11.11 Flashcards
Advantages of hydraulic power
Easy to install/maintain/inspect/ control
Lightweight
Almost 100% efficient.
Easy to spot leaks.
Does not create sparks.
Disadvantages of hydraulic power
Inappropriate fluids damage the system components.
Leaking fluids can cause ignition of fire hazards.
Contamination affects performance and degrades components.
How do you gain higher force in an actuator.
Increase pressure or increase actuator diameter
What are the two types of hydraulic pressure and what do they mean.
Hydrostatic - pressure produced by static or nearly static fluids. Type used in A/C systems.
Hydeodynamic - pressure produced by moving liquids.
True or false.
The different hydraulic systems on large a/c transfer fluid
False, fluid is never transferred , instead a PTU is used.
Define open centre hydraulic systems.
Has flow but no pressure when actuators are idle.
Define closed centre hydraulic systems.
The fluid is under pressure whenever the pump is operating.
The selector valves are arranged in parallel and not in series.
These systems are more instantaneous.
What is a hydraulic power pack system and why is it useful.
It is a compact all-in-one assembly that eliminates the need for centralised hydraulic systems.
Saves lots of weight.
Contamination control in a hydraulic system
Filters are installed.
Care taken during maintenance.
Hydraulic system flushing can be done.
Hydraulic fluid sampling.
Sampling valve normally on HP valve
Needle type valve
Hydraulic system leak test.
Checks for internal leaks within components.
Leak measurement manifold linked to high pressure manifold.
Hydraulic accumulators.
Potential energy is stored in the form of compressed gas, a spring or a raised weight to exert a force against an incompressible fluid.
Accumulate energy and smooth pout pulsations.
Spherical or cylindrical.
Diaphragm type, spring type, or hydro-pneumatic piston type.
What is the primary source of power generation
Mechanically driven pumps (EDPs)
What characterises a non-positive displacement pump.
Produces a continuous flow of, output pressure varies.
Gear type power pump.
Positive displacement type.
Two meshed gears in a housing, fluid is trapped between the housing and the gears.
Gerotor type pump
Positive displacement , fixed volume
Gears turn clockwise together.
Internal gear has one less tooth.
Piston pumps.
Can be constant or variable displacement.
Most common type of pump.
Bent axis piston pump
Constant delivery pump, similar to piston pump.
Emergency pressure generation (hydraulics)
RAT
- variable displacement pump.
- provides hydraulic power if main sources are lost.
Power transfer units.
- mechanical connection between systems to transfer force.
Electrically driven hydraulic pumps.
Which type of filter gives the best filtration quality
Micro glass filters.
Why do filters have a bypass valve and how can your know if it was used.
In case the filter is clogged up, dirty fluid is better than no fluid.
Shown by the filter differential pressure indicators - show when the bypass was used not is the filter is clogged.
Relief valve (hydraulics)
Incorporates an adjustable spring loaded valve.
Ball type, sleeve type, poppet type.
Used as safety devices or as thermal relief valves.
Pressure regulators (hydraulics)
Pressurised by constant delivery type pumps.
Manages the output of the pump
Permits the pump to turn without resistance
