What is a Foot Pump?

A foot pump is one of the hydraulic pumps. Its function is to convert the mechanical energy of a power machine (such as an electric motor and an internal combustion engine) into liquid pressure energy. The cam is driven by the motor to rotate. When the cam pushes the plunger to move upward, the sealing volume formed by the plunger and the cylinder body is reduced, and the oil is squeezed out of the sealed volume and discharged to the required place through the check valve. When the cam rotates to the lower part of the curve, the spring forces the plunger downward to form a certain degree of vacuum, and the oil in the fuel tank enters the sealed volume under the effect of atmospheric pressure. The cam continuously raises and lowers the plunger, the sealing volume is periodically reduced and increased, and the pump continuously sucks and discharges oil.

Foot pump is

The function of the foot pump is to convert the mechanical energy of power machines (such as electric motors and internal combustion engines) into pressure energy of liquids. Working principle: The cam is rotated by the motor. When the cam pushes the plunger to move upward, the sealing volume formed by the plunger and the cylinder body is reduced, and the oil is squeezed out of the sealed volume and discharged to the required place through the check valve. When the cam rotates to the lower part of the curve, the spring forces the plunger downward to form a certain degree of vacuum, and the oil in the fuel tank enters the sealed volume under the effect of atmospheric pressure. The cam continuously raises and lowers the plunger, and the sealing volume is periodically reduced and increased, and the pump continuously sucks and discharges oil ^[1]

Find the cause of the failure and improve the system from the following three points during maintenance:

(1) Check the leakage of the boom cylinder. The easiest way is to raise the boom to see if it has a clear free fall. If the drop is obvious, remove the oil cylinder for inspection, and the seal ring should be replaced if it is worn.

(2) Check the control valve. First clean the safety valve and check whether the valve core is worn. If it is worn, it should be replaced. If there is no change after the safety valve is installed, check the valve spool for wear. The clearance limit is generally 0.06mm, and it should be replaced if it is severely worn.

(3) Measure the pressure of the hydraulic pump. If the pressure is low, adjust it. If the pressure cannot be adjusted, it means that the hydraulic pump is seriously worn. ^[1]

(1) The hydraulic pump is severely worn. Leakage inside the pump is serious during low speed operation; the pump pressure is slightly increased during high speed operation, but due to pump wear and internal leakage, volumetric efficiency is significantly reduced and it is difficult to reach rated pressure. The long-term work of the hydraulic pump intensifies the wear and tear, and the oil temperature rises, which causes the wear of the hydraulic components and the aging and damage of the seals, the loss of the sealing ability, the deterioration of the hydraulic oil, and finally the failure.

(2) The selection of hydraulic components is unreasonable. The specifications of the boom cylinder are 70/40 non-standard series, and the seals are also non-standard. The manufacturing cost is high and the seals are not easy to replace. The small diameter of the boom cylinder will inevitably make the system's setting pressure high.

(3) The hydraulic system design is unreasonable. The control valve and the full hydraulic steering gear are connected in series by a single pump. The pressure setting pressure of the safety valve is 16MPa, and the rated working pressure of the hydraulic pump is also 16MPa. Hydraulic pumps often work under full load or long-term overload (high pressure) conditions, and the system has hydraulic shocks, the oil is not changed for a long time, the hydraulic oil is contaminated, and the hydraulic pump wears out, causing the hydraulic pump casing to burst (later found Such failures) ^[1]

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

(2) Optimize the design of boom cylinder and hydraulic pump to reduce system working pressure. Through optimized calculation, 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) In the process of use, also pay attention to the correct use and maintenance of the loader, regularly add or replace hydraulic oil, maintain the cleanliness of the hydraulic oil, and strengthen daily inspection and maintenance ^[1]

It is suitable for power, construction and other industries to operate in the field. There are two types, domestic and foreign. Domestic prices are several hundred and several thousand cheaper. The cheapest abroad are thousands of dollars ^[1] .