Page 43 - CITS - Welder - Trade Theory

WELDER - CITS

4 Open square butt joint: It is used for plates up to 6mm thickness and when full penetration is required. The
root gap between the plates varies from one half thickness to one thickness of the plate.

When full penetration is required. The root gap between the plates varies from one half thickness to one
thickness of the plate.
5 Single ‘v’ preparation : The next type is that turned ‘single’ ‘V’ preparation which consists in hovelling the
edge of each plate so that a ‘v’ is formed when they are brought to gather. This is the most commonly. Used
type of edge preparation for welding plates up to 12mm thickness, the root gap and root face are kept as
2 mm and the included angle of 70° such type of preparation is known as single ‘V’ Butt joint. This type of
penetration is also used for welding of The pipes. The edge preparation is done either by machining or by
flame cutting.
6 Double ‘V’ preparation: This type of preparation is used if the plates are more than 12 mm thick and are
accessible for welding from both sides. Less weld metal is required to complete a double ‘v’ Butt joint. Heat
distribution is equal from both sides and hence there is less distortion. This preparation the root gap, root face
and included angle will be same as for single ‘v’ preparation.
7 Single ‘U’ & double ’U’ preparation: This type of edge preparation is suitable for if the thickness of the plate
is 15 mm or more the Double ‘U’ is used if the plates are accessible for welding from both sides. The ‘U’ type
edge preparation required less weld metal than the ‘V’ type for the same thickness of plate. Double ‘U’ has the
advantage of equaling heat input from both side and hence causes less distortion.

8 Horizontal butt weld preparation: This type of preparation is required for welding of two vertical plate by a
horizontal weld. The upper plate is beveled to an angle of 45o And the lower to 15o .This difference in the angle
of bevel is required to support the molten metal.
9 Single bevel & single ‘J’ butt preparation: These type of edge preparation are used for welding of plates at
right angle to each other.

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CITS : C G & M - Welder - Lesson 6&7