inspection and basic maintenance of brake systems - la … · march 2003march 2003 fire apparatus...

Slide 2--1111--11March 2003March 2003 Fire Apparatus Driver/Operator 1AFire Apparatus Driver/Operator 1A

Inspection and Basic Inspection and Basic MaintenanceMaintenance

of Brake Systemsof Brake Systems


Types Types

Air brakesAir brakesHydraulic brakesHydraulic brakesSecondary braking systemsSecondary braking systems


Air Brake System Air Brake System

Most large, modern fire apparatus are Most large, modern fire apparatus are equipped with airequipped with air--operated braking operated braking systemssystemsThree braking systems combined Three braking systems combined

ServiceServiceParkingParkingEmergencyEmergency



Air compressorAir compressorPumps air into the air storage tanks Pumps air into the air storage tanks (reservoirs)(reservoirs)

GovernorGovernorControls when the air compressor will pump Controls when the air compressor will pump air into the air storage tanksair into the air storage tanks



Air storage tanksAir storage tanksHold compressed airHold compressed air•• Allow brakes to be used even if compressor stops Allow brakes to be used even if compressor stops

workingworking

Checked daily for condensationChecked daily for condensationNumber and size variesNumber and size varies



Air dryerAir dryerCollects and removes contaminantsCollects and removes contaminantsProvides clean, dry airProvides clean, dry airIn line between the air compressor and first In line between the air compressor and first air storage tankair storage tank



Alcohol evaporatorAlcohol evaporatorReduces the risk of ice in air brake Reduces the risk of ice in air brake components during cold weathercomponents during cold weather

Treadle valve or master control valveTreadle valve or master control valveLocated at the brake pedalLocated at the brake pedalControls entire brake systemControls entire brake systemOverrides other componentsOverrides other components



Safety relief valveSafety relief valveInstalled in the first tank the air compressor Installed in the first tank the air compressor pumps air intopumps air intoProtects the tank and the rest of the system Protects the tank and the rest of the system from too much air pressurefrom too much air pressure



Brake pedalBrake pedalBrakes are applied by pushing down on the Brakes are applied by pushing down on the brake pedalbrake pedalAlso called the foot valve or treadle valveAlso called the foot valve or treadle valve



Brake chamberBrake chamberConverts the energy of compressed air into Converts the energy of compressed air into mechanical force and motionmechanical force and motion

Slack adjusterSlack adjusterThe link between the brake chamber and the The link between the brake chamber and the foundation brake camshaftfoundation brake camshaft


Air Brake SystemAir Brake System

Drums and shoes Drums and shoes Discs and pads Discs and pads TypesTypes

SS--camcamWedgeWedgeDiscDisc


S-Cam Wedge



OneOne--way check valveway check valveAllows air to flow in one direction onlyAllows air to flow in one direction onlyAll vehicles with air brakes must have a check All vehicles with air brakes must have a check valve located between the air compressor and valve located between the air compressor and the first reservoirthe first reservoir



Air supply pressure Air supply pressure gaugegauge

All airAll air--braked vehicles braked vehicles have an air supply have an air supply pressure gauge pressure gauge connected to the air connected to the air tanktankDual air brake systemDual air brake system



Application pressure gaugeApplication pressure gaugeIndicates how much air pressure you are Indicates how much air pressure you are applying to the brakesapplying to the brakes

Low air pressure warningLow air pressure warningRequired with air brakesRequired with air brakes



Air pressure protection valveAir pressure protection valvePrevents air horns/air adjuncts from operating Prevents air horns/air adjuncts from operating when the pressure in the air reservoir drops when the pressure in the air reservoir drops below 80 psi below 80 psi

Stop light switchStop light switchTurns on the brake lights when you apply the Turns on the brake lights when you apply the air brakes air brakes Does with an electric switch that works by air Does with an electric switch that works by air pressurepressure



