Difference between Circuit Breaker and Fuse

Circuit breaker:
Has switching actions to close the circuit or to open the circuit, and
has a trip circuit if load current exceeds the set value.
After tripping, circuit breaker can be reused without replacing any part.

Fuses:
Have only breaking function, and fitted in the circuit to protect the circuit from damaging effect of high current flow.
It breaks the circuit by melting the fuse metal itself.
After breaking, the blown fuse must be renewed.

Actions carried out when Electrical Machines (Motor) flooded with Sea Water

When Electrical Machine is flooded with SW:

• Machine is disconnected from power sources and dismantled.
• All salt deposits washed out with FW.
• If deposited with oily bilge water, wash out with Electro Cleaner.
• Should be heated with lamp, and enclosed or covered up to retain the heat.
• Moisture should be escaped, by lifting the cover continuously or periodically.
• Hottest part of the machine shall not exceed 90°C, while heating.
• IR readings and temperatures taken regularly, until constant value reach about 1 m Ω.
• Then, spray the machine with insulation vanish.
• Assemble and put in service with low load, if possible.

Explain a Dashpot used as a Time Delay device in Over load trips

Dash pot:
Dashpots are fitted for overload trips to get time delay action, so that breaker will not be opened, due to momentary current surge.
When load current is in excess, it attracts plunger of the solenoid.
Plunger or piston moves up against the displacement of viscose oil or silicone fluid, through a small hole on the piston.
Time lag depends upon hole size, and viscosity of oil.
Load current setting for trip is about 25% above maximum, but should not exceed 50%.

Explain Shore connection onboard a ship with class requirements and regulations

Shore connection box is provided at convenient position, to receive shore power supply, so that ship’s generators can be shut down, in port or Dry Docking.

Lloyd’s Requirements:
Connection box contains a circuit breaker or isolating switch with fuses.
Provided full information of supply system, normal ship voltage and frequency for AC current.
Main Switchboard must be provided with a link switch or a circuit breaker, voltmeter, ammeter, and an indicator to show that the cable is energised.
For 3-phase supply with earth neutral, an earthing terminal must be provided, for connecting the hull to shore side.
A phase sequence indicator is necessary to ensure correct connections.
Means shall be provided for checking polarity, and terminals should be labelled.

What are Ship (Marine) Battery Room Safeties and Maintenance carried out

Battery room inspection and maintenance:
Battery installation and its charging rectifier checked.
Battery room environment must be dry and well ventilated.
Battery tops shall be clean and dry, and terminal nuts must be tight and a smear of petroleum jelly applied to prevent corrosion.
Electrolyte at proper level, and shall have correct value of specific gravity by checking with a hydrometer.
Rubber gloves and goggles used when handling electrolyte.
Charging equipment checked for dirt, overheating, loose connection and correct functioning of indicators.
Ventilation arrangement for battery locker checked. Battery installation of both lead acid and alkaline needs good ventilation.
Since both type generates hydrogen gas during charging, no smoking and naked light allowed.
Steel works and decks adjacent to lead acid battery, should be painted with acid proof paint.
[For Cad-Ni cell, alkaline resistance paints.]
Battery Room Safety Arrangement:

Safety is provided by:
Proper ventilation
Prevention of heat source for ignition.

Ventilation:
Independent exhaust fan provided.
Inlet duct should be below battery level, and outlet at top of the compartment.
Prevention of heat source for ignition:
No naked light and no smoking.
Uses of externally fitted light or flameproof light.
Cables of adequate size and they are well connected.
Never placed Emergency Switchboard in this room.
Use insulated spanner and plastic jug for distilled water, to prevent short-circuit.
Room temperature, maintained at 15 ~ 25°C.

MEO Class 4 E-Pariksha important numericals of Ship construction and MET

• Ship Construction
• Marine Electro Technology

Revised regulations (changes) of Marpol Annex V to prevent pollution by garbage from ship

Major changes have been made in the Annex V of Marpol, Regulation for the Prevention of Pollution by Garbage from ships,  which is effective from 1st January 2013. The only discharges allowed are allowed as per Marpol Annex V are listed separately for special area and outside special areas.

