GMAW, FCAW and MCAW on Mild Steel Pipe

Question 1

What are the three (3) important dimensions for pipe?
a)
b)
c)

Answer 1

a) outside diameter (OD)
b) inside diameter (ID)
c) wall thickness (schedule)

Question 2

Are the following statements regarding pipe true or false?
a) OD is identical to the nominal size for all pipe. true/false
b) Nominal size is the approximate ID of standard wall pipe. true/false
c) Pipe schedules are an indication of wall thickness. true/false
d) The terms tube and pipe are interchangeable. true/false
e) OD of a pipe remains the same regardless of its schedule. true/false
f) Pipe 350 mm (14”) and larger is identified by OD. true/false

Answer 2

a) false; OD is approximately equal to ID for pipe sizes up to 12”.
b) true
c) true
d) false; The terms tube and pipe are not interchangeable. Tubing is generally sized to the outside diameter and the wall thickness is lighter in weight.
e) true
f) true

Question 3

What does the term schedule refer to as it relates to pipe?
a) the pipe wall thickness
b) the weight per linear measure
c) available lengths from suppliers
d) maximum pressure the pipe can withstand

Answer 3

a) the pipe wall thickness

Question 4

Define the following positions and welds on pipe.
a) 1G
b) 2G
c) 5G

Answer 4

a) 1G is a groove weld completed in the flat position from above the joint while rotating the pipe with its axis horizontal. It is often called the 1GR.

b) 2G is a groove weld completed in the horizontal position with the pipe axis fixed vertically. There is no rotation.

c) 5G is a groove weld completed with the pipe axis fixed horizontally. There is no rotation and progression may be uphill or downhill.

Question 5

Single Vee preparations on pipe generally have an included angle within the range of:
a) 22.5° - 30°.
b) 30° - 45°.
c) 45° - 60°.
d) 60° - 75°.

Answer 5

d) 60° - 75°.

Question 6

What root gap is recommended for a GMAW roll welded pipe joint prior to tack welding?
a) (1/16” - 3/32”)
b) (3/32” - 1/8”)
c) (1/8” - 5/32”)
d) (5/32” - 1/4”)

Answer 6

c)(1/8” - 5/32”)

Question 7

Do all tack welds become an integral part of the weld? Explain your answer.

Answer 7

No, bridged tacks must be removed as welding progresses. Tacks in the root may become part of the root, but must be fully penetrated and feathered to insure full fusion.

Question 8

Where should the four tack welds be located on a 150 mm (6”) pipe to be welded in the 5G position?

Answer 8

The tacks are generally located at the 12, 3, 6 and 9 o’clock positions.

Question 9

What is the maximum length of tack welds used for joining 150 mm (6”) sch. 80 pipe?

Answer 9

3/4”

Question 10

If a pipe fit-up has a gap that is not uniform, at what location should the widest portion of the gap be placed in preparation for welding?

Answer 10

The widest gap should be placed at the last quarter of the joint to be welded.

Question 11

On an 80 mm (3”) sch. 40 pipe, what is the minimum number and length of tacks required?
a) 2 tacks at 25.4 mm (1”) long
b) 2 tacks at 12.7 mm (1/2”) long
c) 3 tacks at 12.7 mm (3/4”) long
d) 4 tacks at 25.4 mm (1”) long

Answer 11

c) 3 tacks at 12.7 mm (1/2”) long

Question 12

For an open gap root pass, a B-G 49A 5 C G6 (ER70S-6) wire is deposited using:
a) short-circuiting arc metal transfer.
b) spray arc metal transfer.
c) globular arc metal transfer.
d) rotating arc metal transfer.

Answer 12

a) short-circuiting metal transfer.

Question 13

The recommended gun angle and inclination for a GMAW 1G pipe joint is:
a) 90° angle to the joint with a 15° backhand inclination.
b) 45° angle to the joint with a 15° forehand inclination.
c) 30° angle to the joint with a 30° backhand inclination.
d) 60° angle to the joint with a 30° forehand inclination.

Answer 13

a) 90° angle to the joint with a 15° backhand inclination.

Question 14

What mode of metal transfer is recommended for FCAW wire on the fill passes and cap in the 2G position?
a) short-circuiting
b) globular
c) pulsed spray
d) rotating arc modulated pulsed spray

Answer 14

b) globular

Question 15

The root pass is becoming excessively heavy as you are welding a pipe in the 1G position. What corrective action would you take while welding?pipe.
a) Work closer to the 12 o’clock position of the pipe.
b) Work closer to the vertical position, progressing downhill.
c) Slow the travel speed across the centre of the weld.
d) Incline the electrode more into the direction of travel.

Answer 15

b) Work closer to the vertical position, progressing downhill.

Question 16

State two (2) corrective actions that may help prevent the root pass from becoming concave with shrinkage marks showing on the inside.
a)
b)

Answer 16

Any two (2) of the following are correct.
a) Decrease wire feed speed and voltage.
b) Work closer to the top near the 1 o’clock position.
c) Reduce the root spacing.
d) Use a small root face rather than a feathered root edge.

Question 17

What is the recommended root opening for a 75 mm (3”) or larger pipe welded with GMAW in the 5G position?

Answer 17

(1/8” - 5/32”)

Question 18

The preferred direction of travel for GMAW on the root pass in the 5G position is ____________.

Answer 18

The preferred direction of travel for GMAW on the root pass in the 5G position is ____downhill___

Question 19

Is it possible to weld the project in question 19 in the opposite direction?
a) yes
b) no

Answer 19

a) yes

Question 20

Cleaning the root pass prior to the second pass with FCAW is:
a) never required.
b) required only if weave beads are done.
c) required only if stringer beads are done.
d) required if large islands of non-metallic oxides are present.

Answer 20

d) required if large islands of non-metallic oxides are present