Screen box angle.

[Juice]

Hi everyone. What's the best angle to run a powerscreen box? Mine is currently set up at 32 Degrees.
I run a 6' x 4' screen box, with a 20mm woven wire screen mat dropping down to a 4mm piano wire screen.
I'm after course sand predominately. The 20mm is a secondary by product.
I currently run the rotation on the screen box back up towards the feed belt, thereby keeping on the deck as long as possible. ( Clockwise)
I've seen on the net, powerscreens should be run at between 10-22 degrees angle.
However, that's pretty flat, compared to what I'm running now.
Has anybody had experience at running at those sorts of angles?
As a matter of interest, I also get some moderate to heavy pegging on the 20mm rock screen. Would this be attributed to the reverse rotation?
Would love to hear anyone's experiences, ideas, pearls of wisdom!.

 

[grandpa]

The degrees of angle can be increased or decreased in accordance to the material your running.. if your passing a lot of material of the end of your screen then you should decrease the angle. If your screen is cleaning b4 the fine's reach the end of the screen, then you can increase the angle to increase product.

With that said your pegging problem may well be the weights on your screen are too severe. Your screen is throwing to hard driving the rock into your screen cloth making it wedge to the screen thus the pegging. Some counterweight on screen's have adjustable weight. Im not familiar with your screen Juice, so without some pictures its hard to help you. But that's where i'd start looking is at the throw and not so much the angle. Watch your rocks on the 20 mm screen and see if they are jumping out of the holes . If they jump to high you get pegging if they don't jump high enough you get pegging. Keeping in mind adjusting the top deck to screen properly on the 20mm screen may create a problem on the 4mm screen... if I can help further feel free to ask. Gramps.

 

[lantraxco]

If you reversed rotation so the motion is helping material move toward the outfeed then you would need to flatten the angle to slow down the flow of material typically. I had a little exposure to this kind of machine years back and it always seemed to be a bit of a trial and error thing to get dialed in when we changed material or screen size. The units we had were also adjustable on rpm so that added another variable to the mix, lower speeds seemed to give more throw while higher rpm's imparted more energy with less movement of the screen deck. YMMV

 

[JDOFMEMI]

There is no set answer, in my opinion. Too much depends on the material, and what works in one pit is way off base in another.

When I had a pegging problem I switched to Major Wire brand screens. The back to back "W" shape flexes independently and reduces pegging, or it did in my conditions. Some of the rubber screens do the same, at a greater initial price.

Grandpa is right about the weights.

One thing to remember is to change one thing at a time, and keep records of what works and what does not. If you change more than one thing, you don't know which one made the difference.

Another thought, and I am not sure if your box is big enough, but with a 20mm to 4mm spread, you have too broad of a material size on the bulk of the 4mm deck. If you can, change the top half of the upper deck to a smaller size, say 10mm, then go to 20mm on the lower half of the top deck. This will reduce the load of larger material on the top end of the 4mm deck, and increase what you can put through it.
With only a 6' x 4', I am not sure that will work, but it may. I understand the screen deck is probably not split, so maybe a screencloth cut and overlayed? That leads to other problems, but it may be worth trying.

As Lantraxco says, a lot of trial and error goes into setting up a plant in a new pit.