FOS Flashcards
Purpose (FOS)
The purpose of the Fuel Oil Service system is to supply clean Distillate Fuel Oil to the ship’s propulsion engines, Diesel Generators, emergency equipment, steam generators, and the RHIB at the correct pressure.
Service Tanks
Two service tanks, each 21.1 cum.
Provide a reservoir for purified fuel.
Supply and return valves are electronically ganged so that when one tank’s valves are opened, the same valves on the opposite tank automaticall close.
Overflow to DFO tanks.
Duplex Strainer
80 mesh strainer.
Removes particulate from the fuel before it reaches the pumps.
Boost Pumps
Positive displacement, screw type, electric motor driven boost pumps.
Draw fuel from the service tanks via the suction main and dischare it a pressure.
Low speed:
3.6 bar
575 rpm
5.5 cum/h
High Speed:
3.3 bar
1150 rpm
17 cum/h
Pressure Relief Valve
Relieves excess pressure above 3.9 bar.
Pressure Regulatin Valve
Maintains supply pressure at 1.3 bar.
Duplex Filters/Coalescers
Filter out particulate and collect and coalesce entrained water.
Mechanically ganged so one one is clogged, the other can be brought online without an interruption of fuel.
Supply Main
First batch uses Ring Main
Second batch (337) uses a singly line.
Branch lines to the users come off this Supply Main.
Return Main
Single return line.
Returns unused fuel from the DGs, PDE, Emergency Fuel Tank, and Steam Generators to the service tank in use.
Day Tanks
0.4 cum tanks.
Reservoir for fuel to be used by the DDFPs.
Manually filled by opening valves which allow fuel to enter the tank.
Emergency Fuel Tank
1.0 cum tank.
Supplies fuel to the supply main in the event of power failure or failure of the boost pump.
Continually filled by the Supply Main to prevent dwelling. Overflow flows back to the Return Main.
Uses gravity head pressure.
A pneumatic valve opens to allow returns from end users to go to emergency fuel tank rather than the service tank.
Allows 5 minutes at full power.
Located on the forward bulkhead of the FER.
Hand Pump
Rotary hand pump.
Draws fuel from the Suction Main to Emergency Fuel Tank.
2.5 cum/h
Located in the FER
Operational Description
Normally one boost pump on low or high speed, depending on the end user requirement.
1 GT: 5.5 cum/h
PDE: 1.7 cum/h
1 DG: 0.24 cum/h
1 Steam Gen: 0.046 (high fire), 0.023 (low fire)
1 DDFP: 0.03 cum/h
Based on these consumption rates, one pump on high could manage 2 GT at full power
Modes of Operation (List)
Remote-Auto
Remote-Manual
Local-Manual
Remote-Auto
One pump on LOW, selected by MCC.
<1.1 bar for 10s: Switch to HIGH automatically.
Will not start a second pump because if it cannot maintain pressure above 1.1 bar with a pump on high, it is a good indication of a fuel line rupture.
Switching from HIGH to LOW must be done by operator.
