Truck Trailer Refrigeration Maintenance - PowerPoint Presentation

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Truck Trailer Refrigeration Maintenance

Instructor Name: (Your Name)

17

CHAPTERSlide2

Learning Objectives

List components checked and maintained in a routine PM service of a refrigeration unitDescribe item that must be checked while servicing a diesel engineAccurately check and adjust engine coolant strength

Describe refrigeration maintenanceList steps required to perform a compressor pump down

List steps required to perform a low side pump downSlide3

Learning Objectives

Describe the procedure used to replace a filter dryerExplain evacuation techniquesDescribe leak testing procedures

Describe soldering and brazing techniquesList structural item that should be checked during a PMSlide4

Engine Lubricating system

Warm engine to operating temp before drainingHave large enough drain pan, approximately 16.9 quartsReplace engine oil filter on every oil change

Replace drain plug fill with proper quantity of oil, check the engine oil dipstickRun unit, shut down, check level again and adjust if necessarySlide5

Engine Oil Drain Plug and FilterSlide6

Fuel filter Replacement

Remove primary and secondary filtersDo not prime prior to installation, unfiltered fuel can damage injection pumpsTighten secondary filter until gasket contacts, tighten additional half turn

Install primary filter, spin on until just before gasket contactsOperate the prime pump until bubbles surround the top of primary filterSlide7

Fuel filter Replacement (continued

)Tighten the primary filter until gasket contacts, tighten additional half turnStart engine and look for potential leaksSlide8

Fuel Filter

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Bleeding The Fuel System

Fill fuel tankCrack bleeder screw on injection pumpOperate manual hand valve quickly air bubble are replaced by bubble free fuel from bleeder valve, this may take several minutes

Tighten bleeder screw while continuing to operate hand pumpSecure hand pump

Start engine, allow to operate until engine runs clean. This will ensure all air is out of system and alternator is not heavily charging. If it is allow it to recharge batteries or hook up external charger and charge batteriesSlide10

Bleeder Screw and Prime PumpSlide11

Air Filters

Two styles used, older oil bath and dry elementOil bath are serviceableDry element use a disposable element

Many manufacturers use a air inlet restriction gauge on the intake systemReplace filter when indicator the red signal is in view with engine off

Make certain all clamps are tight and fit correctlyReset air inlet restriction indicator after filter is replacedSlide12

Air Filter and Inlet Restriction IndicatorSlide13

Engine Coolant Replacement

Warm engine to operating temp and open drain cock on engine blockRun clean water in top of radiator or expansion tank until clear water is draining from engine blockInspect all hoses and clamps

Remove tension from water pump belt and inspect the water pumpPressure test radiator cap

Pre mix 50/50 solution of antifreeze and de-mineralized waterSlide14

Engine Coolant Replacement (continued)

Close drain cocks on engine blockFill system and warm the engine with the radiator cap on loosely. This will allow trapped air to escape the system. Top off system as necessary and secure the radiator cap

Note: Always comply with environmental regulations in your area for properly disposing of coolantSlide15

Defrost System

Defrost system should be checked on every serviceRun refrigeration unit until box temperature is at or below 38⁰F (3.3⁰C) Depress the manual defrost switch

The unit should shift from cool mode to defrost modeIf unit fail to go into defrost mode consult service manual for defrost cycle checkout procedures

Defrost air switches that sense air pressure on the inlet and outlet of evaporator coil to initiate defrost mode are commonly usedSlide16

Defrost Air SwitchesSlide17

Defrost Air Switch Check

Remove all sensing tubes electrical connections from the air switchConnect ohm meter across switch terminalsConnect magnehelic gauge to the high pressure side of switch

Raise the pressure of the magnehelic gauge until switch closes, as indicated by ohm meter. The gauge reading, in inches or mm of water indicate the set point

If switch does not have continuity, pressurize the gauge to the specifications found in the service manualSlide18

Defrost Air Switch Check (continued)

Turn adjusting screw clockwise until switch closes and indicated by ohm meterRepeat test several times to ensure setting is correct

Remove test equipment and hook up electrical connections.Install sensing tubes to their original positions. The black hose to the air switch side marked black and the clear hose to the side marked clearSlide19

Defrost Air Switches Test SetupSlide20

NOTE:

