Principles Flashcards
Pascals law
Pressure applied on a confined fluid is transmitted undimished in all directions. Acting with equal force on equal areas.
(Specific gravity)
What are the two main reasons why water is no longer used in hydraulics?
Lack of lubrication properties.
It’s corrosive to metal.
Bernoulli’s principle
Bernoulli summarised that the sun of the pressure (potential energy) in point in the system must be constant if the flow rate is constant.
Linear flow
Explain what it is?
Flow is at a low velocity.
Friction is minimised.
No pipework bends.
Turbulent flow.
Explain what it is?
Caused by abrupt changes in pipework and cross sectional area.
Higher flows - velocity flow (increases friction)
Also causes temp to rise due to the friction increase which also drops the viscosity of the oil and degrades the oil properties at the same time.
What is turbulent flow good for?
(Uses)
Due to the by products of turbulent flow it makes it very useful for flushing.
Flow measurement
What’s it measured in?
Flow is measured in velocity and flow rate.
Flow measurement
Velocity and flow rate.
Definition of velocity? Include its measurement.
Velocity is the linear movement of fluid per unit of time.
Measured in (M/S) meters per second
When does velocity change?
Velocity changes when the cross sectional area changes.
What does flow rate mean and what is it measured in?
Flow rate is the measure of the volume of a liquid passing a fixed point per unit of time.
Litres per second
Gallons per min
Cubes per hour
VISCOSITY
What happens based on temp to the viscosity of oil hot and cold?
If the viscosity of oil is too low the oil becomes thin, the leakage rate can increase.
If the viscosity of oil is too high the oil is thick, the systems efficiency decreases because of additional power loss due to the increase in oil friction.
Define Viscosity.
Viscosity is the measure of a liquids resistance to flow. Measured in centistokes.
Viscosity index, what does it range from? And what does it mean?
The viscosity index is ranged from 0 to 200.
The higher the number the less the temperature affects the viscosity, therefore it is deemed a better quality oil.
Identify the different oils:
What does OM, OMD, OC, OEP, OX stand for?
OM- Oil minerals
(hydraulic and gearbox systems)
OMD- Oil mineral detergent
(for props)
OC- Oil compound
(gearbox systems)
OEP- Oil extreme pressure
(large high speed gearbox systems)
OX- Oil synthetic/ miscellaneous (miscellaneous)
OX30 what can it be used for?
OX30 can be used to Flush systems suffering from gross water contamination.
