MAN B&W 5L28/32H, Manual

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08028-0D\H5250\94.08.12
1624468-9.4
Page 2 (3)
B 11 00 0
General
Fuel Oil Diagram
Uni-Fuel
The fuel system on page 1 is designed as a uni-fuel
system, which means that the propulsion engines
and the GenSets are running on the same fuel oil and
are feed from common fuel feed system. The uni-fuel
concept is a unique foundation for substantial savings
in operating costs and it is also the simplest fuel
system, resulting in lower maintenance and easier
operation.
The diagram on page 1 is a guidance. It has to be
adapted in each case to actual engine and pipe lay-
out.
Fuel Feed System
The common fuel feed system is a pressurized
system, consisting of HFO supply pumps, HFO
circulating pumps, preheater and equipment for
controlling the viscosity, (e.g. a viscorator as shown).
From the service tank, the oil is led to one of the
electrically driven supply pumps, which deliver the
oil with a pressure of approximately 4 bar to the low
pressure side of the fuel oil system, thus avoiding
boiling of the fuel in the venting tank in the temperature
range applied.
From the low pressure part of the fuel system, the
fuel oil is led to an electrically driven circulating
pump, which pumps the fuel through a preheater to
the engines. For the propulsion engine please see
the specific plant specifications. The internal fuel
system for the GenSets is shown in B 11 00 0
"Internal Fuel Oil System".
The venting tank is connected to the service tank via
an automatic de-aerating valve, which will release
any gases present.
To ensure ample filling of the fuel pumps, the capacity
of the electrically driven circulating pumps is higher
than the amount of fuel consumed by the diesel
engine. Surplus fuel oil is re-circulated from the
engine through the venting tank.
To ensure a constant fuel pressure to the fuel injection
pumps during all engine loads, a spring-loaded
overflow is inserted in the fuel system.
The circulating pump pressure should be about 10
bar, this provides a pressure margin against
gasification and cavitation in the fuel system even at
a temperature of 150°C.
The circulating pumps will always be running, even
if the propulsion engine and one or several of the
GenSets are stopped. This is in order to circulate
heated heavy fuel oil through the fuel system on the
engine(s), thereby keeping them ready to start with
preheated fuel injection pumps and the fuel valves
de-aerated.
In order to minimize the power consumption when
the propulsion engine(s) is stopped, the main HFO
supply pump can be stopped and the port pumps can
be started.
MDO Operation
The MDO to the GenSets are delivered from a
separate pipeline from the service tank by means of
a booster pump.
The system is designed in such a way that the fuel
type for the GenSets can be changed independent of
the fuel supply to the propulsion engine.
As an optional, the GenSet plant can be delivered
with the fuel changing system, consisting of a set of
remotely controlled, pneumatically actuated 3-way
fuel changing valves for each GenSet and a fuel
changing valve control box common for all GenSets.
A separate fuel changing system for each GenSet
gives the advantage of individually choosing MDO or
HFO mode.
Such a change-over may become necessary, for
instance, if the engine(s) has to be:
– stopped for a prolonged period.
– stopped for major repairs of the fuel system,
etc.
If the fuel type for the propulsion engines has to be
changed from HFO to MDO, then the 3-way valves
immediately after the service tanks have to be
changed.
99.33