CNG Properties and Safety 3

Question 1

What is the Upper Flammability Limit (UFL) of methane in air?

Accepted Answer

15%

Answer

Methane's Upper Flammability Limit is approximately 15% by volume in air, above which there is insufficient oxygen for combustion.

Question 2

Which organization sets the standards for CNG cylinder design and testing in the United States?

Accepted Answer

DOT

Answer

The U.S. Department of Transportation (DOT) sets and enforces standards for CNG cylinder design, testing, and certification under 49 CFR.

Question 3

What does the PRD (Pressure Relief Device) on a CNG cylinder do?

Accepted Answer

Releases gas if cylinder temperature or pressure becomes excessive

Answer

A PRD is a thermal-activated safety device that vents gas from the cylinder if it is exposed to excessive heat or fire, preventing catastrophic rupture.

Question 4

What is the autoignition temperature of methane?

Accepted Answer

537°C (999°F)

Answer

Methane has an autoignition temperature of approximately 537°C (999°F), which is higher than gasoline, making it harder to ignite without a spark.

Question 5

In a CNG fueling station, what is the purpose of a cascade storage system?

Accepted Answer

To store gas at multiple pressure levels for efficient sequential filling

Answer

A cascade system stores CNG in banks at different pressure levels (high, medium, low) and draws from them sequentially to fill vehicles efficiently.

(CNG) Compressed Natural Gas Practice Test

(CNG) Compressed Natural Gas Practice Test

CNG Properties and Safety 3