| 摘要 |
1,112,072. Automatic cleaning of "sand" filters. UNION TANK CAR CO. 20 May, 1965 [27 May, 1964], No. 21492/65. Heading B1D. A filter for liquid has a filtered-liquid storage chamber connected for two-way communication by a valved pipe with the outlet side of its filter chamber, the two chambers being so disposed that filtered liquid can flow by gravity from the storage chamber to the filter chamber, an unfiltered-liquid inlet and a normally-closed backwash discharge outlet connected to the inlet side of the filter chamber, a service outlet communicating with the outlet side of the filter chamber, and a source of gas pressure (e.g. air) connected to the outlet side of the filter chamber by a valveless gas line; liquid is prevented from entering the pressure source, in use, by the positioning of the source, the pressure source is operable to exert sufficient pressure to force gas into the outlet and inlet sides of the filter chamber during a gas scouring cycle, means are provided for opening the backwash discharge outlet to allow liquid from the storage chamber to flow through it, and means are provided whereby the valve in the pipe is closed and the pressure source is actuated during the gas scouring cycle, and whereby the valve is opened to allow passage of liquid from the storage chamber to the filter chamber during a backwash cycle. Fig. 3 shows the "air-scour" phase, but during normal filtration, unfiltered liquid flowing up pipe 46 and over weir 40 reaches inlet chamber 26 via conduit 30, valve 62 being closed. Filtered liquid passes upward through normally-open valve 70 into backwash storage tank 11 and out at 50. On clogging of the filter bed 12, liquid rising in a pipe 54 contacts probe 58 of switch 56. Thereupon valve 62 is opened quickly, valve 70 is closed slowly, and a blower 74 is switched on for a predetermined period. Air passed upwards through the filter bed is discharged along conduits 30 and 34 and up vent pipe 75. When the blower 74 shuts off, valve 70 is opened, and because valve 62 is still open (to drain), tank 11 empties through pipe 48 and upwards through the filter bed, the liquid and foreign matter being discharged along conduits 30 and 34. When the liquid level in tank 11 falls to the lower end of a probe 68 in a pipe 64, a switch 66 operates to close valve 62: the valves being now in their normal positions and the blower not operating, normal filtration resumes automatically. The blower pressure may be chosen to be less than the normal pressure in underdrain compartment 28, in which case the blower may be connected to the underdrain compartments of a plurality of filters. It is switched on (as described), by any filter needing cleaning, and thereafter the air scour takes place only in that filter, the remaining filters continuing their normal operation. |
