GPT System Inspection & Maintenance 3 — Questions and Answers
Question 1: What is the primary purpose of cathodic protection on underground gas piping?
- To increase pipe flow capacity
- To prevent electrochemical corrosion of the metal pipe (Correct answer)
- To mark the pipe's location for excavation crews
- To reduce operating pressure losses
Correct answer: To prevent electrochemical corrosion of the metal pipe
Cathodic protection applies an electrical current that counteracts the electrochemical reactions responsible for corrosion on buried metal pipes.
Question 2: A technician is testing pipe joints with leak detection solution and observes bubbling at a threaded connection. What is the correct immediate response?
- Tighten the joint while the system is pressurized
- Depressurize the line, disassemble, apply new thread sealant, and retest (Correct answer)
- Apply additional sealant over the leaking joint without disassembly
- Reduce system pressure by 10% and monitor
Correct answer: Depressurize the line, disassemble, apply new thread sealant, and retest
The leak must be properly repaired by depressurizing, disassembling, resealing with approved compound, and retesting to confirm the repair.
Question 3: Which of the following is NOT an acceptable method for locating underground gas piping before excavation?
- Calling 811 (one-call utility notification)
- Using a pipe locator or ground-penetrating radar
- Consulting as-built drawings
- Probing with a metal rod to feel for the pipe (Correct answer)
Correct answer: Probing with a metal rod to feel for the pipe
Probing with a metal rod risks puncturing the pipe and is not an approved safe excavation method; utility notification and electronic locating are required.
Question 4: When inspecting flexible gas connectors on appliances, which condition requires immediate replacement?
- A connector that is 3 years old
- A connector that shows kinking, crimping, or corrosion (Correct answer)
- A connector that is longer than 36 inches
- A connector installed in a cabinet enclosure
Correct answer: A connector that shows kinking, crimping, or corrosion
Kinked, crimped, or corroded flexible connectors are structurally compromised and can fail, causing a gas leak or rupture.
Question 5: What is the significance of a 'drip leg' (sediment trap) in a gas piping system, and how should it be maintained?
- It increases gas pressure; it should be adjusted quarterly
- It collects moisture and debris; it should be periodically drained or cleaned (Correct answer)
- It reduces gas velocity; it requires no maintenance
- It acts as a pressure relief; it resets automatically
Correct answer: It collects moisture and debris; it should be periodically drained or cleaned
Drip legs trap condensate and particulates that can damage regulators and appliances, so they must be drained to remain effective.
Question 6: A pressure regulator is found to be 'locking up' (pressure rises and stabilizes above setpoint when no gas is flowing). What does this indicate?
- Normal operation under no-flow conditions
- A failing or worn regulator seat allowing gas to bypass (Correct answer)
- The upstream pressure is too low
- The downstream piping has a blockage
Correct answer: A failing or worn regulator seat allowing gas to bypass
Lockup pressure slightly above setpoint is normal, but excessive lockup indicates seat wear allowing creep, requiring regulator inspection or replacement.
Question 7: Which safety precaution must be taken before entering a confined space that contains gas piping for inspection?
- Turn off the building's main electrical breaker
- Test the atmosphere with a combustible gas detector and ensure adequate ventilation (Correct answer)
- Remove all tools from the space first
- Notify the local fire department 24 hours in advance
Correct answer: Test the atmosphere with a combustible gas detector and ensure adequate ventilation
Atmosphere testing confirms the space is free of explosive gas concentrations before entry, and ventilation prevents accumulation during work.
GPT System Inspection & Maintenance 3
What is the primary purpose of cathodic protection on underground gas piping?