Explain how to check the insulation resistance of a motor, stating the minimum satisfactory value
Firstly ensure the motor is isolated from any electrical supply and prove dead. For an insulation resistance test you will need a meggar tester and test your test voltage based on the rated operating voltage of the motor (500 V DC). I would test the resistance between the windings U-V, V-W, W-U, as well as between each winding (U, V, W) and earth (ground). You should receive a resistance value in megaohm. The minimum satisfactory value is 1 megaohm
Safety precautions when working in battery room ?
- Never use lead acid battery maintenance gear (e.g. Hydrometer, topping up bottles, syringes) on an alkaline battery incase of contamination of the electrolyte
- Ensue the area is ventilated to prevent accumulation of dangerous gases (exhaust fan running, ventilation flap open & door is left open)
- No naked flames or smoking
- When carrying out weekly maintenance (e.g. when using a hydrometer to check its specific gravity) wear appropriate battery maintenance PPE. Batteries should always be transported in the upright position to avoid spillage of electrolyte. Wear rubber gloves, eye goggles and a protective apron
What is the purpose of electrical motors on board ( 3-phase AC induction)
They are used to transform electrical energy into mechanical energy to drive shipboard equipment such as pumps, air-con units and engine room fans.
Motor maintenance requirements
• Regular cleaning of the stator housing using a clean, damp cloth will help prevent any excessive build-up of dust which could cause overheating.
• Ensure bearings are properly lubricated (check lubrication chart and OEM manual)
• Regular insulation resistance testing/ meggar testing (1 megaohm is the lowest satisfactory value) to ensure windings aren’t damaged
• Continuity test done every 3 months to ensures that the phase windings are continuous (electrically complete and unbroken)
• Electrical connections are clean and tight with no defects to insulation on cables
Battery maintenance
• Check the condition of all cable and battery terminals, any damage to insulation or damage/ cracks on the body
• Check for signs of oxidisation and apply a layer of petroleum jelly to prevent this
• Using a hydrometer you can check the specific Gravity (SG) level, SG shows how much charge is in the battery
what would you do if you found someone who has had an electrical shock
• Raise the alarm and call for help
• An electrically insulated hook can be used to pull them away from the source
• Proceed with DR ABC (Danger, Response, Airways, Breathing, Circulation)
• Danger - check the surroundings are clear to enter, identify the source & isolate only if safe to do so
• Response - Check if casualty is responsive to voice
• Airways - Check his airways are not restricted
• Breathing - Check he is breathing & carry out CPR (get a member of crew to get a de-fib)
• Circulation - check blood circulation, continue CPR & De-fib in rotation until emergency services have arrived
On large motors why is it better to have a star delta starter than a direct online ?
Direct-On-Line (DOL) starting applies full voltage to the motor immediately, meaning it’s going to take a lot of current to get the rotor moving, resulting in high starting current, which can lead to voltage dips.
By utilising a star delta starter the motor starts in star (Y) and changes to delta (Δ), this initially reduces the voltage applied to the motor to limit starting current, thus preventing voltage dips and possible trips. Basically preventing lots of overcurrent at once.
How would you put a generator on a dead board ?
If the board is dead, then there is nothing to ‘sync’ to. I would have to override the controls by means of an override switch, which you hold in the override posting while pressing the breaker close button on the running generator.
When would you use a star delta starting method
You would use it with big motors, to start it in 2 steps (star & delta) as apposed to one big step (direct online) causing a large overcurrent at the start which can lead to voltage dips. For instance when u have a motor that is repeatedly tripping after resetting breakers, it’s because the windings are already hot due to overcurrent.
Emergency generator Solas requirements
• Must start automatically within 45 seconds of a main power failure, providing power to critical systems.
• Must be installed above the uppermost continuous deck, aft of the collision bulkhead.
• Independent fuel tank must contain enough fuel for the full 18/36-hour operational period, with a low-level alarm provided.
• Starting Arrangement: Must have two independent starting sources, with the primary capable of 3 consecutive starts, and a second source offering 3 additional starts within 30 minutes.
What are multimeters used for ?
Multimeters are used to measure AC/DC voltage, current & continuity
What indicates reverse power occurring ?
• A reverse power relay Alarm/trip
• Wattmeter significant drop on generator, KW drops to 0. This indicates power is flowing into the generator causing it to act as a motor
MCA guidance/Regulations regarding lithium ion batteries
• Lithium ion batteries should be kept in a secure environment
• There should be fire detection systems fitted
• Fixed fire fighting systems should be installed
• They should have their own box so incase of a fire it is contained
• Seek a checklist/plan regarding the fire
What to do in the event of a black out/ loss of power
• Inform the C/E & engine team
• The emergency generator should kick in within 45 secs as per Solas requirement
• If it fails you may need someone to take over the watch while you head up and try one of the back up starting methods
• With emergency power established it’s all about trying to regain main power
• Start fuel, pre lube & cooling water pumps and connect a main generator to the main switchboard to regain main power
• Then we can shut the emergency generator down and close the tie breaker between emergency s/b and the main s/b so that your main generator can supply everything again
• As watchkeeper I would focus on maintaining essential services such
• Carry out any orders from C/E
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Crankcase & OMD9
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Boiler2
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Main & Auxilairy Systems Questions36
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Watchkeeping2
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Sketch And Describe Questions1
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Electrical14
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Pump Questions3
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Safety Procedures5
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Regulations9
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Ship Particulars/ Questions Asked At The Start2
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Air Compressors/ Start Air4
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Seering Gear3
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Ship Construction3
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Stability2
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Bilge Injection Valve2
