Tài liệu Weld Symbols on a Drawing ppt

Weld Symbols on a Drawing – Refresh
Your Knowledge - ANSI/AWS A2.4-79
The eight elements which may appear in a welding symbol are:-
reference line, arrow, basic weld symbols, dimensions and
other data, supplementary symbols, finish symbols, tail
and specification and process or other reference. Let us
discuss the one by one.
Reference Line: This is the basis of the welding symbol. All
other elements are oriented with respect to this line. The arrow is
affixed to one end and a tail, when necessary, is affixed to the
other.
Arrow: This connects the reference line to one side of the joint in
the case of groove, fillet, flange, and flash or upset welding
symbols. This side of the joint is known as the arrow side of the
joint. The opposite side is known as the other side of the joint. In
the case of plug, slot, projection, and seam welding symbols, the
arrow connects the reference line to the outer surface of one of
the members of the joint at the center line of the weld. In this
case the member to which the arrow points is the arrow side
member: the other member is the other side member. In the case
of bevel and J-groove weld symbols, a two-directional arrow
pointing toward a member indicates that the member is to be
chamfered.
Basic Weld Symbols: These designate the type of welding to be
performed. The basic symbols which are shown in the table Basic
Weld Symbols are placed approximately in the center of the
reference line, either above or below it or on both sides of it as
shown in above figure. Welds on the arrow side of the joint are
shown by placing the weld symbols on the side of the reference
line towards the reader (lower side). Welds on the other side of
the joint are shown by placing the weld symbols on the side of

the reference line away from the reader
(upper side).
Supplementary Symbols: These convey additional information
relative to the extent of the welding, where the welding is to be
performed, and the contour of the weld bead. The “weld-all-
around” and “field” symbols are placed at the end of the
reference line at the base of the arrow as shown in first figure
and the table Supplementary Weld Symbols.
Dimensions: These include the size, length, spacing, etc., of the
weld or welds. The size of the weld is given to the left of the basic
weld symbol and the length to the right. If the length is followed
by a dash and another number, this number indicates the center-
to-center spacing of intermittent welds. Other pertinent
information such as groove angles, included angle of countersink
for plug welds and the designation of the number of spot or
projection welds are also located above or below the weld
symbol. The number designating the number of spot or projection
welds is always enclosed in parentheses.
Contour and Finish Symbols: The contour symbol is placed
above or below the weld symbol. The finish symbol always
appears above or below the contour symbol. The following finish
symbols indicate the method, not the degrees of finish: C—
chipping; G—grinding; M—machining; R—rolling; and H—
hammering.
Tail: The tail which appears on the end of the reference line
opposite to the arrow end is used when a specification, process,
or other reference is made in the welding symbol. When no
specification, process, or other reference is used with a welding
symbol, the tail may be omitted.