For the most difficult of materials we specify the Laidig unloader, which is basically a screw conveyor that rotates around the silo cone and will drag everything to the center outlet. Another unique feature is they will work on flat or cone bottom bins. Click http://www.laidig.com for the company website.

Delmar Schmidt

Melfi Technologies Inc.

www.melfitechnologies.com ■

Talk to SHW and Saxlund in Germany. They specialise in silos for wood chips and difficult to handle materials.

Michael Reid. ■

Dear Bob:

For this product the adecuate design is a flat bottom silo with a planetary extractor.

You can consult the next adress:

http://www.starvrac.com

Good luck!

Fernando Arderus ■

dear Bob,

there´s only one way to remedy your troubles reliable:

A) a correct GEOMETRY of your silo (mainly specified by ANGLE OF HOPPER and SIZE OF OUTLET which has to be larger than the biggest bridge that is possible to occur)

B) a discharge aid that ensures an EVEN discharge of your wood chips OVER THE WHOLE OUTLET

GEROLDINGER has specialiced in the field of handling demanding bulk solids and solving difficult tasks for more than 30 years.

If you are interested in more back ground information regarding discharge problems like bridging .... look at www.geroldinger.com/e/bulksolidstechnology.html

GEROLDINGER is able to supply a reliable solution!

From the actual point of few we are sure that the angle of hopper must be increased up to 70 or 75 degrees.

Regarding the size of outlet we offer you a FREE analysis of the flowtechnical properties of your material to define the largest possible bridge. Finally we are able to work out, manufacture and mount a reliable solution.

Interested? We should be glad to hear from you!

Gottfried Zinkl

Geroldinger GmbH & Co KG

Bulk Solids Logistics - Plants

fon: +43 7766 24 37 - 35 ■

Bob,

John Koorn here and I have just read your message.

When attempting to solve these types of problems that you describe in your posting you must take into account a number of issues. Issues such as material specfications, silo design, local weather conditions, process design of the material to be handled, duration of storage etc. All of these effect the outcome that you desire. Consequently no one application is identical.

Normally to understand the problem in detail a site visit and interview is required. Then with a detailed understanding of the application can one develop a site specific solution.

If you would like to discuss this further feel free to e-mail.

Sincerely,

John Koorn ■

In my opinion, your most economical solution is to use an external pneumatic conveying loop. This loop will always keep the wood chips in motion. This movement will prevent arching and bridging. You can use your present silo as it is now.

Amrit Agarwal

Pneumatic Conveying Consultants ■

Bob,

Have you seen the (4) SHW chip silos at Harmac? They work very well. They were installed as part of the CTS project there in 1997. Sandwell was the engineering company on that project. Also, you may want to look at the chip silo conversion at Crofton.

I have other experience with concrete chip silos equipped with table feeders and bin activators and thoroughly understand your problems and frustrations.

We have done a lot of work at the Powell River mill and are familiar with your equipment. (Actually, I was on-site last week.)

If we can be of help with a study or detail design, please contact me.

Paul Janze

Email: pjanze@sandwell.com ■

Bob,

Sounds like U are stuck with what U have got and U need to develop a solution that has the least cost and work well.

In Australia, we have a facility in the Newcastle Univervisty called TUNRA - these guys do shear and other sim. tests in order to derive key bin/silo design dimensions/criteria.

I would say that they have not done nay testing on frozen wood chips but U could ask them for some input.

To prevent bridging, U will need an outlet diameter/size whihc will not support bridging at all.

Installing a full width screw sounds great but it the chips bridge the full silo diameter - then U are no better off. I have no experience in wood chips but other materials. But, it soulds like that this would not be the case as U can get flow when promoted by the jackhammer.

The level in the silo could be adding to the problem - higher compaction pressure > greater propensity to consolidate and bridge. If this is the case, a continious recirc. system could help or having procedures to limit fill and stored time.

Air cannons are a treatment of a sympton - they do work but U really need to have them fitted in the right spot. So, if money is an issue...U could try and determine the best location for them.

U could try heating if the chips are really frozen to the wall or pre dry them...aim would be to stop the moisture freezing the chips together. Again.....U would know if this is really a viable option.

Cheers

James ■

Bob:

The wood ship is a coarse bulk solid, an for this case the most recomended solution is to use a forced system like Laiding. This kind of materials are no spherical particles; the shape is irregular, in some cases the particle are thin and long and it produce intelocking between them to promote the bride. The phenomena increase the internal strenght and the angle of internal friction increase. Also the aparent density is sometimes low and whit the head increase in the silo, the density change and the flow preperties are modify strongly; the humidity also is a problem because of the cohesion increas and the wal friction increase. Sometimes the vibration is in detriment of the flow; the particles adquire better arregement among them and the interlocking increase. Communly the hopper solution neded a high discharge orifice and no more tha 25 degrees in hopper. A 2d hopper could give us better results. The particle coarse surface makes difficult the internal shear and stop de continuos strain. ■