acceptable) single-pole-dual-throw rated for at least 120-volt AC, 4
amperes or 125-volt DC, 0.5-amperes. Switch enclosure shall be NEMA 12,
except as noted. Materials and pressure ratings shall be compatible with
the service. Flow switch shall be paddle, plunger, differential-pressure,
or ultrasonic type. Ultrasonic flow switches shall be provided with one
flow setpoint, unless otherwise noted. Provide individual adjustment of
setpoint and time response delay. Power input: 115-volt AC, single phase,
60 hertz. Provide NEMA 4 enclosure for electronics and encapsulated sensor
probes. Use only when other types are not recommended for the service.
Flow controllers shall include adjustments for set point, proportional
band, rate, reset, and specific gravity. Provide pressure gages indicating
supply and control pressures. Provide cleanout push button for cleaning
restricted feed orifice without dismantling. Design shall utilize
high-temperature diaphragms and gaskets, and shall provide dust-tight case,
and cooling fins.
2.12.9
Density Elements and Transmitters
Shall be nuclear type and shall be accurate within 0.001-SGU maximum.
Signal shall be linearized. Response of measurement system shall provide
adequate response time when tied to mass flow. Power supply shall be
115-volt AC, single phase 60-hertz. Furnish prefabricated cable as
required from primary element to transmitter.
2.12.10
Fly Ash Level Alarms
**************************************************************************
NOTE: Alarm sequence shall be the following.
Status
Visual
Audible
Normal
Off
Off
Alert
Fast Flash
On
Acknowledge
On
Off
Return to Normal
Slow Flash
Off
Return before Acknowledge Slow Flash
Off
Acknowledge (Reset)
Off
Off
Test
On
Off
**************************************************************************
Each fabric filter baghouse hopper shall be provided with a fly ash level
alarm utilizing nuclear type detectors. The detectors shall be
single-point gamma source and detection units. The detectors shall be
complete with separately mounted electronic units which shall include a
local high level indicating light and relays for use with annunciation
system specified in paragraph entitled "Annunciators." Relays shall be
rated 10 amperes, 120 volts AC. Switch housings shall be dustproof and
shall be mounted as one easily accessible location. Detector and source
electronics shall be located at the hopper control panel. Detector shall
be explosion proof and have waterjacketing. Alarm shall be able to
withstand vibration and temperatures up to 260 degrees C 500 degrees F.
The source shall have a lockable shutter mechanism operated by an external
handle to totally isolate the beam when in the closed position. Electrical
wiring schematic shall be furnished. Electrical supply shall be 115 volts
AC, single phase, 60 hertz. Alarm level shall be located at the 50 percent
hopper capacity level. Each hopper shall have two sensors; one at the
alarm level and one at the empty level. Level reproducibility shall be
within one inch. Outdoor components shall operate between [_____] degrees C
and 93 degrees C degrees F and 200 degrees F. Source for each hopper level
SECTION 15864N
Page 98
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