Hitachi 200 excavator boom, slow slewing compound action
Many machine owners have been puzzled. It is clear that there is no problem with the single action of the excavator, but the composite action fails immediately. Either the action is slow or the action is not fully performed, and the construction effect is always greatly reduced
Recently, a Hitachi 200 owner's love machine fault is very typical. There is a problem when the boom is lifted and rotated. Let's take a look at how to solve the problem
Fault phenomenon:
The owner of Hitachi 200 machine recorded a video for help. In the video, when the machine was digging and loading, a bucket of soil filled with soil was turned to the dump truck, but the boom could not be lifted to the corresponding height, and sometimes it would bump against the dump truck
Reason analysis of slow slewing compound action of excavator boom:
This phenomenon is very common in the actual construction site. Drivers often report such problems. This is the case when some equipment leaves the factory. When rotating and lifting the boom, the rotation is very fast, and the boom cannot be lifted
Therefore, this phenomenon is simply a problem of the design of the confluence oil circuit. Of course, there are also subsequent failures that lead to this phenomenon Then we need to understand the design principle of the combined oil circuit of slewing and boom before troubleshooting. Take this Hitachi zx200-3 as an example:
Swing and boom lift operation
When the boom is raised at the same time as the swing, pilot pressure moves the spool of the swing, boom 1, and boom 2
The pressure from the pump 1 flows through the parallel oil path from the boom 1 spool to the boom cylinder and lifts the boom
Pressure oil from pump 2 flows through the swing spool to the swing motor for swing
At the same time, the pressure oil flows to the boom cylinder through the parallel oil path from the boom 2, joins with the pressure oil from the pump 1 and lifts the boom
This is the compound action: both pumps supply pressure oil to the boom cylinder However, the oil of one of the pumps is supplied to both the swing and the boom, so how much oil is distributed to the boom is the reason for determining the boom lifting speed
Once this principle is understood, the fault causes or fault points will surface:
Fault point analysis
1. The pilot pressure of boom lifting is low, which will cause the valve stem to not fully open and affect the flow
2. The boom main valve is stuck and worn. If it is stuck at a certain position, it may cause small opening, insufficient flow and leakage due to wear
3. Various overload overflow valves, confluence valves and other oil circuits configured in the boom lifting oil circuit have leakage points or one-way valves are stuck and deformed
4. Leakage in the cylinder
5. Regeneration valve for boom 1
For the above fault points, eliminate the causes of slow action caused by the engine and hydraulic pump
terms of settlement:
These fault points mentioned above can only be found one by one and solved accordingly. For old machines, as long as the valve is worn, there will be leakage even after grinding. In this case, we can only reform the system. For example, we can limit the flow of rotation, reduce the control pressure, limit the main valve, etc
On the contrary, if the boom is lifted quickly and rotated slowly, and if there is no fault of other hardware, we can handle it with the same principle
