Pumps Flashcards
Definition of a pump
Pump converts mechanical energy ( via an electrical motor) into hydraulic energy (via the pump)
The different types of pumps?
non-positive displacement pumps (hydrodynamic)
Positive displacement pumps (hydrostatic)
Hydrodynamic pumps (non-positive displacement)
Non positive displacement pumps have no seal between the inlet and the outlet ports which means resistance to flow is increased. The output is reduced. Pump is not suitable for the hydraulic system.
Centrifugal pump
Hydrostatic pumps (Positive displacement)
They provide a specific amount of oil for every stroke, revolution or cycle. They have a positive seal between the suction and discharge.
Cavitation
Cavitation occurs due to low pressure areas. Creating vapour bubbles.
The vapour bubbles pop and implode against the pipework or wherever and cause little indentations on the metal causing erosion from the inside.
vapour bubbles are not air bubbles. Do not confuse cavitation with air entrapment
Cavitation can also occur across control valves.
Different types of positive displacement pumps
1.external gear wheel pump
2.internal gear wheel pump
3.lobe pump
4.gerotor pump
5.screw pump
6. Vane pump
What’s a vane pump used for?
Boost pumps
What is the use of an External gear wheel pump?
Boost pumps
What’s the use for a gerotor pump?
Dynapad boost pumps, guardian filter pack
What are the different types of cylinder pumps you can have?
Single and multi
What is a single cylinder pump?
A single cylinder pump’s outlet is zero to max to zero, giving a stop start characteristics to the system.
What is a Multi-cylinder pump?
Multi-cyclinder pump achieves a much smoother output. (Continuous output rather than a start stop motion.
Radial piston pump
This pump can have either 5, 7, 9 or 11 cylinders.
It consists of an eccentric ring which is fitted to the pump shaft. A tyre is also fitted onto the ring to act as a bearing surface.
As the shaft turns, a reciprocating motion is transmitted to each of the plungers in turn. The reciprocating plungers are kept in contact with the tyre by springs.
When the plunger is pushed into the chamber it creates a pressure in the chamber. The pressure pushes the suction valve and opens the discharge valve.
Multi-cyclinder pumps what characteristics do they have?
Highly efficient
Wide range of capacities
Can achieve a variable output
Used in many large HP applications
Axial piston pump
The pistons are arranged parallel to the shaft are carried in a cylinder block and given their reciprocating motion by a swash plate.
