Mechanical Theory 2 Flashcards
How can fuel be supplied to the ship
- RAS
- Road browser
- Barge
- Jetty storage tanks
- Direct jetty pipeline
what is the purpose of the thrust block
- ensures the shaft is unable to move back and forth
- uses white metal pads
- pads sit in a machined collar
what and when is dry motoring
- after wet - before washing
- fuel is closed
- ignitors are off
- after failed start
what is wet motoring
- after maintenance
- fuel is open
- ignitors are off
- prime and purge
List the hazards and safety precausion when working with fuels
- fire and explosion
- toxicity - ventilation must be made
- dermatits - bad for skin - wear gloves/cream
- pollution - spil kit should be avaliable
what checks are carried out on a running gas turbine
- done hourly - by watch keeper
- pressure/temperature checks
- oil levels
- noise / vibration
- leaks
what hazards are associated with a gas turbine
- moving components
- temperatures / high pressure
- noise
how are the ready use tanks levels maintained
- ball valve
- ball cock
- float valve
name the fuel tests carried out and explain them
- visual test
- color test
- diesel filtration
- water reaction test
what is the function of the coalescer
- removes water droplets
- (10ppm)
what is the purpose of the plummer block
supports the weight of the shaft
Doesn’t prevent thrust
what is the main components of the plummer block
- journal pads
- dynamic oil wedge
- bearings
- Dipstick
- oil cooler
what contaminates can be found in fuel
- sodium
- water
- dirt
- MBG (micro-biological growth)
What is DFTK
- diesel filtration test kit - gives an indication of how quickly filters will block/clog
- must pass 250ml of fuel before hitting 15psi
what is used to transfer fuel from displaced tanks to undisplaced
centrifuge - pulls fuel from the tanks, but also cleans the fuel
what is the purpose of the quill shaft
- maintains alignment of the wheels connected
- acts as a torsion spring
what is the funciton of the A bracket
supports the weight of the shaft on the outside of the ship
describe the term hydrodynamic lubrication
this is where seawater is used as lubrication between the bracket and the shaft
what are the gas turbines fitted to a type 45 and how many
2 x wr21
what are the gas turbines fitted to the type 23 and how many
2 x spey
describe the function of a stern seal
creates a watertight seal between the inside/outside of the ship
what system steps in place if the stern seal breaks
an inflatable emergancy seal deploys
how is the high/low pressure turbine driven
- working fluid (expanding gases)
- from combustion can
- from fuel being burnt
how are the high/low pressure compressors driven
seperate axles
rotation of the turbines
axles are connected to opposing turbines
Give three advantages of a gas turbine
- high power/weight ratio
- low manpower required
- minimum onboard maintenaince
- get away quickly
- ease of operation
what component collects ferrous metals
- magchips
- magnets which collect debris from the oil
What is MBG
Micro Biological Growth
plant organisms growing between the fuel and water
what are the dangers of dirty fuel
will cause filtration devicres to become blocked
what lubricating oil is used in spey gas turbines
OX-22
Name two fire suppression systems to a gas turbine module
BCF
BTM
list and explain the safety devices fitted to a gas turbine
- fire detector - indicates high temperaturs in module, reports data to MCC
- hand trip - manual override, shuts off the fuel supply and aproval is needed
- partical overspeed - if RPM is too high for propeller, this will reduce the fuel to lower the speed
- power turbine entry temperature - monitors temp and will trip if too high
- power turbine over speed - trip if rpm is 110%
what is the purpose of the turning gear
- can be controlled manually or by electric motor
- allows the shaft to be rotated to a desired angle
- used when the ship is in ddock or under maintenance
What is the function of the FL oil system
- used to lubricate the gearbox by maintaining the correct operating temperatures
- if the system is to fail so will the gearbox
whos permission should be sought after to enter a gas turbine module
MEO
marine engineering officer
how often are FL cut-ins carried out
every 24hrs
if pressure drops below 18.5psi, the motor driven pump will kick in
