Filling a Reservoir

[ONEYHB]

Good morning, I performed a calculation to size a supply in the following situation.

Let's say the water source is at a height of 30, the pipe runs 100 meters up to elevation 60, which is halfway along the stretch, after which it drops to elevation 20. When I get the system duty report, the required pressure is always lower than the highest elevation.

In this case, we have a rise of 30 meters and in my understanding the pump should have a pressure greater than 30 meters. But the results are always lower, it is as if the irricad only considered the initial elevation of 30, and the final elevation of 20.

[Dan Crosby]

Without seeing your design in detail (e.g., pump arrangement etc.) I can only make general recommendations. The Irricad solver only evaluates elevations at the ends of pipes, so your observation is basically correct. To get Irricad to account for the elevation rise, place a junction in the pipeline at the highest elevation point. Note that if your pipe is straight you will have to mark the junction as "Permanent" in the junction dialog to avoid it being automatically removed. Any point-item on the pipe line will serve the same function - causing an elevation evaluation, in this case you might consider an air-relief valve (e.g. a misc. hydraulic item) at the top of the rise instead of a plain junction.

Regards,

Dan

[ONEYHB]

Thank you for your help, I am sending you the file of a situation similar to the one I reported. Could you please check it?

[jovivier]

The water supply pressure is being calculated on providing the required pressure at the outlet, and not the highest elevation along the way. However with the permanent junctions along the pipeline IRRICAD tell you the pressure (positive or negative) at these points.
Also note that in your example the outlet has no tolerances set in the database and therefore has no pressure range in which it can operate within.
It is ‘efficient’ for the water supply pressure to calculate a pressure that provides the required pressure at the outlet.

The options in this case are to:-
- add the extra required pressure to the outlet for the water supply to calculate the minimum pressure required at the water source
or
- set the pressure at the water supply manually, based on the required outlet pressure plus the additional pressure required at the highest elevation to avoid a negative pressure.
or
- add a break pressure tank at the highest point (a PRV set to a value above 0) to force IRRICAD to supply this pressure to the highest point.

The IRRICAD Team