Natural Gas Vehicles, General Information; Natural Gas Vehicles, Safety Precautions - freightliner M2 Plus 2023 Manual

Natural Gas Vehicle Information
Natural Gas Vehicles, General
Information
The vehicle can be equipped with a compressed
natural gas (CNG) fuel system, or a liquefied natural
gas (LNG) fuel system.
CNG is made by compressing natural gas to less
than 1% of its volume at standard atmospheric
pressure. It often contains an odor-producing
chemical.
LNG is created by condensing natural gas into a
liquid by cooling it to approximately -259°F (-162°C).
LNG does not have any odor.
For natural gas to burn, it must first vaporize, then
mix with air in the proper proportions (flammable
range is 5 to 15% by volume in air), and then be
ignited.
A typical natural gas fuel system consists of:
•
Fuel supply cylinders that store compressed
gas at high pressure (CNG), or a tank that
stores liquefied gas at an extremely low
temperature (LNG).
•
A vaporizer or heat exchanging device that
changes LNG to gaseous form (LNG fuel
systems only).
•
Pressure relief and manual fuel shutoff valves.
•
A filling connection with a check valve that
prevents the gas from flowing back out of the
fuel filling line.
•
High-pressure and low-pressure fuel filters.
•
A pressure control regulator that reduces the
high fuel tank or cylinder pressure to the lower
pressure needed for the engine.
•
A fuel contents gauge that indicates the fuel
supply in the tank or cylinders.
When vaporized at ambient temperatures, natural
gas is less dense than air, and it rises and disperses.
However, LNG is initially heavier than air due to its
cryogenic temperature. When released in large
amounts, it may drop or pool on the ground before
its temperature rises enough to vaporize. Cold
atmospheric conditions may prevent natural gas from
dispersing quickly when released in large amounts.
Natural gas is nontoxic, but it can cause asphyxiation
if present in very large concentrations.
19.1
Natural Gas Vehicles, Safety
Precautions
DANGER
Natural gas is highly flammable. Failure to
observe the following safety precautions could
lead to the ignition of the natural gas, which
could cause serious bodily injury or death.
Follow these safety precautions when operating or
repairing a natural gas vehicle.
•
Do not start the engine if a natural gas leak is
detected.
•
Do not attempt to cut any fuel supply piping
components.
•
Avoid open flames or sparks near a natural
gas vehicle.
•
Cover eyes and exposed skin when working on
a natural gas fuel system or fueling a natural
gas vehicle.
•
Always purge the fuel lines before performing
maintenance or repairs on a natural gas fuel
system. To purge the lines, close the manual
fuel shutoff valve, and start the engine. Let the
vehicle idle until the fuel lines are empty and
the engine stops.
•
Always use a natural gas detector to test the
system for leaks, whether an odor is present or
not. Routinely inspect the fuel filtering and
regulating mechanisms, and the fuel lines. A
bubble solution can be used to pinpoint the
exact location of leaks.
•
Always tighten fasteners and fuel connections
to the required torque specification. Over-
tightening or under-tightening could cause
leaks.
•
Close the fuel shutoff valve(s) before
performing maintenance and repairs.
•
Do not store a natural gas vehicle indoors for
any extended period of time. Do not bring a
natural gas vehicle indoors unless the
workshop is equipped with a methane
detection and ventilation system.
•
Do not transfer CNG from one vehicle to
another, as a buildup of static electricity could
cause a spark and ignite the fuel.