Inverted Siphons

 Inverted Siphons

When a main dips below the hydraulic grade line, it's referred to as associate inverted siphon. The purpose is to carry the sewer under the obstruction, such as roadway, railway, stream, river, etc. and regain as much elevation as possible. The sewage through such a pipeline (or inverted siphon) will flow under pressure which is greater than atmospheric pressure. Inverted siphons should be resorted to only where other means of passing the obstruction are not feasible, as they require considerable attention in maintenance. As the siphons are depressed below the hydraulic grade line, maintenance of self-cleansing velocity at all flows is very important.

Inverted siphon Designing

[caption id="attachment_1354" align="alignnone" width="494"]Inverted siphon Designing  Inverted siphon Designing[/caption]

  1. Construction of siphon should be simple.

  2. The changes in direction should be easy and gradual.

  3. It is necessary to have a seIf-cleansing velocity of 1 meter per second for the minimum flow to avoid deposition in the line.

  4. The siphon should have two or three pipes of different sizes, laid parallel so that to the average Hows one pipe comes into service and when the flow exceeds the average, the balanced flow is taken up by the second and subsequent pipes.

  5. For the selection of proper sizes of pipes, the minimum average and maximum flows m the sewer should be considered.

  6. The total length of each pipe consists of straight length and the lengths of fall, bends, and rise. Allowance should be made for loss of head due to bends and due to increased friction on account of roughness in the siphon caused due to sitting in the straight length.

  7. The possibility of sitting should be avoided or minimized. '

  8. The design of inlet and outlet chambers should allow sufficient room for entry for cleaning and maintenance of siphons.

  9. Proper bypass arrangements should be provided from the inlet chamber to the nearby stream.

  10. if the length of the siphon is more, hatch boxes at intervals of about 100 m should be provided for the facility of rodding.

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