26
MAINTENANCE
Relay Emergency Valve
(see
Figure 22
)
The relay emergency valve senses the line pressures
and relays the response to the brake chambers. Daily
operating tests are described elsewhere in this manual.
Before conducting further tests, check the tractor air
pressure gauge against an accurate test gauge.
10 Stud Disc Wheel Tightening Sequence
Hub-Piloted (Two piece flange nuts)
Wheel Stud
Torque
Thread Size
ft. lbs. (Lubricated)
M22x1.5
450 - 500
(W/1-1/2” Hex)
Torque Values - Dual Wheels
Dry Threads - No Lubrication
Stud Size
Inner & Outer Capnut
3/4 - 16
450 - 500 ft. lbs.
Backnut Torque
Size
Torque
3/4 - 16
175 - 200 ft. lbs.
Figure 18. Tightening Sequence of Standard Gunite
Disc Wheels
For other wheel brands, follow manufacturers recom-
mended sequence.
WARNING
Block the wheels during these tests
1. Connect the service and emergency lines. When
the pressure reaches 60 -65 PSI (4.14 - 4.48 Bar), the
brakes must automatically release.
1
2
3
4
5
6
7
8
9
10
2. Apply and release the service brake several times.
Check for prompt brake application and release.
3. Release the brakes and stop the engine with the
system pressure between 90 - 100 PSI (6.2 -6.9 Bar).
A two minute check must show a pressure drop of no
more than 6 PSI (0.41 Bar) for the combination vehicle
system.
4. If step “3” indicates possible leakage, apply soap
suds at the relay emergency valve exhaust port. A one
inch (25.4 mm) soap bubble in not less than five seconds
is permissible.
5. Apply soap suds at the pipe plugs and fittings.
Correct all leaks as indicated.
6. With the engine stopped and the pressure at 90
- 100 PSI (6.2 - 6.9 Bar) make and hold a full service
brake application. A two minute check must show a
pressure drop of no more than 8 PSI (0.55 Bar) for the
combination vehicle system.
7. If Step “6” indicates possible leakage, apply soap
suds on the relay emergency valve cover and exhaust
port. A one inch (25.4 mm) bubble in not less than three
seconds is permissible. Correct all leaks as indicated.
8. Place the tractor protection control valve in
“emergency” position or close the cutoff valve on the
emergency line. Disconnect the emergency line cou-
pling. The trailer brakes must apply promptly. Check
for leakage at the emergency coupling. A leak indicates
a leaking check valve or O-rings in the relay emergency
valve. Also check the service line. A leak here indicates
leaking O-rings in the relay emergency valve. Recharge
the system. The brakes must release at 65 PSI (4.48 Bar)
emergency line pressure.
9. Stop the engine with the system fully charged.
Make a series of foot valve applications. Reduce the
pressure to 30 PSI (2.07 Bar). The trailer brakes must
apply automatically at this pressure or at the emergency
setting of the tractor protection equipment.
If the valve does not function properly or leakage is
excessive, it must be repaired or replaced.
Brake Chambers
(see
Figure 23
)
Air pressure on the pressure plate side of the brake
chamber diaphragm pushes the diaphragm against the
push rod assembly. This extension of the push rod
pushes against the slack adjuster, which actuates the
brakes.
Brake Chamber Servicing
If an air leak is detected around the clamp ring, the
bolts can be tightened to stop the leak.
