1 Flashcards
Whats the difference between petrol and diesel engunes
Petrol engines take in a mixture of aur and fuel into the cylinder before it compresses the mixture and ignites with a spark plug
Diesel engines take in just air into the cylinder and then compresses the air and fuel is injected into the hot compressed air and spontaneous combuation occurs
What are the oil tests
TBN (acidity)
Viscosity (thickness)
Water in oil
Insolubles
What are the coolant tests
Salinity (salt content)
Density
Acidity
Engine safety devices
Low lub oil pressure Low coolant pressure High lub oil temperature High coolant temperature Engine overspeed
Whats the procedure for resetting trips
Investigate the cause of the trip
Rectify the fault
Reset trip
How are electrons held in orbit
By a force of attraction
What is the outer most orbit of an electron called
Valence shell and the electron in this outer orbit is called a valence electron
What is electromotive force
It is the force that drives the current around a circuit
What causes potential difference
The imbalance of electrons at the terminals of a battery or generator
What different methods can produce voltage
Chemically Friction Induction Pressure Heat Light
List some insulators
Wood Paper Rubber Mica Insulating varnish Porcelain Plastic Woven fabrics Glass
List some conductors
Copper Brass Silver Carbon Impure water Aluminium Platinum Mercury Gold
State ohms law
Ohms law states that a current flowing through a conductor is the same as the applied voltage across it, providing the temperature remains constant and is inversely proportional to the resistance
What is the ohms law triangle
Voltage = current x resistance
What is the formula fir power
Force x distance
Power = —————————
Time
What are resistors rated in
Watts and ohms
What is the purpose of the fuse
Used to protect the power source and the associated wiring and circuitry up to the piece of equipment
What are the different types of fuses
Cartridge fuse
Fuse link
High rupturing capacity fuse
What are the three main causes of earth faults
Dampness
Insulation becoming hard or brittle with age or heat
Accidental damage
Which ways do the lines of force travel on a magnet
From north to south
What are the two common types of magnets
Bar magnet
Horseshoe magnet
What is the definition of a working fluid
A gas or liquid that can do work by expansion or flow, or can be compressed or made to flow
What is a turbine
A bladed spool designed to rotate when acted on by a working fluid
What is a compressor
A bladed spool designed to do work on a fluid when it is rotated
What is the function of a gas turbine
Converts heat energy into rotary motion for ships propulsion
What are the different propulsion configurations and what do they stand for
IEP - integrated Electrical Propulsion
CODLAG - Combination Of Diesel Electric And Gas
COGAG - Combination OF Gas and Gas
COGOG - Combination Of Gas Or Gas
Advantages of a gas turbine
Allow the ship to get underway quickly Ease of operation and emphasis on remote control High power to weight ratio Minimum ship-borne maintenance Lower man-power requirements
What are the 3 stages of an air intake filter
Stage 1 - spray eliminator (encourages the air to let go of the water)
Stage 2 - knit mesh filter (removes particulate matter
Stage 3 - water separation (water drains into a water trough, which ensures a water seal across the bottom of the filters)
What is Bernoulli’s theorem
As a substances size increases the pressure decreases
The low pressure (depression) will draw the reservoir into the flow
What is the gas turbine cycle
Induction Compression Combustion Power Exhaust
What are the different parts to the gas turbine cooling system
3 part intake filter Splitter/silencer Stone guard Transition duct Cascade bend Engine intake flare
What does the splitter/silencer do
Splits up the air flow stream which reduces air noise and buffeting
What does the stone guard do
Prevents large/coarse particles of debris from entering the gas turbine (1 inch wire mesh to prevent damage)
What does the transition duct do
Provides smooth change from cross section air flow to circular cross section air flow, in preparation for entering the engines air intake casing
What does the cascade bend do
Directs the air smoothly through a 90 degree bend without causing any turbulence to the already smoothed out air flow.
What does the intake flare do
Seals the engine intake from the rest of the module and houses the “water wash ring” used for cleaning the engine
Describe the method of module ventilation
Air is drawn into the module because of the depression formed at the other end Air circulates around the module keeping it cool A depression of air formed by the rushing exhaust gases (Bernoulli theorem) Vent flaps are fitted to seal the module should a fire establish within.
