PIPE WELDING PROCEDURES Second Edition by Hoobasar Rampaul Industrial Press New York, New York LibraryofCongress Cataloging-in-Publication Data Rampaul, Hoobasar. Pipe weldingproceduresI byHoobasarRampaul.··2nd ed. p. cm. ISBN 0·8311·3141·1 1. Pipe--Weldinge. I.Title. TS280.R272002 62I.8'672-·dc2I 2002033938 Industrial PressInc. 200MadisonAvenue NewYork, NY 10016·4078 Second Edition Pipe Welding Procedures Copyright©2003.Printed in the United States ofAmerica. All rightsreserved. This bookorpartsthereofmay notbereproduced, stored in a retrieval system,ortransmittedin any form without the permission ofthepublishers. 2345678910 Contents Forward iv Preface v 1. Introduction 1 2. Essentials ofShielded Metal-Arc Welding Technology 10 3. Heat Inputand Distribution 14 4. Reperation ofthe Pipe Joint 21 5. Uphill Welding the Root Bead on Heavy-WallPipe (5GPosition) 31 6. Welding the Rood Bead by the Gas TungstenArc Welding Process 57 7. The Intermediate and Cover Passes 81 8. WeldingThin-Wall Pipe 100 9. Horizontal Pipe Welding (20) 136 10. Welding Complicated Pipe Joints 158 11. Introduction to Welding Metallurgy 170 12. Distortion in Pipe Welding 198 13. Pipe Welding Defects 207 14. Fitting-UP Pipe 222 15. Qualification ofthe Welding Procedure & the Welder 237 I6.General Welding Safety 243 Index 247 iii Foreward from First Edition Today, most pipe is joined by welding, but this was not always true. for until about 35 years ago pipe was joined by screw threads or by bolted flanged joints. Welding, now considered the best method for connecting pipe, is used even in the most demanding high-pressure and high-temperature service. Much of the credit for this progress must be given to the weld ing industry; however, credit must also be given to the many welders who. through trial and conscientious effort, developed the welding procedures which consistently produce reliable weld joints. A great many welders contributed their efforts toward this end and it is unfortunate that their names have not been re corded. One person who has contributed greatly to the improvement of general pipe welding procedures is Hoobasar Rampaul. He has worked as a pipe welder in refinery construction and maintenance, as a welding inspector, and as a teacher at the Hobart School of Welding Technology where I have been closely associated with him and have often witnessed his outstanding skill as a pipe welder. His success is due to his fine technical knowledge of weld ing as well as to his outstanding manipulative skill. By blending these he has been able to develop and qualify procedures that con sistently result in pipeweldsofthe highest quality. In order to make this skill available to many more welders I have encouraged Mr. Rampaul to write this book. It is a major contribution to the art and technology of pipe welding and I highly recommend it to all those craftsmen who have an interest in thisfield. HOWARD B. CARY Preface Industries, such as power plants, oil refineries, chemical plants, food processing plants, and those that operate cross-country pipe lines, have created a great demand for welders who are capable ofproducing high-quality pipe welds consistently. This book is intended to help meet this need by assisting in the training of pipe welders in trade schools and to help those welders now working at the trade to enlarge their knowledge and improve theirskills. The chapters that treat the various welding procedures describe in detail the correct welding techniques that should be used as the weld progresses around the pipe joint. Possible mistakes are pointed out, and the reasons for using the recommended proce dures are given. For these reasons, the welder who uses this book on the job, or while training, will find it to be a very useful refer ence aid. In addition to the manipulative procedures, a welder should acquire as much technical and theoretical information related to welding as possible. This knowledge is most helpful in learning the craft of pipe welding and in progressing upward on the job. Therefore, there are informative chapters on welding metallurgy, on recognizing and correcting welding defects, on distortion in pipe joints, on fitting-up pipe joints, and on welding complicated pipejoints. The author has gained much valuable experience as a pipe welder in various industries, not only in the United States but in the Caribbean; and he has been associated with the Hobart Broth ers Company as an instructor in pipe welding at the Hobart School of Welding Technology. He would like to thank Mr. Howard B. Cary, Vice President, Hobart Brothers Company, for providing the inspiration to write this book and for his encouragement in its preparation. The author would also like to take this opportunity to acknowl edge, among many others, the help given in the preparation of this book by James Hannahs, Wade'Troyer, Rudy Mohler, Denny Deweese, Nan Kidder, Helen