discriminate individually from any flame that may exist at other
burner locations. Burner flame shall be discriminated
individually from the associated ignitor flame and any other flame
that may exist in the furnace. Ignitor and burner flame
discrimination shall cover the range from startup to full load
operation. Blocking interlocks from closed valves in flame
discrimination circuits to avoid false flame indication are not
acceptable. If required to obtain satisfactory flame
discrimination, extended tube scanners shall be included.
Individual flame detector output level indicators are required.
Provisions for cooling and cleaning shall be provided, if required.
g.
Enclosures: The system logic cabinets shall contain control
devices, power supplies, circuit protective devices, cable plugs,
and terminal blocks. Spare space shall be provided to accommodate
a minimum of 20 percent additional devices. The cabinets shall be
accessible from both front and back, and each shall have gasketed
hinged doors with latches. Each door shall not exceed 600 mm 24
inches in width. Natural draft cooling of the control system
cabinets is preferred. If cabinet cooling fans are furnished, the
loss of any fan shall be alarmed.
h.
Local Termination Boxes: The system shall include local junction
boxes, one at each burner level and one at each pulverizer.
Burner level junction boxes shall contain separate push buttons
and indicating lights for local control of each ignitor group. In
addition, the terminal boxes shall contain terminals for field
wiring, internal wiring, cable connectors for intersystem wiring,
circuit breakers and, if required by the system, relays and
reversing starters. Terminal boards for field wiring shall
include 20 percent spare connections. Also, the system shall
include local pulverizer junction boxes for terminating field
wiring associated with each mill. These junction boxes shall meet
the requirements described above, except local control is not
required.
i.
Interconnecting Cable Requirements: Interconnecting cables
between the logic cabinet, insert panel, local burner junction
boxes, and local mill junction boxes shall be via prefabricated
plug-in cables, including connectors. Flame scanner cables shall
also be furnished.
j.
Buffered Output Signals: Output signals required for tripping,
control, and monitoring shall be fully isolated from each other.
The isolation shall be such that an open or short circuit in the
related equipment shall not affect other control systems.
2.8
BOILER ROOM PANELS AND INSTRUMENTS
2.8.1
Instrument Control Panel
Instrument and control panel shall be sized to contain all controls,
instruments, gauges, and meters. The panel shall be free-standing with
faceplate of not less than 4.8 mm 3/16 inch steel, properly reinforced, and
shall be finished with the manufacturer's standard finish coating. The
units shall be mounted flush on the panel as far as practicable. Controls,
instruments, and other equipment shall be flush mounted, each fitting
neatly into a cutout, and completely covering the cutout and any mounting
screws or bolts. The back of the panel shall be enclosed with sheet metal
SECTION 15559A
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