In the OVERHEAD position (fig. 7-14, view D),
welding is performed from the underside of the
joint. The axis of the weld is in a horizontal plane,
as is the axis of a flat position weld. But the
overhead weld is, you might say, upside down if
compared to the flat position weld. The terms
FLAT, HORIZONTAL, VERTICAL, and
OVERHEAD adequately describe the positions in
which plate is welded. This terminology, however,
does not describe the positions for welding pipe.
When you weld pipe, you will weld in one of three
positions: horizontal rolled position, horizontal
fixed position, and vertical fixed position. Pipe
welding positions are illustrated in figure 7-15. In
each case, the terminology refers to the axial
position and rotational freedom of movement of the
pipe, not to the weld.
In HORIZONTAL ROLLED POSITION welds,
Figure 7-15.--Positions for welding pipe.
the axis of the pipe is horizontal. The joint is made
beginning. There are many details. Each must be
by welding in the flat position, at the same time
worked out in such a way that the completed job
rotating the pipe at a rate equal to the speed of
serves the purpose for which it is intended.
filler metal deposition. Pipe welded in the
horizontal rolled position is first carefully aligned
and tack welded. Then it is placed in a jig, which
To learn how to select a welding process, you
facilitates rotation of the pipe. View A of figure
must first understand the terms in which the job
plans are expressed.
7-15 shows that all welding should be accomplished
between points A and B.
A single part of a structure consisting of several
parts is called a COMPONENT. When a structure
The pipe axis in a HORIZONTAL FIXED
is made up of several components joined by welding,
POSITION weld is the same as in the horizontal
rolled position weld. In this position, however, the
the structure is called a WELDMENT. Typical
pipe cannot be rotated. As a consequence, welding
examples of weldments are gun mounts, machinery
must be accomplished by progression through the
foundations, storage tanks, pressure tanks, frames,
valve manifolds, and fabricated pipe fittings like
overhead, vertical, and flat welding positions. When
you are welding in the horizontal fixed position (fig.
crosses, tees, and elbows. The detailed plan worked
7-15. view B), the weld is started at the bottom and
out for producing the weldment is known as the
WELDING PROCEDURE. The welding
progresses in increments upward to the top of the
procedure specifies the kind of welding materials,
pipe-first on one side, then on the other.
joint design, preheat temperature, interpass
temperature, postheat temperature, the
In the VERTICAL FIXED POSITION, the
chronological order and manner in which a series of
pipe axis is vertical and held in a fixed position.
joints are to be welded, and the way individual
The weld itself is made in the horizontal welding
welds in the series are to be made. The
position (fig. 7-15, view C.)
chronological order of making the various welds in
the weldment is called the WELDING
PROCEDURES AND SEQUENCES
SEQUENCE. Thus, the welding procedure spells
out all the details for producing a given weldment
Whether large or small, simple or complex, the
with a predetermined welding process.
manufacture of any object requires careful planning.
This is especially true when welding is employed to
An important part of the welding procedure is
join parts into an integrated whole. One of the first
the JOINT WELDING PROCEDURE. This term
decisions to be made regarding welding is the
refers to the details pertaining to the materials,
welding process to be used--that is, which of the
methods, and practices used to make a particular
processes is most applicable. But this is only the