Design
Planning a vacuum sewerage system seems to be initially a question of design. There is never only one solution at sewer networks in general, but vacuum systems can be designed in many different ways (e.g. connected area, location of the vacuum station, choice of the length profile etc.). A good design needs a perfect overall picture on all the system’s parameters! Some suppliers of vacuum system components help seriously during the design with their assistance. The use of such experienced help is recommendable and preferable.
In the guidelines mentioned above the control of the following parameters is demanded:
- air-liquid ratio (depending from distances and population density
- energetic loss (derived from the maximum trunk length in between the vacuum station and the furthest interface valve as well as from geodetic steps due to topography)
- network-length (sum of all trunks leading together)
- flow-rate
- vacuum reserve volume (considering also the sewer network)
- maximum tolerable distances in between air inlets (interface valves).
The most significant step in designing a vacuum sewerage system is the choice of a good pipe-routing. System boundaries such as maximum trunk length and additional elevations of the pipe length-profile do not have to be surpassed. As this kind of work requires iterations, design-diagrams have been developed. The maximum trunk length is restricted to 4000 m in absolutely flat terrain. A longer distance can be handled must be done in consultation with a system supplier.
While the norms do not give sufficient information about checking and dimensioning of design parameters, it shall be emphasised, that vacuum sewerage systems could become remarkably larger than the norms show it!
Read more about this topic: Vacuum Sewerage
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