Maintain backpressure into a vessel by submerging the outlet?
Maintain backpressure into a vessel by submerging the outlet?
(OP)
We are flowing water into a basin that is 150 psig upstream. The outlet is above the basin. The design now is to use a restriction orifice to create enough backpressure to prevent flashing & cavitation. The new idea is to submerge the outlet deep enough into the basin such that the pressure at the outlet provides sufficient backpressure (so there is no need for the orifice). Intuitively this seem to make sense and it's simple, but is there something I am not considering here? Will this strategy work?
Thanks
Thanks





RE: Maintain backpressure into a vessel by submerging the outlet?
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RE: Maintain backpressure into a vessel by submerging the outlet?
RE: Maintain backpressure into a vessel by submerging the outlet?
RE: Maintain backpressure into a vessel by submerging the outlet?
Or shot it into the air with a nozzle pressure of 150 psi...
Now can you work out why no one does it this way?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Maintain backpressure into a vessel by submerging the outlet?
But yes, you could control back pressure this way but remember that it takes 10m. of water to create 1 bar back pressure (US 2 ft water== 1 psi). So it takes a very deep tank to crease any significant back pressure.
Best regards, Morten
RE: Maintain backpressure into a vessel by submerging the outlet?
Unless you're talking about the gas situation of course..... then yes, it's approx. 10m for every bar of back pressure assuming your gas isn't very dense.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Maintain backpressure into a vessel by submerging the outlet?
RE: Maintain backpressure into a vessel by submerging the outlet?
RE: Maintain backpressure into a vessel by submerging the outlet?
RE: Maintain backpressure into a vessel by submerging the outlet?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Maintain backpressure into a vessel by submerging the outlet?
Am assuming that youve got the entire pipe liquid filled, or that it will eventually become completely liquid filled.
At low flow when frictional losses are small, the backpressure on the control valve exit would be lowest.
So at low flow, part way through this upriser, where the elevation = the liquid level in the basin, the pressure in the pipe is atmospheric. So the backpressure at the control valve exit at low flow would the static head difference created by the elevation delta between the basin liquid level and the elevation of the control valve.
Dipping this pipe into the basin by d metres doesnt change this backpressure.
RE: Maintain backpressure into a vessel by submerging the outlet?
RE: Maintain backpressure into a vessel by submerging the outlet?
RE: Maintain backpressure into a vessel by submerging the outlet?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Maintain backpressure into a vessel by submerging the outlet?
Flow (max, min and medium), pipelengths and diameters, and placement of components are missing, so no ditailed recommondation can be given.
My general suggestion is to change the valve to e suitable type, for instance a needle valve (German 'ringkolben') and place it directly at outlet with air access above water, or some short distance away with air intake tubing with outlet at valve (not pipe!) outlet.
Yes, this will create both noise and a 'geysir' of water (see link to picture) but you will have a very wide possible control range both for pressure and flow, with almost maintenance-free and long lifetime.
https://commons.wikimedia.org/wiki/File:Erhard-nee...
Note: Several competitors with similar or slightly differing solutions based on the same principles are available on the market. (Someone does it this way!)