1. Hydraulic Systems and Applications

2. References Required Introduction to Naval Engineering (Ch 15) Optional Principles of Naval Engineering (Ch 3 pp 64-74)

3. Objectives A. Comprehend Pascal’s Principle and its applicability to hydraulic theory. B. Comprehend the method of determination of output when given a hydraulic system configuration and input. C. Comprehend the basic operation, principal components, and safety considerations related to hydraulic systems.

4. Primary control boosters Retraction and extension of landing gear Sweep back and forth of wings Opening and closing doors and hatchways Automatic pilot and gun turrets Shock absorption systems and valve lifter systems Dive, landing, speed and flap brakes Pitch changing mechanism, spoilers on flaps Bomb bay doors and bomb displacement gears

5. Introduction/Uses Hydraulic power was harnessed as far back as 6000 BC – China– waterwheel to power bellows on a blast furnace Hydraulics used in many marine applications: – Steering/control systems (rudder, planes) – Deck machinery (anchor windlass, capstans, winches) – Masts & antennae on submarines – Weapons systems (loading & launching) – Other: elevators, presses

6. Advantages Convenient power transfer Convenient power transfer – Few moving parts – Low losses over long distances – Little wear Flexibility Flexibility – Distribute force in multiple directions – Safe and reliable for many uses – Can be stored under pressure for long periods Variable speed control Variable speed control – Quick response (linear and rotary)

7. Disadvantages Requires positive confinement (to give shape) Fire/explosive hazard if leaks or ruptures Fire/explosive hazard if leaks or ruptures Filtration critical - must be free of debris Manpower intensive to clean up

8. Hydraulic Theory Hydraulics – Covers the physical behavior of liquids in motion – Pressurized oil used to gain mechanical advantage and perform work Important Properties – Shapelessness – Incompressibility – Transmission of Force

9. Important Properties “Shapelessness” “Shapelessness” – Liquids have no neutral form – Conform to shape of container – Easily transferred through piping from one location to another Incompressibility Incompressibility – Liquids are essentially incompressible – Once force is removed, liquid returns to original volume (no permanent distortion) Transmission of Force Transmission of Force – Force is transmitted equally & undiminished in every direction -> vessel filled with pressure

10. Hydraulic Theory Pascal’s Law – Magnitude of force transferred is in direct proportion to the surface area (F = P*A) or Pressure in a fluid acts equally in all directions – Pressure = Force/Area Liquid properties enable large objects (rudder, planes, etc) to be moved smoothly

12. Hydraulic Mechanical Advantage

13. PUMP BY PASS VALVE BY PASS VALVE BY PASS VALVE F I L T E R F I L T E R F I L T E R HYDRAULIC POWER-PLANT RETURN HEADER CHANGE 3 SUPPLY HEADER SUPPLY HEADER Accumulator Air Cylinders

14. Basic Hydraulic System Hydraulic Fluid – Usually oil (2190 TEP)- non-corrosive, lubricant, already in use onboard Pressure Source – Hydraulic pump (A-end of system) Pressure user – Hydraulic motor (B-end of system) Piping system (w/ valves, tanks, etc) – Get fluid from A-end to B-end

15. Hydraulic Pump (A-End) Pumps can be positive displacement or centrifugal Waterbury pump Variable-stroke piston pump Tilting box can tilt fwd/aft while pump rotates Angle of tilting box determines capacity and direction of oil flow

16. Hydraulic Pump (A-End) Waterbury pumps are popular because the direction and volume of flow can be altered without changing the speed or direction of the prime mover.

17. Cylinder/Motor (B-end) Piston/cylinder used if desired motion is linear – Hydraulic pressure moves piston & ram – Load is connected to ram (rudder, planes, masts, periscopes) Piston Cylinder RAM Hydraulic Fluid Supply/Return Ports Seal

18. Cylinder/Motor (B-end) Motor used if desired motion is rotary – Essentially a variable- stroke pump in reverse – Used for capstan, anchor windlass, etc

19. Piping System Has to withstand excessive pressure Valves, filters, & HX’s all necessary Accumulators – Holds system under pressure (w/out contin. pump) – Provides hydraulics when pump off/lost – Compensates for leakage/makeup volume – Types: piston, bladder, & direct contact

20. Accumulator Types Piston – Most common Bladder – Gun mounts – Steering systems Direct contact – Least common

21. SUPPLY RETURN VENT &SUPPLY TANK AIR HYDRAULIC-POWERED HYDRAULIC SYSTEM TO SYSTEM CONTROL VALVE CONTROL VALVE SIMPLEX PUMPS HYDRAULIC RETURN

22. Electrohydraulic Drive System Uses hydraulics to transfer power from electric motor to load Rotary: Waterbury pump connected to rotary piston hydraulic motor (speed gear) – Tilting box of A-end controls direction/speed of B-end – Adv: high starting torque, reversibility, high power-to- weight ratio ex: Electrohydraulic Speed Gear or Steering Gear – capstan, anchor windlass, cranes, elevator, ammo hoist

23. Electrohydraulic Steering Gear Same as speed gear except B-end is a hydraulic cylinder to produce linear motion Waterbury pumps connected by piping to hydraulic ram cylinder – Various methods for connecting rams to tillers – Two pumps for redundancy & reliability – Movement of steering wheel through hydraulic system moves rudder

25. Control of System Remote control – Normal method – Control from bridge Emergency – Take local control – Manually position control surface/rudder

26. Take Aways Describe Pascal’s theory and apply it to mechanical advantage problems Describe the properties of oil and how they are advantageous in hydraulic applications List three types of accumulators. Describe the purpose of an accumulator. Give the advantages and disadvantages of hydraulic systems

27. Questions?