CNG - Compressed Natural Gas Fueling Station Operations Questions and Answers

Question 1

A technician is observing the fueling of a vehicle at a fast-fill CNG station that uses a three-bank cascade storage system.
To achieve the most complete fill, in what sequence should the dispenser draw gas from the storage banks?

Accepted Answer

First from the low-pressure bank, then medium, and finally topping off from the high-pressure bank.

Answer

First from the high-pressure bank, then medium, and finally from the low-pressure bank.

Answer

Simultaneously from all three banks until the vehicle's cylinder pressure equalizes.

Answer

Only from the high-pressure bank to ensure the fastest possible fill time.

Question 2

During a routine inspection of a CNG dispenser, an operator notices the hose has significant abrasion, exposing the underlying reinforcement braid. What is the most appropriate action?

Accepted Answer

Immediately remove the dispenser from service until the hose can be replaced.

Answer

Wrap the abraded area with high-pressure tape as a temporary repair.

Answer

Continue using the hose but at a reduced fueling pressure.

Answer

Note the damage in the maintenance log for repair at the next scheduled service.

Question 3

Which of the following best describes the primary operational difference between a time-fill and a fast-fill CNG station?

Accepted Answer

Time-fill stations fuel vehicles directly from a smaller compressor over several hours, while fast-fill stations use large, high-pressure storage vessels for rapid fueling.

Answer

Time-fill stations use cryogenic liquid, while fast-fill stations use compressed gas.

Answer

Time-fill stations are only for public retail use, whereas fast-fill stations are exclusively for private fleets.

Answer

Time-fill stations require the vehicle's engine to be running during fueling, unlike fast-fill stations.

Question 4

A driver pulls away from a CNG dispenser with the nozzle still connected to the vehicle. What safety device is specifically designed to mitigate this exact scenario?

Accepted Answer

A hose breakaway coupling.

Answer

The emergency shutdown (ESD) button.

Answer

The pressure relief device (PRD) on the storage tanks.

Answer

The dispenser's mass flow meter.

Question 5

According to NFPA 52, which of the following is a mandatory requirement for the operator of a CNG fueling station?

Accepted Answer

To have a documented, active maintenance plan for the station equipment.

Answer

To recalibrate the station's compressor on a weekly basis.

Answer

To visually inspect every vehicle's CNG cylinders before allowing fueling.

Answer

To provide a certified attendant for every public fueling transaction.

Question 6

A fleet manager is planning a new CNG fueling station and wants to refuel a large fleet of buses overnight to take advantage of lower off-peak electricity rates. Which type of station would be most cost-effective and suitable for this operational model?

Accepted Answer

A time-fill station.

Answer

A fast-fill station with a five-bank cascade.

Answer

A mobile LNG (Liquefied Natural Gas) fueling tanker.

Answer

A combination-fill station with an emphasis on the fast-fill dispensers.