Hydraulics Flashcards
Define ‘Hydraulics’
A branch of science and technology about the conveyance of liquids through pipes and channels especially as a source of mechanical force or control
Define ‘Pneumatics’
A branch of science or technology about the mechanical properties of gasses.
What happens to the fluid in hydraulics?
It is held in a closed system
What are the pros of hydraulics?
> Fluids are incompressible so can exert extreme pressures
> Hydraulics consume less energy than pneumatics because pneumatics uses continually replenished gas.
> Hydraulics produce highly defined actions
> Hydraulics are self-lubricating and aid anti-corrosion
What are the cons of hydraulics?
Hydraulic fluid is a contaminant and is no suitable for certain applications
What are pumps?
Converts mechanical energy into hydraulic energy
How do hydraulic pumps work?
> Creates a vacuum at the pump inlet which allows atmospheric pressure to force liquid from the reservoir into the inlet line to the pump.
> Delivers liquid to the pimp outlet and forces it into the hydraulic system
> Balls dictate the direction of liquid flow.
What is pressure?
> It does not generate pressure. It produces the flow necessary for the development of the pressure which is a function of resistance to the fluid flow.
What is a positive displacement pump?
Delivers the same amount of liquid for each cycle of the pump action. Delivery remains constant regardless to the changes in pressure.
What is a variable displacement pump?
Delivers the different amounts of liquid for each cycle of the pump action.
List the properties of cylinders?
> Single Port / Dual Port
> Single Acting / Dual Acting
> Returned / Returned by a spring / Returned by an external force
What are 4 different activation methods?
> Lever controlled
> Foot controlled
> Push button controlled
> Solenoid controlled
List the two types of resevoirs
> Non-pressurised hydrostatic
> Non-pressurised atmospheric
List 6 types of valves
> Check valves without spring
> Check valves with spring
> Shut off valve (normally open)
> Shut off valve (normally closed)
> Directional control valves
> Pressure release valves
For a direction control valve, what are the 3 different functions it can perform?
> Stop fluid flow
> Allow fluid flow
> Change the direction of fluid flow
For a pump, what are the 3 different symbols and what do they mean?
> Circle = Motorised
> Triangles = Number of directions of pumping ability (1 or 2 triangles)
> Arrow (from bottom-left to top-right) = Variable displacement [Symbol1]
For a cylinder, what are the 3 different symbols and what do they mean?
Lines (coming out from the side) = Ports
Spring = Returned by spring
Lever/Foot/Push-button/Solenoid = Control method [Symbol2]
What is the symbol for non-pressurised hydrostatic?
[Symbol3]
What is the symbol for non-pressurised atmospheric?
[Symbol4]
What is the symbol for a check valve?
[Symbol5]
What is the symbol for a check valve with a spring?
[Symbol6]
What is the symbol for a normally open shut off valve?
[Symbol7]
What is the symbol for a normally closed shut off valve?
[Symbol8]
Draw a directional control valve, normally closed, 2 ports 2 positions with spring return and level control
[Symbol9]
Draw a directional control valve, normally open, 2 ports 2 positions with spring return and button control
[Symbol10]
Draw a directional control valve, normally closed, 2 ports 2 positions with spring return and solenoid control
[Symbol11]
What is the symbol for automatic valves (pressure relief)
[Symbol12]
What happens when there are two pistons in parallel with diffent weights?
> The lighter piston moves first
> When the ligher piston is fully extended, the heavier one moves
> When the heavier piston is fully extended, the pressure release valve is activated
[Picture25]
What happens when you have pistons in series?
> Regardless of weight, the first piston moves until it is fully extended
> When fully extended, the second piston moves
