120103j GMAW FCAW and MCAW on Mild Steel Pipe

Question 1

Question: What are the three (3) important dimensions for pipe?

Answer 1

Answer: a) outside diameter (OD), b) inside diameter (ID), c) wall thickness (schedule).
Explanation: These dimensions are crucial for identifying and categorizing pipes, ensuring they meet specific standards and fit properly in piping systems.

Question 2

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

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

Answer: a) the pipe wall thickness.
Explanation: The term ‘schedule’ in piping refers to the thickness of the pipe walls, which is critical for determining the pipe’s strength and application.

Question 4

Question: 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.

Explanation: This answer describes various welding positions used for pipes, which are important for welders to understand for proper application.

Question 5

Question: 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

Correct Answer: d) 60°-75°.

Explanation: The included angle for Single Vee preparations is typically within 60°-75° to ensure optimal accessibility for welding and sufficient penetration depth. Angles outside this range can lead to either insufficient penetration (if too narrow) or excessive need for filler material (if too wide).

Question 6

Question: What root gap is recommended for a GMAW roll welded pipe joint prior to tack welding?

a) 1.6 mm - 2.5 mm (1/16” - 3/32”).
b) 2.5 mm - 3.2 mm (3/32” - 1/8”).
c) 3.2 mm - 4 mm (1/8” - 5/32”).
d) 4 mm - 6.4 mm (5/32” - 1/4”).

Answer 6

Correct Answer: c) 3.2 mm - 4 mm (1/8” - 5/32”).

Explanation: A root gap of 3.2 mm - 4 mm (1/8” - 5/32”) is recommended for GMAW roll welded pipe joints to provide enough space for proper weld penetration and to accommodate thermal expansion of the metal during welding. Smaller gaps might not allow sufficient weld penetration, while larger gaps may require excessive filler material and can lead to a weakened joint.

Question 7

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

Answer 7

Answer: 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 ensure full fusion.

Explanation: Tack welds are temporary and are often removed or incorporated into the final weld. They are critical for holding pieces in place before the final welding, but only those that are properly integrated and do not compromise the weld’s integrity become part of the final weld.

Question 8

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

Answer 8

Answer: The tacks are generally located at the 12, 3, 6, and 9 o’clock positions.
Explanation: Placing tacks at these positions helps evenly distribute the pipe’s alignment and tension, providing stability during welding.

Question 9

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

Answer 9

Answer: 3/4”
Explanation: This specific length is chosen to provide adequate hold while minimizing the impact on the final weld quality.

Question 10

Question: 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

Answer: The widest gap should be placed at or near the last quarter of the joint to be welded.
Explanation: Placing the widest gap towards the end allows for better control and adjustment as the welding progresses.

Question 11

Question: 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 (1/2”) long
d) 4 tacks at 25.4 mm (1”) long

Answer 11

Correct Answer: c) 3 tacks at 12.7 mm (1/2”) long
Explanation: Three tacks of 12.7 mm each ensure proper alignment and stability of the pipe during welding without overly influencing the final weld.

Question 12

Question: Draw a sketch of a 150 mm (6”) pipe indicating the location of four tacks. Number them in order of completion.

Answer 12

Answer: Figure 27 shows the correct placement of the weld tacks: 4-Tacks (at 12-3-6-9 o’clock positions)
Explanation: This question requires a visual representation, which is provided in the document, illustrating the proper placement and sequence of tack welds for optimal stability and alignment.

Question 13

Question: 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 13

Answer: a) short-circuiting arc metal transfer
Explanation: The short-circuiting arc metal transfer is appropriate for open gap root passes due to its control and stability in creating a strong, penetrating root weld.

Question 14

Question: 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 14

Answer: a) 90° angle to the joint with a 15° backhand inclination.
Explanation: A 90° angle with a 15° backhand inclination is optimal for GMAW 1G pipe joints as it allows for better control and penetration of the weld, ensuring a strong and consistent weld bead.

Question 15

Question: 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 15

Answer: b) globular
Explanation: Globular transfer is recommended for FCAW in the fill and cap passes of 2G position welding due to its effectiveness in providing deep penetration and good fusion, especially in thicker sections.

Question 16

Question: 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?

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 center of the weld.
d) Incline the electrode more into the direction of travel.

Answer 16

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

Explanation: Working closer to the vertical position and progressing downhill helps control the weld pool, preventing the root pass from becoming excessively heavy. This approach is vital for achieving a consistent and properly sized weld bead in 1G pipe welding.

Question 17

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

Answer 17

Answer: 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.

Explanation: These corrective actions address issues with heat input and weld positioning, which are key factors in preventing concavity and ensuring proper penetration and weld quality.

Question 18

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

Answer 18

Answer: 3.2 mm - 4 mm (1/8” - 5/32”)
Explanation: This root opening size is recommended to allow sufficient space for weld penetration and to accommodate thermal expansion during the welding process, ensuring a strong and defect-free root pass.

Question 19

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

Answer 19

Answer: downhill.
Explanation: Welding downhill on the root pass in the 5G position helps in controlling the weld pool, ensuring good penetration and a smoother, more consistent bead.

Question 20

Question: Is it possible to weld the project in the previous question in the opposite direction?

Answers:
a) yes
b) no

Answer 20

Answer: a) yes
Explanation: It is possible to weld in the opposite direction, but this requires adjustments in technique and parameters to ensure weld quality and integrity.

Question 21

Question: 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 21

Answer: d) required if large islands of non-metallic oxides are present.
Explanation: Cleaning the root pass, especially when large non-metallic oxides are present, is crucial for ensuring good fusion and preventing defects in the subsequent passes.