moving sand

[pvet7521]

The the size of the diameter of the pipe squared, so 4x4 =16 . But I would go 20. And you need at least 35 psi just to get the air down to that depth, I would go 50 or better . You can't have too much air

how much cfm for a 4" airlift at 35 feet ?

 

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[huntsman53]

Am I wrong in my thinking? No matter which method you use, a suction dredge is going to produce a plume of sand and other material that has to go somewhere and is going to very visible and the air lift method is going to stir up the bottom sand and sediments which will likely make it to the surface and be visible due to not only mixing these with the surrounding waters but also because the rising air bubbles will carry some to or close to the surface. In either case, if you are trying to move sand underwater inconspicuously, I don't believe that is going to happen!! So that is why I posed the question in the beginning! I am always wanting to learn such things, so please correct me if I am wrong.


Frank

 

[aquanut]

Do it at night.

 

[chlsbrns]

http://www.vortexdredge.com/images/VORTEX-Choose-a-dredge-large.jpg

 

[ARC]

My compressor is powered by a 4.5 H.P. gas engine and will push air to 125 feet... I cannot breath... but it will push it.
I am currently configured as a 2 diver... and can reach to 100... then 25x 2 out... meaning 100 feet down to a 50 foot spread...
Now I never go to 100 feet... but I could if I wanted to easily with 2 people breathing at same time no prob.
And that is with 4.5 hp motor.
NOW...
As for air suction VS water...
air creates a mess...
the debri and sand is carried up and over you...
it will also mix into the surface water flow...
creating large brownish area... which depending on cuurents and time in...
can extend for a mile...
In other words... you might as well wave a flag with lights...
it will be obvious you are disturbing bottom...

Here is the basic ratio for my Comp's...




SPECIFICATIONS – Single Head Compressor SPECIFICATIONS – Twin Head Compressor
Air Displacement……………………..6 CFM (170 LPM) Air Displacement………………..………12 CFM (340 LPM)
Air Delivery………………………..…..4 CFM @ 50 PSI Air Delivery………………………………...7 CFM @ 50 PSI
…………………………………...(113 LPM @ 345 kPa) ………………………………………… 198 LPM @ 345 kPa)
Engine Run Speed………………….2900 +/- 150 RPM Engine Run Speed………………………2600 +/- 150 RPM

 

[wwwtimmcp]

20cfm at what psi ? or is that at 0psi ?

 

[huntsman53]

Do it at night.

Well, unless you have Underwater Night Vision Goggles, somebody is likely to see the lights underwater.


Frank

 

[aquanut]

Well, unless you have Underwater Night Vision Goggles, somebody is likely to see the lights underwater.


Frank

Frank, I won't admit to anything. No Guts, No Glory! Nothing is without risk, especially in today's grubbermint atmosphere...

 

[SADS 669]

You only need a little light to see what's being or has been moved and no ones gonna see that at 130ft Don't forget they know you are there anyway because of the boat and noise so all you need is smoke and mirrors on the surface for anyone other than law enforcement but then again it's all legit, right?

 

[Bum Luck]

Am I wrong in my thinking? No matter which method you use, a suction dredge is going to produce a plume of sand and other material that has to go somewhere and is going to very visible and the air lift method is going to stir up the bottom sand and sediments which will likely make it to the surface and be visible due to not only mixing these with the surrounding waters but also because the rising air bubbles will carry some to or close to the surface. In either case, if you are trying to move sand underwater inconspicuously, I don't believe that is going to happen!! So that is why I posed the question in the beginning! I am always wanting to learn such things, so please correct me if I am wrong.


Frank

Don't take the overburden to the surface. Stay low.

 

[bobinsd]

I love these old posts. But I need another solution.
i am making a custom ROV which I hope to operate at 300 feet.
i know there is lots of sand and silt and I considered usiing a thruster to "blow holes".
However, it would probably be self defeating. So I am going t o reverse the thruster and imbed it between 2 sections of 4 inch flexible plastic pipe, and drop it just below the drone and visible from one of the cameras. The suction will add to my negative buoyancy and help dig deeper
My question is, which would be the most reliable thruster? Bear in mind that if I lose suction I can reverse the thruster to remove jammed materisl.
Comments?

 

[bobinsd]

I love these old posts. But I need another solution.
i am making a custom ROV which I hope to operate at 300 feet.
i know there is lots of sand and silt and I considered usiing a thruster to "blow holes".
However, it would probably be self defeating. So I am going t o reverse the thruster and imbed it between 2 sections of 4 inch flexible plastic pipe, and drop it just below the drone and visible from one of the cameras. The suction will add to my negative buoyancy and help dig deeper
My question is, which would be the most reliable thruster? Bear in mind that if I lose suction I can reverse the thruster to remove jammed materisl.
Comments?

Has nobody used a thruster motor to clear light overburden?

 

[Sommy]

Has nobody used a thruster motor to clear light overburden?

one option is a large electric bilge pump with an H-bridge of relays to reverse the flow, another option is putting a simple pump on a dredge and using a venturi with a flapper valve to drop large objects if the pump is off
will you have hydraulic power? that makes the pump easier to control.
biggest issue I "see" is how far away you want to drop the overburden and resulting visibility problems that will happen when you disturb the overburden. Remember to put the discharge down current from where you are working and I recommend having a ground pin to help keep you in place as you blow. When I say ground pin, its just a way to keep your ROV in place when you start moving water with any pump/thruster, could be an anchor or anchor system.