Chapter 4

1. Chapter 4 Hydraulic Pumps Hydraulic Pumps • Hydraulic Pump Types

2. The two main types of hydraulic pumps are positive-displacement pumps and dynamic pumps.

3. The two main types of prime movers used in fluid power systems are electric motors or internal combustion engines.

4. Gallons per minute is the number of gallons a pump can force into the system every minute and thus the amount of fluid flow that pump can produce.

5. Volumetric efficiency is the relationship between actual and theoretical fluid flow of the pump.

6. A typical application for a positive-displacement pump includes the fluid power systems on a hydraulic production press.

7. Fixed-displacement pumps are available in various sizes with different displacement ratings.

8. Typical applications for variable-displacement pumps include systems that operate with varied system fluid flow, such as industrial robots.

9. All positive-displacement pumps follow the same basic operational steps to create fluid flow.

10. A gear pump consists of various types of meshing gears.

11. An external gear pump consists of meshing gears that form a seal with the pump housing and operates similar to the four basic steps of a positive-displacement pump.

12. A lobe pump has two external-driven gears and operates similar to an external gear pump.

13. An internal gear pump consists of a small external drive gear mounted inside a large internal gear.

14. Gerotor pump operation is similar to internal gear pump operation, with the inner rotor having one less gear tooth than the outer rotor.

15. Gear pump manufacturers typically provide assembly diagrams for each specific pump.

16. A vane pump contains vanes in an offset rotor and rotates the rotor to produce the flow of hydraulic fluid.

17. Unbalanced vane pumps operate similar to the four basic steps of a positive-displacement pump.

18. A variable-displacement, pressure-compensated vane pump is a pump that automatically adjusts the amount of volume it displaces per rotation by centering the rotor when the pressure in the system starts to build.

19. A balanced vane pump has two inlets and outlets at opposite sides of the pump and contains an elliptical cam ring.

20. A cartridge assembly is located in a vane pump and houses the vanes, rotor, and cam ring, which are all placed between two plates.

21. Vane pump manufacturers typically provide assembly diagrams for each specific pump.

22. Axial piston pumps consist of a number of pistons, a piston block, piston shoes, a swash plate, and a shaft and operate with four basic steps.

23. A variable-displacement piston pump has a swash plate at an angle that can be varied, thereby varying the amount of fluid flow (gpm).

24. Bent-axis piston pumps operate in the same manner as an axial piston pump, but rather than the swash plate being at an angle, the pistons and piston block are at an angle.

25. Radial piston pumps consist of reciprocating pistons in cylinders and can be classified as cam or rotating piston pumps.

26. Cavitation occurs as gas bubbles expand in a vacuum and implode when entering a pressurized area.

27. Hydraulic pumps are available in both double and triple pump designs

28. Hydraulic pump schematic symbols are used to determine general information about the type of pump used in a system.