Chapter 17-Gas Tungsten Arc Welding of Pipe

Question 1

What types of industries require GTAW-quality pipe welds?

Answer 1

• Oil
• Gas
• Nuclear
• Chemical

Question 2

What are the grooves most often used for welding on mild steel pipe?

Answer 2

• Single V
• Single U
• Single J
• Single Bevel-Grooves

Question 3

What condition must the prepared edges of a pipe be in before welding?

Answer 3

37 1/2 inch bevel, leaving a root face of 1/16in. to 1/3in.

Question 4

How is the depth of root penetration measured?

Answer 4

Distance measured between the original surface of the joint and the deepest point of fusion.

Question 5

What problem can incomplete fusion cause?

Answer 5

It can form a stress point. Which can result in premature cracking or failure of the weld at a load well under it’s expected strength.

Question 6

What are the common causes of a concave root surface?

Answer 6

When insufficient filler metal is added to the joint m, or excessive heat is used in the overhead position.

Question 7

What problems can excessive root reinforcement cause?

Answer 7

Reduced material flow, result in clogged pipes, or form stress points that will result in premature weld failure.

Question 8

What can cause root contamination?

Answer 8

Caused by overhearing, poor cleaning procedures, or improper protection from the surrounding atmosphere.

Question 9

What gases are used as backing gases?

Answer 9

Nitrogen and CO2

Question 10

How can filler metal be added to make a root pass?

Answer 10

The addition of filler metal to the joint can be fine by dipping or by pre placement.

Question 11

What information must be supplied when ordering consumable inserts?

Answer 11

• Classification
• Size
• Style
• Pipe Schedule