Reasons for the failure of the hottest hydraulic e

2022-08-19
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Reasons for the failure of the hydraulic excavator

Guide: Liu Wei's PC full hydraulic crawler excavator sometimes has the phenomenon of the whole machine working weakly and moving slowly. We analyze that the main reason is the failure of the hydraulic system. 1. The pressure of the main pump is low. PC excavator adopts double swashplate axial variable plunger

Liu Wei

pc full hydraulic crawler excavator sometimes has the phenomenon of weak operation and slow action of the whole machine. We analyze that the main reason is the failure of the hydraulic system

1. The pressure of main pump is low

pc excavator adopts double swashplate axial variable piston pump. Under normal conditions, the output oil pressure of the main pump is ≥ 30MPa. If the wear between the plunger of the main pump and the cylinder block or between the end face of the cylinder block and the port plate exceeds the standard (the gap between the plunger and the cylinder block should be less than 0.02mm, and the contact area between the end face of the cylinder block and the port plate should not be less than 90%), the output pressure of the main pump will be low, which will be reflected in the working device of the machine, and the whole machine will be unable to work

2. The output flow control valve group of the main pump is faulty

on the premise that the power of the main pump and the engine reaches the best match and gives full play to the role of the engine, the output flow of the main pump of the machine changes with the change of engine power. If the control valve group used to regulate the output flow of the main pump fails, such as the PLS feedback loop is blocked, the LS valve spool is stuck, the PC valve spool is stuck, or the internal coil of the PC EPC solenoid valve is burned out, and if the indoor humidity is too high, the main pump will always be in a constant flow state. If the main pump has been in a small flow state, the machine will be weak and slow when working

similarly, if the swashplate, servo piston and other parts of the main pump that directly control the flow change of the main pump are stuck, the output flow of the main pump will not change

3. The control pressure output by the pressure reducing valve is low

under normal circumstances, the pressure reducing valve can reduce and stabilize the output oil pressure of the main pump at 3.3Mpa to form the control oil pressure. If the conical spool on the pressure reducing valve is not tightly closed due to dirty oil, the output pressure of the pressure reducing valve will be lower than 3.3Mpa. At this time, no matter how the operating handle acts, the control oil pressure is always low, and the movement of the valve core of the main control valve of various working devices is too small, resulting in the flow to the working device is also too small, resulting in the weakness of the whole machine

4. The overflow pressure of the main overflow valve is low

the main overflow valve limits the maximum pressure of the whole hydraulic system to 32.5mpa. For high pressure exceeding this value, the main overflow valve will open for pressure relief to protect the system from damage. If the small hole on the valve core of the main overflow valve is blocked due to poor oil quality and the valve core is normally open, or the set overflow pressure of the main overflow valve is low, the actual overflow pressure will be low, that is, the system pressure will be low

5. The unloading valve is faulty

when the driver starts the engine and puts the operating lever in neutral gear, the hydraulic oil output from the main pump directly returns to the oil tank through the unloading valve, and the unloading pressure is 3Mpa. If the valve core of the unloading valve is not tightly closed due to the dirty oil quality, the output oil of the main pump will pass through the unloading valve to the oil tank during the operation of the machine, so that the system cannot establish high pressure; Similarly, if the 0-shaped seal ring on the unloading valve used to block the connection between pls pressure oil and the oil tank is damaged, the project will also build a fully intelligent production line of aluminum alloy ship materials and a fully automatic robot welding production line, which will also cause the hydraulic oil of the main pump to flow directly back to the oil tank

bypass valve is faulty

ls bypass valve can leak part of p15 pressure oil on LS circuit through two small holes on the valve body (slightly) to increase the softness of machine operation. If the O-ring on the valve body is damaged, PL5 pressure oil will be directly connected with the oil tank, which indirectly leads to the unloading valve being normally open, resulting in the weak and slow action of all working devices

in a word, if the whole machine of pc200-6 excavator is unable to work, it can be largely attributed to the poor oil quality of the hydraulic oil. Therefore, replacing the hydraulic oil filter element on time (stipulated to be replaced every 500 hours) and paying attention to monitoring the hydraulic oil quality (viscosity, fluidity, presence of suspended solids, etc.) have become the key to avoid or reduce such failures

address of the author: the water accessories and east-west General of Guangxi Longlin armed police should be marked with the corresponding signs and specifications. The transportation materials unit of the sixth detachment of the electric power 533409

is selected from "construction machinery and maintenance" miscellaneous to avoid the extension of the plan to damage the records due to human overload

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