Auxiliary Systems

Question 1

Usual pressure in a deaerator?

Answer 1

0.5 bar

Question 2

What is the purpose of a de-aerator?

Answer 2

Removing trapped oxygen and CO2, as they can lead to corrosion and hinder heat transfer as the heat transfer coefficient of air is less than water.

Question 3

Where would the deaerator be located?

Answer 3

At the hottest point in the system, where the water leaves the heater or enters the cooler.

This is to give the gas more kinetic energy to allow for quicker release.

Question 4

What are the causes of a starting air line explosion on ships?

Answer 4

1) Leaking start air valve or jamming at open position.
2) Oil discharged from compressor may deposit a thin film on the internal surfaces of the pipes but not ready for combustion.
3) Hot gas or flame may enter the manifold, vaporise the oil and set fire.
4) High pressure start air coming into contact with this may cause an explosion.

Question 5

How would you prevent a start air explosion?

Answer 5

1) Regular overhaul and maintenance of starting air valve.
2) Test air start valve leakage.
3) Regularly drain off the air bottles.
4) Regularly drain off the air start system.
5) Regularly clean the compressor suction air filter and use an oil wetted suction filter.
6) Feed the minimum cylinder lubrication to compressor.

Question 6

What are the safety devices on the start air line?

Answer 6

1) Safety valve.
2) Bursting disc.
3) Flame trap.
4) Starting air line drain valve.
5) Turning gear interlock.
6) Reversing interlock.

Question 7

What are the 3 main safeties on air compressors?

Answer 7

1) Relief valves - After each stage of the compressor to release excess pressure when the pressure rises above the set value.
2) Bursting disc - Copper disc fitted in the water space of the coolers. If the tube fails, it will burst at a pre-determined pressure and release it.
3) Fusible plug - Fitted to the air receiver so in the event of a fire near the air receiver it will cause the core to melt and release the air.

Question 8

What are the air compressor trips?

Answer 8

1) Lube oil low pressure.
2) Water temperature high.
3) Water no flow.
4) Motor overload.

Question 9

What are the main defects with air receivers?

Answer 9

1) Defective safety valve.
2) High levels of condensate - corrosion and over cycling of compressor.
3) Blocked drain valve.
4) High oil content.
5) No clear indication of the safe working pressure on receiver.

Question 10

What is a running direction interlock?

Answer 10

It is a blocking device that ensures the engine is only started or reversed when some conditions are satisfied.

Prevents the injection of fuel to the engine when the telegraph does not synchronise with the running direction of the engine.

Question 11

What is a turning gear interlock?

Answer 11

Prevents the admission of starting air to the engine cylinders when the turning gear is engaged.

Necessary to prevent the turning gear and motor flying off and puncturing the bulkhead.

Question 12

How do you check the efficiency on air compressors?

Answer 12

Time how long it takes for the receivers to fill.

Question 13

What checks would you perform on the air compressor?

Answer 13

1) Pressure gauges for lube oil and water.
2) Abnormal sounds like knocking.
3) Lube oil or water leakages.
4) Check lubrication sight glass.
5) Check if discharge pressure is normal.
6) Check air temperature in final stage is under limit.
7) Check the flow of cooling water from sight glass.
8) Check free rotation of cooling water pump.
9) Check the relief valves for leakage.
10) Condensate drain function.
11) Compressor is in automatic.

Question 14

What is the purpose of an intercooler on the air compressor?

Answer 14

To cool the air before the next stage of compression, as a higher density of cool air makes it easier to compress than hot air.

Question 15

What maintenance would you carry out on an air compressor?

Answer 15

1) Lube oil change.
2) LP and HP valve overhaul.
3) Replacing lube oil filter.
4) Change air filter.
5) Clean coolers.

Question 16

What interval checks are covered in the manual for an air compressor?

Answer 16

1) Bedplate bolts.
2) LP and HP valves.
3) Cylinder.
4) Pipe connections.
5) Big end bearings.
6) Piston and cylinder walls.
7) Flexible coupling.
8) Safety valves.
9) Main bearings.
10) Piston, gudgeon pin and rings and gudgeon pin bearings.
11) LO pump.

Question 17

What is clearance in an air compressor?

Answer 17

The space between the piston crown and the cylinder head in order to stop the piston striking the compressor head.

