2.5.2.2
Porous Plate
A porous plate supporting underdrain constructed of [fused aluminum oxide]
[polyethylene] [_____] to a thickness of [_____] shall be factory
installed. The maximum pore diameter shall be [_____] microns. The sheets
shall have a porosity between [_____] and [_____] and a minimum flexural
strength of [_____] Pa psi. The plate shall allow a flow of [_____] L
gallons per minute per [_____] mm inch water column pressure. The porous
plate shall be completely sealed with a [polyurethane] [silicone] [_____]
sealant during installation. The sealant shall have, at a minimum, [_____]
hardness and [_____] tensile strength. The sealant shall not contain
asbestos fibers.
2.5.3
Media
The media shall provide uniform voids distribution from coarse to fine in
the direction of flow. All filter materials shall conform to the
requirements of AWWA B100.
2.5.4
Rails
[_____] kg lb ASCE rails with stainless steel splice plates and hardware
shall be mounted on the two main filter walls. Type 304 stainless steel
caps shall be factory installed on each rail. Carriage rail stops of 300
Series stainless steel shall be installed and field adjusted by a factory
service engineer.
2.5.5
Carriage Mechanism
2.5.5.1
Carriage Frame
The traveling carriage or bridge system shall contain and support the
[positive drive mechanism] [pumps] [automatic backwash system] [washwater
removal system] [motors] [limit switches] [_____]. The carriage frame
shall be of welded steel construction. A separate maintenance platform
shall be provided.
2.5.5.2
Carriage Drive
The carriage drive unit shall consist of a gear reducer, sprockets,
stainless steel drive shaft, a NEMA B design single speed [_____] watt TCFC
motor for three phase, [_____] hertz, [_____] volt power supply, provided
with a sealed conduit box. The drive unit shall be designed so that a
torque limiting device is not required and shall have a strength of
[_____]. The gear reducers shall be AGRA approved. The drive shaft shall
be of sufficient size to adequately and safely withstand bending and
torsional loads of starting and operating. Gearing shall be fully enclosed
in an oil-tight cast iron housing with the gears running in oil and
bearings of anti-friction type.
2.5.5.3
Carriage Wheels
The wheels shall be double flanged, hardened Type 304 stainless steel.
Bearings shall be self aligning and shall have lubrication fittings.
Wheels shall be capable of compensating for minor misalignment of rails by
sliding on the shaft. Horizontally mounted wheels within the tank shall
not be used to align the carriage; caster-type wheels shall not be used.
SECTION 11393
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