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Mechanical Theory > Theory 3 > Flashcards

Theory 3 Flashcards

1
Q

Advantages of HP air

A

Easily distributed through the ship
Can be easily stored
Flexibility and reliability of use
Low risk of fire

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2
Q

2 Categories of HP air

A

HP air operating at 276 bar

Reduced HP air operating below 276 bar as required by specific equipment

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3
Q

2 areas of HP air

A

IMS (inside machinery space)

OMS (outside machinery space)

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4
Q

Uses for HP air

A 
Diesel generator starting
GT starting
Ship siren operating
Breathing apparatus charging
Weapons system operation
Hydraulic system accumulator charging
Air driven machinery charging
Cross-connection to low pressure air system (276-8 bar)
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5
Q

Air compression 4 stages

A

Stage 1 - 4 bar
Stage 2 - 17.5 bar
Stage 3 - 68 bar
Stage 4 - 276 bar

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6
Q

How often do HPAC drains operate?

A

Every 30 min

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7
Q

What value is the pressure relief in each stage of air compression?

A

10%

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8
Q

Uses of LP air?

A

Pneumatic tools
Radar waveguides
Emergency stern seal inflation
Pneumatic surveillance panels

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9
Q

Stage relief valves values of HP air

A

1st PRV - 4.4 bar
2nd PRV - 19.25 bar
3rd PRV - 74.9 bar
4th PRV - 303.6 bar

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10
Q

Safety PPE when using HP and LP air

A

Ear defenders

Goggles

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11
Q

Explain dieseling and precaution taken

A

Dieseling is the combustion of mixture of HP air and fuel/oil/oil based grease. Prevented by using silicon grease (synthetic).

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12
Q

Flexible hoses safety precautions

A

Hoses must be “whipped” (bound and tied) to secure both ends and prevent “flailing”.
Hoses are “lifed” - fitted with an expiry date.

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13
Q

Safe working practice when filling air bottles

A

Bottles must be located in purpose built rack.
Operators must wear PPE (goggles and ear defenders).
Hoses must be in good condition and fitted with the correct spanner.
A good condition “O” seal must be used.
Bottles should be filled slowly to avoid overheating.

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14
Q

HPSW pressure

A

7 bar

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15
Q

HPSWM system configuration (water flow)

A

Sucked in from the sea by an electrically driven pump and passes through a strainer. Connected to the ring main using a riser. Ring main runs around 2 deck.

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16
Q

What maintains HPSWM pressure?

A

Relief valves and 10% leak off valves

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17
Q

Uses of HPSW

A 
Fire fighting
Cooling auxiliary machinery
Pre Wet
Fitted bilge and salvage eductors
Emergency cooling to main propulsion (GT and diesel engines)
Making fresh water
Flushing heads
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18
Q

When can SW pumps be operated?

A

Locally (pump control box) and remotely (SCC or machinery control room MCR)

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19
Q

Where are fixed sprays located?

A

Inflam store
Paint lockers
Magazines
Funnel

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20
Q

DC State 1

A

Individual HPSW pumps supply their own section of the ring main. The ring main is isolated by shutting DC State 1 valves to minimise effects from HPSWM damage.

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21
Q

DC State 3

A

At least one pump is running, supplying the whole system. All DC State 1 valves are open. If pressure drops, another pump can be turned on to maintain the pressure.

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22
Q

Why is FW used in cooling systems?

A

Machinery is susceptible to SW corrosion.

Other equipment can be compromised by SW contamination e.g. GT, fuel systems and electric motors.

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23
Q

Problems caused by absence of machinery cooling

A

Fire hazard
Equipment failure
Seizing
Wiping bearings

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24
Q

White Metal melting temperature

A

115 degrees C

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25
Q

Machinery supplied by main propulsion cooling system

A

Lub oil heat exchanger
GT heat exchanger
CPP system heat exchanger
Plummer block heat exchanger

26
Q

Why might a cross connection be made with the opposite side in a cooling system?

A

To allow for strainer maintenance.

27
Q

Machinery supplied by auxiliary machinery cooling system

A

ACP (air conditioning plants)

Diesel generators

28
Q

Explain the circumstances in which the FW and SW cooling systems may be cross connected

A

In an emergency, such as failure of the FW pump. Can only be cross connected with the MEO’s permission.

29
Q

Discharge of water within 12NM of land

A

The oil content is the discharged water is no more than 15ppm.
The ship is underway.
The ship has in operation an oily water separating filter with an oil discharge monitoring and control system.

30
Q

Discharge of water more than 12NM from land

A

Oil content is no more than 15ppm.
The ship is underway.
The ship has in operation an approved oil filtering system.

31
Q

Special Areas as defined by IMO

A 
Baltic Sea
North West European Waters
Mediterranean Sea
Black Sea
Gulf
Gulf of Aden
Caribbean
32
Q

Sources of contamination

A

Bilges
Fuel systems
Oil systems
CPP systems

33
Q

Steps taken to minimise risk of oil entering bilge

A

Keep machinery spotless
Monitor lub oil ready use tank and investigate any losses
No surfactants (chemicals) to be used - Kleen break only
AFFF only used in real fire risk situations
Eductors to be manned at all times when in use
Maximise use of shoreside facilities when alongside

34
Q

Who must be informed of MARPOL incident?

