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151/23/005 > Hydraulics > Flashcards

Hydraulics Flashcards

1
Q

define pascals 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 equation for pascals law?

A

F=PxA

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3
Q

define Bernoulli’s principle

A

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

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4
Q

how is flow measured?

A

flow is measured in velocity and flow rate

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5
Q

why is water not used as a hydraulic fluid?

A
  • lack of lubricating properties
  • corrosive
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6
Q

define viscosity

A

Viscosity is a measure of a fluids resistance to flow normally measured in centistokes

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7
Q

What are the two types of pumps?

A
  • hydrodynamic- non-positive
  • hydrostatic - positive
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8
Q

what are the characteristics of a mulit-cylinder pump?

A
  • highly efficient
  • wide range of capacities
  • variable output
  • large HP applications
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9
Q

How do axial piston pumps work?

A

The pistons arranged parallel to the shaft. It is the angle of swash which determines the length of stroke. The angle of swash can be varied or fixed

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10
Q

What are the three types of actuators?

A
  • linear
  • Rotary
  • Semi-Rotary
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11
Q

define a linear actuator

A

A linear actuator has a reciprocating action

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12
Q

define a rotary actuator

A

A rotary actuator converts hydraulic energy into rotary motion

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13
Q

define a semi-rotary actuator

A

A semi-rotary actuator converts hydraulic energy into partial rotary motion

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14
Q

Describe the procedure for the Motor Leakage test

A
  • isolate return line
  • break system on the drain line
  • supply oil to the actuator by operating the direction control valve
  • collect oil from the Drain line and time how long it takes to collect 1 pint
  • take temp of the oil and repeat the test by isolating the opposite line
  • plot results on a graph obtained from the equipment relevant BR
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15
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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16
Q

What are the common malpractices in RN Hydraulic pumps and motors?

A
  • changing filters too early or late
  • running too hot (35-45)
  • using incorrect oil
  • wrong filter locations
  • not self priming
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17
Q

How hot is too hot for hydraulic pumps and motors, and why?

A

temps above 82 degrees, damage most seals and hose compounds and accelerates degradation of the oil.

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18
Q

describe the safety supervisor system

A

comprises of two solenoid valves, in series between hydraulic supply lines. Identical circuits within each HPU pump motor starter.

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19
Q

How would you 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.
  • check the temperature of the hydraulic fluid during operation
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20
Q

how can cylinders motors be damaged?

A

seals and rings that can be damaged by excess pressure, excess temperature and contaminants.

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21
Q

explain the oil numbering system in the RN

A

the numbering system has two parts, an alphabetical identifier and a numeric identifier for each oil.

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22
Q

When inspecting hoses and lines, what are you looking for?

A

cracking, cuts or dents

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23
Q

When checking the hose routing, what are you looking for?

A

kinks, overstretching or chafing

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24
Q

What would you do if you find a leak at a fitting ?

A

tighten it to make sure it is snug, but do not overtighten as this can cause damage to the thread

25
Q

What would air in the system cause?

A
  • Air Entrainment
  • Heat
  • Loss of lubrication
  • Loss of efficiency
26
Q

What would solid particles in the system cause?

A
  • scoring
  • wear
  • loss of efficiency
27
Q

what would water contamination in the system cause?

A
  • erosion
  • corrosion
  • loss of lubrication
  • loss of efficiency
28
Q

Explain how to fit a Swagelok tube fitting

A
  • Position the jaws of the vice grip on the body
  • Insert the tubing
  • finger tighten the nut
  • mark the nut at 12 o’clock
  • turn the nut 1 and 1/4 turns
29
Q

What does a Pall contamination Monitor (PMC400) test for in the system?

A
  • particulate
  • viscosity
  • water content
30
Q

What is the procedure for shutting down hydraulic machines?

A
  • lower/mechanically secure all suspended loads
  • Exhaust any pressure locked in the system
  • Drain down all accumulators
  • Discharge both end of actuators
  • isolate the electrical control system
  • isolate the electrical power supply
31
Q

What are the common causes of hydraulic system failure?

