Pellets Angle of Repose

[velvetfoot]

I just built a 4x4x4 box to hold pellets. I'm curious how much I'll be able to extract with just one vacuum pickup located in the middle of the box floor. Would anybody know what the angle of repose for pellets might be? I know it'll be a cone of some sort, and it might be somewhat steep, but I'm not sure what to ultimately expect. I loaded it up and time will tell also, I guess.

 

[smwilliamson]

I just built a 4x4x4 box to hold pellets. I'm curious how much I'll be able to extract with just one vacuum pickup located in the middle of the box floor. Would anybody know what the angle of repose for pellets might be? I know it'll be a cone of some sort, and it might be somewhat steep, but I'm not sure what to ultimately expect. I loaded it up and time will tell also, I guess.

I would think the angle of repose would also have to consider fines that silt down as well. Fines create drag so it's hard to say exactly

 

[velvetfoot]

Yeah, that's true I guess. I'm not familiar with pellet stoves, but looking down into the stove hopper and seeing the cone might not be a true indicator either, because the geometry of the hopper might have an effect. That is, if the area was larger and less restricted. Come to think of it, this would be a reverse angle of repose.

 

[Deering]

I think a little under 45 degrees is generally about what I'm seeing in my bin, but I've never actually measured it.

Here's a report from The Netherlands that states that they measured 30%: wbmttt.tudelft.nl/rapport/7442e.pdf
But then this German document says 45-60 degrees. www.depv.de/uploads/media/WoodPellets_storage_120322.pdf

So who ya gonna believe?

 

[velvetfoot]

Interesting. If I assume 45 degrees, I won't need any of my school geometry, which is beyond access to my grey cells.

 

[velvetfoot]

I like that second article-very comprehense. Though, the angles of repose noted in both articles is true repose, from piling up when a storage room or area is filled, not emptied. The second article does not 45 or better yet, 50 degrees for the slopes of a hopper. I wonder if it would called the "cone of repose". lol.

 

[velvetfoot]

I might be wrong, but with this size box and 45 angle of repose, I get a useful volume of 70%. Again, I'm probably wrong.

 

[yrock87]

I might be wrong, but with this size box and 45 angle of repose, I get a useful volume of 70%. Again, I'm probably wrong.

Maybe put some plywood in the bottom at 20 degrees to help the last bit slide in? I assume the angle of repose is only accurate on a flat surface, otherwise you are interested in the static friction of pellets on plywood (or metal, or Teflon, ext) Kinda like your Hopper does.

 

[hossthehermit]

Maybe put some plywood in the bottom at 20 degrees to help the last bit slide in? I assume the angle of repose is only accurate on a flat surface, otherwise you are interested in the static friction of pellets on plywood (or metal, or Teflon, ext) Kinda like your Hopper does.

............ and add some sort of vibrator ..........................

 

[velvetfoot]

I was searching vibrators. The hits I get so far are either large industrial models, or the other kind.

 

[TimfromMA]

I was searching vibrators. The hits I get so far are either large industrial models, or the other kind.

Thats a conversation for another message board.

 

[johninwi]

i don't think i could bring myself to type vibr... into google just wouldn't be worth it.

My basement top fill corn hopper, fills thru window above, end has a dutch door to allow access to pull corn to the chute when it gets low enough. After that i'll need to scoop it into buckets.

 

[velvetfoot]

Excellent hopper! The window fill is key for you as well as the tall, narrow-ish design. No bridging? I'm lifting the bags over the 4' wall and that's not so bad compared with the relatively high hopper on the boiler.

 

[johninwi]

Can you add coil springs to the bottom of you hopper? Might allow it to be easily shaken and may not require a motor?


The size was based mostly on available space, what i was willing to give up and trying to make best use of 4'x8' osb sheets
no bridging but corn flow more like water than a solid, i think pellets would flow fine, the opening in the gate is 4" tall and tapers 2" at the bottom to 4" at the top.

 

[Bridgeman]

How about pouring a couple of bags on a flat surface and measuring the angle? Think of it as a concrete slump test were your checking the angle instead of the slump.
I think a slow pour with a small opening in the corner the bags to a point just above the top center of the growing pile will get you close.
Brands of pellets differ greatly in length and I think this will make a huge diffence in angle.

 

[HVAC tech]

I'm currently having this problem with a new pellet boiler. I've installed the factory option vibrator with no luck. I'm presently experimenting with changing the level of the hopper to increase the angle of repose inside it. I will use an angle finder to determine the angle when I find it and post it here. Though this will include the vibrator action as well.

 

[velvetfoot]

I just looked at the vortex. It seems to be steeper towards the center and then it flattens out. I'm trying not to disturb it.

 

[railfanron]

Just mount a sub woofer to the side and play some of that rap music for a minute that should bounds em down.
Ron

 

[RKS130]

I am pretty sure that the angle of repose -- at least on Thanksgiving -- is that just prefect setting on the recliner where you can watch the game, drink your beer and grab a snack without ever having to move. Just sayin.

 

[velvetfoot]

Well, the intake got exposed today and I topped up the pellet box. It took 41 (40 lb) bags, compared to a capacity of 57 bags which comes to 72% Very close to the number I estimated for a 45 degree angle of repose.

PS: I'm also burning wood.

 

[SidecarFlip]

I just built a 4x4x4 box to hold pellets. I'm curious how much I'll be able to extract with just one vacuum pickup located in the middle of the box floor. Would anybody know what the angle of repose for pellets might be? I know it'll be a cone of some sort, and it might be somewhat steep, but I'm not sure what to ultimately expect. I loaded it up and time will tell also, I guess.

It wi8ll entirely depend on how smooth the interior surface of the bin is. It's not repose btw, in the included angle and even if slicker that cat poop on a doorknob, I'd say it needs to be 30degrees or more even up to 45 degrees. In grain bins, 45 degrees is the normal included angle of the drop cone for grain transfer.
www.gsi.com

 

[velvetfoot]

Yeah, I just topped it up. I'm going to say the total capacity of the box is 55 bags rather than 57, because, as I recall, the lid didn't close fully. So, that brings it to 75% usable capacity, 41 bags, without vibration, moving with a rake, etc. Still not too bad-could go away for awhile on 41 bags.

 

[SidecarFlip]

Smack the side with a 5 pound drilling hammer ocassionally and dispense with the rake.

 

[chadhumm]

I attached pvc to the bottom of a garbage can . Fill it from outdoors , water tight. I used 2 inch pvc which would plug. I moved and will rebuild with 3 inch pvc. with just a pvc shut off at the bottom in. Open to fill the stove. then close. Fill garbage can once every 4 days. Only negative is a garbage can sitting outside the basement window during the winter months. I had a 45 degree angle on it and would have to shake it quite a bit to get it to flow. I imagine pellets would never have worked in this scenario. Hard to imagine it would plug with 3" pvc

 

[purplereign]

For what it is worth this late in the discussion:

The Angle of Repose And Drain for Wood Pellets



The angle of repose and the angle of drain are used in bulk wood pellets storage, especially when designing the storage facilities for wood pellets. The angle of repose is an angle when we pour the wood pellets from the top and generate the standing cone or flat ramp on the horizontal surface. For large scale pellet trade, the angle of repose is 28-32 degrees. The angle of drain is an angle created when the wood pellets draining through an orifice on the flat, it is normally steeper than the angle of repose. The angle of drain is approximately 33 to 37 degrees.