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Pumps.pptx
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- 2. Basic hydraulic systemwith linear hydraulic actuator (cylinder).
- 3. Basic hydraulic systemwith rotary hydraulic actuator (motor)
- 7. A pump, whichis the heart of a hydraulic system, converts mechanical energy into hydraulic energy. The mechanical energy is delivered to the pump via a prime mover such as an electric motor. Pump generates the force necessary to move the load. Due to mechanical action, the pump creates a partial vacuum at its inlet. This permits atmospheric pressure to force the fluid through the inlet line and into the pump. The pump then pushes the fluid into the hydraulic system.
- 8. • The hydraulicpump in a hydraulic system converts mechanical energy in to hydraulic energy (pressure energy). • The pump draws in the hydraulic fluid and drives it out in to a system of lines. The resistances encountered by the flowing hydraulic fluid cause a pressure to build up in the hydraulic system. • Thus the fluid pressure in a hydraulic system is not predetermined by the pump. It builds up in accordance with the resistances – in extreme cases until a component is damaged. In practice it is prevented by installing a pressure relief valve directly after the pump or in the pump housing at which the max operating pressure recommended for the pump is set.
- 10. 1. Dynamic (nonpositivedisplacement) pumps. This type is generally used for low-pressure, high-volume flow applications. Because they are not capable of withstanding high pressures, they are of little use in the fluid power field. 2. Positive displacement pumps. This type is universally used for fluid power systems. As the name implies, a positive displacement pump ejects a fixed amount of fluid into the hydraulic system per revolution of pump shaft rotation. Such a pump is capable of overcoming the pressure resulting from the mechanical loads on the system as well as the resistance to flow due to friction.
- 11. Hydraulic Pump types •PUMPS NON POSITIVE DISPLACEMENT PUMPS POSITIVE DISPLACEMENT PUMPS CENTRIFUGAL PUMP PROPELLER PUMP VANE PUMP GEAR PUMP GEROTOR PUMP LOBE PUMP SCREW PUMP RECIPROCATING PUMP RADIAL PISTON PUMP AXIAL PISTON PUMP
- 12. Non-positive pumps • Theyare used for low-pressure, high-volume flow applications. • Normally their maximum pressure capacity is limited to 17-20 bar. Positive pumps (Gear, vane, piston pumps) • High pressure capability (up to 700 bar or higher) • Small compact size • High volumetric efficiency • Small changes in efficiency • Great flexibility of performance Hydraulic Pump types
- 13. It should beunderstood that pumps do not pump pressure. Instead they produce fluid flow. The resistance to this flow, produced by the hydraulic system, is what determines the pressure. For example, if a positive displacement pump has its discharge line open to the atmosphere, there will be flow, but there will be no discharge pressure above atmospheric because there is essentially no resistance to flow. However, if the discharge line is blocked, then we have theoretically infinite resistance to flow. Hence, there is no place for the fluid to go. The pressure will therefore rise until some component breaks unless pressure relief is provided. This is the reason a pressure relief valve is needed when a positive displacement pump is used.
- 14. Positive displacement pumpshave the following advantages over nonpositive displacement pumps: a. High-pressure capability (up to 830 bar) b. Small, compact size c. High volumetric efficiency d. Small changes in efficiency throughout the design pressure range e. Great flexibility of performance (can operate over a wide range of pressure requirements and speed ranges)
- 15. PUMPING THEORY Pumps operateon the principle whereby a partial vacuum is created at the pump inlet due to the internal operation of the pump. This allows atmospheric pressure to push the fluid out of the oil tank (reservoir) and into the pump intake. The pump then mechanically pushes the fluid out the discharge line.
- 16. Displacement of pump Theflow capacity of a pump can be expressed as displacement per revolution or output in (LPM) (L/min). Displacement is the volume of liquid transferred in one revolution. It is expressed in cubic inches per revolutions. In practice, the pump is rated in terms of how much fluid is supplied per unit of time, and expressed in terms of: litres per minutes (LPM) (L/min). Pumping theory: Due to partial vacuum oil is rushed towards the pump.
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- 24. The two mostcommon types of dynamic pumps are the centrifugal (impeller) and axial (propeller) pumps shown in the above slide. Although these pumps provide smooth continuous flow, their flow output is reduced as circuit resistance is increased and thus are rarely used in fluid power systems.
- 25. construction features ofa centrifugal pump The fluid enters at the center of the impeller and is picked up by the rotating impeller. As the fluid rotates with the impeller, the centrifugal force causes the fluid to move radially outward. This causes the fluid to flow through the outlet discharge port of the housing.
- 26. Although dynamic pumpsprovide smooth continuous flow, their output flow rate is reduced as resistance to flow is increased. pump pressure is plotted versus pump flow reveals that the maximum pressure is called the shutoff pressure ( pressure head )because an external circuit valve is closed, which shuts off the flow. As the external resistance decreases due to the valve being opened, the flow increases at the expense of reduced pressure.
- 28. Positive Displacement Pumps PositiveDisplacement Pumps: This type of pump ejects a fixed quantity of fluid per revolution of the pump shaft. As a result, pump output flow, neglecting changes in the small internal leakage, is constant and not dependent on system pressure. This makes them particularly well suited for fluid power systems. However, positive displacement pumps must be protected against overpressure if the resistance to flow becomes very large.
- 29. Positive displacement pumpscan be classified by the type of motion of internal elements.
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- 34. WORKING PRINCIPLE • Thepump consists of drive gear and a driven gear and closed in closely fitted housing. • The gears rotate in opposite direction and mesh at a point in housing between inlet and outlet ports as the teeth of gear separate, fluid is drawn into the inlet chamber, due to partial vacuum the fluid is trapped between the gear teeth and housing and carried through two separate paths around the outlet chamber. • As the teeth re-mesh, fluid is forced through the outlet port. Close fit of the gear teeth within the housing is required to provide a seal between inlet and outlet ports, minimizing internal leakage.
- 35. Gear Pumps •Work wellat 100 bar and below •Work with a minimum of moving parts •Less expensive to manufacture than piston type pumps
- 36. The operation ofan external gear pump, which develops flow by carrying fluid between the teeth of two meshing gears. One of the gears is connected to a drive shaft connected to the prime mover. The second gear is driven as it meshes with the driver gear. Oil chambers are formed between the gear teeth, the pump housing, and the side wear plates.
- 38. The volumetric displacementcan be represented by The theoretical flow rate is determined next: QT ( m3/min) = VD (m3/ rev) * N (rev/min)
- 40. The actual flowrate QA is less than the theoretical flow rate QT, which is based on volumetric displacement and pump speed. This internal leakage, called pump slippage, is identified by the term volumetric efficiency, ηv, which equals about 90% for positive displacement pumps, operating at design pressure: