Inspection and adjustment of working device of SANY excavator

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1. Preparation for measurement

Lower the working device to the ground and turn off the engine. After the engine is stopped, operate the joystick several times to release the residual pressure in the pipeline. Then unscrew the wing nut on the breathing valve and press the release button to release the pressure in the hydraulic tank.


(1) Remove the hydraulic oil pressure measuring plugs (1) and (2).

● Plug (1): Used for the oil circuit of the rear hydraulic pump.

● Plug (2): Used for the oil circuit of the front hydraulic pump.

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(2) Install the oil pressure test connector and connect it to the hydraulic pressure tester.


★ Use an oil pressure gauge with a capacity of 40 MPa {408 kgf / cm2}.


(3) Start the engine and keep it running until the hydraulic oil pressure rises to the working range.



2. Measurement of unloading pressure


(1) Start the engine.


(2) Measure the hydraulic oil pressure when the engine is running at high idle and all joysticks are moved to the neutral position.


 ★ Note: Shows the hydraulic oil pressure when the unloading valve is unloaded.



3. Measurement of working device overflow pressure


(1) Start the engine and move the cylinder to be measured to the end of the stroke.


(2) Measure the hydraulic oil pressure when the engine is running at high idle speed and the cylinder is under overflow.


 ★ Note: Display the hydraulic pressure when the main relief valve is in the overflow state



4. Measurement of slewing overflow pressure


(1) Start the engine, extend the working device forward as far as possible, and use the bucket to support the ground to restrict rotation.


(2) Measure the hydraulic oil pressure when the engine is running at high idle speed and the slewing oil circuit is overflowing.


    ★ Note: The hydraulic oil pressure is displayed when the rotary motor safety valve is overflowing.


    ★ Note: The slewing motor relief pressure is lower than the main relief pressure.



5. Measurement of the overflow pressure of the traveling oil circuit


(1) Start the engine and lock it.


    Put the pin ① between the sprocket and the crawler bracket to ensure the lock travel.

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(2) Measure the hydraulic oil pressure when the engine is running at high idle speed and the traveling oil circuit is overflowing.


★ The main relief valve displays the hydraulic oil pressure when it is in the overflow state, and the pressure is always high-pressure relief when the hydraulic circuit is overflowing.


Adjustment method teaching


★ Note: The boom safety valve cannot be adjusted


Adjustment of main relief pressure (high-pressure setting side)


★ Note: The high-pressure overflow pressure in the working device and the traveling oil path is abnormal. Adjust the high-pressure setting side of the main relief valve (3) in the following order.

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1) Disconnect the pilot hose.

2) Loosen the locknut (4) and adjust the pressure by turning the adjusting screw (5).


★ If the retainer is turned to the right, the pressure rises. If the retainer is turned to the left, the pressure drops.


★ Adjustment amount of the retainer per turn:


12.5 MPa {about 128 kgf / cm2} lock nut: 53.5 ± 4.9N · m {5.5 ± 0.5 kgf · m}

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3) Check the pressure again after adjustment, and measure according to the above steps.


★ When measuring pressure, connect the pilot hose.


★ If the high-pressure setting side is adjusted, it will also affect the low-pressure setting side, so also adjust it.


2. Adjustment of slewing overflow pressure


★ If the slewing relief pressure is abnormal, adjust the slewing motor safety valve (6) in the following order.

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1) Loosen the locknut (7) and adjust the pressure by turning the adjustment screw (8).


★ If the retainer is turned to the right, the pressure rises. If the retainer is turned to the left, the pressure drops.


★ The adjustment amount of each turn of the adjusting screw: about 6.71 MPa {about 68.4 kgf / cm2}


fasten the screw nut:


78-103N · m {8.0-10.5 kgf · m}

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2) Check the pressure again after adjustment, and measure according to the above steps.