Pipefitter Pipe Fabrication and Joining 4

Question 1

When performing a socket weld on a 2-inch pipe, what gap should be left between the pipe end and the socket shoulder before welding?

Accepted Answer

1/16 inch gap to allow for thermal expansion

Answer

A 1/16-inch gap is maintained before socket welding to allow for thermal expansion and prevent distortion during the welding process.

Question 2

Which pipe end preparation is required for a Class 6000 threaded fitting on a high-pressure steam line?

Accepted Answer

Standard NPT taper thread with sealant

Answer

Class 6000 threaded fittings use NPT (National Pipe Taper) threads with an appropriate high-temperature thread sealant for high-pressure steam service.

Question 3

A pipefitter needs to cut stainless steel pipe using a portable band saw. What blade characteristic is most important for this material?

Accepted Answer

Bi-metal blade with 14-18 TPI

Answer

A bi-metal blade with 14-18 teeth per inch provides the right balance of heat resistance and cutting speed for stainless steel without work-hardening the material.

Question 4

During a hydrostatic pressure test, a threaded joint is found to be weeping. After depressurizing, what is the correct corrective action?

Accepted Answer

Disassemble, clean, re-apply sealant, and reassemble

Answer

The proper fix is to fully depressurize, disassemble the joint, clean the threads, apply fresh sealant, and reassemble to the correct torque.

Question 5

What is the primary purpose of a purge dam when welding stainless steel pipe?

Accepted Answer

To maintain inert gas backing on the weld root and prevent oxidation

Answer

Purge dams are used to isolate the weld zone inside the pipe so an inert backing gas (typically argon) can prevent oxidation of the root bead on stainless steel.

Certified Pipefitter Practice Test

Certified Pipefitter Practice Test

Pipefitter Pipe Fabrication and Joining 4