CNG - Compressed Natural Gas Codes, Standards, and Compliance Questions and Answers

Question 1

A maintenance facility that services CNG-powered vehicles must comply with specific ventilation and heating requirements outlined in NFPA 30A. Which of the following combinations is compliant for a major repair area?

Accepted Answer

A mechanical ventilation system interlocked with a gas detection system and a heater with surfaces below 750°F.

Answer

NFPA 30A, the Code for Motor Fuel Dispensing Facilities and Repair Garages, requires facilities repairing natural gas vehicles to have either continuous mechanical ventilation or a system activated by gas detection. Additionally, it prohibits open-flame heaters and any heating equipment with exposed surfaces that could exceed 750°F, which is well below the autoignition temperature of natural gas.

Question 2

According to CSA/ANSI NGV 2, the standard for CNG vehicle fuel containers, which piece of information is NOT required to be on the cylinder's permanent label?

Accepted Answer

The name of the original vehicle installer.

Answer

The CSA/ANSI NGV 2 and FMVSS 304 standards mandate specific information on the cylinder label to ensure safety and traceability. This includes manufacturer details, date of manufacture, service pressure, DOT certification symbol, container type, and expiration date. The name of the specific vehicle installer is not a required element of the cylinder label itself.

Question 3

A technician is performing a compliant defueling of a CNG vehicle's cylinders before a major repair. According to NFPA 52 and industry best practices, where should this procedure be performed?

Accepted Answer

Outdoors, away from ignition sources, with the vehicle properly grounded.

Answer

To ensure safety, defueling (venting) of CNG cylinders must be performed outdoors in a controlled manner. The area should be clear of ignition sources, and the vehicle must be electrically grounded to prevent static discharge from igniting the vented gas. Venting should be done through a code-compliant vent stack.

Question 4

A CNG-powered truck with a GVWR of 26,000 lbs is involved in a collision resulting in significant damage to the truck bed, but no visible impact to the fuel cylinders or lines. According to FMVSS 304, what is the mandatory action regarding the CNG fuel system?

Accepted Answer

A detailed visual inspection by a qualified inspector is required before the vehicle is returned to service.

Answer

FMVSS 304 explicitly states that CNG fuel containers must be visually inspected for damage and deterioration after a motor vehicle accident or fire, regardless of the vehicle's GVWR or whether damage is immediately apparent on the fuel system components. This must be a detailed inspection performed by a qualified individual.

Question 5

The design and compatibility of CNG fueling nozzles and vehicle receptacles, which prevent a vehicle from being filled at a pressure higher than its rating, are governed by which standard?

Accepted Answer

CSA/ANSI NGV 1

Answer

CSA/ANSI NGV 1 is the standard for 'Compressed natural gas vehicle (NGV) fueling connection devices.' It specifies the design, dimensions, and safety features of nozzles and receptacles to ensure interoperability and prevent cross-filling between different pressure classes (e.g., 3000 psi vs. 3600 psi).

(CNG) Compressed Natural Gas Practice Test

(CNG) Compressed Natural Gas Practice Test

CNG - Compressed Natural Gas Codes, Standards, and Compliance Questions and Answers