Outside Special Areas 
Comminuted or ground food waste (able to pass through a screen with openings no greater than 25mm) allowed at a distance more than 3NM from nearest land
food waste and cargo residues that are not harmful to the marine environmentat a distance greater than 12NM from nearest land
Cleaning agents which are not harmful to the marine environment (contained in cargo hold, deck and external surfaces wash water)
Animal carcasses

Inside Special Areas
Comminuted or ground food waste (specification as stated above) at a distance of 12Nm away from nearest land.
Cleaning agents which are not harmful to the marine environment (contained in deck and external surfaces wash water).

• Ship should be enrouted
• A Revised Garbage Record Book
• Every vessel of 100 GT and above or carrying 15 persons or more shall carry a Garbage Management Plan.
• Ships 12 metres in length or more and fixed or floating platforms are to display placards notifying crew and passengers of the MARPOL Annex V requirements.
• Discharges of any garbage from fixed or floating platforms and from any ship alongside or within 500m of a fixed or floating platform are prohibited

What are Oil Record Book (ORB) entries as per Marpol Annex 1 for ships

Every oil tanker of 150 tons gross tonnage and above and every ship of400 tons gross tonnage and above other than an oil tanker shall be provided with an Oil Record Book Part I and Every oil tanker of 150 tons gross tonnage and aboveshall also be provided with an Oil Record Book Part II


Entries for machinery space operations ORB part 1 (all ships):
(i) ballasting or cleaning of oil fuel tanks;
(ii) discharge of dirty ballast or cleaning water from tanks
(iii) disposal of oily residues (sludge);
(iv) discharge overboard or disposal otherwise of bilge water which has accumulated in machinery spaces
(v) Fuel oil bunker and bulk lube oil;

Entries for cargo/ballast operations ORB Part 2 (oil tankers):
(i) loading of oil cargo;
(ii) internal transfer of oil cargo during voyage;
(iii) unloading of oil cargo;
(iv) ballasting of cargo tanks and dedicated clean ballast tanks;
(v) cleaning of cargo tanks including crude oil washing;
(vi) discharge of ballast except from segregated ballast tanks;
(vii) discharge of water from slop tanks;
(viii) closing of all applicable valves or similar devices after slop tank discharge operations;
(ix) closing of valves necessary for isolation of dedicated clean ballast tanks from cargo and stripping lines after slop tank discharge operations;
(x) disposal of residues.

Marine engineering knowledge (Motor) MEK MCQ for MEO class 4 online questions for marine engineers in india

• Online question 1
• Online question 2
• Online question 3
• Online question 4
• Online question 5
• Online question 6

MEK Motor e pariksha online questions for class 4 engineers

1) Which of the following statements is true, about slow speed engines?
A.A scavenge fire can lead to a crankcase explosion
B.A scavenge fire can lead to deformation of diaphragm plate
C.A scavenge fire can lead to damage to tie rods.
D.All of the above.

2) When using low sulfur fuel oil for Emission Control Areas (ECA???S), ideally the TBN of the cylinder oil used should be:
A.Lower than normal
B.Higher than normal
C.Same as normal
D.Same as normal if the feed is kept higher

3) For a two stroke engine two o-rings are provided on the liner. The function of the top o-ring is to ___________ and function of the lower o-ring is to ____________
A.Seal jacket cooling water, act as secondary seal in case 1st o-ring leaks
B.Seal jacket cooling water, Seal scavenge air
C.Seal scavenge air, Seal Jacket cooling water
D.Seal combustion gases, Seal jacket cooling water

4) The coating which is provided on the valve stem of exhaust valves of modern marine diesel engines is of:
A.Nickel
B.Stellite
C.Chromium
D.Nimonic

5) If the combustion control system of an automatically fired auxiliary boiler fails to sustain burner ignition after a normal shutdown, you should check for a/an
A.faulty photocell detector
B.low steam pressure
C.high voltage on the ignition electrode
D.open air damper

6) What do you mean by surge limit of a turbocharger ?
A.Characteristic curve of a turbocharger
B.Portion of compressor characteristic curve which lies on the left side of the point of maximum pressure
C.A line joining all the points of maximum pressure on compressor characteristic curves , drawn at various speeds of operation
D.Maximum rpm limit of T/C above which surging will start

