Why does Komatsu pca00-2 excavator turn the rotary table in one direction automatically when pulling the boom control lever to raise the boom, or when pulling the travel control lever?
If the rotary table is to rotate, the distribution valve of the rotary table must not be in the neutral position. First of all, it must be confirmed that the distribution valve slides normally. Secondly, check whether a large amount of pilot oil enters the second end of the distribution valve when the P.0. C pilot control valve does not work. If the inspection conclusion is normal, it can be determined that the fault is in the swing flow control valve. Swing flow control valve a. When the rotation is not operated, the valve core a is in the middle position. At this time, the hydraulic oil with considerable zero pressure from the PD port of the jet valve flows through the upper end of the N. C valve of pump 1, then flows through the valve a, and then reaches the oil tank. Once valve A is stuck and valve core a is not in the middle position, PD pressure oil cannot return to the oil tank, and the oil pressure may rise. Because the valve core a is not in the middle position, the openings of the control oil circuit of pump 1, pump 2 and rotary distribution valve are opened. The PD oil pressure from the PD port of jet valve makes it flow into the control oil circuit of rotary distribution valve and pushes the distribution valve to move to one side. Cause the rotary table to rotate automatically.
The piston rod of boom cylinder and the piston rod of middle boom cylinder of Komatsu PC200-5 and pc200-6 excavators will have flange discoloration (local oil temperature is too high). Why?
Because a boom holding valve is installed between the bottom of the boom cylinder of PC200-5 and pc200-6 excavators and the distribution valve, which can prevent the boom from falling automatically. Pc200-6 excavator is also equipped with a middle arm holding valve between the piston rod side of the middle arm cylinder and the distribution valve. Prevent the middle arm from falling automatically.
Because the holding valve is set in the oil circuit, the hydraulic oil in and out of the oil cylinder increases the resistance. Especially when the back pressure of the slide valve is not well released, the slide valve is not opened enough, making the hydraulic oil flow resistance greater. When the resistance is large, the temperature generated by friction is large, resulting in too high local oil temperature. Komatsu other models do not have this phenomenon.
The piston, plunger body and valve plate of Komatsu pca00-3 excavator were replaced with new parts, and the contact surface between the valve plate and plunger body burned out in less than half a day. What is the reason?
There are many reasons. It may be that the purchased parts are unqualified and the oil tank and pipeline are not cleaned well. Excluding the above reasons, the key is that the plunger body and valve plate are not run in. The newly purchased plunger body and the valve plate are in arc contact (pc400-3 and pc400-5), and the contact surface can be put into normal operation only after running in. The running in method can be manual running in first, and then run in after installation. First run in with small throttle for about 4h, and then use medium oil valve for 4H.
Komatsu pc400-3 excavator has normal working pressure. The control pump output pressure and jet valve pressure are also normal. Why do you feel tired?
This requires careful inspection of the servo valve. Check from two aspects: first, disassemble the valve parts and check the color of the valve core and slide valve. If there is a black part, it indicates that there is oil leakage in this part and a new part should be replaced. Secondly, check whether there is abnormal color. If there is any, it is likely that the slide valve is improperly adjusted, so that the oil inlet B and oil outlet C are connected.
Whether the overload valve and distribution valve are damaged and how to judge?
Judgment method of overload valve fault: remove the plug of traveling distribution valve and replace it with the overload valve. If the boom does not descend, it indicates that the overload valve is faulty; Judgment method of distribution valve failure: pull out the distribution valve core and observe its color. If the valve core is black, there has been leakage.
