfer (right) Unacceptable fill ratio with 3/16 in deep chamfer Figure 3-2 3/16 in radius chamfer with voids at the root of 1/8 in depth chamfer (left) and lack of penetration into the fitting of a 3/16 in depth chamfer (right) Both at zero radial gap 3.1.2 Beveled Chamfer Configurations A 45-degree and 60-degree bevel at 1/8 in and 3/16 in depths (Figure 2-1 and 2-3) were utilized to evaluate the SMAW process An acceptable root quality was achievable with the beveled chamfer configuration, although results varied depending on the depth and bevel angle Figure 3-3 shows an acceptable root quality and penetration into the side wall of socket welding fittings with a 45-degree beveled chamfer 3/16 in deep The same chamfer configuration is shown in Figure 3-4, showing various degree of lack of fusion at the root and chamfer face on the fitting In most cases the root quality improved with the shallower chamfer dimensions and larger bevel angle (1/8 in and 60-degrees) although, as seen in Figure 3-5, lack of fusion is still prevalent 3-3 Table 3-2, list observations from cross section evaluations at various radial gaps and chamfer depths and angles for CS and SS Table 3-2 Evaluation criteria for beveled chamfer prep for 2-in SS Socket-Welding Fittings Chamfer Configuration 45-degree bevel by 3/16 in deep chamfer 45-degree bevel by 1/8 in deep chamfer 60-degree bevel by 1/8 in deep chamfer Material Location Voids at root Acceptable Chamfer fill ratio Acceptable Penetration into pipe and fitting SS radial gap of 4 of 4 of SS 50% radial gap of 8 of 8 of SS 100% radial gap of 4 of 4 of CS radial gap of 4 of of CS 50% radial gap of 8 of of CS 100% radial gap of 4 of 4 of SS radial gap of 2 of 2 of SS 50% radial gap of 4 of 4 of SS 100% radial gap of 2 of 2 of CS radial gap of 4 of 4 of CS 50% radial gap of 8 of of CS 100% radial gap of 4 of 4 of SS radial gap of 4 of 4 of SS 50% radial gap of of 8 of SS 100% radial gap of of 4 of CS radial gap of 4 of 4 of CS 50% radial gap of 8 of of CS 100% radial gap of 4 of 4 of 3-4 Figure 3-3 45-degree chamfers at 100% (left) and 50% (right) radial gap with acceptable root welds Both are 3/16 in deep chamfers Figure 3-4 45-degree chamfers at radial gap with minor lack of fusion (left) and major lack of fusion (right) at the root Both are 3/16 in deep chamfers 3-5 Figure 3-5 60-degree (left) and 45-degree (right) chamfers at 100% radial gap with lack of fusion at the root Both are 1/8 in deep chamfers 3.2 General Observations In all cases the weld profile, of the root weld performed with SMAW process with a chamfer, exceeded the effective throat of the standard (non –chamfered) socket weld configuration Although, lack of fusion at the root or side wall of pipe was observed for a majority of the chamfered weld trials Accessibility into the weld cavity produced by the chamfer was considered to be unacceptable for the SMAW process using the 3/32-in electrode diameter Shallower chamfer and larger bevel angle or radius provided some improvement to weldability, but was not sufficient for achieving an optimal root weld with no voids Weld profile at 100% radial gap, which opened up the chamfer geometry by 050 in., also showed some improvement in the weld root, when directly compared to zero radial gap The weld defects found in the chamfered fittings with SMAW were considered, in most cases, to be typical of root conditions found with standard socket weld configurations Variations in the weld process such as smaller diameter electrode (i.e 1/16-in diameter) may improve the ability of the SMAW process to access the root, although would require multiple weld passes to completely fill the chamfer cavity A single pass to fill the chamfer was considered best practice to eliminate slag entrapment In addition, weld voids or slag entrapment was observed in subsequent weld SMAW passes unrelated to the chamfer root weld These weld defect are not desirable but were considered to be typical for SMAW process of small diameter socket welds 3-6 HIGH CYCLE FATIGUE