training presentation

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Training PresentationTraining Presentation

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BMCBulldozer Hydraulic SystemBulldozer Hydraulic System

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BMCCONTENTSCONTENTS

Hydraulic System PrinciplesHydraulic System Principles

Hydraulic System AssemblyHydraulic System Assembly

Malfunctions Analysis and SolvingMalfunctions Analysis and Solving

Pressure Measurement to Diagnose Pressure Measurement to Diagnose hydraulic systemhydraulic system

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BMCChapter OneChapter One

Hydraulic System Hydraulic System PrinciplesPrinciples

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BMCHydraulic Components:Hydraulic Components:

Input: Pumps

Output: Cylinders, Motors

Controls: Valves

Ancillary Equipment: Oil tank, Piping, Filters, Oil Cooler

Hydraulic System PrinciplesHydraulic System Principles

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BMCTransmission & Steering Transmission & Steering HydraulicsHydraulics

SD22 & SD32 Hydraulic System: Transmission and steering control

systems are separated to each other, they draw oil from different pumps, but all the oil is from steering clutch case. The oil flows to the torque converter after transmission and steering, then the oil flows back to steering clutch case.

So, the transmission and steering are one system called transmission & steering hydraulic system.

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BMCSD22 Hydraulic System

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BMCSD16 Hydraulic System:

Transmission and Steering control systems draw oil from Transmission case and Steering clutch Case. Oil flows to torque converter after transmission, then to transmission pan again through oil cooler. However steering clutch oil flows back to steering clutch case.

So, the transmission and steering are two different systems.

Transmission & Steering Hydraulic Transmission & Steering Hydraulic SystemSystem

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BMCSD16 Transmission System

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BMCSD16 Steering and Brake System

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BMCChapter TwoChapter Two

Hydraulic System Hydraulic System AssemblyAssembly

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BMCGear Pump:Gear Pump: Bulldozer Transmission & Steering Pumps are

high pressure gear pumps. Their construction is simple and very efficient.

Transmission Valve:Transmission Valve: SD22, SD32 have the same transmission valve

unit. It is consists of Relief Valve, Return Valve, Pressure Reduction Valve, Speed Control Valve, Safety Valve and Direction Valve.

Relief Valve & Return Valve are for transmission oil pressure, Speed Control Valve is for shift change, Direction Valve is for Forward and Reverse, Pressure Reduction Valve is for First Shift, Safety Valve is for protection of starting machine.

Assembly & OperationAssembly & Operation

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BMCSD22, SD32 Transmission SD22, SD32 Transmission ValveValve

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BMCSD16 transmission valve has no Safety

valve, but other 5 valves’ structure and principle are same as SD22 and SD32.

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BMCSD16 Transmission ValveSD16 Transmission Valve

From PumpFrom PumpTo Torque ConverterTo Torque Converter

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BMCModulating Relief Valve:

The modulating relief valve controls the buildup of oil pressure when the gear shift lever is operated and the clutch engaged, so as to avoid shock during start and off and improves the service life of power shift transmission.

Modulating Time

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BMCSteering Valve

SD32, SD23, SD22 and SD16 steering valves’ structure and principle are the same.

Steering & brake hydraulic system includes relief valve, steering control valve, brake booster valve.

they have a bypass/relief valve, to avoid abnormal oil pressure if the filter is clogged.

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Steering Valve

Steering Relief Valve

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Work equipment control system

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Relief Valve

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BMCChapter ThreeChapter Three

TroubleshootingTroubleshooting & Problem & Problem SolvingSolving

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BMCHydraulic system problems are caused by many

factors.

The Process of identifying a problem:The Process of identifying a problem:

Watch →Test Machine →Check PressureWatch →Test Machine →Check Pressure

Resolving the problem:Resolving the problem:

a. Refer to Operation or Shop Manual

b. Carry out adjustments/fit replacement parts

Methods of TroubleshootingMethods of Troubleshooting

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Transmission Problems SolvingTransmission Problems Solving

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BMCReason:Reason:a. Inner Transmission Box: 1. the gearshift’s cylinder seal damaged or installed wrong 2. Oil path leak 3. if First Shift is inoperative: 1) Ball of anti return valve is broken 2) Oil path rotating seal ring is damagedb. Hydraulic system: 1. the 5 O-rings of clutch oil entrance in the seat of transmission valve are damaged 2. the factors of the pressure reduction valve:If the pressure reduction valve is blocked at closed position, 1st

gearshift is inoperative; if the pressure reduction valve piston hole is blocked, the oil pressure will increase, leading to worn seals, the 1st gearshift is inoperative.

