siphon discharge failure

[ren_]

Hi

I'm working with a float siphon to discharge water into a wetland. the siphon is reaching its drawback height of 0.44m but is not discharging as per design (11 times) its only discharging once per day. I'm wondering what the problem could be. A float siphon is a type of siphon that works on buoyancy principle, when water incoming into the siphon chamber reaches a certain height 0.44m (drawback height)the water exerts a force on the siphon and forces it fall back thereby drawing water in. for a further description of how the siphon works please view the attached file.
Data
Average discharge Ǭ = 0.0351m3/s
Pipe diameter = 110mm
Water viscosity 1*10-3 kg/ms
Density of water = 1*103 kg/m3
Roughness height e for PVC = 0.0015mm
Acceleration due to gravity =9.81m/s2
Area of the siphon chamber 2.6m by 3m

 

[hydtools]

If the system is not discharging, the float box is not sinking. Maybe the box ballast weight is not sufficient to ensure that the box sinks when the water reaches draw down height.

Ted

 

[ren_]

hydtools, we added a few weights to help it sink , maybe not enough?

 

[ren_]

I have attached some siphon photos

 

[ren_]

siphon photo attached

 

[ren_]

flow coming inside the siphon chamber,i think that if the leak is as large as the incoming flow then definitely it would be noticed at the outlet by a flooding at the surface where the plants are

 

[LittleInch]

What's going on with the "vents / overflows"?

One appears to have cloth stuffed in it (the one on the left / furthest away and the one on the right in vertical view looks like it has a hole drilled in it below the water line and is busy jetting in water?? Looks like the rather pitiful amount of water going into it is more than catered for by the leakage down these two pipes.

Unless all the chambers are interconnected it would appear as if only two of the chambers initially flood, hence there might not be enough loss of buoyancy to sink the entire unit.

The angle of the pipes doesn't look enough to me. From other diagrams and a bit of thinking, the angle would seem to have to be quite high ( 50-60 degrees from horizontal) otherwise the end box will float higher and higher. I suspect someone has tried to "adjust" it by those strange cut outs on two of the boxes.

The whole thing is slightly lopsided as well which doesn't help.

Why don't you just create a frame top stop it floating beyond a certain level? or add a clump weight and length of rope / wire to do the same thing? and sort out what ever is happening with the vent pipes.

PS - It would have saved everyone a LOT of time if you'd just attached the photos in the first place....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

The problem seems to be that the design you have is for a dosing siphon. The design of a dosing siphon flushes out the entire tank:

http://www.siphons.com/how-siphons-work.html

I am assuming that you want a siphon that works on/off but does not flush huge volumes. That is why the bell siphon was suggested.

http://www.ctahr.hawaii.edu/oc/freepubs/pdf/bio-10.pdf

The bell siphon is relatively inexpensive. I don't think you will ever be able to adapt the dosing siphon to work in the manner proposed.

The only flow meter that will work for an application like this is an open channel type flow meter.

 

[hydtools]

Maybe that the float boxes are rising too high and flow is going out the vents before the float boxes gather enough water to sink. The discharge will then be no more than the inflow.

Ted