9working hydraulic system_englisg-g9165

Service Manual of RS8160 Road Roller

9 Working Hydraulic System

SERVICE MANUAL

Service Manual for G9165 Grader

I

CONTENTS

9 Working Hydraulic System ................................................................................. 9-1

91 General ................................................................................................................. 9-1

92 Description, Disassembly and Assembly of Main Components ....................... 9-10

921 Working Pump ........................................................................................... 9-10

922 Hydraulic Oil Tank .................................................................................... 9-15

923 Multitandem Valve .................................................................................... 9-23

924 Rotary Control Valve ................................................................................ 9-31

925 Middle Swivel Joint ................................................................................... 9-38

926 Hydraulic Oil Cylinders ............................................................................ 9-44

927 Other Hydraulic Components .................................................................... 9-48

93 Pressure Measurement of Working Hydraulic System ..................................... 9-50

94 Service Precautions for Working Hydraulic System ......................................... 9-51

95 Diagnosis of Common Faults of Working Hydraulic System........................... 9-54


9-1

9 Working Hydraulic System

91 General

G9165 adopts double-circuit double-constant-displacement-pump open-type working hydraulic

system, which consists of an enclosed tank, two high-pressure gear pumps, two multitandem valves

and hydraulic cylinders, rotary valve and the pipelines. System pressure is controlled by pressure

valve inside the multitandem valve and system set pressure is 21MPa. The hydraulic lock that

installed on front wheel tilt cylinder and front and rear frame hinge, and the balance valve installed

on shovel blade lifting cylinder can prevent the shifting due to the weight of equipment itself and

load so as to ensure the safety of moving and the operation accuracy of blade.

The working devices of G9165 grader are powered by two high-pressure gear pumps, and the two

pumps are installed on transmission box PTO port. The left main pump is used supply high-pressure

oil to the left multitandem valve and the right main pump is used to supply high-pressure oil to the

right multitandem valve. Because of the design, the operational stability and accuracy of the grader

are improved, and the machine can continue to work if one of the two pumps is faulty.

Rotation of shovel blade is realized by rotating of the whole rotary gear ring, which is driven by

rotary valve + double oil cylinders and engagement of rotary gear ring and a small gear.

Fig. 9-1 Oil flow route of working hydraulic system

Hydraulic oil tank

Working pump

Multitan-dem valve

Working device

Multitan-dem valve

Radiator


9-2

Fig. 9-2 Working hydraulic principle diagram


9-3

Up/down of shovel blade

The two shovel blade lifting cylinders are controlled respectively by the left multitandem valve and

right multitandem valve, and supplied by two oil lines with the same oil flow, so the two shovel

blades can be lifted or lowered synchronously, working accuracy of the grader is improved. And the

balance valve installed on the lifting cylinder can prevent the shifting due to the weight of

equipment itself and load so as to ensure the safety of moving and the operation accuracy of blade.

Fig. 9-3 Up/down of shovel blade

1 Right blade lifting cylinder 2 Left blade lifting cylinder

3 Right multitandem valve (1A/1B) 4 Left multitandem valve (10A/10B) 5 Balance valve

Swing of shovel blade

Power source of the blade swing cylinder is from the fifth valve group of right multitandem valve.

Fig. 9-4 Swing of shovel blade

1 Blade swing cylinder 2 Right multitandem valve (5A/5B) 3 Balance valve


9-4

Tilt (change cutting angle) and sidesway of shovel blade

Power source of the blade tilt cylinder and blade sidesway cylinder are from the fourth valve group

and third valve group of left multitandem valve, respectively. The middle swivel joint can prevent

the hydraulic pipes from intertwining when the shovel blade is rotating.

Fig. 9-5 Tilt (change cutting angle) and sidesway of shovel blade

1 Left multitandem valve (7A/7B and 8A/8B) 2 Middle swivel joint 3 Blade tilt cylinder

4 Blade sidesway cylinder

Tilt of front wheels

Fig. 9-6 Tilt of front wheels

1 Hydraulic lock 2 Front wheel tilt cylinder 3 Right multitandem valve (3A/3B)


9-5

Power source of the front wheel tilt cylinder is from the third valve group of right multitandem

valve. The hydraulic lock acts as a stabilizing force in the front wheel tilt oil line, eliminating the

swing phenomenon between front wheels and front frame during driving.

Hinge steering

Power source of the steering cylinder is from the fourth valve group of right multitandem valve.

The balance valve acts as a stabilizing force during steering, eliminating the twist phenomenon

between front frame and rear frame caused by load deflection.

Fig. 9-7 Hinge steering

1 Right multitandem valve (4A/4B) 2 Balance valve 3 Hinge steering cylinder

Shovel blade rotation

Fig. 9-8 Shovel blade rotation

1 Left multitandem valve (6A/6B) 2 Rotary control valve 3 Blade rotary cylinder

Power source of the shovel blade rotary cylinder is from the fifth valve group of left multitandem

valve. Pressure oil is allocated to the two rotary cylinders through the rotary control valve. The

rotary cylinders drive the two hardened small gears to rotate the rotary frame, so as to realize blade


9-6

rotation.

Unlike many other grader manufactures, we adopt double-oil-cylinder rotary mechanism rather than

“hydraulic motor + turbine reducer” mechanism. To enable the rotary frame rotate continuously, the

drive arm of the left rotary cylinder and right rotary cylinder are arranged with 90° difference. Two

hardened small gears are used to drive the rotary frame, and in the meantime a gear is used to drive

the rotary control valve element, thus, pressure oil can be supplied to the two cylinders in proper

connecting order to realize continuous rotating of shovel blade.

Up/down of front bulldozing plate (optional module)

Power source of the front bulldozing plate lifting cylinder is from the second valve group of right

multitandem valve. Front bulldozing plate is an optional attachment, and the standard model is not

equipped with this attachment. When the bulldozing plate is not installed, the corresponding oil

ports of multitandem valve are sealed with screw plug.

