Hi Nishant -

We will be happy to help you... we manufacture air blasters and air cannons, as well as complete line of bin, hopper and silo vibrators to aid material flow.

Our technical support team has decades of experiencing solving material flow problems like yours and will work with you to come up with the right solution to your problem. Our technical assistance is offered at no charge - we'll even mark up a photograph of your silo to let you know exactly where to place and how to mount our products.

To get started, you can either give us a call (24 hours) at 800-633-0032, send an email to

href="mailto:vibrators@vibco.com">vibrators@vibco.com (photos of your silo will be helpful) or complete an inquiry data sheet at

href="http://www.vibco.com/technicalassistance." target="blank">http://www.vibco.com/technicalassistance. I've attached a pdf of the data sheet to this message for you.

Hope this helps!

Attachments

vibco_data_sheet_bin (PDF)

■

Yes, I have heard of a similar situation in a coal slot bin in Western Canada. It experienced "earthquakes" during discharging. The bin was designed by one of the premier bulk material specialist companies in the world.

The last I heard, the solution offered by the consultant was to just not fill the slot as full. I never heard if the problem was completely solved. (I was off site by then) I suspect it may not have been because of the size of the bin & the probable costs involved. ■

I personally have come across this silo noise problems in several different industries and in several different countries. On one occassion it related to the climatic conditions.

The safest and more effective solution is to install the correct model of acoustic cleaner which uses non destructive sound waves to debond the material and prevent both material build up on the side walls and bridging over the silo outlet.

Take a few moments to look at the following two links. The first one specifically related to eliminating both ratholing and bridging of material within a silo (and hence the noise as well), whilst the second link will provide you with a general overview of acoustic cleaners together with the ability to download specific application forms.

http://www.sonic-horns.com/silocleaningarticle.htm

www.primasonics.com

Regards

Donald ■

Silo Honking is a well researched area and it is believed to be caused by

1. Slip stick behaviour between material and silo wall or internal slip stick within the stored material.

2. If the silo is on borderline region on flow pattern; then the switch between mass to core flow and visa versa causes honking

3. Sudden collapse of arches and solids dilation also causes honking.

I am very surprised that a number of remedies have been suggested without getting to the proper root cause of the problem. ■

I recently commissioned a new cement grinding plant and had similar problems with slip-stick. They happened in my 240tons clinker and 160tons flaysh bins. I then added a bin vibrator and this has since eliminated the earth quakes.

You might want to try this first since it is to me the easiest solution, however, there is some degree of trial and error to setting the vibrator timing and vibration strength. The first time we started we nearly shook the building down. ■

Systematic inertial loads can occur during silo discharge for a number of reasons, as described in an Ajax publication 'Silo Quaking', causing anything from earthquake like forces that shakes the foundations to 'silo music' that is hurtful to the ears. It is likely to be a growing phenomenon with the increasing specification of mass flow hoppers, as these engage the total mass of the silo contents in movement, which is essentially intermittent for this behaviour to occur. Preventing slip on the walls will usually 'cure' the problem, but then the silo is not mass flow and wall loading may be excessive. Identifying the cause and securing a resolution is a job for the specialist and TUNRA have much experience in this field, so I suggest the job is best left to the experts. ■

Nishant - I have come across this in several silos, including coal in India. The two key requisites are to firstly prevent material building up on the long side walls and hopper walls. Secondly is to ensure, despite the relative narrow discharge area, that maximum flow rate is always and consistently achived.

We can offer a solution to this silo's problems just like we have already achived in a wide variety of silos and hoppers worldwide. Based on the dimensions of your silo, I would recommend the installation of an Acoustic Cleaner model PAS-75 on top of the silo which will prevent material from building up on the side walls, plus the installation of an Acoustic Cleaner Model PAS-350 just above the silo outlet to prevent bridging and ensure maximum material flow. These sonic horns are only sounded for a few seconds at periodic intervals during loading & unloading.

I attach a typical silo top PAS-75 photo along with a typical PAS-350 silo discharge photograph. Please contact us for further details and discussion.

Kind regards

Donald F Cameron

href="mailto:don@primasonics.com">don@primasonics.com

href="http://www.primasonics.com" target="blank">www.primasonics.com

Attachments

typical hopper discharge installation (JPG)

■

Nishant - it seems that you only received a photograph of the Acoustic Cleaner for silo discharge. So please now find attached the photograph of a typical Acoustic Cleaner Model PAS-75 mounted on top of the silo

Regards

Donald F Cameron

Primasonics International Limited

Attachments

typical silo top installation (JPG)

■

Nishant,

If you haven't already, I would encourage you to look into VIBCO's Air Cannons. All VIBCO air cannons include our expert support and most will ship same or next day.

To view the catalog, please go to http://www.vibco.com/aircannons/index.htm

Regards,

Linda K. ■

Hi Nishant,

You mentioned that the problem might be generated at the junction between the silo shell and the bottom cone. That assumes that you have mass flow in the bin.

I raised a question about bin discharge with TUNRA. They replied that they could estimate the discharge from a mass flow bin, but could not predict funnel flow behaviour.

Mass flow is controlled, or affected, by wall friction. In funnel flow the discharge pattern is internal and comes from the top of the product pile. The amount of impact would depend on the development and behaviour of the internal discharge shaft. With 70 mm lump size in a 5.6 m diameter bin it is unlikely that stress arching wall to wall would develop.

Regards - John.Rz ■

Dear Nishant

Some time ago cut copra stored in silos showed such characterstic

there were two screw feeder fitted to the cone of which one was removed whenever there was flow problems and one could see inside the silo from below

It was noticed that as the copra was poked the arch would get steeper and at a particular point the lower edges of the arch would give way and the entire material would slip downward to rest on the material which has collected in the periphery of cone

During tea break the material would keep flowing out and the thumps and bangs were heard

on one occasion when the screw feeder was not fitted back and was left unattended for a long time and consequently the cushioning material collected at the periphery of the cone was not there to brake the falling mass. The cone was hit by the material sliding down and the welding gave way and the cone crashed down and all the material flowed out.

