Theory 3 Flashcards
Advantages of HP air
Easily distributed through the ship
Can be easily stored
Flexibility and reliability of use
Low risk of fire
2 Categories of HP air
HP air operating at 276 bar
Reduced HP air operating below 276 bar as required by specific equipment
2 areas of HP air
IMS (inside machinery space)
OMS (outside machinery space)
Uses for HP air
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)
Air compression 4 stages
Stage 1 - 4 bar
Stage 2 - 17.5 bar
Stage 3 - 68 bar
Stage 4 - 276 bar
How often do HPAC drains operate?
Every 30 min
What value is the pressure relief in each stage of air compression?
10%
Uses of LP air?
Pneumatic tools
Radar waveguides
Emergency stern seal inflation
Pneumatic surveillance panels
Stage relief valves values of HP air
1st PRV - 4.4 bar
2nd PRV - 19.25 bar
3rd PRV - 74.9 bar
4th PRV - 303.6 bar
Safety PPE when using HP and LP air
Ear defenders
Goggles
Explain dieseling and precaution taken
Dieseling is the combustion of mixture of HP air and fuel/oil/oil based grease. Prevented by using silicon grease (synthetic).
Flexible hoses safety precautions
Hoses must be “whipped” (bound and tied) to secure both ends and prevent “flailing”.
Hoses are “lifed” - fitted with an expiry date.
Safe working practice when filling air bottles
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.
HPSW pressure
7 bar
HPSWM system configuration (water flow)
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.
What maintains HPSWM pressure?
Relief valves and 10% leak off valves
Uses of HPSW
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
When can SW pumps be operated?
Locally (pump control box) and remotely (SCC or machinery control room MCR)
Where are fixed sprays located?
Inflam store
Paint lockers
Magazines
Funnel
DC State 1
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.
DC State 3
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.
Why is FW used in cooling systems?
Machinery is susceptible to SW corrosion.
Other equipment can be compromised by SW contamination e.g. GT, fuel systems and electric motors.
Problems caused by absence of machinery cooling
Fire hazard
Equipment failure
Seizing
Wiping bearings
White Metal melting temperature
115 degrees C
Machinery supplied by main propulsion cooling system
Lub oil heat exchanger
GT heat exchanger
CPP system heat exchanger
Plummer block heat exchanger
Why might a cross connection be made with the opposite side in a cooling system?
To allow for strainer maintenance.
Machinery supplied by auxiliary machinery cooling system
ACP (air conditioning plants)
Diesel generators
Explain the circumstances in which the FW and SW cooling systems may be cross connected
In an emergency, such as failure of the FW pump. Can only be cross connected with the MEO’s permission.
Discharge of water within 12NM of land
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.
Discharge of water more than 12NM from land
Oil content is no more than 15ppm.
The ship is underway.
The ship has in operation an approved oil filtering system.
Special Areas as defined by IMO
Baltic Sea North West European Waters Mediterranean Sea Black Sea Gulf Gulf of Aden Caribbean
Sources of contamination
Bilges
Fuel systems
Oil systems
CPP systems
Steps taken to minimise risk of oil entering bilge
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
Who must be informed of MARPOL incident?
MEOOD/MEOOW
Black water sources
Heads Urinals WC Scuppers Medical compartments Any water mixed with this waste
Black water discharge regulations
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.
Grey water sources
Bathrooms Galleys Dishwashers Laundries Sinks
Grey water regulations
No regulations when at sea, only when entering/leaving port and alongside.
Why is VPS (Vacuum Pumping System) used?
Has less moving parts.
What is VPS made up of?
Diesel or electric pumps, manifolds and hoses.
Bilge definition
Spillage, leakage and condensation that accumulates at the bottom of the ship’s hull.
Sullage definition
The left over fluids/sludge after the bilge water has been passed through a separator.
Bilge and Salvage eductors
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.
Bilge System
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.
Sullage System
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.
Steps taken to operate eductors
Open the DOB (Discharge Over Board) valves
Open the motive valves supplied from the HPSWM
Open the bilge suction valves
Raw sewage discharge
Raw sewage discharge causes health hazards and aesthetic problems along coastlines and beaches.
Health hazards from raw sewage
Hepatitis
Gastro-Enteritis
Typhoid
Advantages of using STP
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
Operation of a STP
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.
What causes anaerobic digestion?
Failure of air supply
What is the purpose of micro-organisms in a STP?
Micro-organisms break down sewage to form a clear “effluent”. They produce a top layer of scum what we call “activated floc”.
How long can a Collect, Hold and Transfer (CHT) store sewage for?
12 Days
How is sewage collected in a CHT?
A vacuum draws the sewage from the WC pans, through pipes, to the collection tanks.
What is the flow of sewage in a CHT system?
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.
What use is the VPS alongside?
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.
Who carries out removal of sewage via VPS?
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.
Hazards involved with STP and CHT
Dangerous chemicals – eg calcium hypochlorite
Raw sewage – typhoid, hepatitis etc
Dangerous gasses – hydrogen sulphide (H2S) and methane
What precautions are taken to avoid H2S?
H2S monitor is always used when working with/around a STP or CHT.
H2S concentration levels
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