Fig. 9-9 Up/down of front bulldozing plate

1 Right multitandem valve (2A/2B) 2 Front bulldozing plate lifting cylinder

Up/down of rear scarifier

Power source of the rear scarifier lifting cylinder is from the second valve group of left multitandem

valve. Rear scarifier is an optional attachment, and the standard model is not equipped with this

attachment. When the rear scarifier is not installed, the corresponding oil ports of multitandem

valve are sealed with screw plug.


9-7

Fig. 9-10 Up/down of rear scarifier

1 Left multitandem valve (9A/9B) 2 Rear scarifier lifting cylinder

Up/down of middle scarifier

Fig. 9-11 Up/down of middle scarifier

1 Left multitandem valve (2A/2B) 2 Middle scarifier lifting cylinder

Power source of the middle scarifier lifting cylinder is from the second valve group of right

multitandem valve. Middle scarifier is an optional attachment, and the standard model is not


9-8

equipped with this attachment. When the middle scarifier is not installed, the corresponding oil

ports of multitandem valve are sealed with screw plug.

Locking cylinder

Power source of the locking cylinder is from port A of prefill valve in brake hydraulic system, a

magnetic exchange valve is designed in the circuit to control the cylinder. A rocker switch is

installed in the cab to control the magnetic exchange valve to retract or extend the cylinder.

Fig. 9-12 Locking cylinder

1 Locking cylinder 2 Magnetic exchange valve 3 Rocker switch

Shovel blade floating (replaceable module)

Compared to standard model, the common balance valve is replaced with floating balance valve.

And a duplex solenoid valve is used to control the on-off state of oil line from prefill valve port A to

floating balance valve, so as to realize floating of shovel blade. Two rocker switches installed in the

can are used to control floating of the two blade lifting cylinders.


9-9

Fig. 9-13 Blade floating

1 Right shovel blade lifting cylinder 2 Left shovel blade lifting cylinder

3 Floating balance valve 4 Oil return block 5 Duplex solenoid valve 6 Prefill valve

7 Right lifting cylinder floating switch 8 Left lifting cylinder floating switch


9-10

92 Description, Disassembly and Assembly of Main Components

921 Working Pump

Table 9-1

Fig. 9-15 Working pump

Working principle

When pump shaft rotates as Fig. 9-15, the gear

demeshes on oil absorption chamber side, oil

absorption chamber close volume increases and

partial vacuum will be formed, oil in the tank will

be pressurized into absorption chamber through the

oil absorption pipe under the force of atmospheric

pressure to fill up the inter-tooth space. As the gear

rotates, oil in transition area will be brought into oil

extrusion chamber, the gear meshes on the

extrusion side and the volume decreases to force

oil into oil circuit.

Fig. 9-16 Gear pump working principle

Items Parameter

Nominal displacement 32ml/r

Rated/max. pressure 25/31.5MPa

Rated/max. speed 20MPa

Volumetric efficiency ≥0.92

Number of teeth 14

Direction of turning Left-hand

A


9-11

Composition of working pump

Fig. 9-16 Composition of working pump

1 Retainer ring 2 Retainer ring 3 Antifriction bearing 4 Lip-type seal ring for rotating shaft

5 Front cover 6 Bearing 7 Rectangular seal ring 8 Gasket 9 Lug retainer ring

10 Lug seal ring 11 Side plate 12 Driving gear shaft 13 Driven gear shaft

14 Rivet 15 Label 16 Rear cover block 17 Bolt

Disassembly and assembly of working pump

ATTENTION

Before dismantling the working pump, be sure to carefully read 95 Service Precautions for

Working Hydraulic System in this chapter.

Disassembly of working pump

1. Connect a hose to the oil draining valve on the

bottom of hydraulic tank, and put the other end

in a clean vessel. Open the drain valve of the

tank to drain the hydraulic oil out. (Open the

filling cap of the tank to accelerate the

draining speed)

ATTENTION

Cover the discharged oil to prevent

contamination.

1

Fig. 9-17

1. Oil drain valve


9-12

2. Remove the head board fixing bolts, and take

down the cover plate.

3. Remove the fixing screws of working pump oil

absorption steel pipe, take down the screws

fission flange, and the remove the steel pipe

and O-shape ring.

4. Disconnect the oil outlet rubber hose of

working pump.

1

Fig. 9-18

1. Head board

1

Fig. 9-19

1 Working pump oil absorption steel pipe

1

Fig. 9-20

1 Straight joint


9-13

5. Remove the fixing bolts of working pump,

take down the bolts and gaskets.

6. Hang the working pump with lift appliance,

and then use a copper bar to knock the pump

outward, take down the pump and sealing

gasket.

7. Remove the fixing screws of the straight joint,

take down the screws, fission flange and

straight joint.

Assembly of working pump

1. Use four screws and a fission flange to connect

the straight joint to the pump oil outlet port.

70~80Nm

2. Use four M12 bolts and gaskets, and a sealing

gasket to connect the working pump to

transmission box PTO port.

78~104Nm

1 2

Fig. 9-21

1. Bolt 2 Sealing gasket

1

Fig. 9-22

1. Straight joint

1 2

Fig. 9-23

1. Bolt 2 Sealing gasket


9-14

3. Connect the oil outlet rubber hose to the

straight joint.

4. Put O-ring in the O-ring groove of working

pump oil absorption steel pipe joint. Fix the

pipe on the working pump with four screws

and a fission flange.

70~80Nm

5. Install the head board with bolts

6. Fill hydraulic oil to specified level.

1

Fig. 9-24

1 Working pump oil outlet rubber hose

1

Fig. 9-25

1 Working pump oil absorption steel pipe

1

Fig. 9-26

1. Head board


9-15

922 Hydraulic Oil Tank

It is used to provide oil to the whole hydraulic system. An oil return filter is designed in the tank to

ensure the cleanliness of hydraulic oil.