The position of flaps must be known at all times
When engine is running flaps must be open
What type of compressors are LP and HP compressors
Axial flow compressors ( which use divergent passages between the rotor blades, combined with stator vanes, to increase the pressure of air. Air compression ratio of around 19:1)
What does the LP and HP air compressor do
Act like water wheels, but uses the “working fluid” produced in combustion to drive the corresponding compressors
What does the power turbine do
Drives a shaft into the main gearbox/generator. The remaining 2/3 of energy from the working fluid is used by the power turbine
What lubrication is used in the combustion chamber and gas turbine system
OX22
What do mag chips do
Fitted for early failure detection and are located in the oil return leg. They collect ferrous debris and are inspected every 24 running hours - the debris measured and recorded NEVER WIPED OFF
What are the different safety devices for the gas turbine
Hand trip Fire detectors Power turbine Entry Temperature (PTET) Partial overspeed LP/HP governors Vibration monitors PT overspeed Safety interlocks
What are the different fire extinguishers fitted to a gas turbine module
BCF - Bromochlorodifluoromethane
BTM - Bromotrifluoromethane
What is checked during the watch keeping of a gas turbine
Pressures and temperatures
Oil levels
Any excessive/unusual noises
Any leaks
What is the wet motor cycle (to do with maintenance)
When the engine is spun over using the starter motor, with the fuel ON, but the igniters are isolated and fuses removed
Why is the wet motor cycle done
To prove the fuel system after maintenance
Bleed any air from the fuel system
To prime the fuel system
What is dry motor cycle (in terms of maintenance)
Engine is spun over using the starter motor, with the fuel OFF and the igniters isolated and fuses removed.
Done from the local control position only
What is water washing and why do we do it
Distilled water and compressor cleaning fluid is sprayed into the intake flare when carrying out a dry motor cycle.
Water washing is carried out to prevent the build up of debris and fouling on the compressor blades
What is inhibiting and why is it done
Carried out when the ship is alongside for an extended period of time (over 10 days).
PX24 is sprayed into the engine to cover the engine with a light film of oil to disperse moisture and protect from corrosion
What is the function of the main gearbox
Allow the speed of the prime mover to be reduced to a proportional, more manageable speed for the propeller shaft
Reverse the direction of rotation of the propellor shaft to allow ahead or astern
What is the purpose of the shaft brake
To stop and hold the propellor shaft
What are the shaft brake checks
On Application Of Brake:
ensure no fire risk
All brake pads are applied
The shaft is stationary
On Removal Of Brake:
All pads are released
No fire danger
The shaft is turning
What is the purpose of the thrust block
A large thrust bearing, designed to absorb the force of the propellor so the ship as a whole moves ahead or astern.
Consist of a machined collar on both sides of which are fitted white metal pads (bearings) lubricated by the “Michelle” oil wedge principle
What does the turning gear do
Used to slowly rotate the shaft and propeller in a controlled manner for docking and maintenance purposes
It is mounted on top of the gear case and provides drive onto the upper quill shaft in the gearbox
List the order of the shaft line starting from the propellor
Propeller Main A bracket SKF coupling Intermediate A bracket Stern seal Plummer block Bulk head gland Plummer block Thrust block Gearbox
What are the different ways of embarking fuel
Replenishment At Sea (RAS) Road Bowser/Tanker Jetty Storage Tanks Lighter Barge Fixed Jetty Pipeline
What are the different fuel storages
Filling trunk
Displacement tank - fuel tank that contains some salt water. Acts as fuel storage and ballast for the ship
Un-displaced tanks - fuel storage tank that only holds fuel
Centrifuge- separates oil/fuel from water using centrifugal force.
