This hump will normally flatten out slightly as the silo is emptied.Breeds: Quail: Ca. In mass flow bins, the grain will show a hump below the point where it was filled. In bins exhibiting funnel flow, the top of the grain will form an inverted cone where the center has collapsed into the funnel. It is relatively easy to determine which you have, though if you look at the top of the grain in your bin after withdrawing grain from it. Normally, cone angles >60 degrees will give mass flow - though they can be funnel flow if they are square or if there are problems with the feeding mechanism emptying the tank. How do you know which type of flow you have?Īny silo with a cone angle smaller than 40 degrees will be “funnel flow” unless it has some sort of flow-modifying device inside. The higher the friction, the greater the likelihood that funnel flow will occur. The frictional forces between individual grains as well as against the bin wall cause resistance to flow and create compressive forces within the grain mass that can “lock” it into place. I’ve had customers who were unprepared for this phenomenon send me samples from their last brew that are 70% husk and others report that their extract went down to 50%. When the bin is finally emptied, the brewer will see large amounts of husk coming out of the silo. Over time, the bin can have a layer on top several inches thick. When filling a second time - if the silo isn’t emptied - this layer is quickly suspended in the air and combined with the light material from the second fill. After filling, the light material settles on the top of the grain in a layer. During filling, the falling grain creates air currents inside the silo that suspend the light husk material in the air. Also because the material on top isn’t mixed in, they are prone to a phenomenon known as air classification. In mass flow bins, there is less mixing between batches or lots so changes between them will be more abrupt. Many breweries have mass flow bins, but almost all grain elevators have funnel flow bins, most with flat bottoms because of cost. More importantly, they are also taller because of this - which requires higher ceilings in the buildings and taller (longer) grain handling equipment. Normally they have a steep cone angle of about 60 degrees, which requires a bigger cone needing more material. Mass flow bins are typically more expensive. Old school, low resolution video of Mass Flow from an operator’s computer screen Despite these advantages, they have some cons as well. Mass flow bins allow for first in/first out removal of the grain. They are self-cleaning as the abrasive grain moves along the walls each time the bin is emptied. In mass flow bins all the material moves downward when the bin is emptying (see video). New malt goes on top, older malt comes out the bottom. Mass Flow Binsīins exhibiting mass flow behave the way most people think they should. Additionally, when the bin is finally emptied - the brewer isn’t seeing the malt that was loaded into the silo last but is seeing some random lot from several years ago. This can lead to moisture pick up, increased risk of contamination, loss of enzymes, and flavor issues in malt. This is the opposite of good manufacturing practice for raw material handling. Material in the stagnant zone will not move and can indeed be in the same spot for years if the bin isn’t emptied. In this way, funnel flow bins act as a first in/last out system. If a new batch of malt is delivered on top without emptying, this new material will follow this same pattern and come out of the bin first, before the older malt below. Old school, low resolution video of Funnel Flow from an operator’s computer screen
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