Fig. 9-27 Hydraulic oil tank assembly

1 Bolt 2 Gasket 3 Oil filling filter element 4 Round oil level pointer 5 Tank

6 Bolt 7 Thick gasket 8 Gasket 9 Nut 10 Oil draining joint 11 Ball valve

12 Oil draining joint 13 O-ring 14 Oil return flange 15 Ring magnet

16 O-ring 17 Oil absorption flange 18 Gasket 19 Bolt 20 Sealing gasket

21 Oil absorption filter element assembly 22 O-ring 23 Screw plug 24 Air filter

25 Oil return filter 26 Bolt

Description of hydraulic tank components:

1. Air filter: Since the hydraulic oil in the tank expands when heated and contracts when cooled,

so the hydraulic oil tank must connect with the atmosphere. The air filter is used to balance the

air pressure inside the tank and atmospheric pressure. It also works as a filter to keep the

circulating air clean and dry, to guarantee the cleanliness of hydraulic oil.

2. Oil level pointer: Used to check hydraulic oil level.

3. Oil return filter: Used to filter oil contamination out. If there is too much contamination


9-16

accumulated in filter element, which will increase pressure difference between two sides of the

filter, the filter build-in bypass valve will open if the pressure difference gets to its opening

pressure, oil will be released through bypass valve to ensure the hydraulic system operation

normal.

Oil absorption filter element Oil filling filter element Oil return filter

Air filter Oil level pointer

Disassembly and assembly of hydraulic oil tank

ATTENTION

Before dismantling the hydraulic oil tank, be sure to carefully read the 94 Service Precautions

for Working Hydraulic System.


9-17

Disassembly of hydraulic oil tank

1. Operate the control handles to lower the shovel

blades to the ground and raise the front

bulldozing plate to the highest position, and

then shut down the engine. Then operate the

control handle to lower the front bulldozing

plate to the ground.

2. Connect a hose to the oil draining valve on the

bottom of hydraulic tank, and put the other end

in a clean vessel. Open the drain valve of the

tank to drain the hydraulic oil out. (Open the

filling cap of the tank to accelerate the

draining speed)

ATTENTION

Cover the discharged oil to prevent

contamination.

3. Remove the engine hood.

Refer to 8 Cab & Covering Parts System for

disassembly of engine hood.

4. Remove the fixing bolts of left and right guard

plates, use lifting rope to hang the plates down.

5. Remove the head board.

Fig. 9-28

1

Fig. 9-29

1. Oil drain valve

1 2 3

Fig. 9-30

1 Engine hood 2 Guard plate

3 Head board


9-18

6. Disconnect the brake pump oil outlet rubber

hose and prefill valve oil inlet rubber hose

from the high-pressure filter.

7. Disconnect the oil return pipes from hydraulic

oil tank.

1 2

Fig. 9-31

1 Brake pump oil outlet rubber hose

2 Prefill valve oil inlet rubber hose

1 2 3 4

Fig. 9-32

1 Oil return pipe from port T of

high-pressure filter safety valve

2 Oil return pipe from port T of oil

return block

3 Oil outlet pipe from port T of

priority valve

4 Oil pipe from port O of prefill

valve


9-19

8. Disconnect the hydraulic tank oil outlet rubber

hose from working pump oil absorption steel

pipe.

9. Remove the fixing bolts of hydraulic oil tank

support, lift down the tank.

1

Fig. 9-33

1 Radiator oil return pipe

1 2

Fig. 9-34

1 Working pump oil absorption steel

pipe

2 Fixing clamp

1

Fig. 9-35

1 Bolt


9-20

Assembly of hydraulic oil tank

1. Lift the hydraulic oil tank to the rear frame for

assembling, install and tighten the fixing bolts.

78~104Nm

2. Install the clamps to connect the hydraulic tank

oil outlet rubber hose to working pump oil

absorption steel pipe.

1

Fig. 9-36

1 Bolt

1 2

Fig. 9-37

1 Working pump oil absorption steel

pipe

2 Fixing clamp


9-21

3. Connect the oil return pipes to hydraulic oil

tank.

ATTENTION

Mark the hydraulic pipes orderly to prevent

confusion.

Part 1: Straight joint 45~65Nm

Oil pipe 45~65Nm

Part 2: Oil pipe 45~65Nm


Oil pipe 45~65Nm

Part 4: Oil pipe 45~65Nm

Radiator oil return pipe 120~145Nm

1 2 3 4

Fig. 9-38

1 Oil return pipe from port T of

high-pressure filter safety valve

2 Oil return pipe from port T of oil

return block

3 Oil outlet pipe from port T of

priority valve

4 Oil pipe from port O of prefill

valve

1

Fig. 9-39

1 Radiator oil return pipe


9-22

4. Connect the brake pump oil outlet rubber hose

and prefill valve oil inlet rubber hose to the

high-pressure filter.



5. Install the fixing bolts of head board.

6. Install the fixing bolts of left and right guard

plates.

7. Assemble the engine hood.

Refer to 8 Cab & Covering Parts System for

assembly of engine hood.

8. Fill hydraulic oil to specified level.

1 2 3

Fig. 9-41

1 Engine hood 2 Guard plate

3 Head board

1 2

Fig. 9-40

1 Brake pump oil outlet rubber hose

2 Prefill valve oil inlet rubber hose


9-23

923 Multitandem Valve

The grader is designed with two multitandem valves, and each multiandem valve is mainly

composed of valve body, five valve groups in series, check valve and relief valve. Operate the

control handles to control the valves elements, so as to obtain the motion we desired.

Fig. 9-42 Schematic diagram of multitandem valve

Inlet check valve: Used to prevent reflux of pressure oil, to avoid cylinder dive.

