Fluid Power Flashcards
What is pascals law?
Pressure applied on a confined fluid is transmitted undiminished in all directions and acts with equal force on equal areas and at right angle
Name uses of hydraulics in the RN
Steering gear
Stabiliser systems
Davit and cranes
Winches and capstans
Lifts - stores, weapon etc…
Controllable pitch propellers
Doors
Submarines periscopes, masts and planes
Describe a general service unit / powerpack.
Self-contained unit which has a pump and associated components to power just one piece of equipment.
Equipment supplied effects operational capabilities
To provide good transmission of power what key properties does a hydraulic fluid require?
Must be incompressible
Bonus:
Lubrication, Sealing and cooling
What properties must a hydraulic fluid have?
Incompressibility
Chemical stability
Constant Viscosity
Good Lubricity
Easily Filtered
Non - flammable
Non - Toxic
Easily de - aerated
Easily separable from water
Non - corrosive
Easily sealed
Inexpensive
Readily avalible
Good storage life
Define viscosity.
Measure of a fluid’s resistance to flow, normally measured in centistokes
Name advantages of hydraulic systems.
Reliable
Simple and easy to understand
Infinite speed range
Easily reversed
Ability to withstand overload
No spark risk
High low speed torque
Name disadvantages of hydraulic systems.
Fire risk
Noise
Contamination
Lower efficiency - 85-95%
How is flow measured?
Velocity (changes with changes in cross sectional area)
Flow rate (Set by pump parameters and remains constant)
Name three hydraulic oils used in the RN.
OM33 - General service hydraulics
OX30 - Submarine systems / flushing oil after water contam
OX40 - Type 33 hydraulics and future hydraulic systems
What are the various lifespan considerations when maintaining accumulators?
Shelf life - 5 years from cure date
In service life - 5 years from install date
Combined not to exceed 8 years
Seamless shell to be pressure tested every 10 years.
Name the two typical modes of failure in regards to the bag in a bag type accumulator.
“Pin hole” failure.
“Starburst” failure.
Name the three types of actuators.
Linear
Semi - rotary
Rotary
What markings are included on hydraulic hoses?
Manufactures ID
Date of cure of the rubber by month and year
Longitudinal straight line parallel to the hose axis
What markings are on the hose assembly (usually on a metal band round the hose assembly or connection ferrule)?
DEF STAN 47-2 / 2
NATO stock number
Designed test pressure
Cure date of hose
What markings are on the assembly package?
NATO stock number
Date of cure of the rubber by year of oldest item
Contract number
What factors should be considered when installing hydraulic hose?
Protect from heat emitters
Do not locate when leakages could produce serious fire hazard or damage
shroud where burst would produce a fire hazard
Ensure adequate access for inspection
Protect from traffic and adverse environmental conditions
Route hoses as to not abrade other objects
Whenever possible straight connection at one end
Ensure interfaces are clean and free for damage
Tighten coupling nuts so twisting of the hose is induced
Rubber hoses are not to be painted
Avoid completely straight hose
What are the various service lives for hydraulic hoses?
CAT A - 5 Years (High Risk)
CAT B - 10 Years (Moderate Risk)
CAT C - 15 Years (Low Risk)
CAT D - On Conditions (Very Low Risk)
What is form is the hydraulic hose register?
RN Form S3171
In regards to hydraulic valves, what are the two methods of flow control?
Meter in
Meter out
Describe a meter in flow control valve set up?
Fitted between pump and actuator
Controls the amount of oil going to the actuator
Excess oil delivered by the pump diverted back to the tank
Used where the load continually resists movement of the actuator
Describe a meter out flow control valve set up?
Used when the load might run away - fitted where it will restrict exhaust flow from the actuator
To regulate flow in both directions - it’s installed in the tank line from the directional control valve
One direction - placed between the actuator and directional control valve.
What are the two types of seals from in RN hydraulics?
Static seals
Dynamic seals (sliding motion and rotating shaft seals)
Name some example of different seals used in the RN?
‘O’ ring seals
Dowty seals
Linear seals