A
  • insufficient fluid level
  • air in the system
  • oil contamination
  • incorrect system design and commissioning
  • Fluid leakage
  • wrong fluid type or viscosity
  • excessive temperatures
  • degradation of oil
  • depletion of additives
  • excessive pressure
  • water in system ( emulsification)
32
Q

What are the safety requirements of repacking stabiliser glands?

A
  • safety is of paramount importance, water tight integrity must be maintained
  • fleet diving group are required to assist
  • personnel are to be suitably dressed in mulit-fab suits in the event of a leakages.
  • before carrying out work, check all relevant BRS and SOP’s
33
Q

On completion of packing the stabilisers, what must happen?

A

the stabilisers are to be forced rolled

34
Q

what position after agreement check should the rudder be left in?

A

The rudder is to be pumped back to midships using the and pump.

35
Q

Explain the steering gear circuit

A
  • the supply tanks feed the pumps with a positive suction
  • The power unit delivers oil via axial piston pump and boost pump
  • it incorporates a pair of doubling acting linear actuators (RAMS)
  • The actuators move the rudder and also move the rudder angle transmitter and rudder feeder back unit ( sub system) These send signals (feedback) to the control system.
36
Q

when would rudder locking be used?

A
  • when being towed
  • entering/leaving dry dock
  • Alongside and shut down
  • Divers working on Hull
  • Maintenance on the system
37
Q

When and why are stabilisers used?

A

Stabilisers are used to counteract the natural rolling motion of the ship by applying equal and opposite righting moment. This achieved by two non-retractable fins, which are attached to the ships hull and are acted upon by the flow of water over their surfaces.

38
Q

what are the reasons for fitting stabilisers?

A
  • weapon platform
  • aircraft operation
  • NCBD
  • crew habitability
39
Q

What is the function of linear actuators?

A

The two hydraulic actuators are clevis mounted, heavy duty, double acting type with self-aling bearings at the cap and rod ends

40
Q

What would the fin be locked?

A
  • when being towed
  • entering/leaving dry dock
  • Alongside and shut down
  • Divers working on Hull
  • Maintenance on the system
41
Q

What pressure can a high pressure oil injection injury occur?

A

7 bar

42
Q

What is whipping injury?

A

high velocity, debris injury

43
Q

How how does hydraulic fluid need to be to cause a scolding injury?

A

50 degrees celcius

44
Q

A what temperature do fluorocarbon elastomers decompose?

A

200 - 300 degrees Celsius

45
Q

How is viscosity of an oil indicated?

A

viscosity is indicated by a number. The lower the number the lower the viscosity , the thinner the oil.

46
Q

What are the two types if flexible hoses used?

A
  • two wire braided reinforcement hose
  • wire spiral reinforcement hose.
47
Q

What are the different categories of service life for hose assembly, and what are they used for?

A

CAT A- 5 years- steering gear/upper deck
CAT B- 10 years- Stabilisers
CAT C- 15 years- captains lift

48
Q

what are the two different types of seals?

A
  • static seals
  • dynamic seals
49
Q

what are the two different types of dynamic seals, and the the movements these seals are used for?

A
  • seals for sliding ( reciprocating)
  • rotating shaft seals ( rotary )
50
Q

What are the uses of flexible hoses?

A
  • to permit relative movement of equipment
  • to ensure correct function of shock vibration mounts
  • to provide a noise isolating link
  • to allow for temporary access
  • to allow easier equipment interchangeability
51
Q

what forms of water can be found with in the system, and there ppm?

A
  • dissolved water 200 ppm
  • suspended water 200-300 ppm
    -separated water 500 ppm
52
Q

what are the different types of filtration systems?

A
  • full flow accurate stage filtration
    -bypass filtration
  • external filtration
  • filtration by settlement
53
Q

What is the rating of a flat faced coupling ?

A

720 bar

54
Q

what is the rating of a Aeroquip coupling?

A

270 bar

55
Q

What is the rating of a keelaring coupling?

A

680 bar

56
Q

What is the rating of a swagelock coupling?

A

757 bar

57
Q

What is used to flush a hydraulic system?

A

rustvcto NTP 32

58
Q

What valves are used on Davits?

A
  • speed control valve
  • direction control valve
  • brake valve
  • flow valve
  • lowering valve
  • pilot operated non-return valve
  • throttle and non return vlave
  • governor valve

151/23/005 (13 decks)

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