Page 138 - CITS - Welder - Trade Theory

WELDER - CITS

Procedure for welding heavy wall pipes in 5G & 6G

position welding

Welding heavy wall Procedure for pipes in 5G position weld
Welding Technique
Perhaps the most difficult position in which to weld pipe is in the 5G position. Once this is mastered, welding
pipe in other positions is less difficult to learn. For this reason, it is best to start by learning how to weld in the 5G
position.
Pipe size : OD 168 mm, 7.11 mm thickness

150 mm long - 2 nos.
Electrode : E 6010 - 3.20 mm Welding current : 80 - 110 amperes
Vertical up welding uses lower current and slower travel speed to produce a joint with fewer but heavier beads.
The slower travel speed of vertical-up welding and the high liquid pool melts out gas holes more effectively than
vertical down welding (Fig 1)
Fig 1

Pipe Clamps: One difficulty encountered in assembling pipe to be fabricated / installed, is the positioning of the
pipe before tacking. External line up clamps are made to hold virtually any type of pipe joint. The use of clamps
to secure proper alignment is highly recommended. The pipe joint should be clamped using the external line up
clamp.
Welding in 6G position
6G position welding introduction: 6G is a welding position to which a welder / welding procedure is qualified
to perform circumferential pipe (or tubular structure) weld with the pipe fixed and oriented on approximately 45°
angle inclination. (Fig 2)

Fig 2

The letter “G” in “6G stands for the type of butt weld, called “groove weld” (another type of weld with letter “F”
stands for “fillet weld”) and the number :6 designates the position of the pipes welded. A groove weld is a joint in
two metal pipes with joining edges prepared with angle bevel and the joining space in between them is deposited
with the welding material.
In the 6G welding position, the pipes aligned with slopes at approximately 45° inclination from the horizontal from
the horizontal (X) axis 45° from the vertical (Y) axis. The pipe is in a fixed position, so the welder must move
around the pipe to perform the welding circumferentially. This is a difficult welding position involving horizontal,
vertical and overhead position welding in a single joint welding that requires a great skill, competency, experience
and technical expertise as the pipe / structure us immovable / rotatable.

So welder has to weld the test piece in that position to get qualification. Normally, the pipes are edge prepared
with land (root face/weld face at the butt joint root) between 2mm and 3mm and joined with a 2 to 3mm root gap
with proper alignment. The welder can use approximately 80 amps to start on a tack weld without sticking.

125

CITS : C G & M - Welder - Lesson 33 - 43