When hydraulic excavator is working for a long time, powerless is usually happened to excavator. This article will tell you how to repair the excavator's powerless.Take Komatsu PC200-6 for example.
Let us briefly understand Komatsu PC200-6, Komatsu PC200-6 is a very popular excavator. It is very suitable for almost all kinds of complicated situations, and is highly praised by excavator lovers for its excellent and stable performance.
Komatsu PC200-6 Excavator Parameter Configuration
Machine working weight(kg): 19180
Bucket capacity(m³): 0.8
Boom length(mm): 5700
Stick length(mm): 1840
Country of origin: Japan
Tonnage(ton): 20
Grounding specific pressure(Kpa): 44.1
Swing speed(rpm): 12.4
Walking speed(km/h): 5.5
Climbing ability(%): 70/35°
Main overflow set pressure(Mpa): 34.818
Main pump maximum flow(l/min): 412
Maximum excavation height(mm): 8895
Maximum unloading height(mm): 6065
Maximum vertical excavation depth(mm): 496590
As an excavator lover, when the PC200-6 excavator appeared to be weak and slow in operation, we speculated that the following problems may have occurred.
1. The main pump pressure is low
The PC200-6 excavator uses a double swash plate type axial variable displacement piston pump. Under normal circumstances, the main pump output oil pressure is above 30MPa. If the amount of wear between the plunger of the main pump and the cylinder or between the end face of the cylinder and the distribution plate exceeds the standard (the clearance between the plunger and the cylinder should be less than 0.02 mm, the contact area between the end face of the cylinder and the distribution plate should be no less than 90%), which will cause the main pump output pressure to be low. Which is reflected in the mechanical working device, and the whole machine will work weakly.
2. The main pump output flow control valve group is faulty.
On the premise that the power of the main pump and the engine is highly matched and the engine can be fully utilized, the output flow of the main pump of the machine changes with the change of engine power. If there is a fault in the control valve group used to regulate the main pump output flow, such as the PLS feedback circuit blockage, the LS valve spool stuck, the PC valve spool stuck or the PC-EPC solenoid valve internal coil is burned, etc. The main pump is always in a state of constant flow. If the main pump is always in a small flow state, the machine will be weak and slow when it is working.
Similarly, if the swash plate, servo piston, and the like of the main pump that directly controls the main pump flow change are stuck, the output flow rate of the main pump does not change.
3. The control pressure of the pressure reducing valve output is low
Under normal circumstances, the pressure reducing valve can reduce the output oil pressure of the main pump and stabilize it at 3.3 MPa to form a control oil pressure. If the oil valve is too dirty and the conical valve plug on the pressure reducing valve is not tightly closed, the output pressure of the pressure reducing valve will be lower than 3.3 MPa. At this time, no matter how the operation handle is operated, the control oil pressure is always low, and the movement amount of the spool of the main control valve of various working devices is too small, so that the flow rate to the working device is also small, resulting in the weakness of the whole machine.
4. The overflow pressure of the main relief valve is low
The main relief valve limits the pressure of the entire hydraulic system to 32.5 MPa. For high pressures above this value, the main relief valve will open to relieve pressure to protect the system from damage. If the small hole on the main relief valve spool is blocked due to poor oil quality, the spool is normally open, or 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. The unloading valve is faulty
When the driver starts the engine and puts the operating lever in neutral, the main pump output hydraulic oil is directly returned to the tank through the unloading valve, and the unloading pressure is 3 MPa. If the oil is too dirty, the unloading valve spool will not be closed tightly. When the machine is working, the output oil of the main pump will pass through the unloading valve and pass through the fuel tank, so that the system cannot establish high pressure. Similarly, if the unloading valve is used When the 0-ring seal that blocks the PlS pressure oil and the fuel tank is damaged, the main pump hydraulic oil will also flow directly back to the tank.
6. LS bypass valve is faulty
The LS bypass valve can leak a portion of the P15 pressure oil on the LS circuit through two small holes (slightly) on the valve body to increase the softness of the 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 open normally, causing the working devices to be weak and slow, and if the PC200-6 excavator appears to work. The weakness is largely attributable to the poor oil quality of the hydraulic fluid. Therefore, replacing the hydraulic oil filter on time (specified to be replaced every 500 h) and paying attention to monitoring the hydraulic oil quality (viscosity, fluidity and presence or absence of suspended solids) are the key to avoiding or reducing such failures.
The above is the main repair process for the excavator's weakness. This article only uses the Komatsu PC200-6 as an example. Mainstream excavators such as VOLVO EC360/VOLVO EC460 can also refer to this article. For details, please refer to the official maintenance manual.
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