S Hydraulic Systems Flashcards
What is a single acting actuator?
Hydraulic pressure moves the piston in 1 direction only, a spring supplies the return force
Wha is a double acting balanced actuator?
Hydraulic pressure can move the piston in either direction with equal force
What is a double acting unbalanced actuator?
Hydraulic pressure can move the piston in either direction, but different forces will be generated in each direction
What is a non-return/check valve?
Allow fluid to flow in 1 direction only
What is a selector valve?
Can direct fluid to various parts of the system
Why is a hydraulic reservoir pressurised?
To prevent boiling
What are the 5 uses of accumulators?
- Store energy to keep fluid under pressure
- Provided limited supply in an emergency
- Dampen pressure fluctuations
- Allows thermal expansion
- Cater for small internal leaks
What is an automatic cut off valve (ACOV)?
When system pressure increases above a pre set level a valve opens to create an idling circuit
What drives a hydraulic pump?
Engine
What is a hydraulic motor?
Uses hydraulic pressure to generate rotary motion
Where is the hydraulic filter located?
Downstream of the hydraulic pump
What happens if the hydraulic filter becomes clogged?
- Red filter pop out button or cockpit warning light
- Bypass valve automatically allows unfiltered fluid to flow past blocked filter
What does a pressure relief valve do?
Protects system from over pressurisation
What does a thermal relief valve do?
Dumps excess pressure due to heat inducted expansion
Where does the relief valve send fluid?
Back to the reservoir
What is a restrictor valve (choke valve)?
Reduces fluid flow to slow the speed of operation of a service
What is a priority valve?
Ensures sufficient fluid flow at all times to the primary controls and wheel brakes
What is a shuttle valve?
Allows one service to be operated by 2 independent supplies, selects the most appropriate supply
What is a hydraulic fuse?
- Located upstream of components
- Prevents fluid loss in the event of a major leak
- If flow becomes too great, pressure drops behind the piston and forces it to close
What is a shut-off valve?
Stops hydraulic flow to a service, therefore stopping it, is not self regulating so needs to be operated by a controller
What is a PTU?
Power transfer unit, uses one system to pressurise another
Why is it important to monitor hydraulic temperature?
Excess temp reduces viscosity and lubrication
What 3 parameters of the hydraulic system are monitored?
- Temperature
- Pressure
- Quantity