Main relief valve: The valve a pilot operated cartridge valve, and set pressure of the valve is

214Bar.

Function of valve groups in multitandem valve

Right multitandem valve Left multitandem valve

Fig. 9-43 Multitandem valve

1 Up/down of shovel blade 2 Up/down of front bulldozing plate 3 Tilt of front wheels

4 Hinge steering 5 Swing of shovel blade 6 Rotary cylinder 7 Tilt of shovel blade

8 Sidesway of shovel blade 9 Scarifier 10 Up/down of shovel blade


9-24

Composition and structure of multitandem valve

Fig. 9-44 Structure of right multitandem valve

1 Valve element end cap 2 End cap fixing nut 3 Valve element end cap fastening screw

4 Spring seat 5 Spring 6 Operating valve block assembly 7 Flat gasket—Seal

8 Dust ring 9 O-ring 10 Valve element assembly 11 Valve body

12 Seal assembly 13 Operating valve block assembly 14 O-ring 15 Spring

16 Check valve element 17 End cap fixing nut 18 Oil inlet valve block assembly

19 Oil outlet valve block assembly 20 Nut 21 Fastening screw

22 Fastening screw 23 Nut 24 Relief valve assembly 25 Plug assembly

26 Valve element assembly 27 Valve body


9-25

Fig. 9-45 Structure of left multitandem valve

1 Valve element end cap 2 End cap fixing nut 3 Valve element end cap fastening screw

4 Spring seat 5 Spring 6 Operating valve block assembly 7 Flat gasket—Seal

8 Dust ring 9 O-ring 10 Valve element assembly 11 Valve body

12 Seal assembly 13 Operating valve block assembly 14 O-ring 15 Spring

16 Check valve element 17 End cap fixing nut 18 Oil inlet valve block assembly

19 Oil outlet valve block assembly 20 Nut 21 Fastening screw

22 Fastening screw 23 Nut 24 Relief valve assembly 25 Plug assembly

26 Valve element assembly 27 Valve body


9-26

Disassembly and assembly of multitandem valve

ATTENTION

Before dismantling multitandem valve, be sure to carefully read the 94 Service Precautions for

Working Hydraulic System.

Disassembly of the multitandem valve

1. Remove the fixing bolts of the left and right

guard plates, take down the bolts and guard

plates.

2. Remove the fixing bolts of the plate, take

down the bolts and plate.

1

Fig. 9-46

1 Left guard plate

1

Fig. 9-47

1 Plate


9-27

3. Remove the connecting bolts of the control

pull rod and multitandem valve connecting rod.

Take down the bolts, nuts and gaskets.

4. Disconnect the oil pipes from multitandem

valve.

ATTENTION


confusion.

5. Remove the connecting nuts of multitandem

valve support and frame. Lift down the valve.

1 2 3

Fig. 9-48

1 Multitandem valve connecting rod

2 Control pull rod

3 Bolt

1

Fig. 9-49

1 Oil pipe

1 2

Fig. 9-50

1 Multitandem valve support

2 Nut


9-28

6. Remove the pipe joints.

7. Remove the cotters and connecting pins.

8. Remove the fixing screws of multitandem

valve.

1

Fig. 9-51

1 Pipe joint

1 2 3

Fig. 9-52


2 Cotter 3 Connecting pin

1

Fig. 9-53

1 Screw


9-29

Assembly of the multitandem valve

1. Fix multitandem valve on the support with

screws.

2. Install the cotters and connecting pins.

3. Install the pipe joints to the corresponding oil

ports of multitandem valve.

Pipe joint 35~45Nm

4. Install multitandem valve assembly to the

machine with four M10 nuts.

Nut 45~59Nm

1 2 3

Fig. 9-54


2 Cotter 3 Connecting pin

4 Screw

1 2

Fig. 9-56

1 Multitandem valve support

2 Nut

1

Fig. 9-55

1 Pipe joint


9-30

5. Connect the oil pipes to multitandem valve

orderly.

Pipe 65~85Nm

6. Use bolts to connect the control pull rod and

multitandem valve connecting rod.

7. Install the fixing bolts (M6×20) of the plate.

1 2 3

Fig. 9-58


2 Control pull rod

3 Bolt

1

Fig. 9-57

1 Oil pipe

1 2

Fig. 9-59

1 Bolt 2 Plate


9-31

8. Use M6×20 bolts to fix the left and right guard

plates on cab.

924 Rotary Control Valve

The rotary control valve is installed on top of the connecting rack, and it is the main component of

shovel blade rotary mechanism. Its function is to supply pressure oil to the two cylinders in proper

connecting order to realize continuous rotating of shovel blade.

Fig. 9-61 Rotary control valve

1

Fig. 9-60

1 Left guard plate


9-32

Fig. 9-62 Schematic principle diagram of rotary control valve

Working principle of rotary control valve

During rotation of shovel blade, port AA of rotary

is always connected with chamber A of rotary

control valve, and port BB of rotary is always

connected with chamber B of rotary control valve.

In the initial position, the left rotary cylinder is

fully retracted and in the same line with the drive

arm, it doesn’t output driving force at this point.

The right rotary cylinder is in the middle of its

stroke and cylinder rod is perpendicular to the

drive arm, it outputs the maximum driving force at

this point. The pressure oil from port AA enters

rod-side chamber of the right rotary cylinder

through the valve, and the oil in the piston-side

chamber of the cylinder returns to port BB through

the valve. Under this circumstance, the piston rod

of right rotary cylinder retracts to drive the rotary

frame to rotate anticlockwise via the drive arm and

small gear. Meanwhile, rotary valve element will

be driven by gear to achieve synchronous rotation.

Fig. 9-63


9-33

As the rotary valve element rotates, the pressure oil

from port AA enters piston-side chamber of the left

rotary cylinder and rod-side chamber of the right

rotary cylinder through the valve. Under this

circumstance, the piston rod of left rotary cylinder

extends and that of right rotary cylinder retracts to

drive the rotary frame to rotate anticlockwise

collaboratively.