Question 18

What is an unloader in an air compressor?

Answer 18

An unloader uses solenoid or pneumatic control to release pressure during the starting of the compressor to reduce loading of the compressor due to high start up currents.

Question 19

What is the purpose of a viscotherm?

Answer 19

To measure the viscosity of fuel oil at the fuel injection system.

Question 20

What is viscosity a measure of?

Answer 20

The internal friction of a fluid, the thickness, its ability to pour.

Question 21

What checks would you perform on a FO purifier?

Answer 21

1) Abnormal sounds or vibration.
2) Inlet and outlet fuel pressures.
3) Sludge discharge is not open in normal operation.
4) Proper ejection occurs.
5) Feed water correct pressure.
6) Leakage.
7) Sump oil level.
8) Motor overheating.
9) Product temperature.
10) Solenoid valve operation.
11) Break is disengaged.
12) Belt movement

Question 22

How much capacity must a service tank have? What regulation details it.

Answer 22

Two fuel oil service tanks for each type of fuel used on board necessary for propulsion and vital systems or equivalent arrangements shall be provided on each new ship, with a capacity of at least 8 h at maximum continuous rating of the propulsion plant and normal operating load at sea of the generator plant.

SOLAS II-1/26.11

Due to the maximum UMS time being 8 hours.

Question 23

What is the start-up procedure for a FWG?

Answer 23

1) Close the vent cock.
2) Open the ejector pump valve and sea water discharge valve.
3) Start the pump, slowly opening the ejector outlet.
4) Check the inlet pressure on the ejector is 4 bar or above.
5) Check the condenser air outlet valve is functioning correctly.
6) Open the feed water valve to 0.4-0.6 bar.
7) Start chemical injection if applicable.
8) Check vacuum is at 0.9 bar.
9) Slowly open hot water to fully open.
10) Close hot water bypass to adjust flow rate.
11) Switch on salinity indicator.
12) Check the distillate is visible through the sight glass.
12) Start the distillate pump, adjusting pressure to 1.4-2.2 bar.
13) Monitor the generating capacity with flowmeter over 30 minutes to ensure proper generating capacity.

Question 24

What is the shutdown procedure for a FWG?

Answer 24

1) Open fully the hot water bypass.
2) Close fully the hot water outlet valve.
3) Close the hot water inlet valve.
4) Stop the distillate pump by closing the outlet valve.
5) Cool down the heater by running ejector pump for 30 minutes to supply feed water to the heater.
6) Stop chemical injection.
7) Switch off salinometer.
8) Stope ejector pump and open air vent.
9) Close the overboard valve.
10) Close the valve to the tank

Question 25

Checks on FWG before starting?

Answer 25

1) Ship is not in congested water, canals, and is 20NM away from shore.
2) Jacket water is at sufficient temperature.
3) Drain valve is closed.
4) Shell is in good condition and fully enclosed.
5) Sea water suction is not blocked.

Question 26

How does a flash evaporator work?

Answer 26

1) Sea water is heated to give it a reasonable amount of sensible heat and particular pressure.
2) This is admitted into a chamber at lower pressure which ‘flashes’ turning into steam.
3) There can be multiple chambers at gradually lower pressures, meaning a small fraction of brine water boils at each stage.

Because the phase change does not take place on a plate or tube surface, they are virtually scale free and can operate for up to a year without acid cleaning.

Question 27

How does RO work?

Answer 27

1) High pressure sea water (60 bar) is ‘pushed’ through a partially permeable membrane to remove ions, unwanted molecules and larger particles.
2) This demineralises seawater making it corrosive to lines and undrinkable.

Question 28

What are the water disinfection methods?

Answer 28

1) Neutralisation - To sterilise the water, sodium bicarbonate is added to stop CO2 activity and leave a film on lines and tanks to protect against corrosion.
2) Chlorination - Kill disease carrying organisms in the water.
3) Filtration - Using carbon filters or gravel beds to produce clean water.
4) De-chlorination - Using carbon bed filters to absorb excess chlorine.
5) Electro-Katadyn - Silver ion injection.
6) UV - Sterilisation using short-wave UV rays to kill micro-organisms by disrupting their DNA rendering them harmless.

Question 29

What is the purpose of an ejector and what is its working principle?

Answer 29

Used to maintain a vacuum within the shell and removes brine from the lower part of the shell.

