Lecture Day 2

Question 1

Contaminated fluid is one of the most common causes of hydraulic system troubles

Question 2

Removes contaminates before reaching components

Answer 2

Line Filters

Question 3

Pressure or return (common) lines

Answer 3

Placement

Question 4

Construction – Element, bowl, head

Answer 4

Filter Bowl – Drain at lowest point

Filter head – Inlet/outlet and BYPASS

Question 5

Types of Elements

Answer 5

Most Common – Micronic Type (Surface filter)

Disposable – treated cellulose with pleated paper.

Question 6

Cuno Filter (Edge Filter)– Stacked (pressure side)

Question 7

Differential Pressure Indicator (DPI) provides visual indication the filter is becoming clogged with debris; provides visual warning of impending filter By-Pass

Question 8

Contaminated fluid is one of the most common cause of hydraulic system troubles

Answer 8

Most Common Filter – Micronic Type

Filtering Size 10 – 25 Microns

Disposable – treated cellulose with pleated paper.

Question 9

Pump converts mechanical energy into hydraulic energy (in this case muscle)

Question 10

HAND OPERATING HYDRAULIC PUMPS
Hand pumps – emergency (back-ups) if primary fails

Question 11

HAND OPERATING HYDRAULIC PUMPS
Double action / Movement in either direction = flow

Question 12

HAND OPERATING HYDRAULIC PUMPS

Question 13

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.

Question 14

POWER-DRIVEN HYDRAULIC PUMPS
Four Basic Types

Answer 14

Gear

Vane

Diaphragm

Piston

Question 15

POWER-DRIVEN HYDRAULIC PUMPS
Pumps are coupled to their driving units using drive coupling

Shear Shaft
Drain Port Seal Drain – Shaft Seal Leaking

Question 16

POWER-DRIVEN HYDRAULIC PUMPS Constant delivery – must have pressure relief valve

Angular

Cam

Variable delivery

Compensator – auto/instant varying fluid amount delivered to system

Question 17

CONSTANT-DELIVERY PUMPS

Given quantity of fluid per revolution, regardless of pressure demands

Require Pressure Regulator

TYPES

Question 18

CONSTANT-DELIVERY PUMPS

Gear pumps

Most common, versatile (small aircraft/power-pac)

Extreme Pressure – low volume

Fluid moves around the gears

Question 19

CONSTANT-DELIVERY PUMPS

Angular piston pumps

Cam piston pumps

Vane

Large volume – low pressure

Question 20

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

Answer 20

Angular Piston Pumps

Question 21

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

Answer 21

Cam-piston Pumps

Question 22

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.

Question 23

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

Question 24

ACCUMULATORS
Purpose

Dampen – Shocks/surges

Assist – peak operations/emergency

Absorb – thermal expansion

Preload – source of fluid pressure

Question 25

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

Question 26

ACCUMULATORS Three types Diaphragm Bladder Piston

Question 27

Two hollow hemispheres (bolted together) with a synthetic rubber diaphragm separating the two sides.

Answer 27

Diaphragm

Question 28

Sphere design with screw plug on bottom to insert bladder (balloon)

Answer 28

Bladder

Question 29

Bladder is pressurized with N2 and hydraulic fluid surrounds bladder

Question 30

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

Answer 30

Piston

Question 31

PISTON ACCUMULATOR Reference Maintenance Manuals Any fluid out of air valve = ruptured separator/seal Remove all N2 and hydraulic pressure prior to servicing

Answer 31

Servicing all Accumulators

Question 32

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

Answer 32

AN 6287-1

Question 33

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

Answer 33

AIR VALVES