AIR BRAKES –GENERAL INFORMATION
AIR SYSTEM VALVES
NOTE: Complete detailed Information pertaining to
each of the air brake components may be found in
the Air Brake Components section.
INVERSION VALVE (FIGURE 15)
An inversion valve is used in both initial and refined split
air systems. On straight trucks and buses, this valve Is
installed in the air brake system to apply the parking
brakes on the rear axle along with the secondary service
brakes if air loss occurs in the primary system. The split
air brake system on most tractors functions in a similar
manner as a straight truck except there is no need for an
Inversion valve to apply the parking brakes. The trailer
brakes which operate off the primary or secondary
tractor air system provide braking effort to assist the
tractor brake in an emergency situation if there is an air
loss on one of the systems.
Figure 15 - Inversion Valve
All 6x4 tractors with the refined air system and air
suspension (as shown in Figures 13 and 14) will be
equipped with an inversion valve. The inversion valve is
required on these vehicles should a loss of air occur in
the primary system when operating during bobtail
operation.
On a straight truck which is equipped with trailer towing
provisions, the vehicle will have a split air system which
combines both straight truck and tractor air systems as
previously described.
WARNING: A LOW AIR PRESSURE WARNING
BUZZER WILL SOUND IN THE EVENT OF A FAILURE
IN EITHER THE PRIMARY OR SECONDARY SYSTEM.
UNDER
NO
CIRCUMSTANCES
SHOULD
THE
VEHICLE CONTINUE TO BE OPERATED WHEN A
FAILURE IS INDICATED SINCE AIR PRESSURE
CANNOT BE BUILT UP IN THE SYSTEM UNTIL THE
AIR LEAK IS CORRECTED, EVEN THOUGH AIR FOR
EMERGENCY STOPPING IS RETAINED IN THAT
PORTION OF THE SPLIT AIR SYSTEM NOT HAVING
A FAILURE.
MODULAR CONTROL VALVE (FIGURE 16)
A one piece push-pull (modular control valve) includes
both parking brake and trailer air supply controls. This
valve also is equipped with a shuttle type double check
valve which replaces a double check valve in the
plumbing system. A modular control valve can be
utilized in initial or refined systems.
Figure 16 - Modular Control Valve
MANIFOLDED
TRACTOR
PROTECTION
VALVE
(FIGURE 17)
A manifolds tractor protection valve includes two double
check valve assemblies along with the stoplight switch
port. This valve may be utilized in initial or refined
systems.
Vehicles with these valves also have the feature of
Tractor Park Only and Trailer Charge with Tractor Spring
Brakes Applied (tractor park only). Figures 10, 11 and 12
illustrated the use of a modular control valve and
manifolds tractor protection valve in refined split air
systems. Figures 18, 19 and 20 illustrate the use of a
modular control valve and manifolds tractor protection
valve in initial split air systems.
CTS-4514Y-Page 15