What is fuel tested for
Water - which may contain sodium which can encourage MBG
Dirt
Surfactants - detergents, de-greases, anti waxing agents, chemical additives
What are the different tests for fuel
Visual test
Water reaction test
Colour test
Diesel Filtration Test Kit
List the flow of fuel from a tanker to the ships engine
Tanker Filling trunk Manifold Displaced tanks Centrifuge Undisplaced tanks Fuel transfer pump Service tank Fuel boost pump Fuel boost ring main
What are some facts about the HPSWM (high pressure salt water main)
Maintains approximately 7 bar to a ring main system
Usually runs around 2 deck and in some types of ship 5 deck
It is supplied by electrically driven pumps, taking suction from the sea through a strainer, and connected to the ring main via a riser
What is a High Pressure Salt Water System used for
Firefighting (hydrants,sprays,centre feed hose reels)
Pre-wetting system
Fitted bilge and salvage eductors
Emergency cooling to main propulsion gas turbines/diesel generators
Auxiliary machinery cooling water system
Making of fresh water
Flushing heads
Where would you find fixed sprays
In areas of high fire risk such as: Magazines Paint lockers Inflam stores Funnel
When is pre-wetting used
In a NBC environment to reduce contamination levels of the upper decks
What are the different damage control states and what happens
DC state 1 - individual HPSW pumps supply their own section of the ring main. The ring main is isolated by shutting the state valves to minimise effects from damage
DC state 3 - all main isolating/state valves open, with one pump supplying the whole system. Should system pressure drop a second pump can be started
What machinery is supplied by the main propulsion cooling system
Lub oil heat exchanger
Gas turbine heat exchanger
CPP unit heat exchanger
Plummer Block heat exchanger
What machinery is supplied by the aux circ system
Air conditioning plant
Diesel plant generators
What are the rules for the discharge of water within 12NM from land
The oil content in the discharge water must not exceed 15ppm
The ship is underway
The ship has in operation an oily water separating filter with an oil discharge monitoring and control system
What are the rules for discharge of water more than 12NM from land
The oil content doesn’t exceed 15ppm
The ship is underway
The ship has an approved oil filtering system
List some of the special areas relating to oil pollution regulations
Baltic Sea North west European water Mediterranean Sea Black Sea Gulf Gulf of Aden Caribbean
What are some of the sources of oil contamination
Bilges
Fuel systems
Oil systems
CPP systems
How to minimise risk of oil entering the bilge
Keep machinery spotless Monitor lube oil ready use tanks No surfactants to be used Eductors to be manned when in operation Maximise the use of shoreside facilities when along side
What is black water defined as
Drainage and waste from WC’s, Urinals, WC scuppers, medical compartments, any water mixed with any of these
What is grey water defined as
Waste from Bathrooms, galleys, dishwashers, laundries, sinks
What do bilge and silage eductors do
Used to remove quantities of fluid from bilges very quickly.
What do you need to do prior to going into a confined space?
● The space / compartment is to be cooled
● The space is to be force ventilated for 24 hours minimum
● After 24 hours the atmosphere is to be tested safe before the space can be accessed
● If, after 24 hours the atmosphere is not safe, it is to be ventilated for a further 12 hours and then re-tested
● This procedure is to be followed until the atmosphere is tested to be safe
● A gas free certificate must be issued before any entry is allowed into the space
Explain the man below board? And why do we use it?
Man below board is a system for workers and other personnel to monitor anyone entering or leaving a restricted compartment, you simply add a man below tally on to the man below board on entry and remove it on exiting the restricted compartment
What do you understand by SHIPHAZ and permits to work?
● SHIPHAZ is basically all the hazards found onboard ship, such as working aloft, divers down and working in confined spaces
● Permits of work is the process of getting authorisation before carrying out work in order to minimise risk, work that would need permits to work include:
a) Fuelling
b) Aloft
c) Divers down
d) Hot work
e) Confined spaces
Describe the different WT/DC conditions and where/when used? Whose responsibility is it to maintain WT integrity?