7) A large, low-speed, main propulsion diesel engine uses sea water to directly cool the
A.cylinder heads
B.exhaust valves
C.scavenging air
D.injectors

8) Exhaust Grouping is required in case of ______________ turbocharging in order to _____________________
A.Constant pressure , prevents shockwave generation
B.Pulse pressure , prevent interference with scavenging of other cylinders
C.Constant pressure, prevent interference with scavenging of other cylinders
D.Pulse pressure , prevents shockwave generation

9) Function of a de-superheater is to :
A.Protect superheater from overheat
B.Control superheater steam outlet temperature
C.Increase the efficiency of the boiler
D.Reduce steam temperature for auxiliary uses after steam superheater

10) Which of the following statements is false?
A.Oxidation of lubricant leads to decrease in its viscosity
B.Formation of oxidation acids, sulfuric acid leads to depletion of TBN of lubricant
C.Contamination with water will lead to decrease in the load carrying capacity of a lubricant .
D.Build up of insolubles will lead to increase in viscosity of a lubricant

11) Which of the following conditions is responsible for the fuel oil to atomize when using a steam atomizer in anauxiliary boiler?
A.Expansion of the steam in the furnace.
B.Expansion of the steam in the whirling chamber.
C.Expansion of the steam in the orifice plate.
D.All of the above.

12) After prolonged operation, jerk type fuel pumps wear on the top edge of plunger and edges of spill ports and helix due to erosion by high pressure fuel as it spills. This wear would result in _________________
A.Late start of injection and early end of injection
B.Early start of injection and late end of injection
C.Early start of injection and early end of injection
D.Late start of injection and late end of injection

13) It is a known fact that centrifugal pumps require priming for pumping liquids , as they cannot handle air and will lose suction due to air entry . But on the other hand T/Cs use centrifugal
compressors for supercharging . Which of the following do you think makes a centrifugal compressors to pump air and behave differently than the centrifugal pumps?
A.Presence of air cooler
B.Presence of Labyrinth seal
C.High speed of rotation , very fine internal clearences and large impeller diameters
D.Difference in principle of operation

14) If an operating auxiliary boiler has a water pH reading of 7, you should
A.bottom blow the boiler
B.treat the water with caustic soda
C.treat the water with chemical scavengers
D.reduce the water alkalinity to recommended readings

15) Even if there is an oil mist concentration inside a crankcase, and there is also a hot spot, crankcase explosion will only take place when_________________
A.The hot spot provides the ignition temperature for the oil mist concentration
B.When the oil mist - air mixture is in the flammable range
C.Both A and B
D.None of the abov

16) In case of 2-stroke marine diesel engines, the top part of the liner forming the combustion chamber experiences very high pressure induced mechanical stresses as well as high thermal stresses. Which of the following is a correctly designed liner for catering both the above stresses ?
A.Thick top portion with jacket cooling to take care of both the high mechanical and thermal stresses
B.Thick top portion to take care of high mechanical stresses while bore cooling to reduce thermal gradients
C.Thin top portion to reduce thermal gradients and hence thermal stresses while supporting ribs to take care of mechanical stresses
D.Thick top portion to take care of high mechanical stresses with jacket cooling combined with allowance for thermal expansion to minimize the thermal stresses

17) Which of these fuel oil impurities can cause maximum abrasive damage?
A.Water
B.Ash
C.Catalytic fines
D.Sodium

18) Steam temperature control for the ESD boiler is achieved by :
A.Fitting a de-superheater between 1st & 2nd passes of superheater
B.Fitting an attemperator between 1st & 2nd passes of superheater
C.Bypassing the superheater
D.Gas dampers in boiler uptake

19) Irregular circumferential wear of liner due to diminishing neutralizing capacity of cylinder oil away from lubricating holes is known as:
A.Micro seizure
B.Scuffing
C.Scoring
D.Clover leafing

20) Which of the following is a reasonable statement about water washing of turbine side of a T/C ?
A.It leads to thermal shock and reduces the life of the T/C
B.It leads to thermal shock and not so effective as solid washing
C.If properly carried out keeping rpm , load ,temperature limits & other factors into account , it is quite safe and more effective than solid washing
D.It should never be carried out as most of the engine manufacturers recommend against the same