2.5.6
Automatic Backwash System
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NOTE: If adjustable compression springs are not
required, delete the second sentence.
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A fabricated backwash support frame shall be attached to the travelling
carriage on the effluent chamber side. Adjustable stainless steel
compression springs mounted between the carriage weldment and the backwash
frame shall be furnished to allow adjustment of the backwash valve from
outside the tank while the filter is in use. A backwash shoe shall be
mounted on the frame that can independently follow any irregularities of
the matching backwash surface along the effluent ports. The shoe shall be
constructed of a material softer than the mating backwash surface (strip).
The shoe flexible movement shall be controlled by 300 series stainless
steel springs. The shoe shall attach to the piping by means of a flexible
hose. The piping shall connect to the backwash pump and shall include a
throttle valve to achieve the correct pumping rate. The backwash surface
(strip) shall be factory bolted to the effluent header by means of
countersunk Type 304 stainless steel fasteners.
2.5.7
Washwater Removal System
The washwater hood shall be fabricated from [[304] [316L] stainless steel]
[fiberglass reinforced plastic] [_____]. The hood shall permit the uniform
expansion of the filter media. The hood width shall be [_____] times the
cell width. A [stainless steel] [PVC] [_____] manifold shall be installed
in the upper portion of the washwater hood and shall connect to the
washwater pump. The washwater hood shall contain a [high density
polyethylene] [304 stainless steel] [_____] raking device and a minimum of
two vent pipes extending to [_____] above the overflow weir.
2.5.8
Washwater Launders
The washwater launders shall be constructed from [_____] mm inch [A36
steel] [fiberglass reinforced plastic] [_____] with a [_____] mm inch depth
and [_____] mm inch width and be an integral part of the filter tank wall.
Both backwash and washwater pumping systems shall be capable of discharging
into the launder. A "V" notch weir plate shall be provided to calibrate
and balance the flow of the washwater pumping system.
2.5.9
Equipment Control
2.5.9.1
Automatic Controls
The automatic controls for the filter operation shall be furnished as an
integral part of the carriage mechanism. The automatic controls shall be
mounted on the end of the filter tank. The carriage mechanism and
attaching components shall be factory assembled and tested for mechanical
and electrical operation prior to shipment.
2.5.9.2
Control Panel
The control panel shall be provided with a hinged door for access to the
control equipment. "Hand-off-auto" selector switches with indicating
lights for each pump motor and the carriage motor shall be mounted on the
front of the panel door. A main disconnect switch to de-energize the
control panel with a pendulum handle operator extending through the control
SECTION 11393
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