CNG Properties and Safety 2 — Questions and Answers
Question 1: What is the primary component of compressed natural gas (CNG)?
- Propane
- Methane (Correct answer)
- Butane
- Ethane
Correct answer: Methane
CNG is composed primarily of methane (CH4), typically making up 90% or more of its composition.
Question 2: CNG is stored in vehicle cylinders at approximately what pressure?
- 1,000 psi
- 3,600 psi (Correct answer)
- 500 psi
- 10,000 psi
Correct answer: 3,600 psi
CNG is typically stored in high-pressure cylinders at around 3,600 psi (248 bar) in vehicles.
Question 3: What color are CNG fuel lines typically required to be for identification purposes?
- Red
- Blue
- Yellow
- Orange (Correct answer)
Correct answer: Orange
CNG fuel lines are typically color-coded orange to distinguish them from other vehicle fluid lines.
Question 4: Which property makes CNG safer than gasoline in terms of spill behavior?
- It is heavier than air and settles to the ground
- It dissipates into the atmosphere rather than pooling (Correct answer)
- It is non-flammable at ambient temperatures
- It reacts with water to become inert
Correct answer: It dissipates into the atmosphere rather than pooling
Being lighter than air, CNG disperses upward and dissipates into the atmosphere rather than pooling on the ground like liquid fuels.
Question 5: What is the Lower Flammability Limit (LFL) of methane in air?
- 1%
- 5% (Correct answer)
- 15%
- 25%
Correct answer: 5%
Methane's Lower Flammability Limit is approximately 5% by volume in air, below which ignition cannot occur.
Question 6: Which type of CNG cylinder is made entirely of metal with no composite wrapping?
- Type 1 (Correct answer)
- Type 2
- Type 3
- Type 4
Correct answer: Type 1
Type 1 cylinders are all-metal (typically steel or aluminum) with no composite overwrap, and are the heaviest type.
Question 7: A CNG cylinder must be removed from service when it reaches what condition?
- When it shows any surface rust
- When it exceeds its requalification date or shows structural damage (Correct answer)
- When it has been in service for 5 years
- When it has been filled more than 500 times
Correct answer: When it exceeds its requalification date or shows structural damage
CNG cylinders must be removed from service when they exceed the manufacturer's requalification date or show signs of structural damage, bulging, or deep corrosion.
CNG Properties and Safety 2
What is the primary component of compressed natural gas (CNG)?