Brian,

A safe angle to use is 60 degrees from the horizontal, assuming that all of the sands are free flowing. You should get mass flow at this angle. Make sure that you design the hoppers for the forces that are created by mass flow so that the hoppers are structurally sound.

Regards,

A. T. Agarwal

Consulting Engineer

Pneumatic Conveying Consulting Services

Email: polypcc@aol.com

Ph and Fax: 304 346 5125 ■

You are going to have way more than three tons of sand in that hopper-do not forget that dry sterilised sand is 50 pounds per 2/3 of a cubic foot -what are you loading? sand right off the washer and screen?

The only way your going to gain volume is if you line the 2 slopes of the hopper with a dual set of small air bags using truck air assuming you have a truck with air brakes to agitate and lift the product, other wise you have to use the tried and true method of determining angle of repose -let me know if you do not know how to do that. ■

Brian,

A quantitative answer to success of a slope of 45 degrees can only be given if calculations are run based on test data. But if you can accept some cross-contamination between different grades of sand, a slope of 45 degrees will be satisfactory.

Regards,

A. T. Agarwal

Consulting Engineer

Pneumatic Conveying Consulting Services

Email: polypcc@aol.com

Ph and Fax: 304 346 5125 ■

Greetings from the "Frozen Eastern Wilderness" 1140 feet above mean sea level,

The simplest way to solve your sand problem is to use the Tyler method.

First procure a 12 quart steel pail. Second get samples of the product you wish to move through that hopper dimension in question. I am assuming you are screening concrete and mason sand.

Fill the pail up to the top of the top of the pail with each sample and lift the pail up to chest height and flip it over.

The sand will fall to its normal angle of repose

when the pail is dumped and the you can determine the angle of repose which will determine its flow characteristics in the invereted cone.

Do not forget and I must stress this very much that you are creating an inverted cone of depression for your sand flow!!!!!! It matters not the size of the cone.

As I stated previously you will only gain capacity if you install a set of air bags in the bottom and side of the hopper to gain capacity if you are going to reduce the angle which is the hopper bottom and sides. please e-mail me off the board if you have more questions.

lzaharis@lightlink.com ■

The Angle of Repose

The maximum slope or angle at which loose, cohensionless material remains stable.

From

Dictionary of Geological Terms, 3rd Edition, American Geological Institute

The angle of repose is used only to determine the shape and size of a pile of material. It should not be used in designing a hopper.

Sorry Leon.

BZajac

You can get information that you require at the following link.

http://www.ecgf.uakron.edu/~chem/fcl...%20Lecture.ppt

Regards,

Gary Blenkhorn ■

Why such an elaborate vehicle superstructure? Do you have a headroom, or receiver, restriction preventing you from using the well proven tipper truck? ■

Dear friend

you will have no problem wit6h 45 degrees , do aqllow yoursel to be scared.

You mentioned that you will have a belt conveyor running the length of the bin (at the bottom ,) I do not recall readinf what type of outlet you were planning of using, nor if the sand could be wet.

So if it is dry sand , possibly silica sand (coarse) not fine powder, it should be pretty free flowing .

You did not metioned the storage time nor the distance the sand was to be transported , nevertheless use 45 degre4es , design your outlet at the bottom either multiple or elongated .

I would be glad to check tour design for free.

Regards

Marco Flores ■

I would beg to differ as I can bear witness to complete slides of product-deep mined rock salt at the stock pile-

stock pile in question is a 125,000 tons of minus 1 inch deep mined rock salt with an angle of repose of 45 degrees with a trapezoidal cross section ■

can you please be more specific , it is an interesting Issue .

I do not handle rock salt , but stock pile slides are a common occurrence .

Form of stacking

Do you have a stacker reclaimer or are you stacking with a tripper.

Form of reclaiming .

do you aprroach in a flat front or through a Hopper , sink hole .

How big is the metalic section of your hopper.

And I do agree that Hillary is a very understanding partner. just like a flat sided hopper with a non simetrical elongated exit.

Maybe Bill is also.

Never in , sounds like a long time friend Carlton from J & J from pecisely Billerica . ■

Hola y Saludos, from my corner of the "Eastern Wilderness" @ 1140 feet above mean sea level.

The mine where I worked utilizes asphault base pads with waste salt water recovery sluices with a portable stacker and berms product on both sides before filling the center on the stock piles to create a trapezoidal face.

After initial build up they hire a small dozer to build the stock pile higher and haul tarpaulins to cover piles.

Product recovery is accomplished with front end loaders with boom mounted electronic scales and then loaded in to trucks-very inefficient as they have to repeat weighouts and it is always an accident waitng to happen since it could be done more efficiently with less labor and machinery delivering rock salt to the scale loadout area or a batch plant on the pad. ■

Leon

Do you not think that the higher angle of repose in a salt stock pile is created by the hygroscopic nature of the salt? Our sister mine in Loisiana is very dry and they do not have this problem.

We have buried the odd loader or two in our mine over the years too.

Just curious as always.

Gary ■

Greetings Gary,

my feeling is that since they leave the total pile uncovered until they are ready to tarp makes it that much more dense since it is being compacted and pushed around by a small dozer with finish grade track. they use "no cake as well" The 5 stock piles on or near the mine are a natural moisture magnet as well since they are all exposed to weather year the year round.

Have you ever been to Cote Blanche?-e-mail me at home, so we can talk more -I found out a lot of things about our old mine in La. remind me to tell you about "clear roads":^) ■

The first thing to establish is whether the sand is always dry, as damp sand may give discharge problems. The size of the belt conveyor is also not indicated. Assuming that there is not a flow problem the hopper walls can be at 45 degrees, of even 40, provided that the surface is smooth and the end walls are vertical. If the sand is likely to be damp it would be prudent to make the lower section of wall at 60 degrees up to a width of about one meter, at which stage the walls can be cranked to a lower angle of say 50 degrees. The width of outlet for dry sand may be relatively small but, if wide to enhance the holding capacity of the bin, you could fit an inverted Vee insert along the length of the bin above the outlet slot to reduce overpressures on the belt. Tie ribs across the hopper to support the insert will also significantly stiffen the hopper construction on the flat walls.

Determining the size of opening required for damp sand is more of a problem and is probably best found by a practical trial rig. Inserts could be fitted to improve flow, but this is more of a specialist task, so I hope will not be necessary.

Lyn Bates ■