Thermo King units use color coded sensing tubes. Carriers differentiate tubes by referring one as the high pressure and the other as the low side pressure. Testing and adjusting a Carrier air defrost switch is identical to the procedure previously described, with the exception of the switch settings. Always refer to the appropriate service manual for correct air switch specifications.Slide21

Testing Refrigerant Level

The operating pressures are for units operating on R-12, see service manual for pressures of system being testedOperate system in cool mode., there should be at least 150 psi discharge pressureSuction pressure and box temp are about equal

The ball should be floating in the receiver tankSlide22

Complete Recharge of Refrigeration System

Evacuate the systemConnect manifold gauge set to unit and mid seat the service valvesConnect refrigerant cylinder on scale and connect to manifold gauge set, note weight of cylinder

Open refrigerant cylinder liquid valve and discharge hand valve on manifold gauge setWatch scale and stop when specified amount of refrigerant enters systemSlide23

Complete Recharge of Refrigeration System (continued)

If feed stops before required amount enters system, close discharge gauge valve and cylinder liquid valve.Open the suction hand valve on gauge set and vapor valve on the cylinder

Start system and run at high speed cool, vapor will be drawn in by compressorSet gauge valve so the refrigerant is flowing at 30psi higher then the system suction pressureWatch the scale and close valves when the required weight of refrigerant has entered the systemSlide24

Manifold Gauge Connections Slide25

Manifold Gauge Connections (continued) Slide26

Partial Recharge of Refrigeration System

Connect manifold gauge setConnect refrigerant tank to center hose of gauge setOpen tank in vapor position and purge center hose

Lower box temperature to 0⁰F (-18⁰C) or cover evaporator coil with test bag Start unit with thermostat set to -20°F (-29°C)

Cover condenser until discharge pressure reaches 150 psi (1034 kPa)Add refrigerant to suction side until the receiver sight glass ball floatsSlide27

Compressor Oil Check

Follow manufacturers recommendationsRun unit 15 to 20 minutes in high coolCheck oil level in the compressor oil level sight glassNormally oil level should be one quarter to half way up windowSlide28

Compressor Pump Down

Connect manifold gauges, mid seat service valvesRun unit high speed cool 10-15 minutesWhile unit is running front seat suction valve

When suction pressure at 15020 inches (51-68 kPa) shut unit down. Compressor must hold vacuum before proceeding

If compressor has residual refrigerant it may be necessary to repeat procedureSlide29

Compressor Pump Down (continued

)With compressor in vacuum front seat the discharge service valveUsing manifold gauge bleed some refrigerant from the high side to the low side of system until low side has a 1 to 2 psi 6.9-13.8 kPa) positive pressure

When compressor is opened to atmosphere it is important to have positive pressure or foreign material may be drawn onto the compressor

Note: Never operate unit with discharge valve closed, severe damage could occur

With compressor pumped down compressor oil can be changedSlide30

Compressor Pump Down (continued)

Place drain pan under oil drain plug and remove plugRemove oil fill plug. Replace both plug seals

Install the oil drain plugAdd the quantity as specified in the service manualInstall the oil fill plug

With service valves front seated connect vacuum pump to gauge set

and pull compressor into deep vacuum and check that it holds for at least 5 minutes

Back seat service valves, unit is now ready to return to serviceSlide31

Compressor Oil Drain PlugsSlide32

Low Side Pump Down

Install manifold gauge set, run system 5 to 10 minutesWith system high speed cool front seat receiver outlet valveWhen suction pressure reaches 15 to 20 inch (51-68 kPa) vacuum, shut unit down. Unit must hold vacuum before proceeding

Using manifold gauge bleed some refrigerant from the high side to the low side of system until low side has a 1 to 2 psi 6.9-13.8 kPa) positive pressureService work on low side of system can now be performedSlide33

Evacuation Process

Prior to evacuation ensure all refrigerant has been removedConnect refrigerant hoses to refrigeration unit.Run vacuum to deep vacuum prior to opening service valves to test the service equipment

Mid seat service valvesRun vacuum pump until a 2,000 micron reading is obtained

Turn of vacuum pump and seal from system, wait a few minutes to ensure vacuum holdsSlide34

Evacuation Process (continued)

Restart vacuum pump, allow to run until 500 microns are reached on vacuum gauge. Close off vacuum pump and turn off. Vacuum must hold for 5 minutes, loss of vacuum indicates moisture or leaks in systemRefrigerant can be drawn into system while in deep vacuum, note weight of refrigerant cylinderSlide35

