PROTECTION UNIT OF THE CONTROL VALVE
(AA from illustration 54669Xl)
1. Opening for wet tank. 3. Opening for reserve tank. 5.
Opening for dry tank. 14. Exhaust passage. 15. Valve. 16.
Piston. 17. Spring. 18. Spring. 19. Passage for inlet. 20.
The passage (I) to the wet tank gives protection to the
passage (3) and (5) reserve and dry tanks. If the pressure
in the passage ( I ) to the wet tank goes down to 40 + 5 psi
(280 + 35 kPa), the protection unit activates automatically.
Now, spring (18) for emergency piston (16) moves. When
piston (16) moves it will move valve (15). Exhaust
passage (14) of the protection unit is sealed and inlet
passage (19) lets air from passage (3) or passage (5) go
into the area above piston (16) and causes piston (16) to
move. Piston ( 16) makes the basic part of the control
valve work like the system was operated manually. The
protection unit has check valves (20) which stops air from
going out of one side through the other side because of a
failure in either line. If the air pressure goes below 50 ± 5
psi (345 ± 35 kPa) in passages (3) or (5), the emergency
brake will also activate when passage (I) has full pressure.
Brake Control Valve
The control valve for the tractor and water distributor
brake systems has separate passages for supply air and
delivery air. The same amount of air is delivered to both
systems. But, a failure of either system will not affect the
operation of the other part of the valve. The upper part of
the valve is used to control the tractor brakes and the
lower part of the valve is used to control the water