This could develop into a very interesting thread. Your individual flakes can flex quite readily so any flow promoting activity undertaken within the bin can, and most probably will, become counteracted as the flakes have passed on. Vibration will compress the matter and as soon as the vibration diminishes the matter will expand towards the original volume. Air flow begs the question "What direction should the airflow take?" You can't blow it down because you will get the same irregularity as with the vibrator. What's the point in blowing upwards? It is light material and you want it to fall down. That said, you could suck off the top of the top of the bin if you have a vacuum line installed.

There are plenty of firms out there with specialised knowledge but if you want to drop the flakes out of the bottom of a bin you first need a big enough hole in the bottom of the bin. If you have a thin flat plate, tin snips, and said flakes you can quite easily find the answer. Shaking the flakes about a bit to get them to the hole comes later. ■

Flaky and interlocking materials can present quite a challenge to bin design as they gain strength rapidly with compacting pressure and are difficult to shear, particularly if the flakes tend to have elastic properties or are soft and deformable This points to the need to minimise compaction forces and present a large live flow cross section at the outlet. As John points out, vibration tends to reorient flakes to a closer packing arrangement that forms a stronger mass and is self-defeating.

Steps should be taken to reduce the accumulation of compacting pressure by having high friction or flow inhibiting surface on vertical walls and possibly flow inhibiting inserts across the span at suitable intervals, depending on the size of the storage container. Angles can be fixed toe-in on flat vertical walls, to be self shedding but resist wall slip with inverted 'V' inserts across the width at specific heights.

The lower plane flow convergence should be designed for mass flow, to a large or twin discharge screws, designed for progressive extraction over the entire length that would then provide very favourable discharge conditions. It should be emphasised that the facility should be designed as an integral unit, rather than a bolt on feeder to a separate hopper, and is probably best placed in the domain of an experienced supplier. ■

Originally Posted by fgaona

When PET flakes are storage in a silo, What is the best device to be sure the flakes is unload form the silo?.

the irregular Flake form (10 mm average) and low bulk density (~300 Kg/m3) do difficult to unload from the silo

What do you recommend? bin activador? air flow system? etc.

As an expert in handling poor flowing materials and as the inventor of the Flexair Technology, I have sold and several large bulk silo installations to DuPont for handling their Polyester flake and chip materials. The last thing you want to do is run these materials through a cone or add vibration. Go to www.siloflowsolution.com and watch the Bulk Silo and InFlo video's.

I use a large, flat-bottom / low profile silo with an inflatable liner inside. The secret is to allow the materials on the top of the silo to be discharged first while they are in a "flowable" and "free" condition. I can guarantee the system (not all of it is shown on the video) will work. Thanks. Tim ■

I was interested to look at the videos Tim, but that link didn't work for me in several browsers. I did find a couple of videos on your home page though. ■

This one may be what you are looking for.

https://www.dropbox.com/s/d8et6b2f5n...0Mail.wmv?dl=0 ■