Theory 4 Flashcards by Ewan Baxter

Explain pressure/volume relationship to boiling point

The higher the pressure, the higher the boiling point

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Explain heat transfer

Heat always transfers from hot to cold, By three different methods:

conduction - direct contact
convection - moving hot air
radiation - direct heat source

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explain latent heat

Refers to the temperature required to change the state of a substance

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explain sensible heat

The heat applied to a substance whilst it still remains the same state

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explain superheat

Maintaining a temperature above a substances boiling point (change of state)

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explain the purpose of the compressor

To turn a low pressure gas into a high pressure gas

Pumps refrigerant around the system

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explain the purpose of a condenser

To turn a high pressure gas into a high pressure liquid

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explain the purpose of a TEV (thermal expansion valve)

Turns high pressure liquid into low pressure liquid

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explain the purpose of an evaporator

Turns low pressure liquid into low pressure gas

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What are hydraulic O-rings made from? What temp do they retain their elastic properties till? What happens if they burn

Made from fluorocarbon elastomers, retains properties until 300*c, after which they give of the toxic gas hydrogen fluoride

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What are the two categories of hydraulic oil

Petroleum & synthetic based

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What type of oil is used on submarines? No. & colour

Ox30 - red - synthetic

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What type of oil is used on T23 & T45? No. & colour

Ox40 - green - synthetic

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What type of oil is used on T22, T42 & CVS? No. & colour

Om33 - yellow/orange - petroleum

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What are the desirable properties of hydrolic oil

Transmission of power
Flow easily through lines
Practically incompressible 
Lubricating
Cooling

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What does demulsibility mean

Fluids ability to separate from water

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Why are anti oxidants added to oil

Reduces likelihood of sludge occluding in the oil

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List hydraulic pumps

External gear type pump
Internal gear type pump
Vane pump 
Lobe pump
Piston type pump (single)
Piston/plunger type pump (multi)

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Explain axial piston pump operation

Cylinder 1, plunger at highest point, no axial movement, suction & delivery valves shut
C2, plunger on inlet stroke, suction valve just opening, delivery valve shut
C3, plunger nearing end of inlet, suction closing, delivery shut
C4, plunger starting delivery stroke, suction shut, delivery just opening
C5, plunger at maximum part of delivery stroke, suction shut, delivery fully open

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What does an actuator do? What types are available?

Converts energy (system pressure) into mechanical motion, the types:

Linear; single & double acting
Rotary

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What is the purpose of the return leg

Allows oil used for cooling/sealing the actuator/motor to return to tank

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Advantages of hydrolic system over electric system

Reliable
Simple to understand 
Infinite speed range 
Easily reversed
Ability to withstand overload
No spark risk
High torque at low speed
1/12 size of electric motor

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Uses of ventilation

Cooling electronic equipment
CBRN
Habitability
Machinery space cooling
Galley ventilation

List the types of ventilation configurations, and where they’re used

Fan supply & fan exhaust- machinery space, galley, laundry, w.c.
Fan supply/natural exhaust- store rooms, workshop
Natural supply/fan exhaust- paint stores, inflam stores, spirit rooms
Natural supply/natural exhaust- minor unoccupied compartments & lobbies

Types of filter

* Panel filter- air con systems * Supply filter- air treatment unit (ATU) * Grease filter- galley * Lint filter- laundry * Dust filter- computer/sonar instrument spaces, sickbay * Flameproof gauzes- inflam stores, paint shop, magazine, hanger, vehicle deck

What percentage of air is fresh/ recirculated

Fresh air 33% / Recirc air 67%

Uses of fresh water onboard

``` Laundry Galley Showers/sinks Water heater Medical use Bridge window washers Fresh water hose reels Machinery cooling Gas turbine washing ```

Purpose of reverse osmosis

To remove molecules from a solution using a filter & pressure-Onboard this process is used to produce freshwater from seawater

What is TDS & what’s it measuring

Total dissolved solids- measures salt in seawater (ppm)

How much salt water is rejected

80%

What type of filter is fitted to a reverse osmosis plant? What level do they filter to?

Pre-filter, down to 60 microns

Explain the reverse osmosis pump

Positive displacement. High pressure pump, operates at 10-65 bar. (In-line pulsation dampeners are fitted to smooth out suction pulsations)

Explain the CCV’s (concentration control valve) function

Fitted to discharge lines to increase back pressure, ensuring saltwater is pushed through filter, allowing for reverse osmosis

How is scaling prevented on RO membrane

Using an anti-scalant dosing unit (continuous chemical dosing)

Explain alongside procedure for bringing aboard fresh water

1. Get fresh water hoses & connections from store 2. Unscrew deck cap to filling connection 3. Fit filling gooseneck to filling connection 4. Fit hoses to shore supply 5. Open shore supply valve & flush hoses 6. Conduct water tests 7. Shut shore supply valve 8. Fit hoses to deck filling gooseneck 9. Dip & record tank levels 10. Open tank filling valves 11. open shore supply valves 12. Open ships main fresh water isolating valve 13. regularly check tank levels & test water

What is chlorine limit in fresh water

0.2ppm

How often is water checked for chlorine

Daily

What tests are performed on fresh water

Visual, taste, CHEMest

How often are fresh water levels checked/recorded

Daily ?

How is water heated onboard

Calorifiers

What is an ‘air hammer’ & how is it eliminated

A banging noise in pipes caused by trapped air. Can be eliminated with an air eliminator

What’s the purpose of moisture indicating sight glass? What does it show?

Indicates moisture in refrigerant. Yellow indicates moisture, green indicates no water

What’s the Montreal protocol agreement

Phase out harmful, ozone depleting substances/refrigerants, such as: CFC HCFC Halons

What’s the koyoto summit agreement

Reduce greenhouse gasses, such as: CO2 HFC PFC

Methods for refrigerant leak detection

``` Oil slicks Infrared leak detection system (IRLDS) Sloop Halogen leak detection Spectrolyne dye & UV lamp ```

3 oils used in refrigeration system

OM70 SUNISO 3GS SW68

What does an oil being ‘hygroscopic’ mean

It readily absorbs moisture from the air

From what source should oil be used

A sealed container

What should happen to oil after use

Re-used (closed loop system) Unused oil from container cannot be used and must be disposed of responsible

How can oil be added to refrigeration system

Sump filler pump Hand pump Dosing pot

When will phosgene gas be created

If CFC refrigerants are exposed to high heat source

What is given off when fruit & veg decompose

Carbon dioxide CO2

What is the procedure for entering refrigeration compartments

``` No smoking/hot work Inform rating in charge of watch High & low exhaust fans are on IRLDS work Breathing apparatus work Trapped warning lamps work Accompanied by someone else Doors work ```

What should you do if refrigerant gets in your eye

Don’t rub, wash under running water, opening & closing eyes

What systems are supplied with chilled water

Weapons systems Radar Ships computer systems Air treatment units (ATU’s)

What is the difference between refrigeration & chilled water system

Refrigeration units- direct refrigeration, cools down room Chilled water system- cools water, which then circulates around the ship

What provides cooling for the condenser & motors

Seawater cooling pump