EVALUATIONS Socket weld specimens were fabricated for Shaker Table Testing to compare standard socket welds with the chamfered configurations selected for testing The test specimens were configured to be consistent with past high cycle fatigue tests conducted by the EPRI RRAC Table 4-1 and 4-2 list the test specimens fabricated with the GTAW process and Table 4-3 and 44 list the test specimens fabricated with the SMAW process The chamfer configuration for modified test specimens consisted of a 45-degree bevel approximately 3/16 in deep The pipe section was fully inserted into the fittings with a 1/16 in gap prior to welding Observations The resulting cycles to failure were plotted to compare socket weld configurations with and without a chamfer and 2:1 weld configurations The plots are separated by material (carbon steel and stainless steel) and welding process (GTAW and SMAW) The applied stress amplitude and resulting cycles to failure are listed in Tables 4-1 through 4-4 The GTAW process is plotted in Figure 4-1 for stainless steel and Figure 4-2 for carbon steel The SMAW process is plotted in Figure 4-3 for stainless steel and Figure 4-4 for carbon steel For comparison the Higuchi trend curve for 2-in socket welds are also shown on the plots for the specific materials From the current results the following observations were made: • The 2-in stainless steel socket welds with chamfers welded with the GTAW process, show a significant improvement when directly compared to the standard Code (1:1) welds • Chamfered stainless steel GTAW socket welds with 2:1 profile were consistent with standard 2:1 welds without a chamfer • Chamfered carbon steel GTAW socket welds with 1:1 profile were consistent with standard 1:1 welds without a chamfer • The 2-in carbon steel and stainless steel socket welds with chamfers welded with the SMAW process, were found to be consistent with the standard Code (1:1) welds Additional fatigue specimens are in progress and will be plotted with the current data at the completion of the tests 4-1 Table 4-1 Shaker Table Evaluations for 2-in Stainless Steel Socket welds with GTAW process Specimen Weld Profile Fitting Prep Cycles (Nf) Sa Stress (ksi) Failure Location G-01-2SS-S to Standard 7.04E+05 11.540 Root G-02-2SS-S to Standard 4.77E+06 6.386 Root G-03-2SS-S to Standard 1.57E+06 10.140 Root G-04-2SS-S to Standard 1.19E+07 8.748 Root G-05-2SS-S to Standard 3.17E+05 15.179 Root G-06-2SS-S to Standard 5.54E+05 13.580 Root G-07-2SS-C to chamfer 45-deg, 3/16-in 8.44E+05 20.941 Root in Fitting G-08-2SS-C to chamfer 45-deg, 3/16-in 6.90E+06 19.051 Root G-09-2SS-C to chamfer 45-deg, 3/16-in 1.00E+07 16.819 Runout G-10-2SS-C to chamfer 45-deg, 3/16-in 7.90E+05 23.612 Root G-16-2SS-C to chamfer 45-deg, 3/16-in 7.16E+06 10.314 Root G-17-2SS-C to chamfer 45-deg, 3/16-in 7.84E+05 11.242 Root G-18-2SS-C to chamfer 45-deg, 3/16-in 8.73E+05 13.605 Root G-19-2SS-S to Standard 4.81E+06 8.652 Root G-20-2SS-S to Standard 2.62E+06 8.286 Root G-25-2SS-C to chamfer 45-deg, 3/16-in G-26-2SS-C to chamfer 45-deg, 3/16-in G-27-2SS-C to chamfer 45-deg, 3/16-in G-44-2SS-MI to Standard w/0 gap Not Completed 4-2 Table 4-2 Shaker Table Evaluations for 2-in Carbon Steel Socket welds with GTAW process Specimen Weld Profile Fitting Prep Cycles (Nf) Sa Stress (ksi) Failure Location G-11-2CS-C to chamfer 45-deg, 3/16-in 1.10E+06 11.419 Root G-12-2CS-C to chamfer 45-deg, 3/16-in 1.13E+06 12.802 Root G-13-2CS-C to chamfer 45-deg, 3/16-in 1.01E+06 13.540 Root G-14-2CS-S to Standard 6.55E+06 10.290 Root G-15-2CS-S to Standard 6.13E+06 9.079 Root G-28-2CS-C to chamfer 45-deg, 3/16-in G-29-2CS-C to chamfer 45-deg, 3/16-in G-30-2CS-C to chamfer 45-deg, 3/16-in G-37-2CS-MI to Standard w/0 gap Not Completed Table 4-3 Shaker Table Evaluations for 2-in Stainless Steel Socket welds with SMAW process Specimen Weld Profile Fitting Prep Cycles (Nf) Sa Stress (ksi) Failure Location S-10-SS-S to Standard 1.34E+07 9.665 Runout S-11-SS-S to Standard 3.11E+06 9.958 Root S-12-SS-S to Standard 5.86E+05 