Wilt, Marilyn Tarcea, Judy Parrish, and Lana Shelkon. He would also like to express appreciation to the American Welding Society and the following firms for their assistance in providing illustrations: The Hobart Brothers Com pany, the Tube Turns Division of the Chemetron Corporation, and the H & M Pipe BevelingCompany. V Finally, the author would like to gratefully acknowledge the help and advice given by Karl Hans Moltrecht, Technical and Vocational Editor. Industrial Press Inc., especially for his con tribution in thepreparation ofChapters 11 and 12. Acknowledgment by the Publisher Industrial Press wishes to express its sincere appreciation to Robert O'eon for his invaluable assistance in the preparation ofthe second editionofthis book. vi 1 CHAPTER Introduction Only high quality pipe welds are acceptable in modern industry; for thefailure ofa pipe weld notonly can disrupt theoperationofa plant, it can be the cause ofa serious accident with the possibleloss of life and property. For this reason, a pipe welder must be a thoroughlyqualified person in hiscraft. The objective of this book is to describe the techniques that will result in a successful pipe weld, which must besoundthroughout as well aslook good. The pipe welder will be provided with the related information necessary for him to do his job correctly. To be a successful pipe welder and achieve high quality pipe welds, such as shown in Fig. 1-1, requires practice in welding pipe. It cannot be Fig. I-I. Exampleofa high quality pipeweld. learned by reading a book alone; however, if incorrect techniques are repeated, practice alone will never lead to successful pipe weld ing. Those who will take the time and effort to read this book will learn thecorrecttechniqueswhich, ifpracticed, will result inobtain ing theskills required to be a successful pipe welder. Before starting to learn pipe welding, a person should be pro ficient in weldingin the four basic positions: 1. flat; 2. horizontal; 3. 1 Chapter 1 vertical; and 4. overhead. All of these positions are used to weld pipe. Since the pipe has a round shape, there is usually a gradual transition from one position to another. The welding positions are defined by standardsymbols which are shown in Fig. 1-2. It is important for the welder to learn to identify FLAT POSITION HORIZONTAL posmON liERTlCAL posmON OVEIlHEAD POSITION jG ZG 3G 4G PLATES A'lO A)<IS PLATESANDAXIS PLATES VERTICALAND PLATES HOIIllONTAL OF PIPE HORIZONTAL OFPIPE VERTICAL AXIS OFPIPE VERTICAL TEST POSITION HORIZOIHAL FiXED TEST POSITION 1>1.1 HoRIZONTAL 2G ~G 66 8 o0< -e ) }- AXIS OF PIPE PIPE SHALL NOT BE VERTlCAL TURNEDOf! ROLLEO WHILE WELOING Count'syo!th..Nobart Broth"" Cu. Fig. ]-2. Standardsymbolsdesignatingtheweldingpositions. these positions by their symbols (lG. 2G, etc.). These symbols will be used in this book to identify the various welding positions. When making the weld, the welder is confronted with two pri mary tasks. First he must prepare to make the weld, and second he mustconcentrate hisentire attention on the weldingoperation. In preparing to make the weld, the welder is concerned with the following matters: I. The typeofmetal tobe welded 2. The selection ofthe correct welding electrode 3. The preparation and cleaning oftheedge, or weldjoint 4. The fit-up ofthe pipesto obtain the correct alignment. 2 Introduction After all of the preparations have been made, the welder must give his complete attention to making the weld. He must strike the arc and manipulate the electrode correctly in order to deposit a sound bead. He must watch the molten puddle of metal and, when welding a root bead, he must watch the keyhole(seeChapter 5, Fig. 5-4) constantly. Ever alert to notice small changes that may affect the quality of the weld, he must be prepared to make instantaneous adjustmentsin his weldingtechnique when required. In other words, when the weld is in progress, the welder should see and think of nothing outside the area ofthe weld. Basic PipeWelding Procedures When the pipe is in the SG position, with its axis horizontal as in Fig. 1-3, positions on the pipe can readily be identified by their likeness to the numbers on the face ofa clock. Thus, the top ofthe pipe is in the 12 o'clock position and the bottom is the 6 o'clock position. Twodifferent welding procedures are usedwhen the pipeis in the horizontal position: downhill and uphill pipe welding. Thechoice of the method is not affected by the diameter of the pipe; it depends primarily on the wall thickness and the alloy content ofthe pipe, as explained in the following section. (2 II 9 8 6 Fig. 1-3.Theidentificationoftheweldingpositionsaroundthepipejointbythe numberson theface ofaclock. Downhill Pipe Welding. Regardless of the method used. the pipes mustfirst be tack welded together. Fordownhill welding (Fig. 1-4), the weld is started in the 12 o'clock position and the bead is welded 3