● Everyone’s responsibility to monitor water tight integrity
● WT stands for water tight, there are 3 states:
● State 1 – war time – all red openings on doors above and below water line are shut
● State 2 – is when going in and out of harbour or sewers canals and is a threat to water tight integrity and all red openings on doors below water line are shut (yankee patrol activated to monitor every 15 minutes)
● State 3 – sailing and cruising state
DC stands for damage control there is 2 states:
a) State 1 – All pumps are running; all valves are shut and the HPSWM is divided into zones to minimise battle damage
b) State 3 – One pump is running; other pumps are on stand-by and can be started if the pressure drops and all valves are open (more pumps may be introduced for special flying operations)
What are the face seal checks for your respirator
● Place mask on face and pull straps overhead and tighten
● Inhale sharply to activate the DV first breath mechanism and then breathe normally
● Twist the DV gently to confirm the locking catch is fully engaged
● Open the DV bypass valve and check there is a free flow of air, close the bypass valve
● Shut the cylinder valve and then open it a quarter of a turn. Take a deep breath. Shut cylinder valve and check for no sound of escaping air and that the pressure gauge does not fall more than 10bar in 10 seconds
● Open the cylinder valve fully, breathe normally and check gauge reading is steady. If not, check cylinder valve is fully open. If gauge fluctuates when cylinder valve is fully open, do not use
● Test the distress alarm
● On completion of a successful face seal check, the BA controller removes and retains the set number tally, and enters the wearers name on control board
● Check protective clothing and proceed on task
What weapons/radar systems are on type 45’s and 23’s?
● Type 45 – HMS Dauntless as an example has the sea viper anti-air missile system
It has the Sampson MFR (Multi-Function Radar) it can guide up to 16 sea viper missiles at a time and has 360-degree coverage, it has the capability of tracking 1000 targets at once
● Type 23 – The radar systems fitted are currently being upgraded with the Sea Ceptor SAM system (range of up to 25km) as replacement for sea wolf, which is a sea based supersonic missile defence system. Another weapon system fitted on a 23 is the Boeing harpoon which is a anti-ship missile is capable of striking enemy ships more than 80 miles away
What type of ships do we have in the RN? And why do we need them?
● Type 45 destroyers (6 of them) – based out of Portsmouth they are suited for a range of tasks such as hunting down enemies, defending the fleet from air attacks or providing humanitarian aid ● Type 23 Frigates (12 of them) – Mostly based out of Devonport, although there are 4 based out of Portsmouth, they were originally designed for anti-submarine warfare (ASW), but the addition of the vertical-launched Seawolf point missile defence system and the Boeing Harpoon surface-to-surface missile has expanded its role to include anti-surface warfare ● Air craft carriers (2 of them) – Based out of Portsmouth, they operate as a flag ship and a command and control hub for complex naval and military operations for sustained periods, also carries air craft and offers support to other ships ● Hunt class (6 of them) – Based out of Portsmouth, they specialise in active mine hunting, they use high definition sonar to scour the worlds seabed’s for mines and explosives which are then destroyed by the ships clearance diving team ● Sandown class (15 of them) – Based out of Fas Lane, again these are mine hunters also. ● River II class patrol ship (5 of them) – Based out of Portsmouth, these ships are used for counter-terrorism, counter-piracy and anti-smuggling operations ● River class patrol ships (3 of them) – Based out of Portsmouth, they do the same as River 2 class but in different areas ● Ice patrol ship (1 of them) – Based out of Devonport, HMS Protector’s role is to provide a sovereign and reassuring presence in the UK’s largest overseas: British Antarctica
What new ships have we got coming into the RN?
● Type 26 Frigates – Replacing the current type 23’s as the workhorse of the fleet, undertaking the Royal Navy’s three core roles in warfighting, maritime security and international engagement. They are also designed to protect the new Queen Elizabeth-class aircraft carrier from hostile submarines. ● Type 31 Frigates – These will be the heart of the Royal Navy surface fleet, deterring aggression and maintaining the security of the UK’s interests, they will work alongside the UK’s allies to deliver a warship presence across the globe and enable a forward naval presence
What is the difference between a turbo and supercharge on diesel engines?
● Turbo is driven from exhaust gases
● Supercharge is driven mechanically from the crank (Supercharge is when the pressure is risen above atmospheric pressure in the engine on the induction stroke)
What is UMMS
● Unit Maintenance management system is a database of every problem that has took place and the protocol and a way of fixing. It prints out jobs card and tells you how to do it and when to do it. It is a schedule for future maintenance
● Gives you JICS and links to risk assessments, all known defects, just a database of information that everyone can check
What precautions must you follow when working aloft?
● Wear non-slip footwear
● Wear overalls, trousers tucked into socks
● Remove any loose objects from pockets/person
● Wear in date safety harness
● Secure tools
● Ensure a responsible person is a sentry whilst personnel are aloft, sentry wears hard hat and in communication with the person aloft.