When the left rotary cylinder is perpendicular to

the left drive arm, the right rotary cylinder and

drive arm are in the same line. At this point, only

the left rotary cylinder drives rotary frame to rotate

anticlockwise. Under this circumstance, the

pressure oil from port AA enters piston-side

chamber of the left rotary cylinder, and the oil in

the rod-side chamber of the cylinder returns to port

BB through the valve.

When the left rotary cylinder is 180° to the left

drive arm, the left rotary cylinder and drive arm are

in the same line. At this point, only the right rotary

cylinder drives rotary frame to rotate anticlockwise.

Under this circumstance, the pressure oil from port

AA enters piston-side chamber of the right rotary

cylinder, and the oil in the rod-side chamber of the

cylinder returns to port BB through the valve.

Fig. 9-64

Fig. 9-65

Fig. 9-66


9-34


drive arm, the pressure oil from port AA enters

rod-side chamber of the left rotary cylinder and

piston-side chamber of the right rotary cylinder

through the valve. Under this circumstance, the

piston rod of left rotary cylinder retracts and that of

right rotary cylinder extends to drive the rotary

frame to rotate anticlockwise collaboratively.


drive arm, the right rotary cylinder and drive arm

are in the same line. At this point, only the left

rotary cylinder drives rotary frame to rotate

anticlockwise. Under this circumstance, the

pressure oil from port AA enters rod-side chamber

of the left rotary cylinder, and the oil in the

piston-side chamber of the cylinder returns to port

BB through the valve.

Working principle for clockwise rotation of shovel

blade is similar.

Fig. 9-67

Fig. 9-68


9-35

Disassembly and assembly of rotary control valve

ATTENTION

Before dismantling rotary control valve, be sure to carefully read the 94 Service Precautions

for Working Hydraulic System.

Disassembly of the rotary control valve

1. Disconnect all oil pipes from rotary control

valve.

ATTENTION


confusion.

2. Screw off the three fixing bolts of rotary

control valve, take down the bolts and gaskets.

3. Take down the valve.

4. Take down the transmission shaft, sleeve, and

the gaskets between rotary control valve and

frame.

Fig. 9-69

1 Pipe joint 2 Oil pipe

Fig. 9-70

1 Bolt

Fig. 9-71

1 Gasket 2 Transmission shaft


9-36

5. As shown in Fig. 9-72, use a clamp to fix the

rotary control valve, and then remove the pipe

joints.

Assembly of the rotary control valve

1. As shown in Fig. 9-73, use a clamp to fix the

rotary control valve, and then install the pipe

joints.

2. Install the same number of gaskets as that of

the removed ones. Install the transmission

shaft and sleeve.

Fig. 9-72

1 Pipe joint 2 Rotary control valve

Fig. 9-73

1 Pipe joint 2 Rotary control valve

Fig. 9-74

1 Gasket 2 Transmission shaft


9-37

3. Fix the rotary control valve on frame with

bolts.

4. Tighten the valve fixing bolts.

5. Connect the oil pipes to the corresponding oil

ports of rotary control valve.

Fig. 9-77

1 Pipe joint 2 Oil pipe

Fig. 9-76

1 Bolt

Fig. 9-75


9-38

925 Middle Swivel Joint

The middle swivel joint is installed on top-middle area of swing frame. The middle swivel joint can

prevent the hydraulic pipes from intertwining when the shovel blade is rotating.

Fig. 9-78

a, b — to shovel blade tilt cylinder c, d — to shovel blade sidesway cylinder

Fig. 9-79 Schematic diagram of middle swivel joint

Fig. 9-80 Middle swivel joint assembly

Technical parameters

Rotary torque: 30~60Nm

When assembling the

swivel joint, make sure it

can rotate freely and no

external force is exerted on

it.

1 Screw plug

2 O-ring

3 Rotary shaft

4 Water seal

5 Anti-wear ring

6 Rotary seal ring

7 Rotary body

8 Water seal

9 Baffle

10 Gasket

11 Bolt


9-39

Disassembly and assembly of middle swivel joint

ATTENTION

Before dismantling the middle swivel joint, be sure to carefully read the 94 Service

Precautions for Working Hydraulic System.

Disassembly of the middle swivel joint

1. Disconnect the two oil pipes.

2. Remove the four fixing nuts of cover plate,

take down the nuts and gaskets.

3. Hold up the cover plate gently.

ATTENTION

Be gently when holding up the cover plate,

there are two oil pipes under the plate.

4. Disconnect the two oil pipes under the cover

plate, take down the cover plate.

ATTENTION


confusion.

1 2 3 4

Fig. 9-81

1 To piston-side chamber of blade

swing cylinder oil pipe

2 To rod-side chamber of blade swing

cylinder oil pipe

3 Cover plate 4 Nut

1 2

Fig. 9-82




cylinder oil pipe


9-40

5. Disconnect the four oil pipes from the middle

swivel joint.

ATTENTION


confusion.

6. Remove the fixing nuts of the plate.

7. Remove the fixing bolts of the four pipe

clamps.

1 2 3 4

Fig. 9-83

1 To port 8B of multitandem valve oil pipe

2 To port 8A of multitandem valve oil pipe



1 2

Fig. 9-84

1 Plate 2 Nut

1

Fig. 9-85

1 Pipe clamp


9-41

8. Disconnect the four bottom oil pipes from the

middle swivel joint.

ATTENTION


confusion.

9. Remove the four pipe joints.

10. Remove the six fixing nuts of the middle

swivel joint, take down the nuts and gaskets.

Then take down the bolts and middle swivel

joint.

Assembly of the middle swivel joint

1. Use six M12 bolts and nuts to fix the middle

swivel joint on frame.