12.196 Root S-13-SS-S to Standard 2.13E+06 11.512 Root S-14-SS-S to chamfer 45-deg, 3/16-in 3.25E+06 8.623 Root S-15-SS-C to chamfer 45-deg, 3/16-in 1.27E+06 8.877 Root S-16-SS-C to Standard 1.53E+06 8.158 Root S-17-SS-C to chamfer 45-deg, 3/16-in 1.11E+06 14.391 Root S-18-SS-C to chamfer 45-deg, 3/16-in 3.44E+05 14.150 Root 4-3 Table 4-4 Shaker Table Evaluations for 2-in Carbon Steel Socket welds with SMAW process Specimen Weld Profile Fitting Prep Cycles (Nf) Sa Stress (ksi) Failure Location S-01-CS-S to Standard 3.10E+06 11.018 Root S-02-CS-C to chamfer 45-deg, 3/16-in 1.73E+06 7.911 Root S-03-CS-S to Standard 2.57E+06 12.042 Root S-04-CS-S to Standard 1.05E+07 6.953 Runout S-05-CS-S to Standard 2.71E+06 10.122 Root S-06-CS-C to chamfer 45-deg, 3/16-in 1.05E+07 7.006 Runout S-07-CS-C to Standard 5.17E+06 8.134 Root S-08-CS-C to chamfer 45-deg, 3/16-in 2.71E+06 11.136 Root S-09-CS-C to chamfer 45-deg, 3/16-in 1.16E+06 14.293 Root 4-4 GTAW 2-in Stainless Steel 100 Sa(ksi) 2-in Schedule 80 Stainless Steel Solid Diamond - Standard 1:1 GTAW Welds Hollow Diamond - 1:1 with 45 by 3/16-in chamfer Solid Square - Standard 2:1 ratio welds Hollow Square - 2:1 and chamfer 10 Higuchi -SS (50-mm) G-01-2SS-S G-02-2SS-S G-03-2SS-S G-04-2SS-S G-05-2SS-S G-06-2SS-S G-07-2SS-C G-08-2SS-C G-09-2SS-C G-10-2SS-C G-16-2SS-C G-17-2SS-C G-18-2SS-C G-19-2SS-S G-20-2SS-S 1.00E+05 1.00E+06 1.00E+07 N(Cycles) Figure 4-1 HCF Test Results for Stainless Steel GTAW Socket Welds 4-5 1.00E+08 GTAW 2-in Carbon Steel 100 Sa(ksi) 2-in Schedule 80 Carbon Steel Solid Diamond - Standard 2:1 Weld Hollow Diamond - 2:1 with 45 by 3/16-in chamfer 10 Higuchi - CS (50-mm) G-11-2CS-C G-12-2CS-C G-13-2CS-C G-14-2CS-S G-15-2CS-S 1.00E+05 1.00E+06 1.00E+07 N(Cycles) Figure 4-2 HCF Test Results for Carbon Steel GTAW Welds 4-6 1.00E+08 SMAW 2-in Stainless Steel 100 Sa(ksi) 2-in Schedule 80 Stainless Steel Solid Diamond - Standard 1:1 Weld Hollow Diamond - 45 by 3/16-in chamfer 10 Higuchi - SS (50-mm) S-10-SS-S S-11-SS-S S-12-SS-S S-13-SS-S S-14-SS-C S-15-SS-C S-16-SS-S S-17-SS-C S-18-SS-C 1.00E+05 1.00E+06 1.00E+07 N(Cycles) Figure 4-3 HCF Test Results for Stainless Steel SMAW Socket Welds 4-7 1.00E+08 SMAW 2-in Carbon Steel 100 Sa(ksi) 2-in Schedule 80 Carbon Steel Solid Diamond - Standard 1:1 Weld Hollow Diamond - 45 by 3/16-in chamfer 10 Higuchi - CS (50-mm) S-01-CS-S S-02-CS-C S-03-CS-S S-04-CS-S S-05-CS-S S-06-CS-C S-07-CS-S S-08-CS-C S-09-CS-C 1.00E+05 1.00E+06 1.00E+07 N(Cycles) Figure 4-4 HCF Test Results for Carbon Steel SMAW Socket Welds 4-8 1.00E+08 Export Control Restrictions The Electric Power Research Institute (EPRI) Access to and use of EPRI Intellectual Property is granted with the specific understanding and requirement that responsibility for ensuring full compliance with all applicable U.S and foreign export laws and regulations is being undertaken by you and your company This includes an obligation to ensure that any individual receiving access hereunder who is not a U.S citizen or permanent U.S resident is permitted access under applicable U.S and foreign export laws and regulations In the event you are uncertain whether you or your 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States of America ELECTRIC POWER RESEARCH INSTITUTE 3420 Hillview Avenue, Palo Alto, California 94304-1395 • PO Box 10412, Palo Alto, California 94303-0813 • USA 800.313.3774 • 650.855.2121 • askepri@epri.com • www.epri.com 1012060 ... radial gap of of of SS 50% radial gap of of of SS 100% radial gap of of 3 of CS radial gap of 4 of of CS 50% radial gap of 8 of of CS 100% radial gap of 4 of of SS radial gap of 4 of 4 of SS 50%... gap of 4 of 4 of SS 50% radial gap of 8 of 8 of SS 100% radial gap of 4 of 4 of CS radial gap of 4 of of CS 50% radial gap of 8 of of CS 100% radial gap of 4 of 4 of SS radial gap of 2 of 2 of. .. gap of 4 of 4 of SS 100% radial gap of 2 of 2 of CS radial gap of 4 of 4 of CS 50% radial gap of 8 of of CS 100% radial gap of 4 of 4 of SS radial gap of 4 of 4 of SS 50% radial gap of of 8 of