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ME 151 Course > Hydraulics > Flashcards

Hydraulics Flashcards

1
Q

What is Pascal’s Law

A

Pressure applied on a confined fluid is transmitted undiminished in all directions and acts with equal force on equal areas and at right angles to them.

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2
Q

What is the formula for force

A

F = P x A

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3
Q

What is Bernoullis Principle?

A

In a system with a constant flow rate, energy is transformed from one form to another each time the pipe cross section changes.

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4
Q

How is flow measured?

A

In Velocity and Flow Rate

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5
Q

What are the two reasons why water isn’t used as a hydraulic fluid?

A

Its lack of lubricating properties.
The corrosiveness of water.

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6
Q

What is the definition of viscosity and what is it measured in?

A

A measure of a fluids resistance to flow, measured in centistokes.

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7
Q

What are the two types of pumps?

A

Hydrodynamic pumps (Non-positive displacement pumps)

Hydrostatic pumps (positive displacement pumps)

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8
Q

What are the characteristics of a multi-cylinder pump?

A

Highly efficient.
Wide range of capacities.
Variable output.
Large HP applications.

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9
Q

Describe an axial piston pump.

A

The pistons are arranged parallel to the shaft. The angle of the swashplate determines the length of the stroke. The swashplate angle can be varied or fixed.

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10
Q

Describe the function of actuators.

A

To convert hydraulic energy into mechanical movement.

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11
Q

Describe Linear, Rotary, and Semi Rotary actuators.

A

A linear actuator has a reciprocating motion.
A Rotary actuator converts hydraulic energy into Rotary motion.
A semi Rotary actuator converts hydraulic energy into partial Rotary movement.

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12
Q

Describe the procedure for a motor leakage test.

A

Isolate the return line.

Break system on the drain line.

Supply oil to the actuator by operating the directional control valve.

Collect oil from the drain line and time how long it takes to collect 1 pint.

Take the temperature of the oil and repeat the test by isolating the opposite return line.

Plot results on graph obtained from relevant BR.

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13
Q

What are the two conditions that mandate a hydraulic oil change?

A

Degradation of the base oil.
Depletion of the additive package.

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14
Q

Identify 5 common malpractices in hydraulic pumps and motors.

A

Changing filters.
Running too hot.
Using incorrect oil.
Wrong filter locations.
Not self priming.

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15
Q

Describe the purpose of the Safety Supervisor System.

A

Protects the supply of hydraulic fluid in the system in the event of a fluid leak. Consists of two level switches: ‘low level’ and ‘low low level’. The valves are V3 and V4.

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16
Q

What are four ways to keep your hydraulic fluid in top condition?

A

Keep contaminants out of your hydraulic system.

Change the fluid and filter after the initial 50 hours of use.

Check oil before each use.

Regularly check temperature during operation.

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17
Q

What are three reasons seals can get damaged.

A

Excess pressure
Excess temperature
Contaminants

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18
Q

What are the checks for flexi hoses?

A

Inspect hoses for cracking, cuts and dents.

Check that the hose routing isn’t pinched, kinked or overstretched.

Inspect flex points for kinking or stretching.

Check all fittings on hoses to make sure they are snug.

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19
Q

What contaminants could enter the system if it isn’t sealed properly?

A

Air entrainment.
Solid particulate contamination
Water

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20
Q

What are the effects of air entrainment?

A

Heat
Loss of lubrication
Loss of efficiency.

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21
Q

What are the effects of solid particulate contamination?

A

Scoring.
Wear.
Loss of efficiency.

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22
Q

What are the effects of the ingress of water in a hydraulic system?

A

Erosion
Corrosion
Loss of lubrication
Loss of efficiency

23
Q

What components make up a swagelok tube fitting?

A

Nut
Back ferrule
Front ferrule
Fitting body

24
Q

What are the 5 steps for fitting a swagelock?

A

1) position the jaws of a vice grip on the hex of the fitting body, leaving room for the gap inspection Gauge.

2) insert the tubing.

3) finger tighten the nut.

4) scribe the nut at the 12 o’clock position

5) Turn the nut 1 and a quarter turns.

25
Q

What does the PCM 400 test for?

A

Particulates
Viscosity (1 - 450 centistokes)

26
Q

What is the system often flushed with?

A

Rust Veto (MTP42)

27
Q

What is the procedure for shutting down hydraulic machines?

A

Lower or mechanically secure all suspended loads.
Exhaust any pressure locked into the system.
Drain down all accumulators.
Discharge both ends of actuators.
Isolate electrical control system (Tag out).
Isolate power supply (Tag Out).

