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Second-hand Komatsu PC200-6 Failure Self-Test

Release Time: 2020-02-18

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Views: 202

Second-hand Komatsu PC200-6 Failure Self-Test
Komatsu PC200-6 full hydraulic crawler excavator sometimes appears to be weak and slow in operation. China Machinery has organized 6 possible causes for self-inspection failures for the convenience of users, and provides work efficiency.

1. Low main pump pressure

PC200-6 excavator uses double swash plate type axial variable piston pump. Under normal circumstances, the output oil pressure of the main pump is ≥30MPa. If the amount of wear between the plunger and the cylinder of the main pump or the end surface of the cylinder and the flow plate exceeds the standard (the gap between the plunger and the cylinder should be less than 0.02mm, the The contact area should not be less than 90%), which will cause the output pressure of the main pump to be low, which will be reflected in the working device of the machine, and the whole machine will be weak.

2. Defective main pump output flow control valve group

Based on the premise that the power of the main pump and the engine is optimally matched and the role of the engine is fully exerted, the output flow of the main pump of the machine changes with the change of the engine power. If the control valve group used to adjust the output 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, etc. As a result, the main pump is always in a state of constant flow. If the main pump is always in a low flow state, the machine will be weak and slow in operation.
Similarly, if the swash plate, servo piston, and other parts of the main pump that directly control the change of the main pump flow rate are stuck, the output flow of the main pump will not change.

3. The control pressure output from the pressure reducing valve is too low

Under normal circumstances, the pressure reducing valve can reduce and stabilize the output oil pressure of the main pump to 3.3MPa, forming a control oil pressure. If the conical valve core on the pressure reducing valve is not closed properly due to the dirty oil, the output pressure of the pressure reducing valve will be lower than 3.3 MPa. At this time, regardless of the operation of the operating handle, the control oil pressure is always low, and the spool movement of the main control valve of various working devices is small, resulting in a small flow to the working device, resulting in weakness of the entire machine.

4. Low relief pressure of main relief valve

The main relief valve limits the maximum pressure of the entire hydraulic system to 32.5 MPa. For high pressures exceeding this value, the main relief valve will open to relieve pressure to protect the system from damage. If the orifice of the main relief valve spool is blocked due to poor oil quality and the spool is always open, or if the set relief pressure of the main relief valve is low, the actual relief pressure will be low, that is, the system The pressure is low.

5. Defective unloading valve

When the driver starts the engine and puts the operating lever in neutral, the hydraulic oil output by the main pump returns directly to the fuel tank through the unloading valve, and the unloading pressure is 3 MPa. If the unloading valve spool is not closed tightly because the oil is too dirty, when the machine is operating, the output oil of the main pump will pass through the unloading valve to the oil tank, causing the system to fail to establish high pressure. When the 0-shaped seal ring that blocks the connection of the PlS pressure oil to the fuel tank is damaged, it will also cause the main pump hydraulic oil to flow directly back to the fuel tank.

6. Defective LS bypass valve

The LS bypass valve can leak (partially) the P15 pressure oil on the LS circuit through two small holes in the valve body to increase the softness of machine operation. If the o-ring seal on the valve body is damaged, the PL5 pressure oil will directly communicate with the fuel tank, which indirectly causes the unloading valve to always open, resulting in weak and slow movement of various working devices.
To sum up, if the PC200-6 excavator is weak, it can be largely attributed to the poor oil quality of the hydraulic oil. Therefore, replacing the hydraulic oil filter element on time (specified to be replaced every 500 hours) and paying attention to monitoring the hydraulic oil quality (viscosity, fluidity, and presence of suspended matter, etc.) have become the keys to avoid or reduce such failures. It is hoped that Komatsu PC200-6 will maximize the mining performance and become one of the more popular excavators.

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