Pumps, Valves And Cylinders Flashcards
What are the two categories of hydraulic pumps
Non-positive displacement and positive displacement
The function of the hydraulic gear pump is to
Create oil flow
The most important characteristic of a non-positive displacement pump is that the inlet and outlet passages connect _________.
Hydraulically
Most nonpositive displacement pumps use what force to create flow
Centrifugal.
What’s a typical example of a nonpositive displacement pump
A water pump
Positive displacement pumps do not suffer significant flow loss under pressure. True or false
True
_________ is the volume of liquid that the pump delivers when the pump input shaft rotates one revolution
Pump displacement
Pressure is a result of
Resistance to flow
Pump displacement is expressed in what units of volume per revolution
Cubic inches per rev
cubic centimeters per rev
____ _____ refers to the amount of liquid that the pump delivers in a given period of time
Flow rate
What are the two common units of measurement for flow rate of a pump
Gallons per minute GPM & liters per minute LPM
What are the two factors that determine the amount of flow that a hydraulic pump delivers
The pumps displacement and the pumps input shaft speed
How many cubic inches are in an American gallon
231 in.³
Increasing a pumps displacement or input shaft speed increases what?
Pump flow rate
What are the two classes of efficiency used to evaluate overall hydraulic pump performance
Mechanical efficiency and volumetric efficiency
Mechanical efficiency is an expression of the amount of power required to overcome the_____ ______ ______.
Pumps internal friction
The internal leakage oil sometimes called slippage or slip provides what?
Lubrication for the pumps moving parts
What is the term used to express the amount of flow lost within the pump due to internal leakage
Volumetric efficiency
And increased internal leakage results in decreased volumetric efficiency, slower actuator speed and _____ _____ _____.
Higher oil temperatures
What rating is one of the most important readings assigned to a hydraulic pump?
The pressure rating
What are the two basic types of gear pumps common in heavy equipment hydraulic systems
External and internal gear pumps
What is between the faces of the gears on both External and Internal gear pumps to limit internal leakage
Pressure plates
Internal leakage is an energy or power loss although some flow is required to
Lubricate moving pump parts
What is a common difference between inlet ports and outlet ports
Typically, The inlet port is significantly larger than an outlet port
What type of pump operates in one direction only?
Uni directional pumps
What’s an identifiable external feature of a reversible gear pump?
Inlet and outlet ports are generally the same size
What’s the maximum allowable vacuum at the pump inlet?
5”Hg of vacuum
The pressure at the pump inlet port is affected by what two things?
Amount of restriction to oil flow in the pump inlet line.
the speed at which the pump is driven
The pressure spike created by cavitation implosions can exceed approximately how much?
6.90GPa
Or 1 million PSI
The Inlet of a hydraulic pump must be sealed tightly in order to prevent
Air from being drawn into the inlet and transmitted through out the system
Where is the most commonly located place for a direct acting pressure release valve
Between the hydraulic pump and the directional control valve
How does a direct acting pressure relief valve protects the hydraulic system from damage?
By limiting the maximum pressure in the system
Full flow pressure - cracking pressure equals
Pressure Override
Name three common directional control valve configurations
Poppet, Rotary and Spool
