Milton CAT 772 - Manual (Page 12)

Full Hydraulic Service Brake. The 772
features a full hydraulic brake system,
which offers significant improvements
in reliability, response, control and
serviceability versus an air-over
hydraulic system. There are fewer
components (part by part comparison),
boosting reliability and streamlining
maintenance.
Hydraulic Accumulators. The brake
system is equipped with a primary
accumulator and a secondary
accumulator, which also provides
back-up braking in the event of a failure.
The accumulators automatically drain
pressure after shutdown, reducing the
service time by removing the need to
drain the pressure off the system and
reducing the risk of high-pressure
exposure during maintenance.
The new brake system uses a pump that
is driven off the flywheel 100 percent
of the time and is only loaded when
hydraulic pressure falls below 11 024 kPa
(1,600 psi). The pump will cut out at
13 608 kPa (1,975 psi). In the new system,
oil in this circuit is also sent to the
hydraulic fan system. Any additional
oil is sent to the brake cooling system
along with the oil used in the drive fan.
Improved Reliability. Because oil is now
used to actuate the brakes, Caterpillar has
eliminated the need for two brake master
cylinders, two relay valves, an air dryer
and the retarder valve (found on ARC
trucks only) that were associated with
the air-over-hydraulic brake system.
The air system had complexity, which
affected its reliability. The oil actuated
system is simpler and more reliable.
Oil-Cooled Multiple Disc Brakes. Cat dry
front and rear oil-cooled, multiple disc
brakes are now hydraulically controlled,
reducing maintenance costs.
The 772 brakes provide exceptional,
fade-resistant braking and retarding for
maximum performance and productivity
in all haul-road conditions.
Extended Life Multiple Disc Brakes
(Optional). Extended life friction material
has double the wear life of standard
brakes and is twice as resistant to
glazing for more consistent braking
power with less noise.
Brake Design. Cat rear oil-cooled disc
brakes are designed with large discs and
plates for reliable, adjustment-free
operation and performance. Rear brakes
are completely enclosed and sealed to
prevent contamination and reduce
maintenance.
Long Life. An oil film prevents direct
contact between the discs. This design
absorbs the braking forces by shearing
the oil molecules and carrying heat
away to extend brake life.
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Reliable braking with superior control gives the operator the confidence to focus on productivity.
Brake System