Front brake limiting valveFront brake limiting valveSome apparatus made before 1975 Some apparatus made before 1975 Normal positionNormal positionSlippery positionSlippery position



Spring brakesSpring brakesMeets emergency and parking brake Meets emergency and parking brake requirements requirements When driving, powerful springs are held back When driving, powerful springs are held back by air pressureby air pressureParking brake must be held on by mechanical Parking brake must be held on by mechanical force force



Dual air brake systemsDual air brake systemsUsed for safetyUsed for safetyOperated by a single set of brake controlsOperated by a single set of brake controlsThe first system is the primary systemThe first system is the primary systemOther system is the secondary systemOther system is the secondary system



Antilocking brake systems (ABS)Antilocking brake systems (ABS)On most newer apparatusOn most newer apparatusReduces possibility of being thrown into a skid when Reduces possibility of being thrown into a skid when the brakes are fully appliedthe brakes are fully applied

ComponentsComponentsSpeed sensorsSpeed sensors

ValvesValvesIn the brake line of each brake controlled by the ABSIn the brake line of each brake controlled by the ABSOn some systems, the valve has three positionsOn some systems, the valve has three positions



PumpPumpRestores pressure to the brakes once Restores pressure to the brakes once released by the valves released by the valves

ControllerControllerA computer in the car that watches the speed A computer in the car that watches the speed sensors and controls the valves sensors and controls the valves


Hydraulic Brake SystemHydraulic Brake System

Master cylinderMaster cylinderActs as the holding tank for brake fluidActs as the holding tank for brake fluidWhen the brake pedal is depressed, the When the brake pedal is depressed, the master cylinder forces fluid to each of the master cylinder forces fluid to each of the wheelswheels



Combination valvesCombination valvesEnsures that the front and rear brake systems Ensures that the front and rear brake systems are working together are working together Consists of aConsists of a•• Metering valveMetering valve•• Proportioning valveProportioning valve•• Brake warning lightBrake warning light

Slide 2--1111--3333March 2003March 2003 Fire Apparatus Driver/Operator 1AFire Apparatus Driver/Operator 1ACopyright © 1998-2002 Howstuffworks, Inc.Permission to duplicate granted by Howstuffworks for classroom use only.



Brake pedalBrake pedalBrake linesBrake linesWheel cylindersWheel cylinders

Contains fluidContains fluid--activated pistons that push the activated pistons that push the brake shoes/pads against the drums/discsbrake shoes/pads against the drums/discs



Emergency brakesEmergency brakesManually operatedManually operatedNot dependant on the hydraulic systemNot dependant on the hydraulic system



The operational principles of drum The operational principles of drum brakes/shoes, and the disc brakes/pads brakes/shoes, and the disc brakes/pads are the same as with air brakes are the same as with air brakes


Secondary Brake Systems Secondary Brake Systems

Saves wear on the primary brakes Saves wear on the primary brakes Referred to as retardersReferred to as retardersRetarders employ many existing Retarders employ many existing apparatus componentsapparatus components

Optimized control through the use of rotating Optimized control through the use of rotating engine and drive train forces engine and drive train forces


Secondary Brake SystemsSecondary Brake Systems

Engine retardersEngine retardersCompression brakeCompression brake•• Uses engine to brakeUses engine to brake•• Turns engine into energy absorbing air compressorTurns engine into energy absorbing air compressor

Exhaust brakeExhaust brake•• Uses exhaust from engine to brakeUses exhaust from engine to brake•• Works opposite compression brakeWorks opposite compression brake


Secondary Brake SystemsSecondary Brake Systems

Automatic transmission retarderAutomatic transmission retarderWorks with gear selectionWorks with gear selectionEmpty chamber mounted to rear of Empty chamber mounted to rear of transmissiontransmissionTransmission pump forces fluid into chamberTransmission pump forces fluid into chamber•• Chamber automatically emptiesChamber automatically empties

