Civil Engineering Reference
In-Depth Information
Double butt/groove welds often have the root of the first weld back
gouged or ground. This procedure can be specified by the AWS
welding symbol. A joint requiring back gouging may be specified by
placing the instruction BACK GOUGE in the tail of the reference
line.
Figure 9.6
shows a double-V groove weld with details of edge
preparation and back gouging. The edge preparation is a double-V
with 60° included angles, each side of the joint prepared to depths
of 3/8 in. A root face of typically 1/16 in to 1/8 in (not specified by
the welding symbol) would be obtained by grinding to produce a
root gap of 1/8 in.
Illustration
AWS
3
8
8
60°
BACK
GOUGE
60°
8
3
8
60°
8
3
8
8
60°
9.6
Double-V groove weld with edge preparation and back gouging instruc-
tion (AWS) (dimensions are in inches).
In the example shown in Fig. 9.6, weld sizes are not specified
because the depth of the gouge should be sufficient to remove much
of the root of the first weld so that full penetration is obtained when
the second side is welded. However, it is permissible to specify the
size of the weld on the first side to ensure that it is large enough to
limit the depth of back gouging required.
The AWS standard describes many examples of combinations of
joint edge preparations and weld sizes that can be specified by the
welding symbol. In contrast to this, the ISO system limits the infor-
mation specified by the welding symbol to the type of weld and its
size. There is a limit to the extent of a welding procedure that can
be contained in a welding symbol and it is advisable to supplement
this information with additional notes and drawings.
This is supported by the AWS standard, which recommends that
drawing notes may be used to provide instructions for weld details.
This information need not be repeated in welding symbols and the
information can include details of edge preparations, weld sizes, etc.
The ISO standard follows this practice in principle and recommends
that, in order to simplify the drawings, specific instructions should
be referred to separately or placed close to the welding symbol.