What is the purpose of Personal Protective Equipment and what would you expect to have as an ETME?
● Purpose is to protect user from risks/harm associated with workplace environment.
● PPE expected:
a) Overalls, gloves, goggles, DMS boots, ear defenders, barrier cream, respirator, hardhat/bump cap.
What do you understand by the word COSHH? And list some products that could fall under this category on board?
● COSHH is the control of substances hazardous to health.
● Substances:
b) Paint, Solvents, Bleach, Snoop, Cleaning agent, fuel, hydraulic oil.
What does ‘divers down’ mean to you and what H&S implications must we consider?
● Divers down is divers undergoing external work on the ship below the waterline
● Things that need considered for this is:
c) Shaft brake / Locking gear is to be ON
d) Steering gear is to be isolated
e) Any system discharging underwater, in the vicinity of divers, is to be isolated
f) SWSM pressure is to be reduced to prevent relief valves from lifting
g) All sonar devices / equipment is to be shut down
h) Stabilisers are to be isolated
i) Cathodic protection is to be locked OFF
j) The controllable pitch propeller system is to be shut down to prevent pitch operation
What are the regulations behind ditching gash/grey water and black water at sea?
● 0-4 nm – Only permitted if with an IMO approved Sewage Treatment Plant (STP)
● 4-12nm – Only permitted if an IMO approved system to Comminute and disinfect the sewage is in operation
● 12nm+ - No treatment is necessary
● In regards to Gash it can only be disposed of when alongside.
What SPE’s are carried on HM Ships, and what types of fires can you use them on? How are they identified?
● Stored pressure extinguisher –
a) AFFF
b) Dry powder
c) CO2
d) Wet chemical
● Can only be used on solid or liquid fires
● They are identified by a red painted shell and cream coloured band
Describe a citadel, how to exit a citadel and how to enter a citadel after contamination?
A citadel is a ships biological, chemical and nuclear shelter, formed by closing the ship down to an increase gas tight state. The citadel works by increasing the atmospheric pressure within the ship above external pressure using air filtered by AFU units
What functional tests could be performed to check the condition of a motor
● Free to turn
● Disconnect 3 phases and do a non-contact test between the three phases to prove that the motor isn’t broken down inside and no short circuit
● Then do each phase to earth (insulation resistance test)
● Continuity test between the 3 phases to make sure the resistance between them are all the same
In respect to a typical step-down transformer, how could you reduce the output voltage?
You reduce the output voltage of a transformer by ensuring there are less coils in the secondary winding compared to the primary winding, which increases the current which in turn decreases the voltage
In regards to a 3-phase motor, how would you change its direction of rotation?
You can change the direction of rotation by swapping two of the three phases over
Describe the 2 methods of fuse testing?
● Offload – voltage tester becomes a load and if the lights on the fluke are out the fuse has blown, one of the probes are in the test hole in the output side but the fuse is out and the other probe is in any supply side test hole in the same circuit
● Onload – put the probes in the test points in the fuse carrier with the fuse in and if the fuse is okay the electrical charge will take the path of least resistance
What is GPTME used for (give examples)?
General purpose testing and measurement equipment such as the fluke 89, fluke 110, MIT 420 which is used to carry out electrical tests for example continuity test, insulation resistance test and non-contact test (in accordance with the electric HASWA 1989 the fluke 89 is used to test for current the others can’t, MIT 420 can inject voltage the others can’t, and the ultimate proving for dead is fluke 110 is because its got one continuous cable so there’s no discrepancy, there’s no measurement so it gives you the right indication and there’s no settings)
What are the rules for working on live electrical equipment?
● Do not take risks
● Wear rubber gloves if possible
● Use insulated tools
● Take care not to cause short circuits
● Wear insulating footwear
● Be aware of voltages that are or can be present
● Do not rely on interlocks or other safety devices
● Unless essential do not render interlocks or safety devices inoperative
● Do not work alone, make sure your assistant knows safety procedure and isolation points
● Stand on rubber mats, avoid leaning in bulkheads or equipment
● Work with one hand if possible
● Check all test equipment is in date
What voltage on board is considered to be ‘safe’?
