Theory 1 Flashcards
What is the definition of a system?
A system is a series of interconnecting pipes and components that will deliver a substance from one point to another.
What are the two types of systems?
- Open loop
- Closed loop
What is an open loop?
The working fluid is consumed e.g. Fuel, domestic fresh water
What is a closed loop?
The working fluid is re-sued e.g. lub oil system, fresh water cooling system
Name 3 types of tanks? And what their purpose is?
- Header Tank- Reservoir to top up a system.
- Service tank- supply of clean, water free fuel.
- Drain tank- collects oil returning from a system.
Name 3 types of tank gauges? And what their purpose is?
- Contents gauge- (clock/dial) How much fluid is in a tank.
- Gauge glass- Visual indication to tank level (press the button to read)
- Sounding tube- Used to measure the depth of liquid in a tank (Dip tape)
What is a Strainer?
Removes large course particles, usually metal plates with holes in or a wire basket.
What are the benefits of a strainer?
Usually washable and re-useable
What dose the type of pipework depend on?
- service being supplied (the fluid)
- operating temperatures and pressures
- other types of material used within the system(what the pipework might fit into)
Name the different types of pipework and the services they do?
- Phosphor bronze- High pressure salt water
- Copper - Domestic Fresh water
- Copper Nickel- Lub Oil
- Brass- Castings (valves, couplings, junctions, taps)
- Plastic- Sewage/waste systems and pre-wet
What dose the type of seal used depend on?
pressure
fluid being used
temperatures involved
Name the types of seals used? And a discription?
- Gaskets – Create a seal between two flat surfaces, can be made from various materials including Non Asbestos Fibre (NAF) – Paper – Leather – Cork – Copper - Rubber
- Mechanical Seals – Used on rotating components such as pump shafts
- Keeler Ring Couplings – Used on High Pressure Air system pipework connections
- Gland packing – Silicone, wool, wax – dependent on fluid type, pressure and temp
What is the purpose of valves?
To provide a method of controlling flow or pressure of a fluid or to provide a means of isolating various systems or components.
Name the different types of valves?
globe valve
gate valve
flap valve
Saunders valve
Ball seated cock
Relief Valve
Reducing Valve
Non-return Valve
Pressure Control valve
ROV (remote operation valve)
What is a relief valve?
Prevents over pressurisation
What is a reducing valve?
Reduces pressure for a part of a system
What is a non-return valve?
Prevents reverse flow
What is a pressure control valve?
Maintains pressure in a system at a set level, monitors the outlet pressure from the vavle.
What is an ROV (remote operation valve)?
Rod gearing to manually open or close a valve from another location or automated
What are the two types of pumps used on ship?
Positive displacement
Dynamic Displacement
Benefits of positive displacement pumps?
Less flow, increases pressure.
Benefits of dynamic displacement pumps?
Large flow, low pressure
What is a motor?
Converts electrical energy into mechanical motion to drive a pump.
How does a Bourdon Tube work?
tube extends as pressure increases moving a needle round a dial.
How does a manometer work?
Pressure increases pushed liquid round the U bend
How does a tachometer work?
measures rotational speed
What is a thermometer?
measures temperature
What are the different types of thermometer?
- fixed brass
- standard pocket
- clock/dial face
What is a thermometer pocket?
A plug fitted to systems to screw in a fixed brass thermometer. Filled with oil to aid heat conduction.
Name the different types of pressure and vacuum gauges.
Bourdon tube
Manometer
Tachometer
Thermometer
Thermometer pocket
Flow meters
Voltage meters
What are filters?
They remove small fine particles
What are the different types of filters?
Metallic- Wire wool, steel plates and gauze screens. Re-useable, can be washed and refitted when blocked.
Absorbent- Fabrics, felt, yarn, paper. Not re-useable
What are accumulators?
They are a store of potential energy which is released as required, also used as pulsation
What are the two most common types of accumlators?
Bladder (bag)
Pistion
Where can the engine block/cylinder block be found?
It is the main structure of the engine.
What are the parts that make up a diesel engine?
- engine block
- cylinder and cylinder block
- cylinder head
- cylinder head joint
- sump
- pistion
- piston rings
- connecting rod
- gudgeon pin
- crankshaft
- flywheel
- camshaft
- valves
- pushrod
- cam follower
- rocker arm
- fuel injector
What is a 4-stroke cycle?
The operating cycle of the engine.
What does the 4-stroke cycle consist of?
- induction stroke
- compression stroke
-power stroke - exhaust stroke
What happens in the induction stroke?
inlet valve opens
the pistion moves from top dead centre to bottom dead centre
fresh air is drawn in
What happens in the compression stroke?
piston moves from bottom to top, with the valves shut
the piston moving up causes the trapped air to become compressed and temperature increases.
towards the end of the compression, the injector injects atomised fuel into the heated air at high pressure
what happens in the power stroke?
the atomsied fuel ignites in the heated air and combustion beings
the piton is at now at the top
the combustion gases create pressure, this forces the piston from the top to the bottom
what happens during the exhaust stroke?
the exhaust valve begins to open shortly before the piston returns to the bottom.
the remaining combustion pressure beings to move the exhaust gasses past the open exhaust valve
the piston moves from bottom to top forcing the remain gas out.
what is valve overlap?
the exhaust vale dose not fully close until shortly after the piston reaches top dead centre, and the intake valve opening shortly before the piston reaches top dead centre.
What components make up a fuel system?
- header tank
- tank strainer
- fuel lift pump
- filters
- fuel injection pump
- injectors
What components make up a Lub Oil sytem?
- sump
- sump strainer
- lub oil pump
- priming pump
- filter
- lub oil cooler
- reducing valve
What is the oil test kit called?
kittewake
What are you testing for when testing oil? How often are tests done?
tests are done weekly
- water
- insolubles
- viscosity
What components dose a cooling system consist of?
- fresh water pump
- thermoset
- header tank
- heat exchanger
- vent cocks
- sea cock and strainer
- salt water circulating pump
- lub oil cooler
- discharge overboard valve
When dose coolant testing happen? What are the test looking for?
Coolant is tested weekly.
- salinity
- density
-acidity
What will safety devices detect?
- Low oil pressure
- low coolant pressure
- High oil temperature
- High coolant temperature
- engine overspeed
- fire
What are the hazards of diesel engines? what precautions are in place?
noise- wearing ear defenders
rotating machinery- protective guards
fire and explosion
high temperatures- taking care when around running engines, gloves
