A slotted aperture is a good option for screening pellets, but depending on pellet size etc., a round or square aperture is possible too.

In this case, it would be interesting to know what the diameter/ length of the pellets are and what needs to be separated from these pellets. Any product tolerances we need to take into account? Have you considered a wire mesh with slotted aperture? It offers much more open area which increases the capacity using the same screen area.

And what type of screener are you using? Normally, your screener vendor should be able to answer this question. He has the details of the machine and knows the application? ■

SOME QUESTIONS:

1. do you need to make a "spec" product here? IE: 100% passing 9mm and 5mm? my assumption would be YES.

IF THAT is the case: this typically means all product on that sieve bend gradation chart must pass a "SQUARE" Or clear opening by the rules.

you could try a slotted aperture which in fact would increase your OPEN AREA and TPH but, may cause you to go off gradation or cause your customer to complain "not on spec" key...try one piece of slotted perf and see if sieve analyse is still within proper gradation guidelines OR...go to one piece of slotted wirecloth, heavy diameter wire, probably no hooks and FIX OR HOLD OR T-BOLT it down try to see if it works and if it does try the PERF.

why SLOTS please?

a) need more tph thru put?

b) too much carryover?

Question:

1. are your perf plate now straight squares and are they IN STRAIGHT LINES?

2. what is the width of the margins or steel between the holes?

3. If you go to staggered holes this will help greatly.

4. are you jamming near size in those holes?

all for now. Good luck. George Baker MODERATOR

Originally Posted by mohandes

I would like to use perforated plate with slotted aperture for screening iron ore pellet.

would you please give me your suggestion for the size of aperture for below cut sizes:

1- cut size=9mm

2- cut size=5mm

■

Originally Posted by mohandes

Dear Mr. Baker,

Actually my basic question is:

How we should select the shape of aperture for each application?

for pellet screening, I have seen in other plants that they have used slotted shape, but I don't know why?

I would recommend square apertures using woven wire meshes. We have supplied a large number of screens around the world with this configuration on inclined screens.

As mentioned previously the advantages of wire is open area = increased capacity/efficiency.

What type of screen do you have? ■

The main reason is: more OPEN AREA vs square openings = more tons per hour passing the opening. that is why.

George Baker - Moderator

Originally Posted by mohandes

Dear Mr. Baker,

Actually my basic question is:

How we should select the shape of aperture for each application?

for pellet screening, I have seen in other plants that they have used slotted shape, but I don't know why?

■

Originally Posted by mohandes

So you mean that there is n't any process reason behind the shape pf aperture(round, square or slot)!

In slot shape:

Is there any relation between the ratio of length to width of slot?

There can be a process reason: the shape of the particle can force to select a slotted hole. If the particle that has to pass the screen is elongated with a specified length and width, this could be a reason to select a slotted aperture that allows this particle to pass the screen.

Regarding the relation between length and width of a slotted aperture: this depends on the application. If it is the particle passing the screen that determines the width/ length it can be anything. On wired mesh however, a rule of thumb is to stay within a ratio of max. 3 to 5 (ie. that the length is max. 3 to 5 times the width). Longer slotted holes make the wire (and thus the slotted aperture) to flexible and bigger (unwanted) particles could pass the screen easier by deforming the aperture. Which can partly be resolved by selecting the correct wire diameter..

Good luck! ■