2.3.7
High Voltage Insulators
Provide a minimum of four insulating support bushings for each electrical
bus section. Compression-load the high tension insulators and install
outside of the contaminated gas stream. Provide insulators of materials
suitable for the temperature. Provide best process electrical glazed
ceramic high density 85 percent alumina for temperatures below 454 degrees C
850 degrees F. Provide adequate access for removal and reinstallation of
high voltage insulators. Provide four pad-eyes above each high voltage bus
frame to facilitate lifting of the frame for precipitator maintenance.
Attach pad-eyes to support beams. Each pad-eye and support beam shall be
capable of supporting the entire weight of its respective high voltage bus
frame. Provide other means for lifting high voltage bus frames if
acceptable to Contracting Officer.
2.3.8
High Voltage Insulator and Pressurizing System Heaters
Provide a heating and pressurizing/purging system for the high voltage bus
duct insulators and the discharge electrode support insulators. Furnish
control devices to automatically energize the heaters, as required, when
the temperature of the insulating support bushings falls below [107 degrees
C] [225 degrees F] [_____] and deenergize the heaters when the temperature
reaches [121 degrees C] [250 degrees F] [_____]. The system shall maintain
an insulator temperature of 107 degrees C 225 degrees F when the
precipitator is off line. Provide sufficient pressure to prevent the
infiltration of dust and moisture laden air into the penthouse and to keep
the inside of the high voltage insulators free from the flue gas. Supply a
minimum of 47.20 L/s 100 acfm of heated, filtered air for each insulator.
Direct the purge air downward in swirl pattern across the inside surface of
each insulator. Provide a purge air filter of the disposable or cleanable
type with a filter efficiency of not less than 98.5 percent for dust
particles of one micron or larger. Provide remote annunciation for
malfunctions of the heating and pressurizing system as specified in
paragraph entitled "Annunication and Indication." Provide pressurizing
fans, complete with electric motor, automatic backflow prevention dampers,
inlet filters, and a relief device for filter bypass in case of blocked
filters. Furnish a minimum of two fans for each pressurizing system.
Provide pressurizing fans of equal capacity and requiring the same size
motors. Upon less of any one fan, the remaining fans shall automatically
pressurize the system as required to ensure continued normal operation of
the precipitator. Provide a control system consisting of necessary relays,
pressure switches, flow switches, and control devices. Factory mount
control devices, except those requiring local mounting, and wire in an
indoor NEMA ICS 6, Type 12 floor-mounted control enclosure. Provide each
fan discharge duct with an airflow switch for use in fan control. Furnish
locally mounted NEMA ICS 6, Type 4 combination starters for the fans.
Mount an "AUTO-ON" selector switch for each fan on the door of its
associated local combination starter. Mount indicating lights for system
status on the starter door. Provide each fan control circuit with a
two-position, "AUTO-ON," selector switch. Provide a single normally open
contact, which will close upon start up of the induced draft fans, when the
selector switch is in the "AUTO" position. Provide relays as required to
multiply this signal. Electrically isolate output contacts for controls
motor starters.
2.3.9
Discharge Electrodes and Collecting Surfaces
Provide rigid frame type discharge electrodes.
Rigid electrode, or
SECTION 15862N
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