A

MEOOD/MEOOW

35
Q

Black water sources

A 
Heads
Urinals
WC Scuppers
Medical compartments
Any water mixed with this waste
36
Q

Black water discharge regulations

A

Within 4NM of land - Discharge is only permitted if an IMO approved STP is in operation.
4-12NM - Discharge is only permitted if an IMO system to comminute and disinfect the sewage is in operation.
More than 12NM - No treatment necessary.

37
Q

Grey water sources

A 
Bathrooms
Galleys
Dishwashers
Laundries
Sinks
38
Q

Grey water regulations

A

No regulations when at sea, only when entering/leaving port and alongside.

39
Q

Why is VPS (Vacuum Pumping System) used?

A

Has less moving parts.

40
Q

What is VPS made up of?

A

Diesel or electric pumps, manifolds and hoses.

41
Q

Bilge definition

A

Spillage, leakage and condensation that accumulates at the bottom of the ship’s hull.

42
Q

Sullage definition

A

The left over fluids/sludge after the bilge water has been passed through a separator.

43
Q

Bilge and Salvage eductors

A

Eductors are used to remove quantities of fluid, generally oil/fuel/water, from the bilges very quickly. Excess liquid builds up in the bilges because of leaks, overflows and machinery discharges, and also because of scrubbing down and washing through.

44
Q

Bilge System

A

A bilge system is fitted to remove excess fluid from machinery space bilges to separate water from oil and discharge oil to sullage tanks by means of an oily water separator, with the water being discharged over board.

45
Q

Sullage System

A

The sullage system is designed to retain dirty or waste oil/fuel until it can be properly discharged ashore. The discharge from the bilge system is directed to the tanks of the sullage system or overboard when it does not contain oil/fuel and complies with current MARPOL regulations.

46
Q

Steps taken to operate eductors

A

Open the DOB (Discharge Over Board) valves
Open the motive valves supplied from the HPSWM
Open the bilge suction valves

47
Q

Raw sewage discharge

A

Raw sewage discharge causes health hazards and aesthetic problems along coastlines and beaches.

48
Q

Health hazards from raw sewage

A

Hepatitis
Gastro-Enteritis
Typhoid

49
Q

Advantages of using STP

A

Fewer side ship openings
Allows the ship to operate in non-pollution areas
Easier to shut down in CBRN environments
Simplify pipe runs
Heads and bathrooms can be lower down in the ship
Heads and bathrooms can be used in dry dock

50
Q

Operation of a STP

A 
Raw sewage (Black Water), via a macerator, enters the coarse screen.  This removes large particles.  The waste then enters the aeration compartment.  The aeration diffuser passes oxygen through the waste.  Undigested waste sinks to the bottom, digested waste floats above, starting to separate.  The air lift pump transfers digested waste into the settlement hopper where heavy sludge will sink to the bottom and a clear liquid (effluent) floats on top.  The effluent weirs across into the chlorine contact tank and then weirs across again to the collection tank.  (effluent is disinfected by the chlorine).
Grey water is added to the collection tank which dilutes the high chlorine concentration, but also disinfecting the grey water.  This is now clean enough to discharge over board.
Sludge from the bottom of the settlement hopper is returned to the aeration compartment via an air lift pump.
51
Q

What causes anaerobic digestion?

A

Failure of air supply

52
Q

What is the purpose of micro-organisms in a STP?

A

Micro-organisms break down sewage to form a clear “effluent”. They produce a top layer of scum what we call “activated floc”.

53
Q

How long can a Collect, Hold and Transfer (CHT) store sewage for?

A

12 Days

54
Q

How is sewage collected in a CHT?

A

A vacuum draws the sewage from the WC pans, through pipes, to the collection tanks.

55
Q

What is the flow of sewage in a CHT system?

A

The sewage is collected in a collection tank after being vacuumed in. A discharge/transfer pump will transfer it to large holding tanks after about a day.

56
Q

What use is the VPS alongside?

A

Used to pump sewage and grey water through hoses to be collected in a bowser/tanker. The sewage and grey water hoses must be kept separate to avoid contamination.

57
Q

Who carries out removal of sewage via VPS?

A

As a rule, if in port for less than 72 hours local contractors may be employed to perform this duty. If over 72 hours in port and the crew will carry out this duty. This will normally take a team of 20 personnel, taken from all sections, approximately 3 hrs. It is organised by the ME section and is supervised by the Hull SR.

58
Q

Hazards involved with STP and CHT

A

Dangerous chemicals – eg calcium hypochlorite
Raw sewage – typhoid, hepatitis etc
Dangerous gasses – hydrogen sulphide (H2S) and methane

59
Q

What precautions are taken to avoid H2S?

A

H2S monitor is always used when working with/around a STP or CHT.

60
Q

H2S concentration levels

A

0.03ppm - detectable by odour (rotten eggs)
400-700ppm - dangerous, may result in severe injury or death; coughing, collapse, unconsciousness, breathing will stop unless given artificial respiration immediately
700-1000ppm - immediate threat to life
+1000ppm - immediate unconsciousness resulting in death

Mechanical Theory (1 decks)

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