Vacuum vertical flat surface

Vacuum Filtration on a Vertical Flat Surface, the Disc Filter... 

The filter unit was located entirely inside the respective buildings and was independent of the ventilation system. The unit consisted of a suction box (usually floor standing) to which the filter material was attached usually as a flat vertical surface of an area to give a face velocity of about 0.75 m/s. Dust collected on this surface and was removed with a vacuum cleaner. Cleaned air was directed into an overhead discharge duct with a permeable lower surface. The capacity of the fan in the filter unit was made the same order as that of the main ventilating fan. The overhead duct was located above and as near to the stock as possible so that the clean air flowed downwards towards the stock. This air did not cause a draught because it was discharged at a low speed (0.3 m/s) and as it was recirculated it was at the same temperature as the air in the room. 

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