S l a c k adjuster and air brake chamber
h . E m e r g e n c y Air Line.
s e m i t r a i l e r extends from the air hose coupling (tagged EMERGENCY), on the left side
This air line transmits compressed air to fill the semitrailer reservoir and
maintain proper air pressure, under control of the emergency relay valve, to apply
the brakes on the semitrailer.
E m e r g e n c y Relay Valve.
on the semitrailer air reservoir by a connecting pipe nipple (5). The valve directly
controls the service brakes on the semitrailer.
It speeds brake action by releasing
air from the air reservoir, on the semitrailer, directly to the air brake chambers.
This valve controls the flow of air to and from the semitrailer air reservoir and
automatically applies the brakes if the semitrailer breaks away from the towing
vehicle or if there is a serious leak in the emergency air line.
j . A i r R e s e r v o i r s . The air reservoirs (1 and 2, figure 4-25) are attached to
the chassis frame. The reservoirs are connected by tubing (3) and provide a supply
o f a i r t h r o u g h t h e e m e r g e n c y r e l a y v a l v e ( 4 ) f o r a p p l y i n g t h e b r a k e s . The emergency
relay valve (4) is mounted directly to the left air reservoir by a pipe nipple (5).
The air reservoirs are equipped with drain cocks (6) for draining accumulations of
moisture and for releasing air pressure in the semitrailer brake system.