Analysis of the Causes of Volvo Excavator Oil Pump Malfunction
When a used excavator experiences an abnormal sound at the connection of the excavator oil pump during construction, the following steps can be taken to investigate the cause of the malfunction:
Remove the dust plug under the motor flywheel and check if the rubber sheet or component is still present
If it exists, the coupling element is damaged and needs to be disassembled and replaced
If it does not exist, further check the coupling component for worn splines and racks or loose screws
If the spline rack is worn or the screws are loose, the coupling component needs to be replaced and the screws tightened
If the spline rack is not worn or the screws are not loosened, the hydraulic pump or motor of the excavator needs to be repaired
The above are the troubleshooting steps and solutions provided by China Liehuang Second hand Equipment Supplier for "Volvo Excavator Oil Pump Fault"
A VOLVO-EC360 excavator experienced brake failure during the rotation of the upper turntable when the working time reached 3000 hours, resulting in the inability to stop the rotation in a timely manner; After continuing to work for another 2 hours, the above-mentioned fault symptoms became increasingly severe. During the inspection, it was found that the turntable cannot stop immediately after rapid rotation, but needs to rotate in the same direction for a certain distance before stopping rotation; When the turntable rotates slowly, it must rotate more than 90 degrees in the opposite direction before stopping.
Volvo EC360 excavator (parameter introduction video)
1. Fault analysis
From the fault phenomenon, it can be seen that the main cause is insufficient braking force. There are several reasons for insufficient braking force, so they were investigated item by item.
(1) Brake pad wear and insufficient spring force
Stop the machine on a slope, rotate the upper turntable to a perpendicular position to the slope, turn off the engine, and at this time, the turntable does not rotate towards the lower side due to gravity; Cut off the oil circuit at the brake control valve PG, start the engine, and operate the pilot valve. At this time, the turntable cannot rotate. The above situation indicates that there is no problem with the brake pads and springs.
(2) Due to wear and leakage in other parts, even after stopping the operation of the pilot valve, there is still pressure oil entering the SH (A12) end
The pilot valve returns incorrectly or not in a timely manner; Or the reversing valve 6 is worn, causing the main pump pressure oil to enter the pilot oil circuit through PAs (or PBs) through the wear gap, and then enter the SH (A12) pipeline through shuttle valves 3 and 4; There are leaks in other parts, and pressure oil enters SH (A12) from AM, A1, A13, Psp, etc., causing the brake control valve to not return to its original position and remain connected to the brake piston. However, PG pressure oil continues to enter the brake piston chamber, causing brake pad 11 to separate and unable to exert braking function.
According to pressure testing, when operating the pilot valve, the pressure at SH (A12) was 3.6 MPa. When stopping the operation of the pilot valve, the pressure quickly decreased from 3.6 MPa to 0. Therefore, it is confirmed that the assumed fault point is not a problem.
(3) The throttle hole of regulating valve 2 is blocked, and brake control valve 1 does not return to its original position
After closing the pilot valve, due to the blockage of the throttle hole of the speed regulating valve 2 and the sticking of the brake control valve 1 in the connected position, the pressure in the brake cylinder cannot be released, and the braking device does not work.
Through pressure detection, the pressure in the brake piston chamber decreased from 3.6 MPa to 0 (approximately 3 seconds) after stopping the operation of the pilot valve. However, when the pressure in the chamber was 0, the rotation of the turntable still could not be stopped. This confirms that there is no problem with the speed control valve and brake control valve.
(4) Wear of rotary motor
After stopping the operation of the pilot valve, the oil pressure inside the rotary motor now plays a role in hydraulic braking and works together with brake pad 11 to stop the movement of the turntable. When the sliding shoes, distribution plates, and other parts of the rotary motor wear out, the oil film that should have formed static hydraulic support in these areas is destroyed. Due to the decrease in sealing performance, the pressure oil inside the plunger leaks through the worn parts, which cannot play a role in hydraulic braking, resulting in slow braking of the turntable.
From the above analysis and monitoring, it can be concluded that the focus of troubleshooting should be on the rotary motor.
2. Troubleshooting
According to the pressure detection of the rotary motors A (BH) and B (LH), it is found that the initial pressure of the rotary motor must reach 16MPa before the turntable can start rotating, indicating excessive resistance to rotation; Place the excavator bucket on the ground and operate the pilot valve. The maximum pressure value measured is only 20MPa, which is significantly different from the standard value of 26MPa.
When removing the discharge filter element 7, it was found that there were many metal shavings on the filter element, which was determined to be caused by wear of the rotary motor. So, when disassembling the rotary motor, it was found that there were a large number of metal shavings inside, and there were signs of strain on the surface of the distribution plate. The sealing ring behind the distribution plate had been squeezed out, and there were obvious signs of strain on the surface of the plunger slide shoe, inclined plate, and nine hole plate. The metal on the lower bearing surface had also fallen off in large quantities.
After measurement, the height of the worn bearing is still 29.7mm, while the standard height value for similar bearings is only 29.0mm. Therefore, it is concluded that an unqualified bearing was used during installation. Due to the axial installation being too tight, the radial force on the bearing was too large, causing abnormal wear on the Mazda. The metal shavings that were worn down entered the mating surfaces and pulled them apart.
So, the standard bearings were replaced and the sliding shoes, distribution plates, inclined plates, and nine hole plates were manually ground; In addition, the pipelines and hydraulic oil tank were cleaned, and the hydraulic oil filter and hydraulic oil were replaced. During the test drive after reassembly, the fault disappeared. There are traces of metal shavings, scratches on the surface of the distribution plate, and the sealing ring behind the distribution plate has been squeezed out. There are obvious scratches on the surface of the plunger slide shoe, the inclined plate, and the nine hole plate. The metal on the lower bearing surface has also fallen off in large quantities.
After measurement, the height of the worn bearing is still 29.7mm, while the standard height value for similar bearings is only 29.0mm. Therefore, it is concluded that an unqualified bearing was used during installation. Due to the axial installation being too tight, the radial force on the bearing was too large, causing abnormal wear on the Mazda. The metal shavings that were worn down entered the mating surfaces and pulled them apart.
So, the standard bearings were replaced and the sliding shoes, distribution plates, inclined plates, and nine hole plates were manually ground; In addition, the pipelines and hydraulic oil tank were cleaned, and the hydraulic oil filter and hydraulic oil were replaced. During the test drive after reassembly, the fault disappeared.
