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Testing purging practice questions

18 questions from the gas fitting (natural gas and lp) practice test.

Testing purging practice test

10 questions, graded as you go, with the reason for every answer. No sign-up.

What this covers

Sample questions

Why is oxygen never used as the test gas for a piping pressure test?

  1. It leaks through pipe threads faster than air
  2. It is too light to show up on a test gauge
  3. It causes the inside of the pipe to rust
  4. It can react violently with oil and grease
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D. It can react violently with oil and grease

Pure oxygen under pressure can cause oil, grease and thread-cutting oil in the pipe to ignite explosively. Air, nitrogen, carbon dioxide or another inert gas is used instead.

Reference: IFGC 2021 Section 406.4; NFPA 54 Section 8.1.2

Gas piping must be tested at no less than 1.5 times its maximum working pressure. What is the minimum test pressure for piping that will operate at 5 psig?

Answer in psig.

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7.5 psig

Test pressure = 1.5 x 5 psig = 7.5 psig.

Reference: IFGC 2021 Section 406.4.1; NFPA 54 Section 8.1.4

The IFGC limits the range of a mechanical test gauge to no more than five times the test pressure. What is the highest full-scale gauge reading allowed for a 10 psig test?

Answer in psig.

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50 psig

Maximum gauge range = 5 x test pressure = 5 x 10 = 50 psig.

Reference: IFGC 2021 Section 406.4.1

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