● Up to 30 volts is considered safe to work on, however 24vDC is only safe fitted on board HM ships. However, no voltage should be considered totally safe
What is the importance of earth bonding straps?
If a piece of equipment has a metal casing and it was to fail and cause a earth short, the metal box should not become live because it is connected to the ships hull, the voltage would then take the path of least resistance to the earth strap to the ships hull
How would you find an earth on an electrical circuit?
Half and half method
Describe the connection of shore supply
● Send signal to port ● Raise permit to work ● Rack out breakers ● Prove box ‘dead’ ● Obtain Castel key ● Test shore supply cables ● Bring on and secure cables ● Connect cables ● Inform dockyard
List 5 main breakers to a generic distribution system and explain their use.
● Supply breaker – Connects generator output to the switchboard
● Shore supply / Ship alongside breaker – Connects shore supply or supply from another ship to the switchboard and connects the ships supply to another ship
● Bus bar linking breaker – Connects 2 bus bars of the same voltage in a switchboard together
● Interconnector breaker – Connects 2 switch boards together
● Feeder breaker – Connects the switchboard to the electrical distribution centres (EDC)
What is the power book and when is it used?
● Shows the distribution of all 440 volt services
What is the low power & lighting book and when is it used?
Shows the distribution of all 115 volt services
What is the reference book and when is it used?
This is a book that has a list of all fittings, the number fitted, component symbol and pattern numbers. It is used in conjunction with the power book
Explain breaker discrimination.
The breaker nearest to the fault would be the first to trip, and the supply breaker, being the furthest from the fault would be last to trip
What and where is the earth testing facilities for 24V DC?
An earth test panel on the C&C switchboard provides a facility for testing whether the positive or negative side of the DC supply is earthed. A push button with integral lamp is fitted to the switchboard for the positive and negative side of the DC Voltage supply. To test for an Earth Fault the push button is pressed, if the lamp illuminates then there is an earth fault on that side of the supply (positive or negative)
What do you know about HV?
● Never work on HV above 1000V AC and 1500V DC
● HV live – Informs personnel that the ship is either generating HV, is capable of generating HV or is connected to an external HV shore supply
● HV dead – The ship is no longer capable of generating, distributing or receiving HV. All sources of HV supply are disconnected and isolated. With circuit main earths supplied
● HV safe – Informs personnel that a compartment/area is safe to enter with all forms of HV power source disconnected and the appropriate HV decay periods have elapsed. This term must only be used in conjunction with the clearly identified compartment/area
What equipment have battery backups and why?
● Uninterrupted power supply - In the event of a power failure or blackout, vital supplies can be maintained in order to safeguard equipment and restart equipment as necessary
● Control supplies to main switchboards
● Navigation lights
● AVR’s
When are navigation lights tested?
Tested daily one hour before sunset and normally by the duty ETME
Which law requires us to report work related death or injuries / illnesses? Name four major reportable injuries?
● Reporting of injuries, diseases and dangerous occurrences regulations:
a) Fracture – other than fingers, thumbs or toes
b) Amputation
c) Dislocation of the shoulder, hip, knee or spine
d) Loss of sight – temporary or permanent
e) Chemical or hot metal burn to the eye or any penetrating injury to the eye
f) Injury resulting from an electric shock or electrical burn
g) Any other injury admittance to hospital for more than 24 hours
What does HASWA stand for?
● Health and safety at work act
What does LOLER stand for? Name four requirements for LOLER?
Lifting operations and lifting equipment regulations
a) Strong and stable enough for the particular use and marked to indicate safe working loads
b) Positioned and installed to minimise any risks
c) Used safely i.e. the work I planned, organised and performed by competent people
d) Subject to ongoing through examination and where appropriate, inspection by competent people
What does PUWER stand for?
Provision and use of work equipment regulations
What is LOTO?
LOTO is a method of safely isolating systems and equipment electrically and mechanically
What are the main reasons for using LOTO?
● The isolation of equipment to allow maintenance to proceed without hazard to the maintainer of the equipment
● Where equipment is defective and may be dangerous
● Prevention of selection of a mode of operation which may be unavailable or dangerous
● Where supplies have been provided but equipment has yet to be fitted
What is the procedure for LOTO?