–– When not in useWhen not in use

Driveline Driveline Magnetic field developed with battery voltageMagnetic field developed with battery voltage


Inspection & Basic Inspection & Basic MaintenanceMaintenance

Air BrakesAir BrakesAir brake tests Air brake tests -- DMV DMV Air compressor and governorAir compressor and governor

Air pressure should build to allow apparatus Air pressure should build to allow apparatus operations within 60 seconds of startingoperations within 60 seconds of startingNeed to be operationally tested dailyNeed to be operationally tested daily



Air BrakesAir BrakesAir storage and drain tanksAir storage and drain tanks

Proper mountingProper mountingLooseLooseCleanCleanDrain dailyDrain daily



Air BrakesAir BrakesAir dryer and alcohol evaporatorAir dryer and alcohol evaporator

Securely mountedSecurely mountedConnections intactConnections intact

Safety valveSafety valveIf the safety valve releases air, something is If the safety valve releases air, something is wrongwrong



Air BrakesAir BrakesSlack adjustersSlack adjusters

Look forLook for•• Broken, loose, and missing partsBroken, loose, and missing parts•• Proper angle between push rod and adjuster arm Proper angle between push rod and adjuster arm

–– A little over 90A little over 90°° when brakes released and, when brakes released and, –– Not less than 90 Not less than 90 °° when applied when applied



Air BrakesAir BrakesBrake pedalBrake pedal

Firm when appliedFirm when appliedNot continue to travel to the floor when Not continue to travel to the floor when pressure is appliedpressure is appliedSecurely mountedSecurely mountedOperating properlyOperating properly



Air BrakesAir BrakesBrake drums & shoes/discs & padsBrake drums & shoes/discs & pads

Excessive or uneven wearExcessive or uneven wearMissing componentsMissing componentsCracksCracksOut of shapeOut of shapeOperational failureOperational failureFalls below required standardsFalls below required standards



Air BrakesAir BrakesOneOne--way check valveway check valve

Check for leaksCheck for leaksSecurely mountedSecurely mounted

Air supply pressure gaugeAir supply pressure gaugeMust be above 90 psi to operate safelyMust be above 90 psi to operate safely

Application pressure gaugeApplication pressure gaugeProper operationProper operation



Air BrakesAir BrakesLow air pressure warningLow air pressure warning

Activates below 60 psi ORActivates below 60 psi OROne half the compressor governor cutOne half the compressor governor cut--out out pressurepressure

Stop light switchStop light switchOperates the brake warning lightsOperates the brake warning lights



Air BrakesAir BrakesFront brake limiting valveFront brake limiting valve

LeaksLeaksMountingMounting

Spring brakesSpring brakesMissing componentsMissing componentsLeaksLeaks



Air BrakesAir BrakesDual air brake systemsDual air brake systems

All inspections same as single systemsAll inspections same as single systems



Air BrakesAir BrakesMaintenance should be completed by a Maintenance should be completed by a qualified technicianqualified technician

Due to the complexity of the system and Due to the complexity of the system and safety issues safety issues



Hydraulic Brakes Hydraulic Brakes Hydraulic brake testHydraulic brake test

Pump brake pedal three times and hold for Pump brake pedal three times and hold for five secondsfive secondsPedal should not movePedal should not moveIf it does, there is a leak If it does, there is a leak



Hydraulic Brakes Hydraulic Brakes Master cylinderMaster cylinder

Check fluid levelCheck fluid levelFill with proper manufacturer's recommended Fill with proper manufacturer's recommended fluidfluidCover should not be leaking fluidCover should not be leaking fluidInspect for leaksInspect for leaksWear may cause cylinder to leakWear may cause cylinder to leakMay result in brake failureMay result in brake failure



Hydraulic Brakes Hydraulic Brakes Brake pedalBrake pedal

Firm when appliedFirm when appliedNot continue to travel to the floor when Not continue to travel to the floor when pressure is appliedpressure is appliedSecurely mountedSecurely mountedOperating properlyOperating properly



