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2018-06-26 by Jun Tai


1. What should I pay attention to when grinding the gear end face?
After the gear pump gear wears, it is necessary to grind with a high-precision grinding machine to find a responsible master. For example, the grinder table should be absolutely clean and do not allow dust on the platform. Because the table is slightly unclean, it will offset the ground plane from the vertical line of the bearing hole.

2. What should you pay attention to when assembling the gear pump?
The wear of the pump casing will be a little more in the oil inlet chamber. If the pump casing is symmetrical, it can be turned 180. reuse. For the passive gear, the two ends cannot be exchanged, and the mark is to be taken when removing. Because the gear will wear on one side. The driving tooth is integral with the rotating shaft and cannot be turned over; turning the passive tooth to change the contact point of the meshing lines of the two gears. After the pump is assembled, it is necessary to add a little oil and then rotate it by hand. The hand feels smooth.

3. Should the bearings on the end faces be replaced at the same time when assembling?
Be sure to replace them at the same time. Because of the wear of the pump end face, mainly because the bearing clearance is too large, causing the gear to sway during rotation.

4. After checking that the orifice is not blocked, why can the safety valve pressure not be adjusted?
Most of the situation is due to the tight closing of the cone valve and the valve seat, so that the oil pressure of the C chamber cannot be established.

5. How do you know that the ground plane of the ground gear and the bearing hole have changed?

It can only be found when assembling the gear pump, because the clearance of the end face is very small, generally about 0.05mm. If the end face is perpendicular to the bearing hole, the gear shaft cannot move after the pump is assembled. If the locking screw is loosened a little, but it still does not turn smoothly, then the gear pump is removed and the end face is scratched. This is because the end face plane is not perpendicular to the bearing hole.

6. While the crawler can only move forward and not back?
The overload relief spool in the travel motor is stuck. The travel motor is safe for the protection system. Two overload relief valves are installed in the system. If one of the overload relief valve spools is stuck in the overflow position, the system pressure is lost.

7. The crawler is slow on the side, but if you do a swing at the same time, the crawler can get up quickly. Why? This fault occurs on many excavators. This is because the flow rate supplied to the travel motor plunger pump is insufficient. When the excavator does another action at the same time, it is equivalent to adding another plunger pump flow. The flow of the plunger pump is insufficient, not necessarily because the pump is damaged, and most of them are caused by the fact that the flow control valve is not adjusted.

8. Pull the excavator to move the joystick and feel heavy (almost unmovable) Why?
The travel distribution valve is different from other dispensing valves. The travel distribution valves of most machines are not hydraulically controlled, but are pulled directly by hand through mechanical levers. Because the machine is outdated, or the distribution slide valve has worn out, the clearance between the travel slide valve and the hole becomes larger, the high pressure oil will leak from the oil passage through the gap of the slide valve to the end with the spring, and the spring also has a spring cover tightly covered. When the high pressure is formed in the hood, the shifting valve is moved to the side of the spring, and the lever is very heavy (lighter in the other direction).

9. When operating the two operating poles of the crawler at the same time, the engine speed will drop in an instant or even turn off when the shovel starts, and the reason is more common. This is mainly due to problems with the variable mechanism of the plunger pump. The plunger pump still has a large flow rate when the machine is idling.

10. The traveling oil motor has just been repaired. When the small throttle is used, the crawler will go faster. When the throttle is too large, it will not go. What is the remedy?
This is because the grinding plate has been ground during maintenance and the grinding amount is too much. The pressing force of the distribution plate and the plane of the cylinder is insufficient. When the throttle is small, the oil pressure is small, and there is no leakage between the plane and the plane; when the throttle is large, the oil pressure increases, and the overflow occurs between the planes, which causes the crawler belt to be unable to move when the throttle is large. The remedy can be applied to the spring. If it is a butterfly spring, a butterfly spring can be added.


Guangdong Juntai Hydraulic Technology Co., Ltd.