Page 123 - CITS - Welder - Trade Practical

WELDER - CITS

• Deposit the root run starting from 3 o’clock position to 12 o’clock position using proper blowpipe and filler rod
angles. (I segment)
• Turn the pipe joint in the clockwise direction so that the end of the root run already made in I segment comes
to the 3 o’clock position.
• Continue to weld the root run for the second quarter segment as done for the first segment.
• Similarly, complete root run of 3rd and 4th segments.
• Ensure the root penetration by maintaining a keyhole at the root throughout the root run.
• Clean the root run by steel wire brush.

• Fix No. 7 size nozzle, select 3mmø CCMS filler rod and set 0.15 kg/cm2 gas pressure.
• Set neutral flame and fill the V groove by depositing the 2nd run using slight weaving to the blowpipe so that
both the faces of the V and the root run will fuse properly. Fig 1

• Ensure proper bead size, profile and weld reinforcement as well as avoid undercut and other weld defects.
• Clean the joint and inspect for external defects.

Skill Sequence

Structural pipe welding butt joint on MS plate ø 50 × 3

mm wall thickness in flat position

Objectives: At the end of this exercise you shall be able to
• prepare and weld structural pipe welding butt joint on MS plate ø 50 × 3 mm wall thickness in flat position.

Pipe welding is a highly skilled welding operation, which involves correct alignment and good penetration by
equally melted edges of the pipes. As the welding is to be done on a curved surface, the position of the blow pipe
and filler rod will continuously change as the welding progresses along the joint. To do this you have to put some
extra efforts to get the special skill of welding a pipe joint.
Preparation and setting: Check and ensure correct size of pipes. Prepare two M.S. pipes 50 mm ø and 75 mm
long by hacksaw cutting. As the end faces of a pipe cut by a hacksaw may not be at 90° to the pipe axis, file the
end faces of the pipe to get the 90° angle. Bevel the ends of the pipes by filing.

Clean the pipes and remove burrs, if any. Align the pipes in flat position as shown in Fig 1. Tack the weld joint by
inserting 1.5 mm wire to maintain a uniform root gap. (Fig 2a and 2b) Ensure the tack welded pipes are coaxial.
(i.e., the axis of both the pipes are the same.)

Select the angle iron or channel fixture according to the diameter of the pipe.
Place the tacked pipes on the fixture.
To ensure proper root penetration select nozzle No. 5 and a 1.6 mm C.C.M.S. rod for the root run.
Start welding as shown in the figure and complete the first segment. (Figs 3 and 4) The blowpipe and the filler rod
angles are as shown in Fig 4 at the “start of the weld” and have to be changed to those angles shown at the “stop
weld” continuously and gradually. i.e. weld from 3 o’clock position to 12 o’clock position.

After completion of I segment welded, rotate the pipe joint in clockwise direction until the II segment will come to
the position of I segment.
Deposit the root run on the II segment similar to the I segment.
Further welding is done by rotating the pipe to the III and IV segment.

Note : Ensure proper melting of tacks for good penetration and surface appearance.
It is very important to maintain a keyhole ahead of the molten pool at the root of the joint which will ensure root
penetration.

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CITS : C G & M - Welder - Exercise 24