I'm going to risk making a fool of myself...

The 8x8 opening should be good for the 18" wide conveyor.

Witout knowing the density of the material is hard to say if you can get 90 tons per hour.

I would make a small manifold with four or five nozzles from 1/4 pipe, able to apply a pressure of 5-10 PSI.

By inserting the nozzle arrangement inside about 1 foot from the opening I would try to fluidize the system somewhat.

If it improves the flow than you can find a supplier of proper gadgets for that purpose.

Good luck,



Antonio Reis

Vitrom Mfg Consultants

Your Process and Manufacturing Solutions

Phone: 209.834.1900

Fax: 209.834.1039

www.vitrom.com ■

Gui

Firstly could you clarify. It sounds like the problem is restricted flow from the silo.

Are you getting consistant flow from the silo?

Does the flow stop at anytime while discharging to the conveyor?

Does the flow increase on the by-pass chute going to the hopper?

Your 18" conveyor has more than enough capacity for 90 MTPH as well as the 8x8 opening.

The problem may be in the angle of the chute to the conveyor. Improperly designed chutework can greatly restrict flow from a storage bin or silo. The minimum angle should be 45 degrees but the steeper it is the better for flow. Further complications can occur if the direction of flow changes as it loads onto the conveyor.

Look for any material build up in the chute or foregn material which may be restricting flow.

Managements idea of moving the conveyor directly under the silo may warrant further investigation.

You could try less expensive approaches first before you get into major expense by installing a vibrator on the chute to the conveyor to assist the flow.

A formula for designing the chute can be found at the following link.

http://www.solidshandlingtech.com/articletswc.htm

Good luck,

Gary Blenkhorn ■

Gui

Pictures say a thousand words. If you can get your hands on a digital camera take a picture of the chute and attach it to your next reply. This would give us a better understanding of your layout.

Regards,

Gary ■

Looking at the pics, you may have to fluidize at the top before the valve.

Be careful so that you don't loose control of the flow.



Antonio Reis

Vitrom Mfg Consultants

Your Process and Manufacturing Solutions

Phone: 209.834.1900

Fax: 209.834.1039

www.vitrom.com ■

Looking at the photo's I wonder -

Is that a diverter valve under the hopper cutoff slide valve?

If it is and the inlet to it is 8" x 8", then my gut feel is that the flow of your material under gravity conditions is likely to be sluggish at best.

If you try to add air to improve the flow be cautious. People have been known to end up with most of a bins contents in a big heap on the floor very quickly by adding too much!

IMO a better bet would be to enlarge the bin outlet and stick with gravity flow, adding a feeder to control the rate. ■

Gui

Sorry I didn't get back to you sooner. (Good pics)

It also appears that there is a cut off gate with a cylinder on the chute to the belt. This may be causing part of the flow problem.

The closer that you can get this diverter valve to the silo the less chances of material buildup.

It appears that you have enough room to extend the tail pulley to allow the chute to drop straight onto the belt. Replace the diverter chute below the cut off gate with a new straight down and 45 off chute for bypass. (see photo)

There are many manufacturers of this style of diverter gate in Canada and the USA.

Gary

Attachments

gfv_02 (JPG)

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Gui,

Looking at your problem, U have a nice one. The issue is what can U do on a sliding scale of minor mods vs costs vs effect.

The transfer to the belt does not look good.....U say cement dust, the plant looks clean...

U will need to be carefull about overfilling the belt.

My suggestions are:

Observe the flow behaviour in the chute feeding the belt...look at the belt and also open the hatches....see what is happening and then try to assess/determine why it is behaving like it is.

Is is surging out, is is smooth and even, is it full chute flow at the top of the Y chute etc...

If U get material coming out thru the upper door then the lower part of the chute is the issue.

Be carefull with being able to stop the flow quikcly if U need to.

Look at how the material is loading onto the belt,

What is the rock size...chutes should be at least 5 times the largest length...

From first observation, I think that your bin outlet is not big enough to sustain adeqaute free flowing rates...

The system as it is built looks to be designed to act as a choke feeder - that is the material fills up the chute and loading skirts 100% and the belt draws out the material from the skirts. The rate of transfer is then dependent upon the belt speed and the cross sectional area on the belt.

Hope that this helps U.

James Morrish ■

The photographs show a steep wall, conical hopper leading through a slide valve to a bifurcated chute, one side of which delivers to an inclined belt conveyor. There appears to be a number of flow impediments in the system. A cone is not a good shape for rapid flow and, despite the other benefits given, mass flow generally discharges slower than a non-mass flow hopper of similar outlet size. A bulk material consisting of dust and fine cement powder will suffer ‘air retarded flow’ from this size of opening as the void demand of expansion is resisted by the poor permeability of the settle mass.

The outlet of this hopper appears to be smaller than the cross section of the subsequent chute. If that is eight inches square the hopper neck seems to be about six inches diameter, which has less than 50% of the cross sectional area. The two-way diverter has a wide, flat section in the central regions that must be larger than the diverting flap and provide a base of static product that inhibits slip. The outlet port to the conveyor belt also appears to have a bearing and pivoting device that suggests a shaft and possible flap across the opening that must offer a significant resistance to flow. The extraction geometry to the belt implies a shallow, 90 degree transfer, with possibly a parallel bed depth to the upwards moving belt.

Injecting an uncontrolled supply of air is a recipe for disaster in the form of flushing and a huge pile of spillage. However, a few simple changes will give a substantial increase in the rate of flow. A self-seating flow insert in the hopper will provide a large, annular flow channel from the body of the hopper and permit dilated flow to the outlet, especially if supported by limited volume air injection at the effective slot. It maybe practical to modify the swing flap by fitting side plates that covers the central flow region. It is probably best to replace the final chute section to the belt with a new shape that offers progressive extraction, expansion at the change in flow direction and a profiled exit contour that matches the repose angle of the material on the belt. Extending the belt conveyor backwards looks to be a sound idea as this provides more headroom and better product flow conditions for the changes. The required capacity seems to be quite attainable, given these alterations. ■

I am with Lyn Bates

You do not hacve a deflector plate under the silo.

coarse and fine materials are handlred.

My guess is that you have two hammer operated slide gates in the legs of the diverter.

If you are flowing to the conveyor normally you will form a sort of rock box in the flat floor and in the idle leg.

This rock box will further reduce your x section area and is a function o0f your material properties.

so the rock box migt and probably extends into the bottom of the silo further reducing your effective flow section.

Aereation can increase your output rate . as you will decrease the friction and might reduce or eliminate the rock box dimentions.

you can also flood the whole room with solids. be carefull if you are to try aereation.

By the way i am also an Industrial eng. An have been working in solids flow and mat mandling for almost 30 years .

It is a fun area .

Use air filters , and if possible ear protection. after prolongued exposure your lungs will look as limestone caves if you are not carefull.

If you are limmited in space you can use a divertor that eliminates the rock box , you will have some wear but it will flow better. there are many designs. I of course have my own.

remember any diverter in this application must be able to work under static column conditions.

Good luck.

Marco ■