I. INTRODUCCIÓN
1.4 Formulación del problema
Ideally the change to MDO should be undertaken whilst the main engine is running but under some circumstances it may be necessary to flush the fuel system with MDO whilst the engine is stopped. It should be remembered that the main engine is normally manoeuvred on HFO with HFO still remaining in the fuel system whilst the engine is stopped. Heavy fuel oil is recirculated from the main engine fuel manifold outlet back to the fuel mixing unit from where the FO booster pump takes suction. When changing from HFO to MDO during
engine standstill, the HFO in the fuel lines must be replaced by MDO and the HFO is flushed back to the HFO service tank, or the LSHFO service tank if the engine is operating on LSHFO, as it is replaced by MDO.
The procedure described below assumes that the fuel system is still circulated with hot HFO supplied from the HFO service tank.
a) Shut off the steam supply to the FO heaters.
b) Shut off the trace heating steam.
c) Sludge the MDO service tank to remove any water.
Regarding temperature levels before changeover, see ‘Changeover from Heavy Fuel to Diesel Oil during Running’.
d) Open the MDO service tank quick-closing outlet valve F-103V.
This valve will always be left open to supply MDO to the generator engines in the event of a blackout.
e) Open the MDO supply cross connection valve F-142V to supply MDO and close the HFO line supply valve F-141V to shut off HFO.
f) Close the operating HFO service tank quick-closing valve, either valve F-101V (or the LSHFO service tank valve F-102V).
g) Close the fuel mixing unit inlet valve F-128V. Ensure that there is sufficient ullage in the HFO service tank or the LSHFO service tank to accommodate the oil displaced from the fuel system. Ensure that the return 3-way control valve (F-139V) is positioned to the HFO service tank return. When operating on LSHFO position the 3-way valve to the LSHFO service tank.
h) The fuel oil feed booster pumps will pump MDO into the fuel system and displace the HFO.
i) When the HFO is replaced by MDO, open the inlet valve to the fuel mixing unit F-128V. It will take about 10 minutes for all of the HFO in the system to be displaced by MDO; a check can be made on the temperature of the inlet line to the fuel mixing unit as a drop in temperature will indicate the return of MDO rather than heated HFO. Some MDO will be pumped to the HFO service tank (or the LSHFO service tank if that has been operating) but the quantity will be small and the MDO will be diluted in the HFO in the tank.
j) When the system is filled with MDO the viscosity controller may be shut down if required.
Maersk Seletar Machinery Operating Manual
k) When convenient, the FO feed and booster pumps may be stopped.
g) Close the HFO service tank quick-closing valve F-101V (or the LSHFO service tank valve F-102V if LSHFO is being supplied).
The return valves on the HFO or LSHFO tank must be left open as there is no provision for return of fuel to the MDO service tank.
note: If, after the changeover, the temperature at the heater suddenly drops considerably, the transition must be moderated by supplying a small amount of steam to the heater.
note: The generator engines will be changed to MDO operation at the same time as the main engine and the operation of the generator engines must also be monitored during this changeover period. In order to prevent generator engine instability problems occurring at the same time it is preferable to change the generator engines to MDO operation separately: see section 2.6.2 of this machinery operating manual.
Maersk Seletar Machinery Operating Manual
To Oily Bilge Tank (Dirty Side) To Oily Bilge Tank (Dirty Side) To Overflow
Tank
TI
TI DPS
PI
DPAHMC MS
Illustration 2.6.2a Generator Engines Fuel Oil Service System
Key Fuel Oil Marine Diesel Compressed Air Steam Condensate Waste Oil Electric Signal Heavy Fuel
Oil Service Tank (188.3m3)
Heavy Fuel Oil Settling Tank (157.6m3)
Low Sulphur Heavy Fuel Oil Service Tank (157.6m3)
Low Sulphur Heavy Fuel Oil Settling Tank (157.1m3)
F-102V F-110V F-101V F-104V
F-227V F-140V
F-141V F-142V
AuxiliaryTo Boiler Marine Diesel
Oil Service Tank (162.4m3)
F-103V
To Fuel Oil Overflow Tank F-105V
F-107V
F-112V F-113V F-249V
F-241V
F-114V Fuel Oil Feed Pumps
(18.5m3/h x 5kg/cm2) PI F-106V
F-109V
F-108V
Fuel Oil Booster Pumps (33.9m3/h x 12kg/cm2)
Fuel Oil Auto Backflushing Filter Bypass Filter
PI
F-185V F-139V F-130V
F-184V
F-226V Set at 6.5kg/cm2 Set at 5.5kg/cm2
MixingFuel Unit
TI
PI F-186V
F-228V
No.1 Fuel Oil Heater
No.2 Fuel Oil Heater
F-120V FromMain
Engine
CI PI
Generator Engine Marine Diesel Oil Service Pumps
(4.8m3/h x 8kg/cm2) PS
CI F-231V PI
F-229V
Generator Engine Emergency Marine Diesel Oil Pump
(1.26m3/h x 6kg/cm2)
Starting Air
F-206V S
To Main Engine
TIAHL MC TX PIALMC
PX LAHMC LS
DPS DPAHMC No.4 Generator Engine
F-155V PIALMC
PX LAHMC LS
DPS DPAH MC No.3 Generator Engine
F-154V PIALMC
PX LAHMC LS
DPS DPAHMC No.2 Generator Engine
F-153V PIALMC
PX LAHMC LS
DPS DPAHMC No.1 Generator Engine
F155V Return Flow Meter
Supply Flow Meter
Flow Meter
Control Air
Control Air
Control Air
Maersk Seletar Machinery Operating Manual
2.6.2 Generator enGines fueL oiL serViCe systeM diesel oil service pump (electrically powered)
Manufacturer: Taiko Kikai Industries Co. Ltd..
No. of sets: 2
Type: Screw Type NHGH-5MTB
Capacity: 4.8m³/h at 8kg/cm²
emergency diesel oil pump (pneumatically powered)
Manufacturer: XX
No. of sets: 1
Type: Screw
Capacity: 1.26m³/h at 6kg/cm²
introduction
generator engines and this is set to maintain the oil pressure at 8.0kg/cm2. Fuel oil from the main FO line passes through a flow meter to the generator engine supply manifold and then to the individual generator engines.The HFO line to the generator engines is fitted with a spill valve (set at 10.0kg/
cm2) and this prevents excess pressure building up in the generator engine fuel supply manifolds. The fuel released by this valve flows to the return fuel line and back to the fuel mixing unit via a flow meter.
There are supply and return connections to the generator engines from the generator engine MDO service pumps for flushing and for operation on MDO when required. Individual generator engines may be changed to MDO operation with the other engines operating on HFO. The MDO common return line from the generator engines is fitted with a pressure regulating valve (set to 2.0kg/cm2) and this maintains the desired backpressure in the generator engine fuel manifolds when operating on MDO. Return MDO flows back to the MDO service tank. The supply pressure in the MDO manifold from the generator engine MDO service pump is maintained by a pressure release valve set at a pressure of 6.0kg/cm2.
Each generator engine fuel main inlet is fitted with a quick-closing valve which is operated from a control station outside the generator room concerned.
The high pressure fuel injection lines on the engine are sheathed and any leakage from the annular spaces formed by the sheathing is led to the leakage alarm tank on the engine and then to the dirty section of the oily bilge tank.