A loose liner unbalance motor bin vibrator can keep the material flowing evenly or if the geometery permits 2 or 3 Electromagnetic bin vibrators can be fitted to avoid slugish and un even flow of material

Hope my experience with cut copra is of some help

Thanks ■

Originally Posted by Nishant

Hi everyone

I have come across a coal silo that is causing significant vibration when material being discharged. We believe that material is hanging up possibly in the transition zone from cylinder - to - cone. The vibration occurs when material is being discharged, and causes a sudden 'jolt' on average every 30 seconds. This is a concern to the supporting structure.

The silo capacity is 300T and holds coal (particle size approx 70mm). It is fed by a belt conveyor at 180TPH, and discharges at around 20TPH. In-feed and discharge do not occur simultanously.

The silo consists of a 10m cylinder (5.6m diameter) and 12m cone. The outlet diameter is only 0.61m (due to its connection to a weigh feeder). The silo is made of varying thickness of steel and is unlined.

I would llike to know whether anyone has come across a similar situation, and what steps they took to alleviate the problem. We are looking into employing air blasters mounted on the cone as the most simplest solution, but if anyone has other suggestions I would appreciate your thoughts and comments.

Thanks

Bins hang up material all the time- minus one inch rock salt is notoriuos for this as well..

Any easy fix is a poly liner material attached to the interior of the cone-slip and slide no hang ups poly liners are used on dump trailers for wet dirt , sugar beets, sticky mud etc. it slides right out.

second option is not loading the bin as full or loading at a slower rate than the take away system under it to alleviate the hang ups.

third option is a narrow apron feeder fed by a hopper under the cone of the silo-

The cone should have a section circular section removed to allow full flow into the hopper feeding the apron feeder

Illustrating how bagging lines are fed with overhead bins -the receiving bin delivering the material to the bagging line is wider than the opening of the chute dropping the material by gravity to permit filling with no spills as the material in the chute is confined by the wider hopper.

The hopper must be taller and wider than the opening feediing it to avoid spill overs from the flowing coal. ■

We have same in our 400T bin with a slot discharge - drag chain for mill dosing

It is very hard to see what is happening unless you have a very good light

The issue was not a real worry for us...you might to try observing the flow from the top at lower bin levels to see what is going on.

It is obvious that there is not mass flow occuring 100% of the time

This is effected by

mositure/size of the coal

silo wall slip conditions

extraction system/hopper design

The hopper outlet size may seem small but you will have preferential extraction ie from the rear of the hopper > hence, you really then have a small "outlet". The material is being drawn down in a small cone/funnell - this will grow unit it gets to a size that will collapse.....your rumble.

With our drag chain - the design prevents trying to improve the extraction.

I do not know what the hopper/weighfeeder interface design is like...but for better extraction > it should be

In plan view - tapered bin opening - say 5deg from rear to front. the width at the rear should be the min arch dim or greater.

In side elev. the skirt plate are then tapered upwards from rear to front.

At the front discharge - there should be an adjustable shear gate and the arrangemnt of this shoudl prevent choking.

Pls seek some advise from TUNRA - Australia.

We tried a bin vibrator but with a 400T bin and heavy steell....you need a realyl BIG one to make any damn difference at all.......

Thanks

James ■

Hi Nishant, I have first hand experience at removing the aforementioned blockages and have recently completed a project for E.on's coal fired kingsnorth power plant and have case studies availible for your information. If you would like to send me your email address i can forward them onto you.

Best Regards

David McClusky

Cardox International limited ■

Originally Posted by Nishant

Hi everyone

I have come across a coal silo that is causing significant vibration when material being discharged. We believe that material is hanging up possibly in the transition zone from cylinder - to - cone. The vibration occurs when material is being discharged, and causes a sudden 'jolt' on average every 30 seconds. This is a concern to the supporting structure.

The silo capacity is 300T and holds coal (particle size approx 70mm). It is fed by a belt conveyor at 180TPH, and discharges at around 20TPH. In-feed and discharge do not occur simultanously.

The silo consists of a 10m cylinder (5.6m diameter) and 12m cone. The outlet diameter is only 0.61m (due to its connection to a weigh feeder). The silo is made of varying thickness of steel and is unlined.

I would llike to know whether anyone has come across a similar situation, and what steps they took to alleviate the problem. We are looking into employing air blasters mounted on the cone as the most simplest solution, but if anyone has other suggestions I would appreciate your thoughts and comments.

Thanks

==========================================================

As Lyn and Mantoo have put so well your silo it is both honking and quaking.

It happens with halite all the time

Where is the point of entry into the silo? is the silo loading occuring in the center of the silo roof with the arc of belt discharge/throw? Is there a chute under the head pulley that allows the coal to have a one sideded loading effect upon the bin?

And as you have a narrow drawdown it is problematic in itself as you have a low drawdown volume also. unless you have mass flow from the cone area the problem will continue.

Lining the lowest portion of the silo with non stick material may solve the entire problem quickly and-

Lowering the high limit bindicator(tilt switch) is even simpler as you are delivering 9 times the draw down tonnage per hour anyway.

Allowing the delivery feeder belt to run 20 minutes every hour would be the quick fix for this problem rather than continually and the simplest zero cost solutiona long with simply lining the cone and a lower ring of the silo with non stick sheeting.

Lining the cone and low ring can be done during a shut down/empty silo period in any case.

Bigger tonnages in wet environments with material that loves water do not help much either. ■