CNG Compression Technology and Equipment

Question 1

What type of compressor is most commonly used in CNG fueling stations for achieving the high pressures required for vehicle fueling?

Accepted Answer

Reciprocating piston compressor

Answer

Reciprocating piston compressors are the industry standard for CNG stations because they can achieve the high pressures (3,600 psi) needed for vehicle fueling.

Question 2

What is the standard service pressure for CNG vehicle storage cylinders in the United States?

Accepted Answer

3,600 psi (248 bar)

Answer

3,600 psi (248 bar) is the standard service pressure for CNG vehicle cylinders in the US, as established by NFPA 52 and industry standards.

Question 3

What is the primary purpose of an intercooler between compression stages in a multi-stage CNG compressor?

Accepted Answer

Cool the compressed gas to improve efficiency and protect downstream components

Answer

Intercoolers cool the compressed gas between stages, reducing the work required for subsequent compression stages and protecting valves and seals from heat damage.

Question 4

In a multi-stage CNG reciprocating compressor, what happens to the gas at each successive compression stage?

Accepted Answer

Pressure progressively increases as volume decreases at each stage

Answer

Each compression stage progressively increases gas pressure while reducing volume, with the cumulative effect delivering gas at full CNG service pressure at the final stage.

Question 5

What is the function of a moisture separator or coalescing filter in a CNG compression system?

Accepted Answer

Remove water vapor and entrained liquids from compressed natural gas

Answer

Moisture separators remove water vapor and liquid water from compressed gas to prevent corrosion, hydrate formation, and contamination of vehicle fuel systems.

(CNG) Compressed Natural Gas Practice Test

(CNG) Compressed Natural Gas Practice Test

CNG Compression Technology and Equipment