what type of system is the FL system
closed system
When would we inhibit
maintenance periods, when the engine is off for long periods
what is used to inhibit the shaft
PX-24
what are the three different ways air is split, when in the combustion can
- primary air - 15% - intial combustion
- secondary air - 10% - protection layer between can and flame
- tertiary air - 75% - acts as the working fluid
explain the three stages of the air intake system
1st stage - spray eliminators - uses baffleplats to create a difercult path
2nd stage - knitmesh filter - removes particulates
3rd stage - water trough - collects spray and uses a monometric leg to create a one-way flow
What is ment by CODLAG
Combination of Diesel electric and gas
What is ment by IEP
intergrated electronic propulsion
why must ignitors be turned off for motoring
- they carry 10,000v - which can be lethal
- can be unburnt fuel
- they need to be discharged due to high voltage
what checks are carried out when realesing the shaft brake
- all pads are clear
- no fire danger
- shaft is turning freely
what is the function of the SKF coupling
a method of disconnecting the shaft safely without causing damage
what is the name of the driving gear
primary pinion
how can we change direction in the gearbox
add a second gear of the same size
what is the purpose of the main gearbox
- ahead and astern propulsion
- downsize the speed to a suitable rate for the propeller
- variations of speed and power
name three different types of gear wheels
- straight spur
- helical
- double helical
- worm wheel
- single gear reduction
- double gear reduction
- double gear reduction - dual tandem
where can the shaft brake be operated from
SCC
Ship Control Center
What is a relief valve
Spring loaded valve - opens to relieve excess pressure to stop over pressurisation
Purpose of the boost pump
Draws fuel from a service tank and delivers it to the supply ring main
What is the filter size on the pre-filters
5 microns
What are the reasons for testing fuel
- Sodium in a system can cause corrosion
- Water in a tank encourages MBG
- Dirt causes the filters to block up
Explain the water reaction test
Mixture of 20ml distilled water and 80ml fuel is left to settle in a test tube.
The interface should be no more then 2ml (cloudy area)
Explain the fuel transfer from the tanker to the ring main
- Tanker
- Filling trunk
- Manifold
- Displaced tanks
- Centrifuge
- Undisplaced tanks
- Fuel transfer pump
- Service tank
- Fuel boost pump
- Fuel boost ring main
When are fuel tests taken
When the ship is prior embarked
What is the max fill for a displaced tank
90% (of fuel)
(Tank gets filled with salt water to act as a ballast)
What is the max fill for a undisplaced tank
95%
Never filed with salt water
Passes through a centrifuge before hand
Explain the purpose and function of a centrifuge
- separates oil/fuel from water using centrifugal force
- process is called polishing
- uses gravity - the heavier will sink to the bottom and the lights will spill over the top
- 5000 RPM
Who is involved in RAS
- Whole ship evolution
- everyone must be prepared and aware
- because close to the supply ship, it is relatively hazardous
How often is water washing performed
Spey - 100run hours or 2 monthly
Wr21 - 150 run hours
what are the 5-strokes of a gas turbine
- induction
- compression
- combustion
- power
- exhaust
explain the purpose of a serkstat
maintains the oil temprature
controls the flow direction between bypassing or using the lube oil cooler
what is the purpose of the bulkhead glands
- creates a watertight seal between each compartment the shaft travels through
- supports the weight of the shaft also
what is the purpose of the bulkhead glands
- creates a watertight seal between each compartment the shaft travels through
- supports the weight of the shaft also
what is a fixed-blade propeller
- propeller is bolted directly to the shaft
- ahead and astern is controlled by the gearbox
what is a CPP and what does it do
- contolable pitch propeller
- angle of the blades can be changed to control direction of the ship
- uses a hydraulic system
Explain the Order of the fuel boost system
- Service tank
- Remotely operated suction valve
- Boost pump
- Prefilters
- Coalcescer
- Pressure maintaining valve
- Supply boost ring main