2. Install the four pipe joints.

45~65Nm

3. Connect the four bottom oil pipes to the

corresponding oil ports of middle swivel joint.

65~85Nm

1 2 3 4

Fig. 9-87

1 To rod-side chamber of blade tilt

cylinder oil pipe

2 To rod-side chamber of blade

sidesway cylinder oil pipe

3 To piston-side chamber of blade tilt

cylinder oil pipe



1 2 3 4

Fig. 9-86

1 To rod-side chamber of blade tilt

cylinder oil pipe

2 To rod-side chamber of blade


3 To piston-side chamber of blade tilt

cylinder oil pipe




9-42

4. Use bolts, nuts and gaskets to fix the plate on

bottom of middle swivel joint.

5. Use M10×20 bolts and pipe clamps to fix oil

pipes on the connecting plate.

6. Connect the four upper oil pipes to the middle

swivel joint.

Pipe joint 45~65Nm

Oil pipe 65~85Nm

1 2

Fig. 9-88

1 Plate 2 Nut

1

Fig. 9-89

1 Pipe clamp

1 2 3 4

Fig. 9-90






9-43

7. Connect the two oil pipes under the cover

plate.

Oil pipe 65~85Nm

8. Use the bolts and nuts to fix cover plate.

9. Connect the two top oil pipes.

Oil pipe 65~85Nm

1 2 3 4

Fig. 9-92




cylinder oil pipe

3 Cover plate 4 Nut

1 2

Fig. 9-91




cylinder oil pipe


9-44

926 Hydraulic Oil Cylinders

Fig. 9-93 Structure of hydraulic oil cylinder

1 Piston fixing nut 2 Piston seal 3 Piston 4 Cylinder tube 5 Cover

6 Wearing ring 7 O-ring 8 Back-up ring 9 Seal ring for shaft 10 Dust ring

11 Piston rod 12 Cylinder cover nut 13 Flat gasket

Specification of hydraulic oil cylinders applied in the grader working hydraulic cylinder

Table 9-2 Unit: mm

Cylinder name Product code Cylinder

diameter

Piston rod

diameter Piston travel

Hinge steering cylinder 4120004770 115 50 303

Shovel blade lifting cylinder 4120004769 90 50 1379.5

Shovel blade swing cylinder 4120004768 90 50 693.5

Locking cylinder 4120004765 80 60 63.5

Shovel blade rotary cylinder 4120004766 80 35 279.5

Shovel blade sidesway cylinder 4120004767 90 50 1346

Shovel blade tilt cylinder 4120004771 100 50 260.5

Front wheel tilt cylinder 4120004762 100 50 169


9-45

Precautions when disassembling hydraulic oil cylinder:

1 Be sure to unload the hydraulic system (pressure relief) before disassembling the cylinder.

Otherwise high-pressure oil in the circuit will spray out at high speed when disconnecting the

hydraulic oil pipes, safety accident may occur. Thus, before disassembling you should loosen

the regulating handle or pressure adjusting screw of relief valve to unload the hydraulic circuit

first, and then turn off the power source to shut down the entire hydraulic system. At this point,

you can start to disconnect the oil pipes. To prevent getting hurt by residual pressure oil, you

should loosen the pipe joint slowly and pay attention to check whether there is overflowing oil,

be careful in this process.

2 Hydraulic oil cylinder is the actuator of hydraulic system. So before removing the cylinder, be

sure to hang or support its driven device (working device) properly to prevent hurting people or

crushing the machine. Before disassembling, you can start the machine and operate the control

handles to let the cylinder move to suitable position for the convenience of assembling, and do

not forget to unload the hydraulic system after that.

3 Before disassembling the hydraulic oil cylinder, you should pay attention to check whether the

cylinder is designed with hydraulic lock. If so, remove the hydraulic lock first. Otherwise the

cylinder will contain pressure oil locked by the hydraulic lock, which will make it difficult to

disassemble the cylinder and bring potential hazard to the people and machine. When removing

the hydraulic lock, you can use clean cloth to wrap up the connecting area (pipe joint, or

something similar) first, to avoid splashing of high-pressure oil.

4 When disassembling the hydraulic oil cylinder, you should be aware of the main structure of

the cylinder, never do the disassembling work blindly. Since different hydraulic oil cylinder has

different size, structure and use purpose, they are intended to be disassembled in different ways.

So before the disassembling, you can refer to the cylinder engineering drawings provided by

our company. If the drawings are not available, you should check the cylinder carefully and set

a proper disassembly sequence.

5 In a general way, when disassembling the hydraulic oil cylinder, you should drain the hydraulic

oil in the cylinder out first, and then remove the end cover, then pull out the piston rod and

piston assembly. When disassembling the components, do not hammer fiercely. If it is

inevitable, a copper bar should be used to avoid damaging the parts. Some parts need to be

disassembled with special tools, these tools must be available. For fine thread part, you can use

a copper rod to vibrate it first, and then use special wrench to loosen it gently, do not bump it

fiercely. Some bolts were coated with thread locking sealant when assembling, which are hard

to disassemble, and the thread may get damaged if you remove the bolt forcibly. In this case,


9-46

you can heat the bolt to let the sealant fall out first.

6 Pay attention to avoid damaging the piston rod thread, oil port thread, piston rod surface and

inner wall of cylinder sleeve. Long and thin part (piston rod) should be placed on suitable

support to prevent getting deformed or distorted. Do not use sharp tools to disassemble the

seals to avoid scratching them. If the seals are difficult to disassemble, you can soak them in

water to soften them, and then remove them. Before and after disassembling the cylinder, you

should always take measures to prevent the parts and components from getting contaminated by

dust and impurities. For example, the maintenance work should be performed in clean

environment, and use plastic cloth rather than cotton cloth to cover the disassembled

components and parts.

