Suction dredge nozzle information

[Comdive]

Hello Guys,

First post on this very interesting and informative site, I'm looking for a some advice from the experienced dredging people on this site, I am from England and am looking to remove a considerable amount of sand and small pebbles/rocks from the seabed at approx 30ft depth, I was looking at buying a 4 inch suction nozzle from an ebay site based in the USA (photo below) but as this job will be coming up in the next week, the delivery time is too long. So I am looking at getting one made from a local blacksmiths at short notice. I am thinking of a 4 inch suction pipe supplied from a 2 inch pressure hose same as in the photo but I am wondering will I have to reduce the diameter of the pressure pipe as it enters the suction pipe, I am sure I have read somewhere that the reduction should be approx times 4 so that would make the reduction diameter at 1/2 inch as it joins the suction hose.
I have a Honda GX engine driving a Koshin pump which will deliver 240 GPM.

Being a commercial diver I have always used large diameter underwater air lifts supplied with large compressors which move massive amounts of sea bed, I am hoping this dredge will move a decent amount of material.

Thanks in advance


Sorry the site will not let me attach a picture of the suction nozzle.

 

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[brianc053]

Hello Guys,

First post on this very interesting and informative site, I'm looking for a some advice from the experienced dredging people on this site, I am from England and am looking to remove a considerable amount of sand and small pebbles/rocks from the seabed at approx 30ft depth, I was looking at buying a 4 inch suction nozzle from an ebay site based in the USA (photo below) but as this job will be coming up in the next week, the delivery time is too long. So I am looking at getting one made from a local blacksmiths at short notice. I am thinking of a 4 inch suction pipe supplied from a 2 inch pressure hose same as in the photo but I am wondering will I have to reduce the diameter of the pressure pipe as it enters the suction pipe, I am sure I have read somewhere that the reduction should be approx times 4 so that would make the reduction diameter at 1/2 inch as it joins the suction hose.
I have a Honda GX engine driving a Koshin pump which will deliver 240 GPM.

Being a commercial diver I have always used large diameter underwater air lifts supplied with large compressors which move massive amounts of sea bed, I am hoping this dredge will move a decent amount of material.

Thanks in advance


Sorry the site will not let me attach a picture of the suction nozzle.

Welcome to the site Comdive. Treasurenet is an amazing forum with a very helpful community of active users. I'm sure you will get great advice from someone more knowledgeable than me on large-scale deeper water dredging. (I only have a 3" dredge that I use in a river, not even with compressed air).

I can help with the picture situation, however. You have at least two options:
- upload the picture to Imgur, and then use the Treasurenet picture icon and the URL of the picture from Imgur to post the picture in your thread.
- Use the TNet app on your phone to upload the picture directly. You'd have to download the picture to your phone's Photos app, then you can upload it via TNet directly.

I hope that helps and you're able to upload the picture, and good luck with your project!

- Brian

 

[russau]

Welcome to T-Net for your first post ! Not knowing anything about a Koshin pump ( High pressure or volume pump ??) I'm not sure it'll work. You need a high pressure pump and at 30 foot I would get a larger pump than you need! In-fact I'd go with a bigger engine / pump and a 6 inch nozzle and gear to get the job done quicker. To me , bigger is better & quicker !!!!!! I'm sure you have seen pictures of this suction nozzle's shape at the venturi part. and I would aim that port directly towards the tubing that goes to the flair at the sluice box or exit tube to where you plan to dump your waste sand. Keep your pressure pipe full size until you get to the "U" shaped tube that is on your suction nozzle. REMEMBER that your ports need to correspond to the pump spec's that your using to get the most out of your set-up ! Good luck !

 

[N-Lionberger]

At 30 feet down a suction nozzle isn't going to cut it, you would need to run a power jet.

 

[vpnavy]

...Sorry the site will not let me attach a picture of the suction nozzle...

1st - I noticed this was your very first post - so, Welcome Aboard! Take a look at Sub-Forum: England for information directly related to your country.

2nd - If you are having problems posting pictures - take a look at: How to post pictures with your story...

 

[Comdive]

Thanks for all your help and advice guys, I'm going to get a few photos and I'll re post.
I should of said I am not looking to take any sand up to the boat or through a sluice, this is just moving a lot of sand from a underwater rock face to about 20 feet away to get to the clay below and hopefully what's sitting on the clay.

Thanks again.

 

[mikep691]

Thanks for all your help and advice guys, I'm going to get a few photos and I'll re post.
I should of said I am not looking to take any sand up to the boat or through a sluice, this is just moving a lot of sand from a underwater rock face to about 20 feet away to get to the clay below and hopefully what's sitting on the clay.

Thanks again.

Most nozzles of that type are reduced from 2" pressure to 3/4" at the junction with the 4". I wouldn't build your nozzle with a 90 degree bend though. Even with sand and pebbles, you'll have many plug ups.

 

[russau]

From your picture's (#1 of 2 ) it appears that your wanting to reduce size from the hose (supply) to the 180 degree tube with a fitting...........you really want to keep the supply hose diameter as big as the supply hose after the 180 degree bent tube so that you will maintain FULL pressure until you enter into the 4 inch tube and have that reduction pointed directly into the flows direction . This will help any blow out's in the outside of your nozzle at the out side of the 45 degree bend. It should last a long time IF you do that . BUT that orfice (venturi opening) is the important detail that makes it all work to the max. Good luck and let us know how it worked out for you !

 

[N-Lionberger]

If you are running underwater and not to the surface you should go bigger than 4" I have a subsurface 6" for clearing overburden under my 4" it's way faster.

 

[njcommercialdiver]

when i needed to move overburden or unbury a pipe, i used a 5" suction nozzle with a 20ft section of lay flat hose to get it away from me

 

[ratled]

If you are not looking for much vertical lift and just want to move it about 20' it might work with enough power. This might help you better understand your task