Based upon Venturi effect that shows the reduction in fluid pressure when it flows through a choked section of pipe.

Bernoulli’s Principle states that the fluid’s velocity must increase as it passes where its pressure must decrease.

Question 30

What regulation speaks to how quick a steering gear must move?

Answer 30

SOLAS Chapter II-1 Regulation 29

Must be capable of going 35 to 35 at deepest seagoing draught at maximum service speed.

35 to 30 in 28s.

Question 31

How does a 4-ram steering gear work?

Answer 31

A tiller with two arms is keyed to the rudder stock, which is then connected at each end through swivel blocks (Rapson’s slide) to the pistons of the rams.

The rams operate diagonally by pushing hydraulic oil through two and creating suction in the other two.

Oil pressure varies between 100-175 bar depending on the size of the rudder, with two pumps and one in standby.

In emergencies the use of only 2 rams can be permitted.

Question 32

What tests and checks should you do on the steering gear and what regulation dictates this?

Answer 32

SOLAS Chapter V Regulation 26: Testing and Drills

Within 12 hours of departure:
1) Full movement of rudder according to the required capabilities of steering gear.
2) Visual inspection of steering gear and connected linkage.
3) Operation of communication between bridge and steering gear compartment.

Question 33

How does a rotary vane steering gear system work?

Answer 33

1) Oil is supplied under pressure from the pump to one of the sizes of the rotor moving vanes, with the suction side of the pump connected to the other side.
2) This pressure differential causes rotational movement.
3) To rotate in the opposite direction the discharge and suction are swapped around.

Question 34

What tests must be carried out within 12 hours prior to ship departure?

Answer 34

1) Main steering gear and system.
2) Auxiliary steering gear and system.
3) Remote control systems of steering gear.
4) Steering position indicator on bridge.
5) Emergency power supply to one of the steering units.
6) Rudder angle indicators showing actual rudder position.
7) Power failure alarms for remote steering gear control system.
8) Power unit failure alarms for steering gear unit.
9) Automatic isolating arrangements and other automatic equipment.

Question 35

What are you checking in the steering flat?

Answer 35

1) Machinery including motors, leakages from rams, seals and pipes.
2) Oil leaks from the rams should be reported to 1/E who will decide when to tighten the glands.

Question 36

What are you checking in the steering flat?

Answer 36

1) Machinery including motors, leakages from rams, seals and pipes.
2) Oil leaks from the rams should be reported to 1/E who will decide when to tighten the glands.
3) Check for tightness of linkages.
4) Check water level in bilges.
5) Check emergency fire pump for leakage.
6) Check lashings of drums of oil, paint and chemicals.

Question 37

What is the minimum temperature of the incinerator furnace and what regulation dictates this?

Answer 37

MARPOL Annex VI Regulation 16

No waste shall be fed into the combustion chamber until the gas outlet temperature is above 850 degrees.

Should reach 600 degrees within 5-minutes of start-up.

Question 38

Why are their temperature restrictions on incinerators and where can they not be used?

Answer 38

To ensure minimum black smoke is emitted at the time of starting due to incomplete combustion.

Must not be used at ports, harbours or estuaries.

Question 39

What records should be made after incineration, in what log and what regulation dictates this?

Answer 39

MARPOL Annex V Regulation 10

Garbage Record Book

1) Date and time at start and stop.
2) Position of ship at start and stop.
3) Categories of garbage incinerated.
4) Estimated amount incinerated in cubic metres.
5) Signature of officer in charge of operation.

Question 40

What deck equipment did you have on board?

Answer 40

1) Windlass
2) Anchor
3) Chain locker

Question 41

What are the dangers associated with chain lockers?

Answer 41

The metal starts to rust which is oxidisation, using up the oxygen in the space making it deadly for entry.

Question 42

What is the purpose of wear rings on a pump?

Answer 42

Seal the HP and LP sides of the pump.

Question 43

What is TC surging?

Answer 43

When the outlet pressure from the compressor wheels drops due to loss of air flow from the engine.

As the pressure it was previously delivering is greater than what it can now supply it creates a back pressure which drives the compressor the other way causing significant audible vibrations.

Question 44

Why do we close the discharge valve before starting a centrifugal pump?

Answer 44

The starting current will be reduced as there is no discharge head and minimum resistance to the pump.