Paccar Peterbilt 320, Operator'S Manual

Page: 69 / 212

PART 5: SEAT AND RESTRAINT SYSTEMS Inspection of the Restraint System
Inspection of the Restraint System
WARNING! Failure to properly inspect and
maintain restraint systems can lead to seri-
ous injury or loss of life.
Without periodic
inspection and maintenance to detect unsafe
conditions, seat restraint components can wear
out or not protect you in an accident.
The typical three-point seat systems in passenger cars may
seem very similar to the three-point seat belt system in
heavy duty vehicles, but there are some key differences
that all users of this system should be aware of:
• In typical passenger vehicle automotive seat belt ap-
plications, the normal life of the vehicles is usually 8
to 10 years and the total mileage frequently does not
exceed 125,000 miles (200,000 km). Heavy duty ve-
hicles often see this type of mileage in a very short
period of time, and accumulation of mileage in excess
of 500,000 miles (800,000 km) during the vehicle life-
time is not unusual.
• A signi fi cant difference in the two systems is the
amount of movement of webbing in the system. In
an automotive application, there is little movement of
the seat belt system, except when the user puts on or
takes off the belt. In trucks, however, there is almost
constant movement of the belt through hardware due
to ride characteristics and seats which are designed
to move, in order to enhance driver comfort. There
can even be movement of the webbing in the seat
belt system when the belt in not being used. Relative
movement between the seat and the cab, which nor-
mally occurs whenever the truck is in operation, can
cause wear of the seat belt webbing.
• Environmental conditions represent another major dif-
ference in the systems in automobiles and heavy duty
and specialty vehicles. Unlike the automotive environ-
ment, heavy duty and specialty vehicles may be very
dirty, and have more exposure to the sun’s damaging
ultraviolet rays, thus resulting in a reduction of the life
of the seat belt system.
The high mileage associated with heavy duty vehicles and
possible wear of the 3-point seat belt system, the continual
relative movement of the system, the possible contact with
the vehicle seat or other parts of the cab structure, and the
potential exposure of this system to severe environmental
conditions make it crucial to inspect the three-point seat
belt systems regularly. It is recommended that the seat
belt system in a vehicle be inspected every 20,000 miles
(32,000 km) or more often if the vehicle is exposed to se-
vere environmental conditions. Any seat belt system that
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