1. Gearshift inoperative1. Gearshift inoperative

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BMCReason:Reason:

1. Incorrect adjustment of the direction valve position2. Forward and reverse clutch disc distorted or broken, it

locked, the clutch can’t separate completely.

2. The machine drives on Neutral Gearshift2. The machine drives on Neutral Gearshift

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BMCReason:Reason:

The machine will not drive on any gearshift position, it’s because the clutch can’t get oil.

1. Transmission pump damaged, it can’t draw oil.2. Transmission pump seal leak.3. Transmission case oil level is down.4. Oil piping leak, problem with pump.5. Relief valve is blocked, 5 clutches have no oil

pressure.

3. The machine will not drive3. The machine will not drive

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BMCReason:Reason:1. the clutch can’t get oil, suction piping leak.2. Relief valve’s relief spring is broken, it delays the

pressure increase in time.

4. Gearshift Lag4. Gearshift Lag

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BMC5. Hot machine no drive, but cold machine 5. Hot machine no drive, but cold machine

is normal.is normal.

Reason:Reason:The suction pipe is aging or worn or distorted,

and the suction ability is not good.The oil is thin, clutch can’t engage properly,

so the hot machine has low power.

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BMCReason:Reason:

Relief valves blocked, the valve can’t move correctly, the oil pressure is low and the clutch can’t engage.

6. Transmission Torque Reduced6. Transmission Torque Reduced

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BMCReason:Reason:

a. Torque converter problem:1. return oil pump filter is blocked2. the seal leaking

b. Hydraulic system problem:1. oil quality is not good2. oil quantity is low, or oil leak3. insufficient cooling.

7. Torque converter over heating7. Torque converter over heating

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BMCReason:Reason:

Relief valves blocked or inlet blocked, the high pressure bulges the cover. Must clean the relief valve.

8. Steering filter cover bulged8. Steering filter cover bulged

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BMCReason:Reason:

Pulling the steering lever to the end and the pressure normal, the reason is that steering lever is adjusted incorrectly.

9. Poor Steering Control9. Poor Steering Control

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BMCReason:Reason:

1. “S” tube o-ring is damaged2. Clutch intake oil rotation seal is damaged3. Clutch piston seal is damaged

10. One side no steering, another side is normal10. One side no steering, another side is normal

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BMCReason:Reason:

1. The tube between steering pump and filter is damaged, so oil can’t pass through.

2. The oil becomes thin as the machine warms up, or the seal is worn, oil leak, oil pressure decrease.

11. Cold machine has steering, 11. Cold machine has steering, but hot machine has not steeringbut hot machine has not steering

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BMCReason:Reason:

This phenomenon shows that another side can’t transfer power, maybe another side steering direction valve block at open position.

12. Pulling one steering lever, the machine will stop12. Pulling one steering lever, the machine will stop

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BMCReason:Reason:Steering suction oil system seal is damaged and steering

pump can’t get enough oil, the pressure is down.

Due to steering pump drawing air, the oil filter has not oil, it leads transmission pump to draw air too. So sometimes transmission failure is caused by steering system damage.

When the pump draws air, there are sharp whistle, and there are many air bubbles in oil.

13. Sometimes steering is intermittent13. Sometimes steering is intermittent

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BMCReason:Reason:

a. Brake band is worn out, need adjustment or replacement

b. Brake linkage are adjusted incorrectly

c. Brake booster valve don’t seal well

14. Braking is poor14. Braking is poor

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BMC15. Pushing force is 15. Pushing force is poorpoorReason: Reason:

a. Engine

b. Torque Converter

c. Transmission

d. Steering Clutch

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BMCCheck for the position of problem:Check for the position of problem:a.a. If the universal joint rotates, the malfunction If the universal joint rotates, the malfunction

is after engine or torque converter.is after engine or torque converter.b.b. If the universal joint does not rotate, then the If the universal joint does not rotate, then the

malfunction is before transmission or steering malfunction is before transmission or steering clutch.clutch.

c. If bevel gear rotates, the problem is at steering clutch; if bevel gear does not rotate, the problem is at transmission.

