Gold Prospecting Forums - General => Do It Yourself Projects => Topic started by: The Big Tim on May 11, 2009, 06:12:02 AM

Title: Spray Bar
Post by: The Big Tim on May 11, 2009, 06:12:02 AM
I'm building a Sluice Box recirculator.
Om unsure of what size holes to drill in my spray bar & how far apart they should be.
Om using a 1 & a half inch hose and a 1100 GPH Bilge pump.
The Shovel box is approx 9" wide.

I would really appreciate any help.

Title: Re: Spray Bar
Post by: GollyMrScience on May 11, 2009, 10:29:17 AM
Hi Big T here is a copy of some ideas I had on spray bars that was posted in the Do it yourself section of the forum - if you do a search you should find it and some other ideas as well.
If you are using a standard submersable bilge pump keep in mind that they are not made to generate a lot of pressure so you want to be sure that you don't choke the volume of the pump by not having a big enough outlet.

I higher pressure pump would just shove harder to get more water through a smaller hole thereby creating more water volume with more force. The submersables are not so powerful that they can take a lot of back pressure without giving up on volume.

If you look at the curves or specs on the pump you will see that it is rated for 1100 gallons per hour at maybe 3 feet of head but as your head (back pressure) increases the volume drops right off real fast.

On a 9 inch sluice that 18 gallons of water a minute under ideal conditions for the pump will be important.
If using the two tank system I discussed with you earlier be sure to suspend the pump up in the tank so it is not resting in the sludge on the bottom. Some guys put a stocking stretched over the inlet to protect the pump as well.

To get the most out of your unit and if you intend to recirculate water you should think of screening material before the sluice.
A hand screen into a tub or five gallon bucket.

Your sluice doesn't have to work so hard and if water is precious you will cut down on water losses. Every grain of sand you process - every chunk of rock gets coated with water and when that stuff is taken out of the holding tank it robs you of water that has to be made up again.

In many placer gravels over half of the raw material will screen off on a 1/2 inch screen.
In a recirculating system that means half the volume of material has to be processed for each full raw ton. So that means 1/2 the material for each ton processed and lots less water loss for every ton processed.

In a dry situation you would set up an incline screen and shovel directly onto it letting minus 1/2 inch fall through and ony take the minus stuff to the sluice.

After screening a bunch of material the screen is moved over and the pile of oversize raked flat and a metal detector run over it to check for nuggets.

The minus material is processed and if water is really dear you use a screen sieve in the holding tank.
The screen sieve sits in one corner of the tank and as you scoop material out to discard you scoop it into the sieve. The material will drain some of the water back into the tank before you discard.

Anyway her are my thoughts on spray bars:
All sorts of thoughts on this one but I can tell ya that you do NOT want to make holes smaller than the intake screen on your pump. For example if you have a 1/4 inch screen over the intake and you cut 1/4 inch or smaller holes the holes in your spray bar will clog in short order with crud that the pump is sucking up. Even in clean looking water it is amazing the stuff that comes up through that hose. You can also get a rough idea o how many holes of certain diameter by figuring out the sum of the holes equal to the same diameter as the hose to your unit. So 1 1/2 inch hose equals how many 1/4 inch holes kind thing.

Truth be told I dont use a spray bar and I have no problems with hole clogging or uneven spray pattern or dry material in the shovel in box.

I use a hinged grizzly shovel in box such that the shovel in box is at a low angle and the grizzly is steeper. If the material is well liquified before it hits the grizzly the material will be through the grizzly in a flash. The hinged grizzly is not a neccessity and as long as I set the shovel in box/grizzly combo at an angle just able to let most rocks roll off the grizzly I am good. In that case the standard shovel in box with the grizzly built into it and sitting at whatever angle the shovel in box is set is fine.

For most of my work the outlet into the shovel in box is 1 1/2 inch. It is pointing up the shovel in box so that the water hits the new materials and then rolls it around in the box prior to washing it down and across the grizzly. If I want a bit more pressure or harder hitting spray I restict the outlet down to one inch and then put a spreader plate over the end. A spreader plate is what I use on my commercial wash plants. Simply a piece of plate metal shaped like a fan that is bent across the outlet just a bit such that it intersects the water stream and causes it to fan out. Non clogging and works fine. Take a garden hose and rest a flat hand on the nozzle just above the water stream. Slowly tilt your flat hand down into the water to see the effect I am getting at.

If you insist on using a spray bar make sure to construct it with a threaded end or ends depending on how you introduce water into it. You want to be able to spin off the ends and flush the spray bar pipe. Saves time and energy or you will be sitting at the riverside poking a sharp stick though every itty bitty hole to clear crud out. After an few minutes of that every 15 minutes or so (esecially if dealing with a lot of suspended organics in the water) you will want to be opening up the spray bar holes or taking that sharp stick and poking yourself with it in frustration.

Title: Re: Spray Bar
Post by: ClickTheYellowChick on May 11, 2009, 05:56:32 PM
I'm building a Sluice Box recirculator.
Om unsure of what size holes to drill in my spray bar & how far apart they should be.
Om using a 1 & a half inch hose and a 1100 GPH Bilge pump.
The Shovel box is approx 9" wide.

