(1)
Purge
(2)
Igniter control
(3)
Pulverizer control
(4)
Feeder control
b.
Furnace Purge and Boiler Monitor: The furnace purge control shall
incorporate prelight off and post purges of the furnace to ensure
that the boiler is free of any accumulation of combustibles.
Completion of the furnace purge shall be indicated to the
operator, after which the operator shall reset the master fuel
trip relay. A furnace purge shall be required on any master fuel
trip. The boiler monitor shall prevent starting any fuel
equipment if the furnace firing permissives are not met. The
furnace purge control shall provide indications to the operator of
the status and the progress of the furnace purge. Permissive
indications shall be extinguished when the MFT is reset.
c.
Mill Start-Stop Sequences: The operator shall start and stop the
mill in three steps (ignitor, pulverizer, feeder) following fixed
sequences. The system shall be capable of transferring between
the startup and shutdown sequences at any time. Each mill shall
be monitored and should any unsafe conditions occur, that mill
shall be tripped. A mill first out indication shall be provided
to indicate the initiating cause of trip. The first out
indication shall be deleted only upon reset of the mill trip
relay. Startup and shutdown sequence indications shall be
provided to allow the operator to follow the progress of the mill
startup or shutdown sequences. These indications shall show the
next step to be performed, as well as the progress through the
sequences.
d.
Ignitor Control: An ignitor group consists of the ignitors
associated with a pulverizer burner group. Ignitors associated
with a burner group shall be controlled from a separate
electropneumatic ignitor control package. Sequential starting of
ignitors between burner groups shall be provided. The ignitors
associated with a burner group shall be started and stopped from
the insert panel and local push buttons. An ignitor fuel trip
(IFT) first out indication shall be provided to indicate the
initiating cause of the IFT. This indication shall be
extinguished only when the IFT relay is reset.
e.
Fuel Safety Subsystem: The fuel safety subsystem comprises the
MFT system, IFT system, and pulverizer mill trip (MT) systems. A
mill trip system shall be provided for each mill. Each fuel
safety system shall provide the protection for its respective fuel
and shall include a dedicated hardwired relay which may be
directly operated from the operator insert panel. The master fuel
trip system shall provide overall boiler protection, shall also
include a dedicated hardwired relay, and shall directly trip all
other fuel safety system relays. The system shall be designed to
deenergize to trip.
f.
Flame Monitoring: Individual self-checking flame scanners are
required for each burner. Ignitor flame safety devices shall
SECTION 15559A
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