GPT Inspection & Quality Control 2 — Questions and Answers
Question 1: During a visual inspection of a newly installed gas pipe joint, a technician notices a slight discoloration around the fitting. What is the most appropriate first action?
- Perform a leak test with an approved detection solution (Correct answer)
- Repaint the discolored area to prevent corrosion
- Document and ignore if no odor is present
- Immediately shut off the gas supply to the building
Correct answer: Perform a leak test with an approved detection solution
Any discoloration around a fitting could indicate a leak or heat damage, so a leak test with an approved detection solution is the required first step.
Question 2: Which standard governs the minimum inspection requirements for gas piping installations in most US jurisdictions?
- NFPA 54 (National Fuel Gas Code) (Correct answer)
- ASME B31.8
- API 1104
- OSHA 29 CFR 1910.119
Correct answer: NFPA 54 (National Fuel Gas Code)
NFPA 54, the National Fuel Gas Code, sets minimum inspection and installation requirements for gas piping systems in the US.
Question 3: A pressure test for a medium-pressure gas system (0.5–2 psi) must hold for a minimum of how long to be considered acceptable under NFPA 54?
- 15 minutes (Correct answer)
- 5 minutes
- 30 minutes
- 1 hour
Correct answer: 15 minutes
NFPA 54 requires a minimum 15-minute pressure test hold time to verify the integrity of medium-pressure gas piping.
Question 4: When inspecting a gas pipe for corrosion, which condition would require immediate replacement of the pipe section?
- Wall thickness reduced below minimum specified by the manufacturer (Correct answer)
- Surface rust with no pitting on an above-ground section
- Minor surface oxidation on a galvanized fitting
- Slight color change on a black iron pipe
Correct answer: Wall thickness reduced below minimum specified by the manufacturer
When corrosion reduces wall thickness below the manufacturer's minimum specification, structural integrity is compromised and replacement is mandatory.
Question 5: What type of gauge is required when performing a pressure test on gas piping systems to ensure accurate readings?
- A calibrated gauge with increments not exceeding 10% of the test pressure (Correct answer)
- Any available analog gauge from the service vehicle
- A digital gauge regardless of calibration date
- A gauge rated for twice the working pressure only
Correct answer: A calibrated gauge with increments not exceeding 10% of the test pressure
A calibrated gauge with increments not exceeding 10% of the test pressure ensures accuracy and is required for valid pressure testing.
Question 6: During a quality control inspection of threaded pipe connections, how much thread engagement is typically required for a gas-tight joint on standard iron pipe?
- 80% thread engagement as a minimum
- 2–3 full threads exposed beyond the fitting (Correct answer)
- Full thread burial with no exposure
- 50% engagement is sufficient with pipe dope
Correct answer: 2–3 full threads exposed beyond the fitting
Industry standard requires that 2–3 full threads remain exposed beyond the fitting to confirm adequate engagement without over-tightening.
Question 7: A gas pipe inspector finds a section of CSST (corrugated stainless steel tubing) installed without bonding. What is the primary hazard of this deficiency?
- Lightning-induced arc damage that can perforate the CSST wall (Correct answer)
- Excessive flow restriction causing appliance malfunction
- Condensation buildup leading to internal corrosion
- Incompatibility with natural gas composition
Correct answer: Lightning-induced arc damage that can perforate the CSST wall
Unbonded CSST is vulnerable to arc damage from nearby lightning strikes, which can perforate the tubing and cause a gas leak or fire.
GPT Inspection & Quality Control 2
During a visual inspection of a newly installed gas pipe joint, a technician notices a slight discoloration around the fitting.
What is the most appropriate first action?