Page 176 - CITS - Welder - Trade Practical

WELDER - CITS

EXERCISE 40 : Pipe butt weld butt joint on MS pipe 25mm
o.d. 3mm w.t. horizontal position 5G

(fixed) - arc welding

Objectives

At the end of this exercise you shall be able to
• cut bevel the pipe for welding
• tack pipes for butt welding
• make root run by rotation method
• make filling run by rotation
• clean the job and inspect for defects.

Job Sequence

• Cut the pipes to the given size.
• File pipe ends to be at right angle to the pipe axis.
• Grind the edges to 30° to 35” bevel maintaining 1.5 to 1.75mm root face.
• Remove the burrs and rust from the pipe ends.
• Check the perpendicularly of the work piece using the try square.

• Arrange the 2 pipes to form as a butt joint.
• Use a fixture or V profile of an angle iron to align pipes in 6G position.
Note: Wear protective clothing (safety apparels)

• Switch on the machine and select a 3.15mm dia electrode for tacking and the root run and set 100 amps
current.
• Put 4 tacks at regular intervals adjusting 2mm root gap between the pipes using spacers.
• Ensure that each tack ends with a keyhole.
• Check and ensure that the pipes are in line after tacking.
• Set 110amps for a 3.15mm dia electrode for root run.
• Deposit the root run in flat position by rotating the pipe.

• Welding using the keyhole technique ensures root penetration.
• Remove slag from the root thoroughly.
• Deposit the second and third run using 3.15mm dia electrodes i.e. the same ad for the root run.
• Clean and inspect the joint.

a To ensure uniform and correct reinforcement
b To ensure that the weld face is free from porosity, slag inclusion, unfilled crater, overlap and edge of plate
melted off/insufficient throat thickness.

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