7 The disassembled parts and components should be inspected carefully, damaged and aged

part/component should be replaced. In the case that the cylinder had severe internal or external

leakage problem during normal use, if the piston rod and cylinder tube are in good condition,

then the problem must be caused by worn or aged seals. If the cylinder tube was subject to

strike damage, you should use internal dial gauge to check whether the tube is deformed. Check

the cylinder tube, piston rod and other moving parts for scratch and pull damage, replace the

repair the damaged parts according to the damage condition. If the damaged part is determined

to be repaired, you should grind to flat the damaged area with fine oil stone first, and then

polish it with abrasive paper.

Precautions when assembling hydraulic oil cylinder:

1 All parts and components should be cleaned and dried before assembling, parts and

components that need to be coated with sealant when assembling should be cleaned with

cleaning agent or acetone. Curing time of the sealant is about 20min, which means you should

tighten the coated part/component to required torque in 20min.

2 Install the seals correctly. When installing an O-ring, do not drag/expand it to the state of

permanent deformation or roll along the shaft to assemble it, otherwise it may get twisted and

result in oil leakage. When installing a Y-ring, V-ring or stepped labyrinth seal ring, pay

attention to the installing direction, a reversely fitted Y-ring, V-ring or stepped labyrinth seal

ring will cause oil leakage. For Y-ring, its lip should face the pressure oil chamber, and pay

attention to differentiate if the Y-ring is for shaft or for hole, do not install a wrong Y-ring.

V-ring is composed of a back-up ring, a seal ring and a compression ring. The back-up ring can

deform the seal ring for sealing, when installing the seal ring, the side with open mouth should

face the pressure oil chamber. When adjusting the compression ring, it should be limited to no

oil leakage, do not compress it too tight to avoid oversized sealing resistance. For stepped


9-47

labyrinth seal ring, the stepped end should face the pressure oil chamber. If the seal is for

moving part or fits with moving part, coat it with hydraulic oil when assembling. Disassembled

seal ring and dust ring should be replaced with new ones.

3 Bolts and lock nuts for pressure-bearing part/component are disposable, do not reuse them.

Pressure-bearing part/component should not be replaced arbitrary, original spare

parts/components are preferable. Most of the fixing or connecting bolts have tightening torque

and tightening order requirements, some of them even have tightening angle requirements. So

when tightening the bolts, be sure to use a special wrench or torque wrench and follow these

requirements. Bolts of the same component should be tightened to the same torque

symmetrically. Long and thin part (piston rod) should be placed on suitable support to prevent

getting deformed or distorted when tightening the fastening bolts.

4 Some piston seals will swell after being assembled, which may get cut or scratched when

assembling the piston and piston rod assembly. In this case, you should use cone shrinking

sleeve to shrink the seal. If there is no cone shrinking sleeve, you can make one by yourself

according to the dimensions of piston and cylinder tube. Generally, the taper of the sleeve

should be about 30°, and diameter of the small end of the sleeve should be equal to that of the

cylinder tube. After assembling the piston and piston rod, you should measure the coaxiality

and straightness in the overall length.

5 All moving parts and components should be coated with hydraulic oil for lubrication when

assembling. The fine thread of some large part should be coated with lubricating grease, if the

thread was subject to burn damage, coat it with molybdenum disulfide grease for lubrication.

6 After the maintenance, you must perform pressure leak tests before putting the machine into

operation again. If the cylinder is designed with hydraulic lock, the hydraulic lock mustn’t be

installed during the tests. When performing the test, you should retract and extend the cylinder

for several times at low pressure to discharge the air, and pay attention to check for any

abnormal phenomenon. Then increase the pressure gradually to check for leakage.


9-48

927 Other Hydraulic Components

Hydraulic lock

The hydraulic lock is composed of two pilot operated check valves. When the reversing valve is in

neutral position and the hydraulic system is loaded, the hydraulic lock can keep the cylinder stopped

at the original position.

For working hydraulic system of G9165 grader, the front wheel tilt circuit and up/down of scarifier

circuit are designed with hydraulic lock.

Table 9-3

Fig. 9-94

Balance valve

The balance valve can change resistance coefficient automatically according to working condition

(pressure difference) of the system. When the system pressure varies in a certain range, the balance

valve can keep the oil flow the same.

For working hydraulic system of G9165 grader, the hinge steering circuit, shovel blade swing

circuit and up/down of shovel blade circuit are designed with balance valve.

Table 9-4

Fig. 9-95

Floating balance valve

Compared to common balance valve, the floating balance valve is designed with floating function.

When there is pressure oil acts on the control port D, the two check valves inside the floating

balance valve will open. At this point, both piston-side chamber and rod-side chamber of shovel

Item Parameter

Rated pressure 240Bar

Rated flow 55L/min

Opening pressure 2.1Bar

Pilot ratio 4:1

Items Parameter

Control pressure area ratio 4:1

Set pressure 240Bar

Flow 70L/min

Max. working pressure 350Bar


9-49

blade lifting cylinder are connected to oil return channel, and the shovel blade is in floating

condition under the weight of working device and its own weight.

Fig. 9-96

Duplex solenoid valve

The duplex solenoid valve is used to control the on-off state of oil line from prefill valve to control

port of floating balance valve, so as to realize floating of shovel blade.

Table 9-5

Fig. 9-97

Cross relief valve

Fig. 9-98

Items Parameter

Rated pressure 207Bar

Voltage 24V


9-50

93 Pressure Measurement of Working Hydraulic System

Pressure measuring tools

Pressure gauge with measuring range of 40MPa, piezometer tube

Pressure measuring points

Oil inlet port of multitandem valve

Fig. 9-99 Right multitandem valve Fig. 9-100 Left multitandem valve

Pressure measuring method

Raise the cylinders to build pressure.

Standard working hydraulic system pressure

214.1±3.5Bar.


