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SAFETY MEETING. Off Highway Trucks. Brakes. There are four separate controls used for braking Service Brake Retarder Secondary Brake Parking Brake. Dual Piston. Yellow- Secondary Parking Spring Applied /Oil Released Purple - Service/ Retarding Air Over Oil Applied.

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SAFETY MEETING

Off Highway Trucks


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Brakes

  • There are four separate controls used for braking

    • Service Brake

    • Retarder

    • Secondary Brake

    • Parking Brake


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Dual Piston

Yellow- Secondary Parking

Spring Applied /Oil Released

Purple - Service/ Retarding

Air Over Oil Applied


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Service Brake

  • For general braking

  • Aids Retarder

  • Front brake switch

    • On: front and rear wheel brakes

    • Off: rear wheels only

  • Not for downhill retarding


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Retarder

  • For long downgrade braking

    • Rear brakes only = 777 and down (unless 777 is equipped with “wet” front brakes)

    • All brakes = 785 and up

  • Use service brake to assist

  • Lever stays in position


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Secondary Brake

  • Red Lever / Foot Pedal

  • Test when ready to move

    • Apply secondary brake

    • Release the parking brake

    • Put transmission in 1st gear and bring rpm to 1200

    • Truck should not move--if it moves, do not operate

  • Applies front and rear brakes


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Parking Brake

  • Applies only the rear wheel brakes

  • Use when

    • at rest

    • loading

    • dumping


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Front Brake Switch (769-777)

  • Leave in ‘on’ position for emergency use

  • All brakes apply when service brake used

  • Use manual retarder or ARC when descending grades


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Automatic Retarder Control

  • More efficient than manual retarding

  • Leave ‘On’ during normal operation

  • Will allow transmission to upshift one gear if on or off

  • It applies brakes to maintain constant rpm


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Downgrade Retarding

  • Watch brake oil temperature

  • Stop and cool brake oil

  • Speed = Heat


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Braking/Retarding - Manual/Auto

  • Manual

    • Select proper gear for grade

    • Proper rpm 1700 – 2300 RPM (769D – 775E)

      • Below 1700 RPM brake oil flow is inadequate.

      • Hold truck at proper RPM unless unsafe.

  • ARC

    • Verify switch is on.

    • Select proper gear for grade

    • Operating range – 2160 – 2300 RPM (769D – 775E)

  • Note: If brake oil temp. climbs quickly, lower the gear.


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    RETARDER (rule of thumb)

    • What ever gear you travel up hill empty, you travel one gear LOWER down hill when loaded.

    • What ever gear you travel uphill loaded, you use one gear higher coming down empty.

    • What ever gear you travel uphill loaded, come down loaded in the same gear.

    • RememberHEAT is the guideline, if brakes get hot slow down. Gear down to keep over heating under control


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    ARCengine over speed protection

    • If engine approaches an unsafe engine speed ARC will engage the brakes even if the ARC is OFF.

    • An overspeed condition will occur at 2100 rpm. If the operator ignores this, the ARC will engage at 2180 rpm. If the speed continues to increase, the power train will upshift one gear, or if it is in the top gear, it will engage the torque converter drive at 2300 rpm.


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    RETARDER

    • for long downgrade braking

    • retarder applies 80% of available pressure, which is easier to modulate than the 100%.

    • avoid continuously engaging & disengaging

    • observe brake oil temperature

    • use service brake to assist

    • do not use for PARKING brake!

    • select proper gear for downhill


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    RETARDER

    • When do you use retarder vs. service brake?

      • Down grades

      • Load/Dump area

    • What factors could affect when to use the retarder or service brake?

      • Site specific issues.

      • Conditions (weather, materials, etc…)


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    Park Brake Reset Valve

    When the air system is drained, the parking brake reset valve will not allow the parking brake to be released until the system is full of air and the operator manually has to push this yellow button down.


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    Brake Tests

    • When do you conduct them?

      Start of shift

    • Which ones?

      Service, Secondary and Park Brakes

    • How?

      Apply brake being tested, release park brake(unless it is under test), gradually increase engine speed to approximately 1200 rpm, truck should not move. Do not operate if it does and have necessary repairs made.


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    Supplemental Steering (769-777)

    • Check Daily

    • Key in ‘run’ position, test switch up

    • Check steering

    • Test switch down


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    Secondary Steering Test (785-797)

    • The engine must be shut off with the emergency shutdown switch while leaving the key start switch on. When this switch is used, the bleed down solenoid is not energized and the accumulators will not allow the oil to go back to the steering tank. The truck can now be tested with the engine stopped.

    • VIMS monitors the accumulator pressure and refers to this as the, “High Steering Pressure Switch”.


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    Secondary Steering Check

    • When engine is off and the oil is cold the oil should be between the FULL and ADD marks of the upper gauge.

    • Accumulators(primary- secondary) - engine should be running and the level should not be lower than the engine running mark in the lower sight glass. If the oil is low have the nitrogen charge checked in the accumulator. If the charge is low, it could allow excess oil to be stored in the accumulators.

    1

    2


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    Steering accumulator check

    CHECK WITH

    ENGINE STOPPED

    AND OIL IS COLD

    “FULL”

    CHECK WITH

    ENGINE RUNNING

    AND OIL IS HOT

    “FULL”


    Tcs switch l.jpg
    TCS Switch

    • Find a clear, level, large area ;shift into 1st gear, low idle

    • Turn steering wheel all the way to the left/right and drive in a complete circle

    • Press and hold TCS test switch on

    • Machine will stop; outside brakes will release

    • Release test switch

    • Repeat test while moving the other direction


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    Brake Release Switch

    • Brake release switch- parking brake off, engine start switch to on, brake release switch to the on position hold until VIMS indicates the parking brake is released.

    • FYI can be used for lower the bed with dead engine;

      1. Start switch to on

      2. Hoist to body down position

      3. Hold brake release for 20 sec

      4. If it does not go down, hold hoist in raise position for 15 seconds. Move hoist to lower, if it still does not go down, there is a problem!


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    Truck Payload Management System

    • Payload Operator Display

    • May be part of VIMS

    • Load Indicator Lights

      • Green = keep loading

      • Flashing red = last pass

      • Red = truck is full

    • ‘ON/OFF’ switch

    • Test Switch

    • Also tracks:

      • total weight hauled

      • total loads


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    THANK

    YOU