Pressure through a Pipeline
Pressure through a Pipeline
(OP)
Hi guys, I have a question about water pressure through a 1.5" PVC pipeline.
The supply pressure is around 700kPa (from a reservior on a hill). The water line runs about 10m to a pressure regulator which is currently set to 200kPa. This water is then used to power a venturi to suck up powdered carbon. The doseline then runs about 30 m with 12 bends and rises about 6 m high. (maybe 400kPa friction and lift pressure here?)
My supervisor is telling me the doseline needs replacing as there is too much backpressure on the venturi - however I don't think so.
I can increase the pressure to around 500kPa with the PRV and decrease it right down also.
But I don't know how to explain to him that the doseline is OK..
Thanks for any help.
Heath
The supply pressure is around 700kPa (from a reservior on a hill). The water line runs about 10m to a pressure regulator which is currently set to 200kPa. This water is then used to power a venturi to suck up powdered carbon. The doseline then runs about 30 m with 12 bends and rises about 6 m high. (maybe 400kPa friction and lift pressure here?)
My supervisor is telling me the doseline needs replacing as there is too much backpressure on the venturi - however I don't think so.
I can increase the pressure to around 500kPa with the PRV and decrease it right down also.
But I don't know how to explain to him that the doseline is OK..
Thanks for any help.
Heath





RE: Pressure through a Pipeline
What altitude is the assembly.
RE: Pressure through a Pipeline
You have not stated the flow rate or the application.
I would not expect this to work at 200 kPa. It will probably take at least 400 kPa.
Not sure what the application is, but it is usually easier to transfer carbon as a wetted slurry instead of sucking up carbon.
RE: Pressure through a Pipeline
The water at pressure is supplied to the venture which takes in the carbon powder and coveys it into the raw water as a slurry. This is for odour, colour, organics removal of the raw river water for drinking water.
I think using a headloss calculator I could say the headloss would be 400 KPa after the venture based on length-bends-height. But would I explain how this works when I have a 700Kpa supply pressure and a PRV that can adjust venturi pressure.. I don't even know how to ask the question haha.
RE: Pressure through a Pipeline
If you have this installed, turn it on and test it.
RE: Pressure through a Pipeline
I might do some research into venturis
RE: Pressure through a Pipeline
I can't work out how your OP says inlet pressure I 200kPa, but you somehow have calculated 400kPa friction. something wrong there.
"he says the pressure on the gauge shouldn't be zero" Which guage? where is it? - see my first point.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Pressure through a Pipeline
If so, try to keep the venturi running at high motive medium (HP water supply) flow always - some change in the control scheme may be required to save on carbon consumption at low demand.
This may be easier to modify than to raise the entire venturi to a higher elevation so that the water-carbon solids-air stream flows continously downslope into the raw water line to avoid this 6m riser.
RE: Pressure through a Pipeline
I have attached a pdf diagram of the carbon system. What I basically wish to do is explain why the pressure at the 200kpa gauge is 200kpa instead of zero.
My supervisor is stating the pressure at the 200kpa gauge should be near on zero as the system is open ended, I want to be able to explain to him why not properly.
Thanks,
RE: Pressure through a Pipeline
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.
RE: Pressure through a Pipeline
So your 200kPa = 20m approx head.
6m is vertical lift, another 4m loss across the venturi, maybe 2m exit loss so looks plausible that 20m will be about right as you have a lot of bends and quite a high velocity. When you do your friction losses in the pipe remember to use internal diameter. 1 1/2" pipe is not clear if this is OD or ID.
Having air in the system will add pressure losses which is difficult to quantify, but I can't see otherwise how the carbon and water will be drawn in unless you adjust the flow rate just right.
Is this a working system?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Pressure through a Pipeline
RE: Pressure through a Pipeline
RE: Pressure through a Pipeline
What's the problem??
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Pressure through a Pipeline
But I have opened the pipework up at a couple of areas and the inside wall was clean. I also believe a gritty (sand like) carbon slurry is unlikely to foul a pipe..
I could be wrong but I will test the lowest pressure it will run anyway.
RE: Pressure through a Pipeline
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.
RE: Pressure through a Pipeline
RE: Pressure through a Pipeline
But your sketch shows this check valve on a vertical riser. Even with this on the horizontal, the min required rho-v2 is probably just about adequate to get good lift. But not with a swing check on a vertical riser. Suggest relocating this (no matter what type it is).
RE: Pressure through a Pipeline
You might be on the button there georgeverghese, I turned off the wetting jet and decreased the pressure on the PRV until the flow stopped and filled the cone. It seemed to be the 130kpa mark where it would stop sucking at the venturi and at 140kPa run OK.
The non-return is a ball type. i.e. the water is just pushing up a plastic ball which then seats on an o-ring when the flow stops. If this valve type were put on the horizontal it would then need a spring to push the ball for seating. This spring way require more pressure to overcome than the current setup. I think the ball valve was chosen over a swing as they are more reliable.
I now have the pressure up around 400kpa to get awesome cone wetting and reduced the venturi flow down until just above the minimum before it starts to fail.
I think that's optimizing it well enough.
Thanks for all your help people.
RE: Pressure through a Pipeline
Just remember that georges friction loss calculation is only valid for 10m3/hr.
as you throttle back on flowrate through the venture, then these losses will reduce, but also the venture will add pressure loss itself.
If you can keep the cone so it always has a little bit of water in the bottom then that is the best otherwise you will be pulling air into the system. Now you've got the pressure down a bit perhaps your supervisor will be happier?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Pressure through a Pipeline
Sluicing Eductor
The operating results will be difficult to predict because of the materials that you are handling. You may have material clumping, bridging, different volumes of sluicing water, effects due to shape of hopper, etc.
Performance chart is listed here:
Performance Chart
Here is a picture of an eductor that was used on a recent project. These eductors are used to sluice media in order to load water treatment vessels with media. This eductor includes a pump to add water pressure.
Suggest that you optimize the operation and then demonstrate it to your boss. Don't believe that there are any simple calculations for this. The best calculation that you may develop will just be an operating range.
RE: Pressure through a Pipeline