CNG Fuel System Components 3

Question 1

A Type 4 CNG cylinder is constructed from:

Accepted Answer

Plastic liner fully wrapped with carbon fiber composite

Answer

Type 4 cylinders use a high-density polyethylene (HDPE) or nylon plastic liner that is completely overwrapped with carbon fiber composite for maximum strength at minimum weight.

Question 2

What is the standard service life of most Type 3 and Type 4 CNG cylinders in the US?

Accepted Answer

20 years

Answer

FMVSS 304 and NGV2 standards typically allow CNG cylinders a 20-year or 15-year service life depending on cylinder type and manufacturer specifications.

Question 3

The CNG excess flow valve closes automatically when:

Accepted Answer

Gas flow exceeds a preset rate due to a downstream leak or rupture

Answer

The excess flow valve senses abnormally high flow caused by a broken line or fitting and shuts off to prevent rapid uncontrolled gas release.

Question 4

Why are CNG fuel system components required to be electrically bonded?

Accepted Answer

To prevent static electricity buildup that could ignite gas

Answer

Electrical bonding provides a continuous conductive path so that static charges dissipate safely rather than sparking in the presence of natural gas.

Question 5

Which valve on a CNG cylinder prevents gas from flowing backward from the system into the filling nozzle during fueling?

Accepted Answer

Check valve

Answer

The check valve allows gas to flow only one direction—into the cylinder—and prevents backflow toward the dispensing equipment when the nozzle is disconnected.

(CNG) Compressed Natural Gas Practice Test

(CNG) Compressed Natural Gas Practice Test

CNG Fuel System Components 3