External gear pumps are rotary, positive displacement pumps equipped to handle thin and thick fluids in both pumping and metering applications.
Hydraulic pumps are divided according to their displacement principle into the following categories:
- Gear
- Vane
- Piston principle
External gear pumps
The formation of the geometric stroke volume takes place between the tooth chambers and the housing walls.
The external gear pump is not suitable for low drive speeds as its total degree of efficiency is too low in the lower speed range.
Geometrical stroke displacement
V8 = m . z . b . h .
V8 = geometrical stroke displacement
m = module
z = number of teeth
b = tooth width
h = tooth height
External gear pump function
By rotating the upper gear wheel in the direction of the arrow, the lower gear wheel is moved in the opposite direction. In this case it is referred to as the “meshes” on two gear wheels.
The oil is absorbed from the suction chamber, pushed around the outside of the gear chambers, and displaced again from the tooth gaps on the pressure side.
In the pressure areas of engagement, tooth gaps of one wheel can be closed by teeth from another wheel before being emptied. Therefore, relief holes must be drilled in the housing so that this trapped operating fluid can be discharged.
Depending on the manufacturer, this operating fluid is used to lubricate the bearings and guided to the input side.
This also provides pressure compensation on the bearing reinforcements, which causes them to be pressed more firmly against the gears as pressure increases, thus reducing the gap size and improving the degree of efficiency.
The hydraulic pumps are made of different materials and are available on the market in special designs for certain applications.
Permitted operating parameters such as negative pressure on the input side, permanent or peak pressure in the output, viscosity area, contamination loads, and the type of operating medium are very different depending on the manufacturer and types.
In the same way there are different variants in relation to the mode such as duration, intermittent or reverse mode.
The hydraulic pumps are available as individual pumps, multiple pumps, and pump combinations.
Up until the previous century, a three-wheel version was also built, which was used in the field of lubricating oil for hydropower and combustion motors.
Repair to these hydraulic pumps is generally not economical, meaning that no individual components are available.
External gear pump application
The external gear pump is a simple, robust, and inexpensive construction with high operational reliability.
However, it has a high degree of unevenness and is relatively noisy.
External gear pump application range
The external gear pump’s broad application range includes the following:
- Industrial and mobile applications as predominantly auxiliary drives, especially for operational pressures up to 280 bar,
- Agricultural drives,
- Cooler and fan drives,
- Bypass flow systems in hydraulic systems,
- Winter road maintenance devices, and
- Oil production facilities.
Applications include:
- Simple winch drives, and
- Small auxiliary devices in the low-pressure range.
External gear pump technical data and characteristics
External gear pump technical data and characteristics are as follows:
- Constant flow rate
- Maximum pressure of approximately 300 bar
- Robust and contamination resistant
- Design can also be used as a hydraulic motor
For further information call HYDAC Australia on 1300 449 322 or email info@hydac.com.au
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