Keeping a slave boiler pressurized.
In a two-boiler system it’s often a problem to keep the slave boiler at
operation pressure when the steam demand is low. This problem does not appear
when the vessel is loading or unloading in a harbor since those operations
normally need both boilers. On the other hand, when the ship is at sea and only
one oil-fired boiler is used then the slave boiler tends to cool down far below
the required stand by conditions.
Different methods have been used to solve this problem. Installing steam
heating coils in the bottom of the boiler is one method and a sophisticated
start-and-stop method for the slave boiler’s burner to keep the pressure
at desired level is an other.
These installations will be unnecessary if you happen to have an
EGE, exhaust gas economizer.
Just connect the exhaust gas economizer to the slave boiler instead of the
master boiler. This operation method will guarantee normal operation pressure
on both boilers all the time at sea.
The method has been used in many ships and the chief engineers are satisfied
with the result.
A two-boiler system has other advantages as well. It provides a
fully automatic, very flexible and economic operation with maximum safety and
availability ensured by the two separate units. At inert gas production, one
boiler can be operated at a preset fixed output while the other will follow the
load variations automatically.
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