9-51

94 Service Precautions for Working Hydraulic System

The most common fault for high-pressure and high-precision hydraulic devices is that fouling (alien

material) occurs in the hydraulic circuit. Thus, pay special attention to the cleanliness when adding

hydraulic oil or removing and refitting the hydraulic devices.

1. Pay attention to working environment.

Avoid adding hydraulic oil, replacing filter or

repairing machine in rain or at windy and dirty

place.

2. Removing and servicing machine on

outdoor site.

Chances are that fouling will enter the

equipment if removal and service are done on

outdoor site; moreover, it is difficult to

appraise equipment’s performance after

eliminating the faults. So this is only suitable

for replacing components. Removal and

service of the hydraulic devices should be

conducted in special dust-free workshop and

the performance of the hydraulic devices

should be appraised with special testing

device.

3. Seal up the openings.

After removing the pipes or components, all

openings should be sealed with cap, adhesive

paper or plastic bag so as to prevent fouling or

dirt from entering them. If you let the openings

be exposed or clogged with rags, fouling is

liable to get into them or the leaking oil will

stain the surrounding places, which is not

allowed to happen. Instead of draining oil on

the ground, you should collect the drained oil

and take it back to handle it on your own.

Fig. 9-101

Fig. 9-102


9-52

4. Prevent any fouling or dirt from entering

the system during the oil refilling operation.

Prevent any fouling or dirt from being mixed

into the hydraulic oil when refilling hydraulic

oil and be sure to keep the oil filler and the

surrounding surface clean as well as use clean

oil pump and container. Utilizing oil cleaning

device will filter the fouling deposited during

the storage period from the oil, which is more

effective for refilling oil.

5. The hydraulic oil should be changed when

the oil temperature is high.

When the hydraulic oil or other oil is hot, their

fluidity is good and the deposited sludge is

easy to be flushed away by the oil. Therefore,

it is recommended to change oil when the oil is

hot. Discharge the old oil fully (not only the

oil in the hydraulic oil tank but also the oil in

the filter and plugs of the pipeline) as possible

as you can when changing oil. If there is old

oil residual, the fouling and deposited sludge

will be mixed with the new oil, shortening the

service life of the new oil.

6. Flushing operation.

The fouling, oil sludge and old oil in the

hydraulic oil circuit should be flushed away

with rinsing oil when changing oil after the

disassembly and assembly of the hydraulic

devices. Normally, flushing is conducted for

two times: primary flushing with rinsing oil

and secondary flushing with specified

hydraulic oil.

Fig. 9-103

Fig. 9-104

Rinsing

oil


9-53

7. Cleaning operation.

Get rid of the sludge and fouling in the

hydraulic oil circuit with oil cleaning device

after repairing the hydraulic device (pump,

control valve, etc.) or when the machine is

operating. The oil cleaning device is used to

remove the ultrafine granule that cannot be

removed by the filter in the hydraulic device,

which is a very effective cleaning tool.

8. Torque requirements

The securing operation should be conducted in strict accordance with the torque required in this

manual during the process of removal, refitting and service of the hydraulic system. Excessive

or insufficient torque will lead to hydraulic oil leakage.

ATTENTION

For the torque that is not indicated, please refer to relevant requirements in Chapter 0

General of this manual.

9. Deflation (air bleeding) of working hydraulic system

After replacement of hydraulic pump, hydraulic cylinder, hydraulic pipe, joint and all kinds of

valves, bleeding operation must be done.

The specific bleeding steps are as follows:

1) Open the filler cap of hydraulic tank.

2) Start the engine; run the engine at idle for 5 minutes, and then retract and extend all

cylinders from bottom for about 2~3 times, keep the stroke within 50~60 mm.

3) Keep the engine run at low speed, and then retract and extend all cylinders fully for about

3~5 times to bleed the air in hydraulic circuit.

4) After the bleeding, set the machine and working device in standard position, check

hydraulic oil level and tighten the filler cap.

5) Shut down the engine, check for leakage.

Fig. 9-105


9-54

95 Diagnosis of Common Faults of Working Hydraulic System

Table 9-6

S/N Fault phenomenon Possible causes Elimination methods

1

System pressure is

insufficient or no

pressure

The pump is seriously worn, and

has severe internal leakage Replace the pump

Hydraulic oil temperature is too

high Refer to Fault 7

The hydraulic circuit has leakage

problem

Find out the leaking point

and fix it

Relief valve is abnormal or

clogged

Repair or replace the

valve

Spring failure Replace the spring

2 System flow is small

Low oil level in hydraulic tank, the

pump is not able to absorb enough

oil

Stop the machine and fill

oil to specified level

The hydraulic oil viscosity is too

big because of low temperature,

the pump is not able to absorb

enough oil

Warm up the oil

Severe internal leakage problem Replace or repair the

faulty component

3

Hydraulic oil and

transmission oil are

mixed with each other

Pump shaft seal failure Replace the pump oil seal

4

Hydraulic pump

produces abnormal

noise and vibrates

The hydraulic system is infiltrated

with air

Deflate the system as

required

Low oil level in hydraulic tank. Stop the machine and fill


Hydraulic pump failure Replace or repair the

pump

5 Heavy manipulation

Multitandem valve element gets

stuck by dirt Clean the valve element

Multitandem valve spring failure Replace the spring

6 Action failure of

hydraulic cylinder

There is air accumulated in the

cylinder

Deflate the cylinder as

required

Piston seal is damaged Replace the seal

7 Too high oil

temperature

Long-time overload operation Take a break

System pressure is too high Adjust

Low oil level in hydraulic tank. Stop the machine and fill


Environment temperature is high Stop the machine and let

it cool down

Severe internal leakage problem Replace or repair the

faulty component

9working hydraulic system_englisg-g9165

Documents

hydraulic cylinders

working pump

hydraulic components

hydraulic oil cylinders

hydraulic lock

pressure valve

system pressure

balance valve