slight circular motion make the second, third, and fourth
passes. This motion of the electrode permits greater
control and better distribution of the weld metal.
Remove all slag and oxides from the surface of each pass
by chipping or wire brushing before applying additional
beads to the joint.
Many of the welding difficulties in metal-arc weld-
ing are the same as in oxygas welding. A few such
problems include undercut, cracked welds, poor fusion,
and incomplete penetration.
Table 7-3 provides an illustration of the most com-
mon welding problems encountered during the arc-
welding process and methods to correct them.
Every welder has the responsibility of making each
weld the best one possible. You can produce quality
welds by adhering to the rules that follow.
1. Use only high-quality welding machines,
electrodes, and welding accessories.
2. Know the base material that you are working
3. Select the proper welding process that gives the
highest quality welds for the base material used.
4. Select the proper welding procedure that meets
the service requirement of the finished weldment.
5. Select the correct electrode for the job in
6. When preheating is specified or required make
sure you meet the temperature requirements. In any
case, do not weld on material that is below 32°F without
7. Clean the base metal of all slag, paint, grease,
oil, moisture, or any other foreign materials.
8. Remove weld slag and thoroughly clean each
bead before making the next bead or pass.
9. Do not weld over cracks or porous tack welds.
Remove defective tack welds before welding.
10. Be particularly alert to obtain root fusion on the
first pass of fillet and groove welds.
11. When groove weld root gaps are excessive,
build up one side of the joint before welding the pieces
12. When fillet weld root gaps are excessive, be
sure you increase the size of the fillet weld to the size of
the root gap to maintain the strength requirement. In
some cases, it is advantageous to make a groove weld l
to avoid extremely large fillet welds.
13. Inspect your work after completion and
immediately remove and replace any defective weld.
14. Observe the size requirement for each weld and
make sure that you meet or slightly exceed the specified
15. Make sure that the finished appearance of the
weld is smooth and that overlaps and undercuts have
Welding is the simplest and easiest way to join
sections of pipe. The need for complicated joint designs
and special threading equipment is eliminated. Welded
pipe has reduced flow restrictions compared to me-
chanical connections and the overall installation costs
are less. The most popular method for welding pipe is
the shielded metal-arc process; however, gas shielded
arc methods have made big inroads as a result of new
advances in welding technology.
Pipe welding has become recognized as a profes-
sion in itself. Even though many of the skills are com-
parable to other types of welding, pipe welders develop
skills that are unique only to pipe welding. Because of
the hazardous materials that most pipelines carry, pipe
welders are required to pass specific tests before they
can be certified
In the following paragraphs, pipe welding positions,
pipe welding procedures, definitions, and related infor-
mation are discussed.
PIPE WELDING POSITIONS
You may recall from chapter 3 of this manual that
there are four positions used in pipe welding (fig. 3-30).
They are known as the horizontal rolled position (1G),
the horizontal fixed position (5G), pipe inclined fixed
(6G), and the vertical position (2G). Remember: these
terms refer to the position of the pipe and not to the weld
PIPE WELDING PROCEDURES
Welds that you cannot make in a single pass should
be made in interlocked multiple layers, not less than one
layer for each 1/8 inch of pipe thickness. Deposit each
layer with a weaving or oscillating motion. To prevent
entrapping slag in the weld metal, you should clean each
layer thoroughly before depositing the next layer.