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Application of Double Gear Pump in Shearer Height Adjustment System
Release time:
2020-01-05
When the hydraulic oil passes through the net block, due to the presence of elbows, joints, net openings, and sudden changes in cross-section, etc., the flow resistance is generated in the local area due to changes in flow or flow direction, resulting in pressure loss, resulting in an increase in oil temperature.
The height adjustment system of the shearer is generally hydraulic height adjustment. The hydraulic system has a single pump and a double gear pump. The oil circuit system can be simplified as the main oil circuit, control oil circuit and brake oil circuit. The main oil circuit controls the two hydraulic cylinders to lift the rocker arm. The required flow rate is relatively large, and the required larger oil pressure is slightly less than the oil pressure of the high-pressure relief valve. The control oil circuit only controls the action of the manual hydraulic switch network, and the required flow rate is small. The brake oil circuit uses oil to compress the brake pads to achieve braking efficiency. The same required flow rate is small, and the oil pressure required for the oil circuit is about 2MPa. This paper compares the hydraulic system.
1. Fuel tank heat dissipation:
When the hydraulic oil passes through the net block, due to the presence of elbows, joints, net openings, and sudden changes in cross-section, etc., the flow resistance is generated in the local area due to changes in flow or flow direction, resulting in pressure loss, resulting in an increase in oil temperature.
The principle of double gear pump system in the main oil because there is no pressure drop, power waste is mainly in the control circuit. From the calculation results, in order to meet the heat dissipation requirements of the fuel tank, the single pump configuration fuel tank is larger than the double pump fuel tank, which is unfavorable to the design of the shearer requiring a short fuselage.
2. Life of control valve:
In the single-pump hydraulic system, the oil of the main oil circuit enters the control oil circuit as a whole, and the flow rate is large, and a thicker hydraulic pipe must be used in the control. At the same time, during control, the oil passes through more small holes, and the pressure loss is more serious. The large flow rate also means that more impurities may enter the control oil circuit with the liquid flow, which may easily cause blockage of the electromagnetic steering network or pipeline, resulting in downtime and maintenance accidents. In the double pump system, because the control oil circuit is a relatively separate circuit, the small pump sucks oil through the main oil return pipe, enters the pump body, and passes through the fine filter to ensure the quality of the oil, which greatly reduces the occurrence of hydraulic system failures.
3. Power loss:
The oil enters the control oil circuit after passing through the middle position (H) of the hydraulic cylinder net group of the left and right rocker arms through the pump. When not in operation, it returns to the oil tank through a low-pressure overflow net (2MPa) without passing through the electromagnetic commutation net. There is a high pressure overflow net (20MPa) at the outlet of the oil pump. When the oil is adjusted to high, the oil first enters the oil cylinder and then enters the control oil circuit. When the pump is working at full load (I .e. the outlet oil pressure is 20MPa), the oil pressure supplied to the hydraulic cylinder by the hydraulic pump is 18MPa, which shows that 10% of the power is wasted.
This problem does not exist in the double gear pump system. When the main pump oil is not adjusted, it directly returns to the oil tank after passing through the middle position (H) of the left and right rocker arm hydraulic cylinder net groups. The control system uses a 4mLhr small hydraulic pump to control, and there is a low pressure overflow network (2MPa) in the control oil circuit to ensure the oil pressure of the control system and the brake system. When the height is adjusted, the main pump oil passes through the hydraulic cylinder, and the remaining oil is connected with the oil tank. When the load is full, the pressure drop is the high pressure overflow set pressure (20MPa). It can be seen that there is no problem of power waste in this system.
From the above analysis, it can be seen that the application of double gear pump system in the shearer height adjustment system can obviously reduce the waste of power, reduce the rise of oil temperature, shorten the length of the fuselage and increase the life of hydraulic components.
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