Welding Symbols CWU

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Welding Symbols CWU Powered By Docstoc
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Welding symbols form shorthand for the draftsman, fabricator, engineer, and welding
operator. A good symbol can convey more information than several paragraphs of
writing. Welding symbols are a simple way of defining how a part is to be welded. It is
not necessary to be a welder to understand the basic principles behind the system, and
as an added bonus AWS (American Welding Society) has taken steps to unify the
American system with ISO (International Standards Organization). Symbols found on
drawings will indicate the required type of weld, specific welding and machining
dimensions, and other specifications.

The welding symbol consists of eight elements may all be present at once, but in most
instances will contain only a portion of the eight.

                           1.   Reference line
                           2.   Arrow
                           3.   Basic weld symbol
                           4.   Dimension and other data
                           5.   Supplementary symbol
                           6.   Finish symbol
                           7.   Tail
                           8.   Specification, process, or reference

Figure: 1
AWS Welding

WEC 01/07 MET 357                        1
The symbol is used on drawings of parts to be welded. Whenever two or more pieces
of a welded part (weldment) are placed together, their surfaces and edges form a joint.
The drawing of the part to be welded indicates how the parts will be assembled and
what type of welded joint will be made.

The complete welding symbol will tell the welder how to prepare the base metal, the
welding process to use, the method of finishing, and much more information regarding
each weld. Dimensions may be in SI metric units or conventional U.S. units.

A complete welding symbol contains all the information about a welded joint. Part of the
welding symbol is the basic “weld symbol” which describes what type of weld to use.

Fillet Symbols:                         Figure: 2

Groove Symbols:                                              Figure: 3

Plug or Slot Symbol:                    Figure: 4

Welding Symbols Applied to Reference Line:

Figure: 5

WEC 01/07 MET 357                       2
Reference Line
The reference line is always drawn as a horizontal line. It is placed on the drawing near
the joint to be welded. All other information to be given on the welding symbol is shown
above or below this horizontal reference line. All information shown on a complete
welding symbol is always shown in the same position as indicated in Figure 1 above.

The arrow may be drawn from either end of the reference line. The welding symbol
may appear in any view of the welding drawing. The arrow always touches the line
which represents the welded joint.

The tail is used only when necessary. If used it may give information on specifications,
the welding process used, or other details required but not shown by the welding
symbol. A number such as 1, 2, 3, etc., may be used in the tail to refer the user to a
note elsewhere on the drawing. Companies may use their own number or letter codes
in the tail to indicate the welding process, procedure, finishing method, or company

                                         Figure: 6 Additional Weld information

If no tail is used, somewhere on the drawing there is a note such as, “Unless otherwise
specified, all welds will be made in accordance with Specification XXXX”.

Basic Weld Symbol
The basic weld symbol shown on the complete welding symbol indicates the type of
weld made on a weld joint. It is also a miniature drawing of the any metal edge
preparation required prior to welding.

The Arrow Side and Other Side
On a drawing of a welded part, the arrow of the welding symbol touches the line to be
welded. The metal joint has two sides. The side of the metal which the arrow touches
is always the Arrow Side. The opposite surface from the arrow is called the Other
Side (I know, I know).

WEC 01/07 MET 357                       3
On many weldments there is no inside or outside, top or bottom, left or right because of
the joint position. To simplify the location of the weld, the terms arrow side and other
side are used.

          Figure: 7

On the welding symbol the arrow side weld information is ALWAYS SHOWN BELOW
the reference line. The other side weld information is ALWAYS SHOWN ABOVE the
reference line.

Root Opening and Groove Angle
The Root Opening is the space between the metals at the bottom of the joint (root).
This root opening may be specified on the drawing in metric units, fractions of an inch,
or as a single-place decimal of an inch. The root opening size appears inside the basic
welding symbol on the complete welding symbol.

The included angle or total angel of a groove weld is shown above the basic weld
symbol. When preparing the edges for welding, half the groove angle is cut on each
piece so that when placed together, the combined angles will total the angle shown.

Figure: 8 Groove Root and Size Designations

When a bevel or J-groove weld is used, only one piece of metal is cut or ground. The
arrow of the welding symbol is bent to point to the piece to be cut or ground.

Figure: 9 Groove Designations

WEC 01/07 MET 357                       4
Length and Pitch of Welds
In many welded parts it is not necessary to weld continuously from one end of the joint
to the other. To save time and expense, where strength is not affected, short sections
of weld may be spaced across the joint. This is called INTERMITTENT WELDING.

On intermittent welds, the LENGTH DIMENSION is used to indicate the length of each
weld. The PITCH DIMENSION indicates the distance from the center of one weld
segment to the center of the next. The length and pitch dimension is always shown to
the right of the basic weld symbol on the welding symbol.

When intermittent fillet welds are required on both sides of a welding joint, they may be
one of two types. One type is chain intermittent; the other is staggered intermittent
welding. The welds of either side of a CHAIN INTERMITTENT WELD begin and end at
the same spot. STAGGERED INTERMITTENT WELDS are offset so the welded
segments do not line up on each side of the joint. This is shown on the welding symbol
by offsetting the fillet weld symbols.

                                                       Figure: 10 Intermittent Welds

Weld All Around and Field Weld Symbols
Directions given on a welding symbol are no longer any value when the weld joint
makes a sharp change in direction such as going around a corner. When the joint
changes direction sharply, a new welding symbol must be used or a weld-all-around
symbol may be used.

The WELD-ALL-AROUND SYMBOL is used when the same type weld is used on all
edges of a box or cylindrical part.

Some parts are assembled and welded in the shop. It is often necessary to take parts
into the field to make final assembly and welds.

WEC 01/07 MET 357                       5
When welds are to be made in the field away from the shop, a FIELD WELD SYMBOL
is used as shown in figure 10 below. If a weld is to be made in the shop, the field weld
symbol is not used.

Figure: 11

Protect them, there are no spares issued

WEC 01/07 MET 357                       6

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