CNG Codes, Standards, and Compliance 2 — Questions and Answers
Question 1: Which NFPA standard specifically governs vehicular fuel systems using compressed natural gas?
- NFPA 52 (Correct answer)
- NFPA 54
- NFPA 58
- NFPA 30A
Correct answer: NFPA 52
NFPA 52 is the Vehicular Gaseous Fuel Systems Code covering CNG and LNG vehicle fuel systems.
Question 2: Under DOT regulations, CNG cylinders used on vehicles must be re-qualified or condemned after what maximum period from manufacture?
- 10 years
- 15 years
- 20 years (Correct answer)
- 25 years
Correct answer: 20 years
Most CNG vehicle cylinders have a 20-year service life from manufacture date per DOT and cylinder manufacturer specifications.
Question 3: Which federal agency requires CNG fueling stations to comply with process safety management (PSM) rules if they exceed threshold quantities?
- OSHA (Correct answer)
- DOT
- EPA
- PHMSA
Correct answer: OSHA
OSHA's PSM standard (29 CFR 1910.119) applies to facilities handling flammable gases above threshold quantities.
Question 4: CSA NGV 1 is a standard that applies to which CNG component?
- Fueling station compressors
- Compressed natural gas vehicle fuel containers (Correct answer)
- CNG dispenser hoses
- Natural gas odorization systems
Correct answer: Compressed natural gas vehicle fuel containers
CSA NGV 1 establishes requirements for compressed natural gas vehicle fuel containers (cylinders).
Question 5: What pressure does NFPA 52 define as the maximum allowable working pressure (MAWP) for a standard CNG vehicle fuel system?
- 2,400 psi
- 3,000 psi
- 3,600 psi (Correct answer)
- 5,000 psi
Correct answer: 3,600 psi
NFPA 52 defines 3,600 psi (24.8 MPa) as the standard service pressure for CNG vehicle fuel systems.
Question 6: Which organization publishes the NGV 2 standard for basic requirements of compressed natural gas vehicle fuel containers?
- ANSI
- CSA Group (Correct answer)
- ASME
- SAE International
Correct answer: CSA Group
CSA Group (formerly Canadian Standards Association) publishes NGV 2, which is widely adopted for CNG cylinder requirements in the US.
Question 7: When must a CNG vehicle fueling station operator obtain a variance from NFPA 52?
- When installing a dispenser rated above 5,000 psi
- When proposing an alternative material or method not explicitly covered by the code (Correct answer)
- When the station serves more than 50 vehicles per day
- When CNG is dispensed to vehicles over 26,000 lbs GVWR
Correct answer: When proposing an alternative material or method not explicitly covered by the code
A variance or alternative method approval is required when an operator wants to use materials, equipment, or methods not addressed or differing from NFPA 52 provisions.
CNG Codes, Standards, and Compliance 2
Which NFPA standard specifically governs vehicular fuel systems using compressed natural gas?