WW-F-2849
3.10.2 Filter leaves and elements. The leaf assemblies and elements shall
be designed to retain their shape with an operating pressure of up to 60 psig
(415 kPa). All arrangements specified in style A through D shall fit into the
discharge pipe without leakage to the feedwater effluent. All parts shall be of
corrosion-resistant steel construction suitable for the feedwater specified
herein.
3.10.2.1 Style A. Vertical filter leaves in group 1 tanks shall consist of
heavy-duty metal screens made up with frames. Vertical, tubular elements shall
consist of helically wound wedge-wire screens, circular woven metal screens held
together by longitudinal stiffeners of metal rods, or constructed of circular
sintered metal elements. Vertical filter leaves shall be assembled to a
manifold discharge pipe. Vertical tubular elements shall fit into a common
horizontal header or tube sheet.
3.10.2.2 Style B. Horizontal filter trays in group 1 tanks shall consist of
circular, heavy-duty metal screens supported by perforated/reinforced metal
plates located about a central discharge pipe. The assemblage of leaves and the
discharge pipe shall be held in correct relation to each other by a tiebolt or
equivalent means independent of the fastening means for any other component.
3.10,2.3 Style C. Vertical filter leaves in group 2 tanks shall consist of
heavy-duty metal screens made up with frames. They are assembled either to a
centrally located discharge pipe or to a manifold discharge pipe, normally
located at the bottom of the tank.
3.10.2.4 Style D. Horizontal filter plates in group 2 tanks shall consist
of rectangular, heavy-duty metal screens, supported by perforated/reinforced
metal plates and assembled to a manifold discharge pipe.
3.10.3 Precoat tank. A precoat supply tank of welded carbon steel shall be
furnished for mixing of the precoat and feedwater. Unless otherwise specified
(see 6.2), the volume shall be at least 50 percent greater than the volume of
the filter tank. The tank shall be provided with a cover to protect the tank
contents from contamination. The tank shall be painted or treated to resist
corrosion from chemicals specified (see 3.6.3), used in treating the feedwater.
The tank shall be equipped with a feedwater inlet, precoat mixture discharge,
precoat mixture inlet, drain, and liquid level gage connections. Unless
otherwise specified (see 6.2), a motor-driven, propeller-type agitator shall be
provided, securely attached to, and arranged for ready removal from the tank.
When specified (see 6.2), in lieu of a propeller-type agitator, the precoat
mixture shall be agitated by circulating it with the feedwater through one or
more nozzles. In either case, the agitating means shall provide ample mixing at
all times. The propeller and shaft of the agitator shall be constructed of
corrosion-resistant steel. Unless otherwise specified (see 6.2), the agitator
motor shall be a totally enclosed, nonventilated type, capable of operating on a
system of 208 volts, single phase, 60 Hertz (Hz).
3.10.4 Precoat Pump. The precoat pump shall be the electric-motor-driven,
centrifugal type. All parts in contact with the precoat material and feedwater
shall be of corrosion-resistant steel. The pump shall be designed to operate
without vapor lock or cavitation and so located that priming will not be
necessary. The pump shall be equipped with a pressure-operated bypass. The
pump shall be designed to handle at least 10 percent more than the maximum
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