Soldering and Brazing Safety

Work in well ventilated work spaceWear protective (non flammable) clothesWear proper eye protection

Maintain all soldering and brazing equipmentRemove all flammable materials prior to soldering or brazingSlide36

Most Common Alloys for Silver Brazing

Sil-Fos 5Sil-Fos 6Sil-Fos 15

Phoson +Slide37

Six Steps for Leak-Proof Silver Brazed Joints

Tight filament of jointClean joint contact areaCorrect use of brazing flux on the join

Stress relief on joint while brazingCorrect heating and alloy flow techniques

Final cleaningSlide38

Six Steps for Leak-Proof Silver Brazed Joints (continued)

Joint fitment- Cut squarely, Debur the cut, Joint clearance no more than .005” (0.127 mm)Joint Cleaning- Clean completely of all oil, grease, rust or oxides, clean inside with solvent or tubing brush, clean outside with 320 grit sanding cloth

Joint Fluxing- Flux must not get inside the system, fit tubes part way then apply fluxJoint Stress Relief- support so it will not hinder expansion and contractionSlide39

Tools and Procedures For Brazing Tubing JointsSlide40

Six Steps for Leak-Proof Silver Brazed Joints (continued)

Joint HeatingHeat with number 5 oxyacetylene tip

Air propane and air acetylene can be used on tubing up to 1 inchUse neutral flameStart heating ½ to 1 inch from end of fitting

Heat evenly around circumference of tubing

Bulk of heat should be concentrated on the fittingDo not stop moving the torch, fitting can quickly over heatSlide41

Six Steps for Leak-Proof Silver Brazed Joints (continued)

Joint Heating (continued)

When flux becomes clear apply alloy to the joint seamIf temperature is correct alloy will flow into joint

Once enough alloy has been applied pass torch at base of joint to expel any gas in jointFinal Cleaning- Use wet rag or brush to remove al flux on outside of jointSlide42

Heating TechniquesSlide43

Heating Techniques

Vertical Down SilverBrazing Joint

Vertical Up SilverBrazing JointSlide44

Heating Techniques

Horizontal SilverBrazing Joint

Soft Solder TechniqueSlide45

Heat Sinks

When soldering or brazing around components that may be damaged by heat, a heat sink should be used. A heat sink will absorb damaging heat that can destroy components such as vibrasorbers and service valves. If a heat sink is not available use a wet rag wrapped around vibrasorber will draw enough heat to prevent damage.Slide46

Heat Sinks

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Summary

A PM on a refer unit includes engine, fuel system, compressor, drive belt, refrigeration system, Glow plugs, and structural checksEngine oil and filters should be changes according to manufacturers recommendations

Fuel filters should be changed during engine serviceBleeding purges air from the fuel system

Air cleaners filter all combustion air

Belt tension and condition should be checked at all PM servicesSlide48

Summary

Glow plugs preheat combustion air to aid startingEngine coolant should be checked periodicallyThe coolant system should be flushed when dirty

The purpose of the defrost cycle is to remove accumulated ice from the evaporator coil

The defrost air switch is responsible for initiating a defrost cycleThe defrost termination switch is responsible for terminating the defrost cycle

Refrigerant levels should be checked during every PM Slide49

Summary

The compressor oil should be checked whenever a refrigerant leak is suspected or when components have been serviced or replacedA low side pump down can be performed whenever service work is required on low side of system. This procedure allows service of all components downstream of receiver to compressor to be serviced without removal of refrigerant

To remove refrigerant from compressor, a compressor pump down is requiredSlide50

Summary

The compressor oil can be changed or service work can be performed on compressor or suction service valve when the compressor is pumped downThe evacuation process removes air and moisture from the refrigeration system after it has been openedAlways follow safety precautions when soldering or brazing refrigeration components

Causing inert gas to flow through joints will prevent copper oxide from forming on inside of tubingTo produce a trouble-free silver brazed joint always follow the six stepsSlide51

Summary

Follow correct heating procedure for the type of joint you intend to brazeSoft solder requires the same preparation as silver brazing; the difference is the melting point of the solderThe structural integrity of the unit should be examined on a PM. This would include examining the engine and fuel tank mounts, visual inspection of unit; checking cleanliness of coils; checking evaporator drainage; and inspecting the defrost damper door system