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How to Check and Repair Hydraulic Pump

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Author : Peter
Update time : 2019-10-29 21:17:09
How to Check and Repair Hydraulic Pump
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At present, there are only two types of hydraulic plunger pump used by various excavators. One type is inclined shaft pump (such as A8V/ Hitachi pump) and straight shaft inclined disc pump. The typical type is K3V series pump.
At present, the variable principle of hydraulic pump used by excavators is basically one, which requires the high-pressure oil (hydraulic power) driving variable mechanism of the pump itself.
The variable mechanism of the pump includes "servo valve, slide valve and variable piston".
Variable piston is a small hydraulic oil cylinder, hydraulic cylinder into a bar with rodless cavity, variable piston into big diameter and paths, variable piston big diameter inlet diameter (large) when the pressure is higher than the path of fluid power variable piston to path direction, variable piston rod on the pin to drive the pump in inclined plate movement, swash plate Angle increase, the elongation of the plunger stroke of the pump discharge of oil quantity increase, excavator fast.
When the pressure of the path is higher than that of the large diameter, the hydraulic force pushes the variable piston back, the Angle of the inclined plate becomes smaller, the plunger stroke in the cylinder decreases, the displacement of the pump decreases, but the pressure decreases.
At present, the variable piston path end in the hydraulic piston pump of all kinds of excavators is communicated with the P port of the pump, that is, the pressure of the variable piston path end is as high as the pressure of the pump.
The large diameter end of the variable piston oil channel communicates with the three oil ports on the regulator.
One of these three oil orifons is the t-hole (drain hole) in the komatsu -7 pump called the g-hole.
An oil port is a proportional valve, also known as hole E.
An oil port is the servo valve to oil, also called D hole.
Regulator is based on feedback servo pressure, proportional valve pressure to determine the control oil into the large diameter of the pressure is how much, if the pressure is twice the size of the path, variable piston neutral.
 
The preparation work before repairing the pump: before repairing the pump, first of all to determine the repair of the pump to repair the part of the pump, determine what the pump has.
 
1. How long is the total service life of the pump?
It doesn't matter how long the pump lasts. If it lasts more than ten years, the pump is basically of no maintenance value.
Because the steel also has a certain periodicity, the steel base will produce the separation layer and the pump shell deformation.
 
2. How long has it been since the last repair of the pump?
Which parts were replaced in the last repair of the pump?
The last pump maintenance personnel maintenance level?
 
3. What is the maximum service pressure of the current pump, bar?
Variable mechanism of the pump to adjust the sensitivity, (response) feedback speed?
What is the service temperature of the pump?
 
4. Does the excavator hang the hydraulic hammer?
How long does the excavator use the hydraulic hammer?
 
5. What kind of noise does the pump make?
Is the noise mechanical or hydraulic?
 
What type of hydraulic fluid should be used?
What is the oil quality now?
Put the hydraulic oil inside the hydraulic tank of the excavator completely clean, check the oil quality?
Check how many impurities are in the tank bottom plate?
What kind of impurities are they?
If the quality of the hydraulic oil deterioration, it is necessary to ask the machine to replace the hydraulic oil.
 
Repair pump is a pump for a variety of different symptoms, to take different maintenance methods.
For a pump whose pressure is up to the standard but whose pump flow is small (the excavator moves slowly), the main purpose is to check the gap between the various parts of the variable mechanism of the pump, such as the gap between the variable piston of the pump and the hole of the pump shell. The standard gap between the large end diameter of the variable piston and the small end diameter of the variable piston and the hole of the pump shell is 0, 008mm.
What is the maximum clearance? 032mm.
When the maximum clearance is exceeded, it needs to be repaired to the standard clearance.
Our maintenance method is to use grinding rod to grind the inner hole and increase the piston diameter.
The pore diameter of large gap is mainly large stoma, and it should be noted that the hole after drilling can not appear cone hole phenomenon.
Large hole and small hole must ensure coaxiality, I use the grind bar and professional factory customized.
When the piston needs to increase its outer diameter, our factory adopts the method of supersonic flame spraying cermet to process the black wear-resistant ceramic layer on the piston diameter. This black ceramic layer has a special wear resistance, which is the most advanced surface engineering technology in the world today.
But: the price is also very high, three to four times more expensive than the conventional method.
The rotary oil seal on the main shaft of the pump is worn into a ravine.
The following two methods can also be used: one is the electroplating method of hard chromium plating layer, in order to ensure the bonding strength of the coating, first need to first rod outer diameter surface layer with the cylindrical grinder grinding 0,15 mm or so, remove the metal surface of the fatigue layer, so as to ensure the bonding strength of the coating.
Plating must be greater than the aperture of 0,1 mm, to ensure that the grinding machine processing.
 
Second, the brush plating method to increase the piston diameter.
 
Variable piston rod is also equipped with a replacement of a ball - shaped pitchfork, pitchfork friction serious spherical also need to be replaced.
Matching sets with the fork also require special attention.
 
Standard of K3V series pump parts:
 
K3V063 pump plunger and cylinder body standard clearance 0.
014mm, maximum clearance 0.
028 mm
 
Maximum clearance between plunger rod and slipper 0.
3 mm
 
Spring length: 30.
2 mm ~ 31.
3 mm
 
After the ball hinge is assembled with the return plate, the bottom surface of the ball hinge is 9 to the nine-hole plane of the return plate.
8 ~ 10 mm.
5 mm.
 
K3V112 pump plunger and cylinder body standard clearance 0.
Maximum clearance of 22mm 0.
039 mm
 
Maximum clearance between plunger rod and slipper 0.
3 mm
 
Spring length: 40.
3 mm ~ 41.
7 mm
 
After the ball hinge is assembled with the return plate, the bottom surface of the ball hinge is 8 to the nine-hole plane of the return plate.
8 ~ 9 mm.
8 mm
 
K3V140 pump plunger and cylinder body standard clearance 0.
Maximum clearance 0.
043 mm
 
Maximum clearance between plunger rod and slipper 0.
3 mm
 
Spring length: 47.
1 mm ~ 47.
9 mm
 
After the ball hinge and the return plate are assembled for one, the bottom surface of the ball hinge shall be 12 on the nine-hole plane of the return plate.
5 mm ~ 13.
5 mm
 
K3V180 pump plunger and cylinder body standard clearance clearance 0.
0375.
Maximum gap 0.
078 mm
 
Maximum clearance between plunger rod and slipper 0.
35 mm
 
Spring length: 40.
1 mm ~ 40.
9 mm
 
After the ball hinge and the return plate are assembled for one, the bottom surface of the ball hinge shall be 12 on the nine-hole plane of the return plate.
5 mm ~ 13.
5 mm.
 
After the above parts exceed the standard, they need to be replaced