ICC Natural Gas Systems and Safety 2 — Questions and Answers
Question 1: What type of pipe is most commonly specified for new natural gas distribution main installations due to its corrosion resistance and ease of installation?
- Cast iron
- Polyethylene (PE) (Correct answer)
- Galvanized steel
- PVC
Correct answer: Polyethylene (PE)
Polyethylene (PE) pipe is the predominant material for new natural gas distribution mains because it is corrosion-resistant, flexible, lightweight, and can be joined using heat fusion without the need for cathodic protection.
Question 2: What is the primary function of a pressure regulator station on a natural gas distribution system?
- To measure total gas consumption for billing purposes
- To reduce high transmission pressure to safe distribution system pressure (Correct answer)
- To remove moisture and impurities from natural gas
- To inject odorant into the natural gas stream
Correct answer: To reduce high transmission pressure to safe distribution system pressure
Regulator stations step down high-pressure gas from transmission pipelines to the lower operating pressures used in distribution systems, ensuring safe delivery pressure to end users.
Question 3: Per 49 CFR Part 192, at what maximum concentration of natural gas in air must the odorant be detectable by a person with a normal sense of smell?
- At 1% gas concentration in air
- At or below 20% of the lower explosive limit (LEL) (Correct answer)
- At 50% of the lower explosive limit
- At the upper explosive limit (UEL)
Correct answer: At or below 20% of the lower explosive limit (LEL)
Federal regulations require that odorant be detectable at concentrations at or below one-fifth (20%) of the lower explosive limit, ensuring leaks can be smelled well before the gas reaches a hazardous concentration.
Question 4: Which records must an ICC-certified contractor maintain and make available for inspection following any natural gas facility installation?
- As-built drawings and pressure test records (Correct answer)
- Only the original work order and customer invoice
- Customer payment receipts and utility approval letters
- Inspection photographs only
Correct answer: As-built drawings and pressure test records
Contractors must maintain as-built drawings showing actual installation details and pressure test records documenting that the required strength and leak tests were performed and passed.
Question 5: When a natural gas leak is discovered during construction or excavation, what is the immediate first action the contractor must take?
- Continue work and report the leak at the end of the shift
- Evacuate the area and immediately notify the gas utility and emergency services (Correct answer)
- Attempt to stop the leak using pipe clamps or repair fittings
- Cover the leak area with soil to prevent potential ignition
Correct answer: Evacuate the area and immediately notify the gas utility and emergency services
Immediate evacuation and notification of the gas utility and emergency services is the required first action, as natural gas leaks create explosion and asphyxiation hazards that require trained utility responders.
Question 6: What is the approximate lower explosive limit (LEL) of natural gas (primarily methane) in air?
- 2.5%
- 5% (Correct answer)
- 10%
- 15%
Correct answer: 5%
The lower explosive limit of methane (the primary component of natural gas) is approximately 5% by volume in air; below this concentration, the mixture is too lean to ignite.
Question 7: What joining method is required when connecting polyethylene natural gas pipe sections in the field?
- Threaded pipe connections
- Solvent cement (glue) joints
- Heat fusion (butt fusion or electrofusion) (Correct answer)
- Compression couplings only
Correct answer: Heat fusion (butt fusion or electrofusion)
Polyethylene gas pipe must be joined using heat fusion techniques—either butt fusion or electrofusion—which create molecular bonds as strong as the pipe itself, as required by 49 CFR Part 192 and manufacturer specifications.
ICC Natural Gas Systems and Safety 2
What type of pipe is most commonly specified for new natural gas distribution main installations due to its corrosion resistance and ease of installation?