● All normal and alternative isolation points have been identified
● Obtain permission from authorising technical rate
● Equipment user and other personnel that may be affected must be informed
● A separate LOTO form is to be filled in for each individual isolation point
● The next sequential number is to be identified from the LOTO Log Index
● All details to be completed in the front of the LOTO Log
● All the LOTO information is to be recorded on a LOTO Safety Certificate
What pumping arrangements do we have onboard HM ships and what are the pumping rates?
● Routine and portable discharge 15 tonnes per hour
● Salvage eductors kick out 75 tonnes per hour
● Weda pump, placed below water level using size 3 hoses and pump out about 100 tonnes per hour (2 man lift) (test It to see it works before taking it for use, once it works take it for where needed and test again before using)
Give examples of Hydraulic system on board?
The raising and lowering of the anchor due to the actuator using hydraulic pressure and turning it into mechanical movement
Describe or sketch refrigeration cycle?
● Compressor – A positive displacement pump that raises the pressure of the refrigerant. Refrigerant leaving the compressor is a high pressure, hot gas. The compressor provides the motive force for the refrigerant around the system
● Condenser – The refrigerant is pumped into the condenser as a high pressure, hot gas. It condenses the refrigerant into a warm, high pressure liquid. It uses a salt water cooling system. Refrigerant leaving the condenser must be a liquid, therefore, an amount of sub-cooling must be seen to cool the refrigerant sufficiently to ensure that no gas remains, sub-cooling is just cooling a substance into a sensible phase removing all latent heat
● Thermal Expansion Valve (TEV) – This is used to slow the flow rate of the refrigerant, thereby dramatically lowering the pressure and temperature to a now very cold, low pressure liquid. It is cold enough to absorb heat from the refrigerator room.
● Evaporator – Extremely cold refrigerant enters the evaporator as a low pressure, low temperature liquid. The refrigerant is then evaporated. Latent heat energy is absorbed from the room into the liquid refrigerant which changes it from a liquid into a gas. The refrigerant must exit the evaporator as a gas, any liquid carried over will damage the compressor. Superheating the gas guarantees no liquid carry over
Describe the shaft line? Shaft brake checks?
● The shaft line is broken up into 3 sections:
a) Tail shaft
b) Intermediate shaft
c) Thrust shaft
● First you have the Gear box which:
a) Transmit power from the prime mover to the shaft
b) Allow for variations in speed and power
c) Allow for changes between ahead and astern thrust
● Then the thrust block:
a) To absorb the forces by the action of the propeller and transmits it to the ship’s hull, so that the ship moves ahead/astern
● Plummer block:
b) Used to support the weight of the shaft, within the ship, without absorbing any thrust.
● Bulk head gland:
c) To maintain watertight integrity as the shaft passes through compartments, without absorbing any thrust
● Then we have another Plummer block
● Stern seal:
d) Maintains a water tight seal as the shaft passes through the ship’s hull
● Intermediate A bracket:
e) These brackets take no actual thrust but support the weight of the propeller shaft
● SKF Coupling:
f) Consists of an inner and outer sleeve which form an interference fit (inter-locking wedges) on both tail and intermediate shafts. The outer sleeve slides over the inner sleeve clamping the two shafts together. It allows for ease on removal if damage to the propeller
● Main A bracket
● Propeller
● Shaft brake checks are carried out whenever the brake is applied as there exists a danger of overheating/fire braking out due to friction, on application of the brake:
g) Ensure no fire risk exists
h) All brake pads are applied
i) The shaft is stationary
● On removal of the brake:
a) All pads are clear
b) No fire danger exists
c) The shaft is turning
Where are harmonic filters used
In the bus bar stage of the high voltage electrical distribution system
What do harmonic filters do
- Ensure the quality requirements of the power supplies
- smooth the sine wave of the voltage supply
- cooled via a dedicated air to water heat exchanger
- fed from the ships chilled water system
Name 3 types of shoring build and when would they be used?
● Acro Props ● EMMS damage repair clamp ● Dome and shore ● Strongbacks ● When there’s a threat to the water tight integrity
