By Dan Hernandez
No matter the welding process being used, proper preparation before you get started is key to ensuring quality in the finished
weld. Taking the necessary steps to prepare the
weld also can reduce the risk of weld failure as well
as wasting time and money on rework and consumables.
Proper weld preparation in pipe welding helps
prevent problems such as weld inclusions, slag
entrapments, hydrogen cracking, lack of fusion,
and lack of penetration. Consider the following key
points for cleaning and preparing the weld joint and
avoiding some common mistakes to achieve success in pipe welding.
Cleaning and Prep
Joint preparation and cleaning go hand-in-hand.
Which happens first depends on the state in which
the pipe is received. Some welding operators, espe-
cially on outdoor job sites, may be responsible for
cutting the pipe and beveling edges. But in some
applications, often performed in pipe shops, the
cutting and beveling are handled by someone else
before the welder receives the pipe.
Proper joint preparation—and whether it’s beveled, grooved, or notched—is often dictated by the
qualified weld procedure, which should ensure access to the joint and proper penetration and weld
strength for the application. Once the pipe is cut
using an oxyfuel torch, plasma cutter, cutting machine, or other tool, and the bevel is established
with a grinder or by machining, be sure to clean the
inside and outside of the pipe joint and the bevel.
If the pipe was cut with a machine, it’s likely a
lubricant was used, so be sure to remove it during
cleaning to reduce the risk of hydrogen inclusions.
Cutting with an oxyfuel torch or plasma cutter typically leaves a slag or oxide layer on the cut edge. Be
sure to clean this to prevent inclusions and porosity.
Remove any paint, oils, and dirt on the base ma-
terial before welding; otherwise, these materials
could make their way into the weld and cause in-
clusions or porosity that could harm weld integrity
and cause it to fail. Clean the area 1 to 2 inches from
the weld joint and the tie-in points, where the lac-
quer coating on the pipe’s outside surface meets the
While some welding processes or filler metals
are more forgiving to dirt or mill scale on the material, don’t rely on the belief that dirt and oil can be
burned off during welding. Any foreign material in
the weld can cause problems later.
Part Fit-up and Tacking
Proper part fit-up ensures that the joint is set uni-formly from start to end, resulting in weld consistency throughout the part. It helps prevent problems
with lack of penetration or too much penetration,
issues that can decrease the service life of the finished weld.
Part fit-up involves several key steps, including
matching the inside diameter (ID) of the two pieces
of pipe to be welded and making sure you have a
proper gap between the pipes for the root pass.
To match the pipes’ IDs, first take measurements
to ensure everything will line up properly, then do
some dry runs before actually attaching the pipe
with tack welds to establish the gap. The IDs should
be as close as possible to perfectly aligned. If the IDs
are not aligned, use a grinder on the inside of the
pipe to match up the diameters. Mismatched IDs are
more common with large-diameter pipes.
better pipe welds
Need to save time and money? Start with good weld prep
In pipe welding applications, proper weld preparation
helps prevent problems such as weld inclusions, slag
entrapments, hydrogen cracking, lack of fusion, and
lack of penetration.