Causes and improvement measures of serious wear of hydraulic gear pumps in China

Time of issue：

2022-11-29

Source：

Severe wear of the hydraulic pump of the excavator has a fatal effect on the excavator, so such problems must be solved in time for the excavator. When repairing the hydraulic pump of the excavator, find the cause of the fault from the following three points:

(1) Check the internal leakage of the boom cylinder
The simple way to do this is to raise the boom to see if it has a noticeable free fall. If the drop is obvious, disassemble the cylinder for inspection, and replace the sealing ring if it has been worn.

(2) Check the control valve
FIRST CLEAN THE SAFETY VALVE, CHECK WHETHER THE VALVE CORE IS STILL UNCHANGED, AND THEN CHECK THE WEAR OF THE CONTROL VALVE CORE, ITS CLEARANCE USE LIMIT IS GENERALLY 0.06MM, AND THE WEAR SHOULD BE REPLACED.

(3) Measure the pressure of the hydraulic pump
If the pressure is low, it is adjusted, and the pressure still cannot be adjusted, which indicates that the hydraulic pump is seriously worn.

First, the main reasons why the boom load cannot be lifted are:

1. The hydraulic pump of the excavator is seriously worn
Serious leakage in the pump when running at low speed; At high speed, the pump pressure increases slightly, but due to the wear and internal leakage of the gear oil pump, the volumetric efficiency decreases significantly, and it is difficult to reach the rated pressure. The long-term work of the hydraulic pump aggravates the wear, the oil temperature rises, resulting in the wear of hydraulic components and the aging and damage of the seals, the loss of sealing ability, the deterioration of the hydraulic oil, and finally the occurrence of failure.

2. The selection of hydraulic components is unreasonable
The boom cylinder specification is 70/40 non-standard series, and the seals are also non-standard parts, which is expensive to manufacture and inconvenient to replace seals. The small bore of the boom cylinder is bound to make the system set pressure high.

3. The hydraulic system design is unreasonable
The control valve and the full hydraulic steering gear are connected in series with a single pump, the safety valve is set to 16MPA, and the rated working pressure of the hydraulic pump is also 16MPA. The hydraulic pump often works under full load or long-term overload (high pressure), and the system has hydraulic impact, long-term oil change, hydraulic oil is contaminated, aggravate the wear of the hydraulic pump, so that the hydraulic pump casing bursts (such failures were later discovered).

2. Improvement and effect

(1) Improve hydraulic system design
After many demonstrations, the advanced priority valve and load sensing full hydraulic steering gear form was finally adopted. The new system can prioritize the distribution of flow to it according to the steering requirements, regardless of the size of the load, the speed of the steering wheel can ensure sufficient oil supply, and the remaining part can be fully supplied to the working device circuit, thereby eliminating the power loss caused by excessive oil supply to the steering circuit, improving the system efficiency and reducing the working pressure of the hydraulic pump. Reduce severe wear of excavator hydraulic pumps.

(2) Optimize the design of boom cylinder and hydraulic gear pump shape
Reduce system operating pressure. Through optimized calculations, the boom cylinder adopts the standard series 80/4. THE DISPLACEMENT OF THE HYDRAULIC PUMP IS INCREASED FROM 10ML/R TO 14ML/R, AND THE SYSTEM SETTING PRESSURE IS 14MPA, WHICH MEETS THE LIFTING FORCE AND SPEED REQUIREMENTS OF THE BOOM CYLINDER.

(3) Strengthen daily inspection and maintenance
During use, we should also pay attention to the correct use and maintenance of the loader, regularly add or replace hydraulic oil, maintain the cleanliness of hydraulic oil, and strengthen daily inspection and maintenance. In this way, serious wear of the hydraulic pump of the excavator can be avoided.

Technology updates push gear pumps to intelligence

Technology updates push gear pumps to in...

Gear pumps are rotary pumps that rely on the change and movement of the working volume formed between the pump cylinder and the meshing gear to transport liquid or increase its pressure. It consists of two gears, pump body and front and rear covers to form two closed spaces, when the gear rotates, the volume of the space on the gear disengagement side changes from small to large, forming a vacuum, sucking the liquid in, and the volume of the space on the gear meshing side changes from large to small, and the liquid is squeezed into the pipeline. The suction chamber and discharge chamber are separated by the meshing lines of the two gears. The pressure at the discharge outlet of a gear pump depends entirely on the resistance at the source of the pump.