12.4 Valves – 12 Common Pneumatics
Maintenance Manual Ottawa T2 4x2
12.4 Valves
page
–
Tractor Protection Valves
Located in the circuitry between the tractor and the trailer, a
special valve responds to the trailer air supply knob, or to a bro-
ken trailer air line, by cutting off the air supply to the trailer sys-
tem.
page
–
Proportioning Relay (Bobtail) Valve (Optional)
Available as an option, this valve is designed to detect if a trail-
er is connected to the brake air system. When a trailer is not
present, the valve causes the front brakes to do a larger per-
centage of the work than when a trailer is present.
Connected downstream of the primary reservoir, system air en-
ters its supply port. If no trailer is present, pistons in the valve
are repositioned so that, when the pedal is applied, a larger
percentage of air goes to the front brakes causing them to as-
sume a greater part of the work of stopping the tractor.
If a trailer is present and the trailer supply valve is opened, a
portion of the trailer supply air enters the proportioning valve
through its control port. The valve restores its internal pistons
to their original positions. Air passes normally through the valve
to the rear and trailer brakes.
page
–
Quick Release Valves
Each brake chamber connects to its own quick release valve
nearby. This valve responds to the release of the foot pedal.
The purpose of this valve is to dump the air out of the spring
chambers much more quickly than would be possible if the air
had to travel back through the supply lines.
page
–
Anti-Compounding Valve (Optional)
Also available is an anti-compounding valve that prevents the
service brakes from adding to (compounding) the effort exerted
by the parking brakes. It protects against brake cracking and
damage to the linings.
page
–
Double (Two-Way) Check Valves
These are used to sense pressure from front and rear, or sup-
ply and service, and allow the dominant pressure to actuate the
trailer brakes, the stop light switch and release the parking
brakes. A two-way quick release valve combines the two func-
tions in a single housing.
Summary of Contents for Ottawa t2
Page 1: ......
Page 47: ...38 0 8 Electrical Instruments 0 Machine Complete Maintenance Manual Ottawa T2 4x2 ...
Page 53: ...44 1 11 Start Stop 1 Engine Maintenance Manual Ottawa T2 4x2 ...
Page 55: ...46 2 Transmission Maintenance Manual Ottawa T2 4x2 ...
Page 57: ...48 3 Driveline Axle Maintenance Manual Ottawa T2 4x2 ...
Page 73: ...64 5 4 Diagnosis Hydrostatic Steering 5 Steering Maintenance Manual Ottawa T2 4x2 ...
Page 81: ...72 7 11 Diagnosis Boom 7 Load Handling Maintenance Manual Ottawa T2 4x2 ...
Page 83: ...74 8 Control System Maintenance Manual Ottawa T2 4x2 ...
Page 145: ...136 11 2 Safety 11 Common Electric Maintenance Manual Ottawa T2 4x2 Chassis Power Board ...
Page 153: ...144 12 5 Air Dryer 12 Common Pneumatics Maintenance Manual Ottawa T2 4x2 ...
Page 155: ...146 D Error Codes Maintenance Manual Ottawa T2 4x2 ...
Page 261: ...252 0 4 Fastener Torque Values F Technical Data Maintenance Manual Ottawa T2 4x2 ...