BELARUS-920.4/952.4 Operating manual
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Check the drive of the two-wire brake valve “B” (Figure 2.7) as follows:
1. Connect a pressure gage with a scale of 1 MPa min. to the coupling head (with yellow
cap) of the tractor pneumatic drive.
2. Turn on the compressor and fill the cylinder with air to reach pressure of 0.77 to 0.8 MPa
as per the pressure gage located on the instrument panel.
3. Air pressure as per the pressure gage connected to the coupling head (with a yellow cap)
of the control manifold must be equal to zero. Move the interlocked brake pedals to a full travel.
The pressure must rise to 0.65…0.8 MPa Release the brake pedals. Engage the parking brake by
shifting its handle to the maximum extent. The pressure must be raised to 0.65…0.8 MPa.
If the
pressure according to the pressure gage connected to the control connection line head does not cor-
respond to the above values, perform the following actions:
4. Check availability of a clearance gap of 1 to 2 mm between the finger 2 and the upper
edges of the grooves in the arms. If there is no gap, remove the finger 2 and adjust the length of the
arm by turning the end 1.
5. Check and adjust as necessary compressing of the spring 3 to a size of 35±1.25 mm by
rotating the nuts 4 and lock them. Check valve operation according to clause 3.
6. If air pressure as per the pressure gage connected to the coupling head has not reached
the required value, replace the brake valve “B”.
ATTENTION: WITH THE BRAKE VALVE “B” (FIGURE 2.7) AND ITS DRIVE
CORRECTLY ADJUSTED, PRESSURE AS PER THE PRESSURE GAGE CONNECTED TO
THE COUPLING HEAD (WITH A YELLOW CAP) MUST BE EQUAL TO ZERO WHEN THE
INTERLOCKED BRAKE PEDALS ARE NOT PRESSED AND WHEN THE PARK BRAKE IS
FULLY DISENGAGED.
2.4.3 Trailer brake hydraulic drive
2.4.3.1 General information
The tractors "BELARUS-920.4/952.4" can be equipped with trailer brake hydraulic drive.
Trailer brake hydraulic drive is interconnected with service brake control of tractor “BEL-
ARUS-920.4” and secures actuation of wheel brakes of trailer or semi-trailer, equipped with the
system of brake hydraulic drive. Hydraulic connecting line is powered from pump of hydraulic lift
linkage, which provides pressure from 10 to 15 MPa, and is designed as single-line brake system.
Hydraulic drive linking-up conforms to standard ISO/5676 dated 1983.
Trailer brake hydraulic drive consists of mechanically controlled brake valve 3 (Figure
2.8), which is actuated by pull-rod 2, connected to tractor parking brake pedals, and clutch 1 that
connects brake drive system of trailer or semi-trailer with tractor brake hydraulic drive. Trailer
brake hydraulic drive is powered sequentially from pump 6 of tractor hydraulic lift linkage by
means of high-pressure hoses 4, 5.
ATTENTION: TRACTOR, EQUIPPED WITH TRAILER BRAKE HYDRAULIC
DRIVE, CAN NOT BE GANGED UP WITH TRAILERS THAT HAVE SERVICE BRAKE
HYDRAULIC DRIVE.
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