15. Pushing force is 15. Pushing force is poorpoor

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BMCCheck for the Pressure:Check for the Pressure:

a. If the pressure is right, it must be that there is mechanical malfunction or inner failure.

b. If the pressure isn’t normal, we must diagnose, by referring to the manual.

15. Pushing force is 15. Pushing force is poorpoor

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BMCChapter FourChapter Four

Pressure Measure for Pressure Measure for DiagnosisDiagnosis

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BMC1. Important Measurements1. Important Measurements

a. Oil brand, quality and grade are correct, steering case oil level correctb. Warm-up engine, ensure coolant and oil temperature are in 70-90oCc. Engine is at operating speed

2. Measurement Method2. Measurement MethodMeasure the oil pressure at engine full speed and idle speed.

3. Measure Points, Standard Pressure (theoretic data in 3. Measure Points, Standard Pressure (theoretic data in manual) manual)

Pressure Measurement Pressure Measurement to Diagnose hydraulic problemsto Diagnose hydraulic problems

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Examples forExamples for

Diagnosing Pressure MeasurementsDiagnosing Pressure Measurements

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BMC1. Machine will not move on selecting a gear

Measure relief valve pressure: low is 0.1, full speed is 0.3MPa.

Due to this low pressure, gear clutch can’t get enough force, the machine can’t move.

Discharge the air in steering filter, the pressure raised, but once engine stops 10 minutes later start again, the pressure is low again. This means that air is in the pump, replace the O-ring, and the problem is solved.

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BMC2. Speed is low in any gear

Measure transmission relief valve pressure: low is 0.4MPa, full speed is 0.7MPa

Due to this low pressure, discharge the air from filter, it is not helpful.

Then check the return valve, then find the valve piston is blocked, the oil is leaking from output. Clean the valve piston, reset it again, the problem is solved.

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BMC3. Power is down on the mid rpm

Measure transmission relief valve pressure: low is 1.0MPa, full speed is 3.5MPa, the pressure changed too much with increased engine speed, it means that the relief valve need to be adjusted.

After checking, finding the valve piston is blocked with many carbon and corrupted hollows. After cleaning valve piston, reset it again, the problem is solved.

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BMC4. Torque converter power decrease

Measure transmission and steering relief valve pressure: both are normal.

Measure the entrance of torque converter, the oil pressure is 0.4MPa

Check torque converter safety valve, if spring is broken, replace it, the problem is solved.

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BMC5. If hydraulic oil temperature high, long term working, then the valve will block easily

Measure transmission valve, the pressure is normal.Measure the entrance of torque converter, low speed

pressure is 0.1MPa, full speed oil pressure is 0.5MPa.

Due to the entrance pressure being low, the oil flow is low and cooling poor, so the temperature is high.

Check torque converter, check the seal of inner oil path for damage, replace it, the problem is solved.

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BMC6. No steering at low speed, but at increased engine rpm, the steering is ok.

Measure steering relief valve pressure: low speed pressure is 0.4MPa, full speed oil pressure is 1.1MPa;

And steering clutch oil pressure is low.At the same time the valve is faulty. It means that steering relief valve is the problem, check

it, if the spring is broken, replace it, the problem is solved.

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BMC7. Cold machine steering is normal, but after working, the steering is very heavy

Measure steering relief valve pressure: low speed oil pressure is 0.5MPa, full speed oil pressure is 1.1MPa;

Steering relief valve oil pressure is low, it is caused by a blockage of relief valve.

Disassemble and clean it, the problem is solved.

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BMC8. One side steering is not serviceable

Steering relief valve pressure is normal, other side steering brake pressure is normal too, but this side steering brake pressure is low.

It show this booster or its piping has a leak. Disassemble booster, check the piping entrance o-ring is

damaged, replaced it, the problem is solved.

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BMCThe End of This Training ModuleThe End of This Training Module

Thanks Your Cooperation !!!Thanks Your Cooperation !!!

The End of This Training ModuleThe End of This Training Module

Thanks Your Cooperation !!!Thanks Your Cooperation !!!

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