Last stage of water filtration for thermal desalination units, power plants and process or cooling systems is normally performed by rotating screens that can remove particles grater than 2mm.
TRAVELLING BAND SCREENS
FAI Travelling Band Screensare mainly composed of one heavy superstructure connected with two sliding continuous guides, made in bent section irons, with vertical and horizontal stiffeners. Two chains rotate inside the guides by means of one shaft with sprocket wheels driven by one gearbox, oil lubricated, with electric motor.
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FAI rotary screens, tailor manufactured to withstand required static or dynamic differential heads, water velocity, head loss and mesh size, are of a proven design and operating since 1978 in water intakes located in different countries with the heaviest environment condition, dealing with large quantities of debris.
Automatic and manual operation are always available by combined differential level control, time switch and local push buttons linked by serial links or hardwired with PLC or central DCS.
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The shaft is supported by self aligning roller bearings installed into waterproofed housings with two chains retention devices easily actuated from the operating deck.
The electric motor, directly coupled to the driving shaft and provided with minimum grade of protection IP 55, can be selected with two or three speed pole or adjustable speed by means of frequency controller.
The screens are protected against over loads, preventing damages to the structures, drive system or mechanical parts, by one or two torque limiters:
- electrical with proximity switch
- mechanical clutch type installed between the motor and the shaft.
The panel frames, fixed to the rotating chains, are studied to slide close to the guides in order to maintain a constant sealing. FAI Travelling Band Screens do not require any gaskets, neither between guides and panels, nor between each panel. All distances between components that involve water flow are lower than the selected mesh size to minimize seawater bypassing the screen. Removable mesh panels are fixed to the panel frame by bolts.
When the screening system shall be capable to deal with large quantity of jellyfishes or sea grass the mesh panels are completed with lifting buckets.
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The flow pattern can be selected according to customer preferences or Intake System design.
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Back washing system is provided by two washing pipes with replaceable nozzles able that give a constant water flat jet that cover three times the surface of each filtering mesh. The backwashing is initiated by motor operated or pneumatic actuated valves and fed by water coming from the main header or dedicated washing pumps.
Splash housing is provided to cover the upper part of the screen over the ground level with doors and manholes for inspection or maintenance purpose.
Test facilities are available in our workshop. All structures can be entirely assembled and tested.
Within certain limit FAI Travelling band screens con be transported and installed in the civil structures completely assembled and ready fur use.
Drum screens
| FAI Drum screens are designed for the fine cleaning of large volume of water reducing at minimum maintenance requirement... |
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The screen is mainly composed of one heavy shaft, supported by self aligning double roller bearings, installed into waterproofed housings lubricated from deck level, and one cylindrical structure frame lined with filtering mesh or holed plates.
The screen is driven by one drive unit with nylon pinion installed at the deck level with electric motor and gearbox, connected by shaft to a driving pinion.
The motor can be selected with two or three speed pole or adjustable speed by means of frequency controller and is provided with minimum grade of protection IP 55.
The flow pattern of drum screens is normally from the outside to inside. This choice ensure to maintain clean the drive gear while the load, resulting from the differential level across the mesh, acts downward on the concrete foundation. Anyway the installation with flow from outside to inside is also possible.
Sealing between the rotating structure and the concrete civil works is achieved by adjustable and replaceable UV-resistant neoprene gaskets, shaped to reduce the friction against the steel seal ring embedded to the channel walls while the load of the water flow maintain.
Back washing system is provided by two removable washing pipes with replaceable nozzles able that give a constant water flat jet that cover the surface of filtering meshes or plates. The backwashing is initiated by motor operated or pneumatic actuated valves and fed by water coming from the main header or dedicated washing pumps.