Soda Ash
If you reduce the incline angle you will have more product wear/grinding against product which is a so so proposition for soda ash.
The angle of repose is the point where material stops moving and maintains its position in a stock pile setting etc., and would not apply to an active screen in my opinion.
If you are using a "Rotex" type of screener-
a. determine if your screener can have several gradations of screen cloth installed on the screen bed like the "Rotex" to improve your cut that is the first thing I would do to improve you scalping with the smaller sieve cloth at the top and the larger sieve cloth at the bottom.
I know the "Rotex" Brand screener can be implemented in this way.
I am sure my buddies George Baker, and Gary Blenkhorn will touch on this as I usually miss something.
lzaharis ■
Stationary Screen; Direct Vibration On Cloth
This isn't a Rotex screen am having problems with.
The screen body doesn't move at all. Instead, the material is propelled due to the incline angle of the screen and the speed is checked by having flexible mats on top of the screen cloth.
Underneath the screen cloth are rods that are excited by 2 Nos. motors per rod and this rod is in direct contact with the cloth.
That being the case, if I were to lower the incline angle from the current 36 to say 20~ for arguments sake....what would propel the soda ash forward on the screen.
This is a Rhewum screen ■
Screener
The only thing that would propel it is fear as the rods are doing the work and you may end up with a huge amount of minus product which would be ok for soda ash.
I would seriously look at changing the screen cloth as it may need new cloth only because it may be plugged or plan on using low pressure air to clean the screen fabric every day. ■
1mm Screening
Dear Bonch: An interesting problem, I reread it a few times.
the Screener:
- Driven by invicta type of motors to give a linear movement.
- the 36 degree angle is or would be designed assuming their is NOT a huge stroke. If we do not have a huge stroke, we need angle, or gravity or mother nature to help us. Hence 36 degrees. Tyler hummer screens and J&H screens, a hummer copy or vs versa do this steep angle.
- Steep angle is needed for typically FINE SCREENING apertures. Well, 1mm is not only fine.....BUT, very very fine. Vibrating screen rules indicate minus 3/8" is considered fine or hard screening......finer equals harder, no matter whose screenbox is utilized.
- A Couple of possible changes or things to look at: the motor offset settings....what are they set at?? For a 1mm opening, we DO NOT NEED to have a large offset. If we STROKE the -1mm too high off the deck surface...it may in fact be stratified most of the travel length down the deck. If it is up in the AIR, it is not conversely trying to attempt to pass the 1mm opening in the wirecloth. If still in the air at the end.....equals FINES PASSING in the OVERS. May try setting stroke a little less agressive on both sides...of motor
- I believe what you described is.....no body movement, which to me means the wirecloth is being "PULLED" upwards and relaxed by the vibrating rods.
- CONFIRM speed of motors. This will CONFIRM probable number of theoretical introduction opportunities the material has to try and PASS. if speed is too slow.....may be not enough attempts are given to effectively get the fines out. If too fast....maybe up and down so quickly....material is going back up in the air, before it has a chance to pass....equals fines carryover.
- What you are describing at 36 degrees with a tad oversize opening to try to pass 1mm material....is typical for steep angle screening. We get FORE-SHORTENING OF THE OPENING at 36 deg slope angle.....big time!!! If wirecloth opening at 36 deg is proven to be too small.....we get unders or fines in the overs.
- Assuming speed, angle and wirecloth openings are basically ok.....you may indeed have a BED DEPTH PROBLEM. if the particle depth measured at the discharge end of the wirecloth is too deep.....by the rules....of VSMA...you in fact have FINES CARRYOVER...in the overs....UNDESIRABLE. At 1mm you should not measure more than 3 times the opg for depth at the discharge end....or 3mm generally....TOPS 4mm - deeper than that equals overload = carryover of fines
- Bed depth may be too deep, if the screen area is NOT FED evenly down the full width of the screenbox. If material is not fed "humanely" to the full area.....you will have carryover.
- Assuming all above is ok.....feed is not SURGE LOADING for too deep of bed depth....etc etc.....you may in fact need a LONGER SCREEN BOX...to be more efficient.
- is this a one deck or two deck? You may need a LOAD RELIEVING top deck wirecloth to help yourself screen efficiently.
There is a few points to chew on. Good Luck. George baker ■
Rubber Curtains...
One more point i thought of:
I think i read that you are using a "flexible cloths" to slow down material. It is quite feasible, this may be "INCREASING" the bed depth, so it is so deep, you create fines carryover problem. ■
Pic Of The Rhewum Screen
Some Data
The screens have been set up as Mr. baker has described...the picture actually helps some.
Motors;
0.6 Kw, running at 2600 rpm working 1760 Newtons. 8 on each side of the screen to make a total of 16 motors.
That's the setup.
Plant is running and I will confirm actual settings on opportunity.
But from that background, would you be able to recommend settings for "hard screening"? ■
Direct Vibration Screens
Hallo,
I have a screen that employs a series of motors to excite the screen cloth. Above the cloth are flexible mats that slow down the material from accelerating on the incline set at 36 degrees.
Typically the screen gives me good efficiency with respect to eliminating oversize crystals; the downside is that it carries with it material that ought to be in the product stream.
I desire a cut point of 1 mm. Due to said problem, I obtained a 1.4 mm aperture size cloth which due to the angle is effective at 1.15 mm.
Lately i am contemplating reducing the incline angle. The hitch is the product, soda ash has a repose angle of 31 degrees and am thinking it is a consideration.
In addition, my experience is based on screens that have a circle throw and the cloth is excited by balls under the deck.
In this kind of screen, with a less incline angle, would the material have forward motion?
What would be a good solution.
The margin to go higher on aperture size is exhausted as I now retain 2% material at 1.00 mm and this I do not desire. ■