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HYDRAULIC BRAKES OF TRAILERS
The control of the hydraulic brakes of trailers (semi-trailers) and the control of the
tractor brakes is designed in such a way that the braking effect of both the vehicles is
synchronized. The working pressure is applied by oil delivered by a permanent gear
pump of the hydraulic system. A brake valve is installed in the circuit downstream of
the pump.
The brake valve of the trailer is controlled by the pressure of the brake liquid from the
main brake cylinders depending on the force applied onto the brake pedal. At the
maximum depression of the brake pedal the pressure at the coupling must amount to
12 - 15 MPa. The brake valve makes sure that the brake function overrides the hy-
draulic function. When bleeding the tractor brakes do not forget to bleed the brake
valve as well. If during depression of the foot brake pedals shocks occur in the hy-
draulic circuit, it is necessary to bleed the hose from the brake valve to the quick-
coupling.
During driving with a hitched trailer or semi-trailer the pedals of the foot brake
must be connected and secured with a latch.
During braking with one brake pedal the hydraulic brakes of the trailer
are not in operation.
DRIVING OPERATION
81
P11NX231
CONNECTING AND DISCONNECTING
QUICK-COUPLINGS OF HYDRAULIC
BRAKES OF THE TRAILER
When connecting and discon-
necting the quick-couplings pay
increased attention with regard to
the residual oil that remains in the
socket or on the plug of the
quick-coupling.
For environmental reasons after
every disconnection of quick-
couplings this residual oil must be
removed with any textile material.
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