Acknowledgment by the Publisher
Industrial Press wishes to express its sincere appreciation to Robert O’Con for his invaluable assistance in the preparation of the second edition of this book.
Only high quality pipe welds are acceptable in modern industry; for the failure of a pipe weld not only can disrupt the operation of a plant, it can be the cause of a serious accident with the possible loss of life and property. For this reason, a pipe welder must be a thoroughly qualified person in his craft.
The objective of this book is to describe the techniques that will result in a successful pipe weld, which must be sound throughout as well as look 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. 1-і - Example of a high quality pipe weid.
learned by reading a book alone; however, if incorrect techniques are repeated, practice alone will never lead to successful pipe welding, Those who will take the time and effort to read this book will learn the correct techniques which, if practiced, will result in obtaining the skills required to be a successful pipe welder.
Before starting to learn pipe welding, a person should be proficient in welding in the four basic positions: 1. flat; 2. horizontal; 3.
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 standard symbols which are shown in Fig. 1-2. It is important for the welder to learn to identify
Courtesy of the Hobart Brothers Co.
Fig. 1-2. Standard symbols designating the welding positions.
these positions by their symbols (1G, 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 primary tasks. First he must prepare to make the weld, and second he must concentrate his entire attention on the welding operation.
In preparing to make the weld, the welder is concerned with the following matters:
1. The type of metal to be welded
2. The selection of the correct welding electrode
3. The preparation and cleaning of the edge, or weld joint
4. The fit-up of the pipes to obtain the correct alignment.
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 (see Chapter 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 adjustments in his welding technique when required. In other words, when the weld is in progress, the welder should see and think of nothing outside the area of the weld.