Piping Pipe Welding and Fabrication

Question 1

What welding process is most commonly used for root pass welding on carbon steel process piping?

Accepted Answer

Shielded Metal Arc Welding (SMAW) or Gas Tungsten Arc Welding (GTAW)

Answer

SMAW (stick) and GTAW (TIG) are most commonly used for root passes on process piping due to their precision and ability to produce high-quality root beads.

Question 2

What is the purpose of preheat in pipe welding?

Accepted Answer

To reduce the risk of hydrogen-induced cracking and improve weld quality

Answer

Preheating reduces the cooling rate of the weld, minimizes hydrogen cracking risk, and reduces thermal shock in the heat-affected zone.

Question 3

What is a Welding Procedure Specification (WPS)?

Accepted Answer

A document prescribing the variables to be used when making a production weld

Answer

A WPS specifies the welding variables (process, filler metal, preheat, interpass temperature, etc.) required to produce a weld meeting code requirements.

Question 4

What does PWHT stand for in pipe fabrication, and why is it performed?

Accepted Answer

Post-Weld Heat Treatment — done to relieve residual stresses and improve material properties

Answer

PWHT is performed after welding to reduce residual stresses, improve ductility, and prevent stress corrosion cracking in susceptible materials.

Question 5

What type of joint preparation is most commonly used for butt welds on pipe with wall thickness greater than 3/16 inch (4.8 mm)?

Accepted Answer

Single-V groove bevel

Answer

Single-V groove preparations are standard for pipe butt welds, allowing full penetration and access for root, fill, and cap passes.

Piping Practice Test

Piping Practice Test

Piping Pipe Welding and Fabrication