Lecture Day 2 Flashcards
Contaminated fluid is one of the most common causes of hydraulic system troubles
Removes contaminates before reaching components
Line Filters
Pressure or return (common) lines
Placement
Construction – Element, bowl, head
Filter Bowl – Drain at lowest point
Filter head – Inlet/outlet and BYPASS
Types of Elements
Most Common – Micronic Type (Surface filter)
Disposable – treated cellulose with pleated paper.
Cuno Filter (Edge Filter)– Stacked (pressure side)
Differential Pressure Indicator (DPI) provides visual indication the filter is becoming clogged with debris; provides visual warning of impending filter By-Pass
Contaminated fluid is one of the most common cause of hydraulic system troubles
Most Common Filter – Micronic Type
Filtering Size 10 – 25 Microns
Disposable – treated cellulose with pleated paper.
Pump converts mechanical energy into hydraulic energy (in this case muscle)
HAND OPERATING HYDRAULIC PUMPS
Hand pumps – emergency (back-ups) if primary fails
HAND OPERATING HYDRAULIC PUMPS
Double action / Movement in either direction = flow
HAND OPERATING HYDRAULIC PUMPS
A filter is rated by the size of particles it will remove, and these sizes are measured in microns, with one micron equal to one millionth of a meter or 0.000039 inch.
POWER-DRIVEN HYDRAULIC PUMPS
Four Basic Types
Gear
Vane
Diaphragm
Piston
POWER-DRIVEN HYDRAULIC PUMPS
Pumps are coupled to their driving units using drive coupling
Shear Shaft
Drain Port Seal Drain – Shaft Seal Leaking
POWER-DRIVEN HYDRAULIC PUMPS Constant delivery – must have pressure relief valve
Angular
Cam
Variable delivery
Compensator – auto/instant varying fluid amount delivered to system
CONSTANT-DELIVERY PUMPS
Given quantity of fluid per revolution, regardless of pressure demands
Require Pressure Regulator
TYPES
CONSTANT-DELIVERY PUMPS
Gear pumps
Most common, versatile (small aircraft/power-pac)
Extreme Pressure – low volume
Fluid moves around the gears
CONSTANT-DELIVERY PUMPS
Angular piston pumps
Cam piston pumps
Vane
Large volume – low pressure
PISTON PUMPS (CONSTANT)
Referred as Axial Piston Pump
Stationary group and Rotating Group
Piston lines up with valve plate
Inlet port – draws fluid in
Outlet port – pushes fluid out
Angular Piston Pumps
PISTON PUMPS (CONSTANT)
Rotating-cam
Cam Rotates, Cylinders stationary
Return spring pushes piston up bore for intake
Stationary-cam
Identical except cam stationary and cylinder block rotates
Cam-piston Pumps
VARIABLE-DELIVERY
PISTON PUMP
Demand Principle cam pump
Compensator spring – moves spider/sleeves to cover relief holes in cylinder when pressure is required
Spider/sleeves uncover relief holes in cylinder with pressure is adequate.
VARIABLE-DELIVERY
PISTON PUMP
Stroke Reduction pump
Compensator assembly mechanically controls the yoke (tilt of the cylinder block)
At full tilt=full flow
0 degree=zero flow
ACCUMULATORS
Purpose
Dampen – Shocks/surges
Assist – peak operations/emergency
Absorb – thermal expansion
Preload – source of fluid pressure
ACCUMULATORS
Accumulator has fluid on one side and nitrogen (N2) on other. Has a specific separator depending on style.
N2 Charge provides initial pressure against the separator
Fluid flows into lower chamber (by pump operation )
N2 provides constant expansion (pressure) against fluid
ACCUMULATORS
Three types
Diaphragm
Bladder
Piston
Two hollow hemispheres (bolted together) with a synthetic rubber diaphragm separating the two sides.
Diaphragm
Sphere design with screw plug on bottom to insert bladder (balloon)
Bladder
Bladder is pressurized with N2 and hydraulic fluid surrounds bladder
PISTON ACCUMULATOR
Utilizes a free floating piston
N2 on air side and fluid on other
Drilled passage between fluid side and piston wall provide lubrication passage
Piston
PISTON ACCUMULATOR
Reference Maintenance Manuals
Any fluid out of air valve = ruptured separator/seal
Remove all N2 and hydraulic pressure prior to servicing
Servicing all Accumulators
AIR VALVES
Very high pressure held by a metal-to-metal seal.
To fill, open valve and add nitrogen
To release, open valve and depress core with proper tool
AN 6287-1
AIR VALVES
Very high pressure held by metal seal has no valve core
Stem is retained in the body of the valve with a roll pin
To fill, install hose and open valve
To release, open valve very slowly and use caution
AIR VALVES
