Properties and Safety Flashcards

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

Answer: 15%

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

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

Answer: DOT

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

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

Answer: Releases gas if cylinder temperature or pressure becomes excessive

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.

What is the autoignition temperature of methane?

Answer: 537°C (999°F)

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

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

Answer: To store gas at multiple pressure levels for efficient sequential filling

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

When a CNG vehicle is involved in a collision, what is the first safety concern regarding the fuel system?

Answer: High-pressure gas release or cylinder integrity

The primary concern after a collision involving a CNG vehicle is the integrity of the high-pressure cylinders and the potential for pressurized gas release.

Which gas is added to CNG to give it a detectable odor for leak identification?

Answer: Mercaptan (odorant)

Mercaptan (typically ethyl mercaptan or similar thiols) is added as an odorant to natural gas so leaks can be detected by smell.