Design of siphon filter

Some problems in the design of siphon filter are the same as those in the common fast filter, so I won't repeat them here. Some special problems in design are discussed here. The depth of siphon filter is deeper than that of ordinary fast filter, because it includes the flushing head. At present, the depth of siphon filter designed in China is 4.5 ~ 5m. Its constituent dimensions are as follows:

The total depth of the filter = h1+H2+H3+H4+H5+H6+H7+H8 (3.40).

Where H 1 is the height of the water collecting space at the bottom of the filter, which is generally 0.3m

H2-the peak of low resistance water distribution system;

H3—— the thickness of filter material layer, determined according to the design requirements;

H4—— expansion height of filter material layer during flushing, H4 = H3 * e %；;

H5—— the total height of the flushing drain tank, where H5= the clear height of the flushing drain tank+the structural thickness of the tank bottom (about 0.1m);

H6—— the height difference between the outlet control weir and the top of the flushing drain tank, that is, the flushing head (1.0 ~1.3m);

H7—— the maximum filtration head is1.5 ~ 2.0m;

H8—— the protection height of the filter is 0.1~ 0.3m. The flushing head in siphon filter is only about1.65,438+0 ~1.3m, and its water distribution system can only adopt low-resistance water distribution system. There are many kinds of low resistance water distribution systems, such as double-layer orifice plate, orifice net, triangular orifice plate, perforated filter brick and slit filter head. Filter head should be used for small area filter, and double-layer orifice plate should be used for large area filter.

Small resistance water distribution system with slit filter head is widely used in siphon filter, valveless filter, pressurized filter and ion exchanger. The production practice proves that it can ensure the operation, save gravel cushion and reduce the depth of filter layer. The disadvantage is that the installation is complicated and the cost is high, with about 40 ~ 60 pieces installed per square meter. The clearance area of each filter head is 100 ~ 350mm2, and the total clearance area accounts for about 0.5 ~ 2% of the filter area.

There are two ways to connect the filter head with the filter plate: when the filter plate is steel plate or cast iron plate, the filter head can be directly screwed into the thread of the hole on the steel plate without a base; when the filter plate is reinforced concrete plate, the short pipe can be embedded in the base and then connected with the filter head. Vacuum siphon system is an important part of siphon filter, which consists of vacuum pump, vacuum tank, pipeline (including control valve), water inlet and flushing siphon.

In a vacuum system, a water sprayer can be used instead of a vacuum pump. Vacuum tank can be set for centralized control, or without vacuum tank, air can be directly pumped by water jet or vacuum pump to form siphon.

The sizes of the water inlet siphon and the flushing siphon are selected according to the flow rate passing through them, and their sections can be circular or rectangular. The material can be welded steel plate or cast iron pipe. The vacuum pump is selected according to the vacuum pumping capacity of the siphon in a predetermined time, and the appropriate allowance is considered. The time to form the flushing siphon is about 2 ~ 5 minutes.

In the standard design, the siphon system can also adopt hydraulic automatic control (or manual operation) instead of vacuum system, and there is no need to set up another vacuum pump.