Basic Of Welding Symbol – Symbolic Representation of Welding Symbol

INTRODUCTION to Welding : 
Welding is a process of fastening the metal parts together permanently by the application of heat (fusion welds) or pressure (pressure or forge welding) or both (resistance welding). Both ferrous (steel, cast iron) and Non-ferrous metals (like brass copper and alloy) can be joined by welding.

The welding is cheaper, stronger, easier and faster than riveting. The various types of welding process are
a. Gas welding
b. Arc welding
i. Metal Arc Welding (MAW)
ii. Gas metal Arc Welding (GMAW)
iii. Submerged Arc Welding (SAW)
iv. Tungsten Inert Gas Welding (TIG)
v. Metal Inert Gas Welding (MIG)
c. Forge Welding
d. Resistance Welding
e. Thermit Welding
f. High Energy Welding

The welded joints are broadly classified into

a. Butt joint b. Lap joint c. Corner or Fillet joint d. Tee joint e. Edge joint

SYMBOLIC REPRESENTATION OF WELD
The standard welding symbol is given below.

 Arrow Line and reference Line

The position of the arrow line with respect to the weld is of no special significance. The side of the joint on which the arrow line is drawn is called “arrow side”. The side of the joint remote to the arrow line is called “other side”. The reference line has significance on the weld side. If the weld symbol is placed BELOW the reference line, the welding should be done in the “ARROW SIDE”. If the weld symbol is placed ABOVE the reference line, the welding should be done in the “OTHER SIDE”. If the weld symbol is placed both ABOVE and BELOW the reference line, the welding should be done in both the “ARROW AND OTHER SIDES” 

Basic Weld Symbol

The basic symbols recommended by Bureau of Indian Standards (BIS) for specifies the type of weld are shown in the fig

Size of weld
The size of the weld is height of the isosceles triangle in the case of fillet welds. In other cases, the size will be the minimum distance from the surface of the paert of the bottom of penetration.

Finish and contour symbol
The contour symbols are
a. Flat (flush)
b. Convex
c. Concave
Finishing welds other than cleaning shall be indicated by finish symbols.
Chipping – C, Grinding – G, Machining – M

Welded and unwelded length
Length of weld means it is the length to be welded once, after that pitch equal to unwelded length is not welded and this process is continued for the whole length of the side.

Weld all round
If the weld should be made all round the joint, a circle should be placed at the point connecting the arrow and the reference line.

Site weld
When some of the welds (the welded structures) are required to be made on site during erection. They should be designed by a filled in circle at the point connecting the arrow and the reference line.

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