Hydraulic Brakes Hydraulic Brakes Brake drums & shoes/discs & padsBrake drums & shoes/discs & pads

Excessive or uneven wearExcessive or uneven wearMissing componentsMissing componentsCracksCracksOut of shapeOut of shapeOperational failureOperational failureFalls below required standardsFalls below required standards



Hydraulic Brakes Hydraulic Brakes Brake linesBrake lines

Physical damagePhysical damageLeaking fluidLeaking fluid

Wheel cylindersWheel cylindersLeaking fluidLeaking fluidSticking wheel cylinder can cause brake to Sticking wheel cylinder can cause brake to dragdrag



Hydraulic BrakesHydraulic BrakesBrake liningsBrake linings

Same as air brake systemsSame as air brake systems



Hydraulic BrakesHydraulic BrakesMaintenance should be completed by a Maintenance should be completed by a qualified technicianqualified technician




Secondary BrakesSecondary BrakesInspections should includeInspections should include

Proper mountingProper mountingLoose or missing componentsLoose or missing componentsPhysical damagePhysical damageLeaks (if applicable)Leaks (if applicable)

Most failures are discovered during Most failures are discovered during operational testsoperational tests



Secondary BrakesSecondary BrakesMaintenance should be completed by a Maintenance should be completed by a qualified technicianqualified technician



NFPA OutNFPA Out--ofof--service Criteriaservice Criteria

Air BrakesAir BrakesService brakes that have a drop of more Service brakes that have a drop of more than 2 psi in one minute than 2 psi in one minute LeakLeak--down rate (time) is more than 3 down rate (time) is more than 3 psi in one minutepsi in one minuteBrakes out of adjustmentBrakes out of adjustmentDefective system componentsDefective system components



Air BrakesAir BrakesIneffective braking operationIneffective braking operationIneffective parking brakeIneffective parking brakeAir compressor that fails to build air Air compressor that fails to build air pressurepressureAir compressor that fails to maintain 80Air compressor that fails to maintain 80--90 psi pressure in the system90 psi pressure in the system



Air BrakesAir BrakesFriction surfaces, brake shoes, or disc Friction surfaces, brake shoes, or disc brakes with grease or oilbrakes with grease or oilLining, pads, rotors, or drums worn Lining, pads, rotors, or drums worn beyond manufacturer's minimum beyond manufacturer's minimum specificationsspecificationsActivated ABS warning indicatorActivated ABS warning indicator



Hydraulic BrakesHydraulic BrakesComponents with a Class 2 leakage or Components with a Class 2 leakage or are defectiveare defectiveFriction surfaces, brake shoes, or disc Friction surfaces, brake shoes, or disc brake pads with grease or oilbrake pads with grease or oilIneffective braking or parking brake Ineffective braking or parking brake operationoperation



Hydraulic BrakesHydraulic BrakesWarning light activated or pedal that Warning light activated or pedal that falls away/drifts when brake pressure falls away/drifts when brake pressure appliedappliedLining, pads, rotors, or drums worn Lining, pads, rotors, or drums worn beyond manufacturer's minimum beyond manufacturer's minimum specificationsspecificationsActivated ABS warning indicatorActivated ABS warning indicator



Secondary Braking SystemsSecondary Braking SystemsNone stated None stated


CCDH OutCCDH Out--ofof--service Criteriaservice Criteria

Air brakesAir brakesOnly indicates driving test failure, not outOnly indicates driving test failure, not out--ofof--service criteriaservice criteria

Hydraulic brakesHydraulic brakesIf fails DMV hydraulic brake testIf fails DMV hydraulic brake test

Secondary braking systemsSecondary braking systemsNone stated None stated

inspection and basic maintenance of brake systems - la … · march 2003march 2003 fire apparatus...

Documents