Combined Pneumatic Drive Of Trailer Brakes; General Information - Belarus 1822.3 Operator's Manual

Air is taken to the pneumatic drive from the engine intake manifold through the line
2 (Figure 3.9.2). The air is compressed in the compressor 1 and delivered to the tank 9
through the pressure regulator 10 maintaining required pressure in the tank. From the
tank, compressed air goes to the brake valve 4 and to the feed line 5 with the connecting
head 6 (with red cap) that is always under pressure. The brake valve 4 is connected
through the control line 8 with the connecting head 7 (with yellow cap). There is no pres-
sure in it. Brakes of trailers and agricultural machines are controlled in two modes: direct
and automatic.
Direct control of the brakes is executed at the cost of pressure rise in the control
line 8 to 0.65 - 0.8 MPa when the tractor decelerates. In such case, the feed line 5 remains
under pressure, and delivery of compressed air to the trailer pneumatic system is retained.
Automatic control of the brakes (automatic braking) is executed in case of coupling
break and disconnection of the trailer due to pressure drop in the trailer feed line.
At the end of the connecting lines the valve-type coupling heads 6 and 7 are in-
stalled. The coupling head valves prevent air loss in case of use of the pneumatic drive
without a trailer (for example, for tire inflation). When the trailer brake lines are connected
to the tractor lines, the coupling head valves open, ensuring passage of compressed air
from the tractor pneumatic drive to the trailer. Hereby, it is recommended to connect the
pneumatic lines with no pressure in the cylinder 9 of the tractor. Tires are inflated through
the air bleed valve 11 of the pressure regulator 10.
Note – Rules on checking and adjustment of the brake valve of the double-line
pneumatic drive are given in clause 3.9.4.2.3.

3.9.4 Combined pneumatic drive of trailer brakes

3.9.4.1 General information

The combined pneumatic drive provides brake control of trailers and agricultural
machines, equipped both with single-wire and with two-wire pneumatic brake drive as well
as tire inflation. A diagram for the combined pneumatic drive is shown in figure 3.9.3.
1 – compressor; 2 – line from engine intake manifold; 3 – condensate drain valve; 4 –
brake valve (single-line); 5 – connecting line; 6– feed line; 7, 8, 9 – connecting heads; 10 –
control line; 11 – brake valve (double-line); 12 – tank; 13 – pressure regulator; 14 – air
bleed valve; 15 – air pressure sensor; 16 - emergency air pressure sensor.
Figure 3.9.3 – Diagram of combined pneumatic drive of trailer brakes
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