RMGA Gas Distribution Systems 2 — Questions and Answers
Question 1: What fusion method creates a joint between two polyethylene pipe sections by heating the pipe ends and pressing them together?
- Electrofusion
- Butt fusion (Correct answer)
- Socket fusion
- Solvent cement fusion
Correct answer: Butt fusion
Butt fusion heats the squared pipe ends to a molten state and then fuses them together under controlled pressure to create a joint as strong as the pipe.
Question 2: What is the purpose of a pressure test performed on a new gas distribution main before it is placed in service?
- To measure the gas quality
- To verify the integrity of the pipe and joints before gas introduction (Correct answer)
- To calibrate the pressure regulators
- To determine the maximum flow capacity
Correct answer: To verify the integrity of the pipe and joints before gas introduction
Pre-service pressure testing confirms that new piping and all joints are leak-free and structurally sound before gas is introduced.
Question 3: What does the term 'squeeze-off' mean in the context of polyethylene gas pipe?
- Reducing operating pressure at peak demand
- Mechanically flattening a PE pipe to stop gas flow (Correct answer)
- Removing moisture from the gas stream
- Installing a mechanical coupling on a damaged pipe
Correct answer: Mechanically flattening a PE pipe to stop gas flow
Squeeze-off is the process of mechanically compressing a polyethylene pipe flat to stop gas flow for maintenance or emergency response.
Question 4: What instrument is used by gas utility workers to detect the presence of natural gas in air?
- Manometer
- Combustible gas indicator (CGI) (Correct answer)
- Differential pressure gauge
- Infrared thermometer
Correct answer: Combustible gas indicator (CGI)
A combustible gas indicator (CGI) measures the concentration of combustible gas in air and alerts workers to potentially dangerous accumulations.
Question 5: How is natural gas odorized before distribution to customers?
- Mercaptan (ethyl mercaptan or similar) is injected into the gas stream (Correct answer)
- A yellow dye is added to the gas
- The gas is mixed with a small percentage of propane
- Radioactive tracers are added for detection
Correct answer: Mercaptan (ethyl mercaptan or similar) is injected into the gas stream
Mercaptans (thiols) are injected into the gas stream to give odorless natural gas a distinctive rotten-egg smell detectable at low concentrations.
Question 6: What does a gas distribution operator mean by 'locating and marking' a pipeline?
- Installing new pipeline route markers
- Identifying and marking the horizontal position of buried pipeline before excavation (Correct answer)
- Painting color codes on exposed pipe
- Updating pipeline records in GIS software
Correct answer: Identifying and marking the horizontal position of buried pipeline before excavation
Locating and marking involves using electronic equipment to find buried pipelines and placing surface marks to guide safe excavation by others.
RMGA Gas Distribution Systems 2
What fusion method creates a joint between two polyethylene pipe sections by heating the pipe ends and pressing them together?