GB1072171A - Filters - Google Patents

Abstract

1,072,171. Filter beds for water. PERMUTIT CO. Ltd. May 23, 1966 [May 26, 1965], No. 22399/65. Heading B1D. In a water filtration plant in which a filter bed 4 is backwashed by filtered water from a tank 2 above and downstream of bed 4, the head of water upstream of bed 4 during filtration builds up in a vertical riser 14 and eventually overflows branch 15 when bed 4 becomes clogged, thereby filling a float tank 16 and opening a valve 13 which connects the upstream side of bed 4 to waste 21. Tank 16 is divided by a weir 17 into chambers 18, 19, chamber 18 having a bleed hole 22 and a float valve 23 opening into chamber 19. Water overflowing from branch 15 into chamber 18 lifts valve 23 to close it, flows over weir 17 into chamber 19 and opens valve 13. Thereafter bed 4 is backwashed by water from tank 2 (arrows), and as the pressure above bed 4 falls flow from branch 15 ceases and chamber 18 begins to empty through hole 22. Finally valve 23 opens, chamber 19 partly drains and valve 13 closes to restore normal filtration flow. In Fig. 1, two filter beds 4, 4' are located in separate compartments of a tank 1, with common tank 2 and false floor 5, so that forward flow water from one bed assists in backwashing the other. Fig. 2 (not shown) illustrates an arrangement whereby each float tank 16 of a multi-bed system has an electric depth probe (28) controlling drain cocks (27) on other float tanks, whereby when one float tank 16 is full and the corresponding bed 4 is being backwashed, the cocks (27) of other float tanks are held open, so that only one bed can be backwashed at once. Tank 2 has an overflow 8 for filtered water. A plurality of beds could be located in separate housings.