I would really appreciate any help.


Hi, Tim!

Down here we have a "rule of thumb" that says if you can get a golf ball to bounce merrily down your riffles, you have enough water flow to get the job done.  I understand Tiger has a couple of wet ones up on eBay.... <-laugh->  J.K.

Seriously tho', regarding your spray bar, I started with small 1/8" ones, and as I used my golf ball guide as an indicator of water velocity, then I went back and made some holes bigger and left some alone.  There's always going to be more "water escape velocity" closest to the inlet, and down at the plugged end cap, as well, just speaking of physics of resistance here.

On to one of the points Golly made...about the way to deal with hole plugging schtick?

Well, here's what I do.  I made one of the ends of my PVC spray bar fit tightly, and the other end, a pop-on or twist-on end cap.

Inserted into the "removable end's opening," I shoved a baby bottle brush into the spraybar as far as it would go.

Then, I drilled a hole through the removable pipe cap end. 

After I poked the twisted wire handle of the baby bottle brush through the now "holey" pipe cap, I then twisted a loop "grabber handle" in the end of that bottle brush.

Then I snapped the end cap back on.

Now, when my spray bar gets ornery, I just grasp the looped end of the bottle brush, give it a few back & forth, twisty, tug and push motions.  And I haven't lost more than 15 seconds of sluicing time.

Being a gal, I guess it comes naturally to think in terms of using a baby bottle brush.  But, you probably can find a more "manly variety" and do just as well, if not better. <-yahoo_>

A chimney sweep brush installed in a really BIG spray bar might do the trick as well.  Those are certainly "MANLY!!" <-yes_>
Title: Re: Spray Bar
Post by: GollyMrScience on May 11, 2009, 06:33:36 PM
hmmmmm manly.

Toilet brush? For most guys that is probably still in mint condition even after years of ownership.  <-shock_>

Title: Re: Spray Bar
Post by: ClickTheYellowChick on May 11, 2009, 11:33:42 PM
You are a SCREAM!!!  What a great comeback!! [email protected][email protected][email protected]* {-applause-}
Title: Re: Spray Bar
Post by: The Big Tim on May 13, 2009, 09:36:19 AM
Thanks everyone, you are all so helpful.
I have my recirculating system all set up and working.
I have ran any material through it yet but it seems to have a nice flow.
How high should the current be in the sluice box?
How can i test it to ensure i have enough current to make the system efficient?

Thanks again,
Title: Re: Spray Bar
Post by: GollyMrScience on May 13, 2009, 06:22:01 PM
Hi Tim;

A good rule of thumb is that the water should be around 1.5 times as deep as the biggest stone expected down the sluice.

So if running 1/2 inch minus the water should be 3/4 inch deep at whatever the angle is you've chosen.

This is another reason switching to low profile expanded mesh is important if water volume is an issue.

If you were running angle iron riffle the water would have to be whatever the 1.5 times as deep factor is plus the height of the riffles and sometimes that is way more than a bilge pump can give you.

A start test on angle and flow is to drop a stone of the largest size you are running into the top of the sluice. You should see it move in a steady though not fast way down the sluice.

Clunka ka clunka ka clunk sort of thing not whoosh or pitta pitta pitta  and definitely not zip.   [email protected]* Kinda hard to describe!!!!
Title: Re: Spray Bar
Post by: ClickTheYellowChick on May 13, 2009, 07:36:03 PM

well at LEAST with my bouncy bouncy golf-ball aid, all he has to listen closely enough to hear is someone hollerin'


Title: Re: Spray Bar
Post by: The Big Tim on May 14, 2009, 04:36:50 AM
Hey guys,
I tried a stone approx the size of a Pepsi stopper.
It sort of hung on one of the riffles for about 10 seconds until it free up on its own then slowly tumbled down through the sluice.
Should i adjust the angle another inch or so to make is steeper of should the angle be fine the way it is?

Thanks again,
Title: Re: Spray Bar
Post by: GollyMrScience on May 14, 2009, 08:12:08 AM
Try it a couple of times and if it does not hang up you are close.

In a sluice the angle is the major adjustment and then the water can be used as the fine adjustment.

The angle does adjust water flow in the greater degree and has the greatest effect.

As the last bit of fiddle factor you can adjust the water volume a bit but generally I like to run with as much wash as I can get for bank run material so will accomodate that with angle.

Star processing and checking gold loss versus riffle loading till you get the system tuned for the area you are working.

Megan's golf ball trick is a good one - keeps the prospector's downstream wondering too.  <-thinking->  <-laugh->

Be sure your sluice is level too.
Easiest way is to check height of water on the sidewall at the end. Water acts as a level so it will tell you when your sluice is off level real quick.
Title: Re: Spray Bar
Post by: Richelsdorfite on November 29, 2009, 09:49:08 AM
Why do not use high pressure nozzle and pump like Karcher cleaners ?

It seems to be a good idea especially if the land is poor in water ressources.
A small one use 360 liters by hour and have a 110 bars nozzle pressure.
With combiantion of a trommel, I think it is a good design.