freightliner WALK-IN VAN CHASSIS Operator's Manual page 65

CNG Workshop Precautions
Because natural gas is less dense than air, it rises.
The shop ceiling needs to be equipped with a vent
system that will allow the gas to escape and dissi-
pate.
Use only safety fluorescent extension shop lights.
Ordinary light bulbs can explode if dropped, possibly
causing a fire.
The shop must be equipped with an alarm system
that activates when gas concentration in the air be-
comes dangerous.
Fire extinguishers should be the CO
minimum) and should be strategically located, highly
visible, and easily accessed.
Permit no smoking or other ignition sources in the
shop area.
Servicing the CNG System
Observe the following safety precautions when ser-
vicing natural-gas-powered vehicles:
•
Before making non-CNG system repairs on a
CNG vehicle, close the shutoff valve at the out-
let of the CNG container, and keep it closed
throughout the repair procedure. Have the
CNG system checked by a qualified technician
before reopening the fuel shutoff valve.
•
Allow only qualified technicians trained in auto-
motive CNG system repair to perform repairs.
•
Close the fuel shutoff valve(s) before perform-
ing maintenance and repairs, and when storing
the vehicle inside. Open the valve(s) only if
natural gas is needed to operate the engine or
to check for leaks.
•
Vent the gas outdoors to a safe location.
•
Always use a natural gas detector to test the
system for leaks, whether an odor is present or
not. Commercial compressed natural gas nor-
mally contains an odor-producing chemical to
enable users to detect leaks by smell. But be-
cause the odor-producing chemical can fade, a
leak detector is necessary.
•
Routinely inspect the fuel tanks, the fuel filter-
ing and regulating mechanisms, and the fuel
lines. Use a natural gas detector to check for
any leaks. A soap-and-water solution can be
used to pinpoint the exact location of leaks.
Compressed Natural Gas Fuel System
Major Repair and Replacement of
CNG Parts
When a vehicle is involved in an accident or a fire
type (ABC
causing damage to the fuel tank, the fuel tank must
2
be replaced. If damage occurred to other parts of the
fuel system, also replace those parts.
Any and all replacement parts (valves, fittings, tub-
ing, etc.) of the CNG fuel system must be designed
specifically for CNG automotive use and must be offi-
cially approved and rated for the pressures and con-
ditions that pertain.
Install parts and components in accordance with the
manufacturer's instructions.
Replace (do not repair) damaged fuel lines. When
replacing fuel lines, install the lines securely in a pro-
tected location, or shield them from heat sources and
from contact with unsecured objects. Before assem-
bly, apply a natural gas-impervious pipe thread joint-
ing material to all male pipe threads. Ensure that all
lines and fittings are clear and free of cuttings,
threading burrs, and scales, and that the ends of all
lines are reamed. Protect lines passing through a
panel by means of grommets or similar devices. Lo-
cate joints and connections so that they are acces-
sible.
Do not use aluminum or copper pipe, tubing, or fit-
tings between the fuel tank and the first-stage pres-
sure regulator because of the high pressure involved.
Ensure that shutoff valves have a rated service pres-
sure not less than the rated service pressure of the
entire fuel supply system, and that they are capable
of withstanding a hydrostatic test of at least four
times the rated service pressure.
Replace leaking fuel tanks; repair or replace
any lines, devices, or connections that are
leaking.
•
Always tighten fasteners and fuel connections
to the required torque specification, since over-
tightening or undertightening could cause gas
leakage. Tightening to the correct torque speci-
fication is critical to the system.
8.4