28
Q

What are some common faults on hydraulic systems?

A

Insufficient fluid level.
Air in the system.
Oil contamination.
Incorrect system design.
Fluid leakage.
Wrong fluid type or viscosity.
Excessive temperatures.
Degradation of base oil.
Depletion of additives.
Excessive pressures.
Water in system.

29
Q

What are the requirements for repacking stabiliser glands at sea.

A

Maintain watertight integrity.
Fleet driving group are required to assist.
Personnel are to be suitably dressed (multi fab suits).
Check all relevant BRs before working.

30
Q

On completion of repacking stabiliser glands, how is the packing proven?

A

The stabiliser is to be forced rolled

31
Q

What position after agreement checks should the rudder be left at?

A

Pumped back to midships using the hand pump.

32
Q

Describe the steering gear circuit

A

Supply tanks feed the pumps with a positive suction.

The power unit delivers oil via an axial piston pump and boost pump.

Incorporates a pair of double acting linear actuators (RAMS)

The actuators move the rudder, rudder angle transmitter, and rudder feedback unit. (Sub system).

These send signals (feedback) to the control system.

33
Q

When is the rudder locked?

A

When being towed.
Entering/leaving dry Dock.
Alongside and shutdown.
Divers working on Hull.
Maintenance on the system.

34
Q

When is the fin locked?

A

When towing or being towed.
Entering or leaving dry Dock.
Divers working on Hull.
In harbour shut down.
For maintenance on the system.

35
Q

Describe the linear actuators in the stabiliser system.

A

Two hydraulic actuators that are clevis mounted, heavy duty, double acting type with self aligning bearings at the cap and rod ends.

36
Q

What is the purpose of stabilisers and how do they work?

A

To counteract the natural rolling motion of the ship by applying equal and opposite righting moment. This is achieved by means of two non-retractable fins, which protrude from the ships Hull.
A sensing device continuously monitors the ships roll and transmitts appropriate signals to the mechanism, controlling their angle of tilt relevant to their movement through the water.

37
Q

What are the four reasons for fitting stabilisers.

A

Weapon platforms.
Aircraft operations.
NCBD
Crew habitability.

38
Q

What are the four types of injuries that can be sustained from hydraulic systems.

A

HP oil injection injury - 7 bar
Whipping injury
High velocity debris injury
Scalding injury

39
Q

At what temperature do fluorocarbon elastomers release toxic gasses?

A

Between 200°C - 300°C

40
Q

What are the two types of flexi-hoses used in hydraulic systems?

A

Two wire braid reinforcement hoses.

Wire spiral reinforcement hose.

41
Q

Where are CAT A, B, and C hoses used?

A

Cat A used in steering gear and upper deck.

Cat B used in stabilisers.

Cat C used in captains lift.

42
Q

What are the two types of seals?

A

Static and Dynamic

43
Q

What are the two types of dynamic seals?

A

Reciprocating (seals for sliding).
Rotary (rotating shaft seals).

44
Q

What are the uses of flexible hoses?

A

To permit relative movement of equipment.

To ensure the correct function of shock vibration mounts.

To provide a noise isolating link.

To allow for temporary access (flushing, etc)

To allow easier equipment interchangeability.

45
Q

Describe the concentrations of water in hydraulic oil in its different forms (dissolved, suspended and separated).

A

Dissolved: up to 200ppm

Suspended: 200 - 300ppm

Separated: 500ppm

46
Q

What are the 4 types of filtration systems.

A

Full flow accurate stage filtration.
Bypass filtration.
External filtration.
Filtration by settlement.

47
Q

Name four types of coupling?

A

Aeroquip Coupling
Keelaring Coupling
Swagelock Coupling
Flat faced

48
Q

What pressure are Aeroquip Couplings rated to?

A

207 bar

49
Q

What pressure are Keelaring couplings rated to?

A

680 bar

50
Q

What pressure are swagelock couplings rated to?

A

757 bar

51
Q

What pressure are flat faced couplings rated to?

A

720 bar

52
Q

What components make up a flight deck crane hydraulic system?

A

Hydraulic Power Pack
Air blast cooler
Load control manifold
Line mounted valves
Dual joystick lever operated controlls.

53
Q

What valves are used in the control unit for a davit?

A

Speed control valve.
Direction control valve.
Brake valve.
Flow valve.
Lowering Valve.
Pilot operated non return valve.
Throttle and non return valve.
Governor valve.

ME 151 Course (10 decks)

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