Pump changes the mechanical power supplied by electric motors or internal combustion motors to hydraulic power as the heart of system . Pump just makes the fluid flow and the level of created pressure depends on the amount of the resistant load that hydraulic system operator overcomes . in the case of Choosing pumps with fixed displacement followings should be considered:
- The diameter of the openings of the pump
- Working pressure at the output of the pump
- Working pressure at the input of pump
- The rotational speed of the pump
- The volume of oil transportation.
- Effective flow rate
- power of pump’s actuator motor
- Working temperature of oil
- viscosity grade
- Filtration
- cavitation in pumps
The first step in choosing the supply circuit and determination of the appropriate pump for a given application in the hydraulic systems, is determining the required pressure and flow in the circuit. The flow and pressure’s curves in a time cycle must be considered. Then the synchronization in use of different elements should be determined. Thus the maximum required flow will be determined. To determine a suitable supply circuit the followings should be noticed:
- in case of sizing of pumps in fact, they add about ten percent to the flow determined through theoretical calculations .
2.in case of Choosing a relief valve (Pressure Reducing), adjustment pressure should be ten percent higher than the system working pressure.
Both (1) and (2) causes more power to be injected in the hydraulic system.
By setting working pressure and flow rate of oil consumption, the required power for the pump rotator electromotor in system is calculated by the following equation :
P (kW) = [Q (lit / min) × p (bar)] / 600
Types of pumps are as follows:
- Gear pumps (fixed displacement)
- External gear
- Internal gear
- Spiral
- Vane pumps (feathers)
- Piston pumps (fixed or variable displacement)
- Linear design (axial)
- Radial design (radial)
Summary of pumps can be seen in the following table:
