(2) A circuit breaker and contactor alarm relay with two normally
open contacts for each hopper zone. The contactor shall have a
120-volt operating coil.
(3)
"START UP," "ON LINE," "OFF," selector switch for each hopper.
(4) 120 V red "ON" light and 120 V white "LO TEMP alarm light
with integral transformers for each hopper zone.
(5) Auxiliary relays and equipment required for operation of the
heating and alarm systems.
(6)
Device and enclosure nameplates.
(7)
Fused control transformer having a 120 volt AC secondary.
2.5.4
Fly Ash Level Alarms
Provide each hopper with a fly ash level alarm utilizing nuclear type
detectors. The detectors shall be single point gamma source and detection
units. Provide the detectors complete with separately mounted electronic
units including local high level indicating light and relays for use with
annunciation system herein specified. Provide relays rated at 10 amperes,
120 volts AC, or 125 volts DC continuous duty. Provide dustproof switch
housing for hoppers and mount at one easily accessible location. Locate
alarm indicators and detector and source electronics at the hopper control
panel. Provide detector that is explosion proof, waterjacketed, and able
to withstand vibration and temperatures up to 427 degrees C 800 degrees F.
Provide the source with a lockable shutter mechanism operated by an
external handle to totally isolate the beam when in the closed position.
Furnish electrical wiring schematics. Electrical supply shall be 120
volts, single phase, 60 hertz. Provide two sensors for each hopper--one at
the alarm level and one at the empty level. Locate alarm level at the 50
percent hopper capacity level.
2.5.4.1
Temperature Range Requirement
Level reproducibility shall be within one inch. Outdoor components shall
operate between minus 40 and 93 degrees C 40 and 200 degrees F.
2.5.4.2
Cesium Source Safety Systems
Provide Cesium 137 source for each hopper. Design source head with a
spring return off system in the event of remote cable actuator failure.
Interlock source with hopper access doors to prevent entry into hopper
unless source has been secured. Hopper access door key shall only open one
pair of hopper doors.
2.5.4.3
Hopper Level Indicator
Hopper level signals, based on hopper level status indicator system, shall
report to a microprocessor through a coaxial cable system. Provide each
hopper with two indicators, one for full and one for empty. A flashing
light shall indicate a wall buildup. Loss of power for any period of time
shall not require a recalibration. Provide NEMA ICS 6, Type 4 enclosure
for microprocessor.
SECTION 15862N
Page 39
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