While many agricultural users believe that fans are to be used for holding the cover on the piles many have paid the price of losing their cover when a storm has eliminated their electrical power and the fans. A Power Out™ Retention System resolves this because it will hold a cover on the pile without fans. In addition when stockpiling or picking up the commodity a fan vacuum fan system in ineffective when the end of the pile is completely open.
Most agricultural aeration engineers will agree the perforated side wall at best will only replace about 1/3 of the intake area necessary to achieve a good aeration design. Wall intake only provides inflow of air to the area running from the top of the wall to the longest exhaust bottom pipe thus walls provide no cross air movement to the entire top of the pile. That is not the case for a round pile assuming the entire center core of the pile is and exhaust plenum and the walls are of sufficient height to provide enough intake opening so as to match the required CFM exhaust area to balance each other thus note increasing the static load on the exhaust fans thus reducing their required performance base on the grain and moisture level.
Once the base is sealed and a vacuum is created the only purpose of any fan is to offset intake air from refilling the cavity with the commodity. A fan or fans used without intake is not aeration.
  • There are four factors necessary to determine the number of fans.
  • The moisture content of the grain. (This provides the amount of air needed for safe storage and is usually stated in terms of 1/10 cfm/bushel to 2/3 cfm/bushel
  • The static load of the grain at the highest point or most often the center.
  • The CFM (cubic feet of air per minute) an aeration fan will deliver base on the adjustment for the static load.
  • The number of bushels of the commodity to be contained in the storage unit. Only with these three pieces of information can the number and horse power of the fans be determined.
An envelope™ is a grain storage unit which encapsulates and seals a commodity protecting it from moisture, air and wind.
A Centerfill, also known as Stadium Storage is a round commodity pile with or without a wall taking the shape of a cone using its natural angle of repose and which the mass of the stockpile provides a truss system to support a cover. The stockpile is built from the center and flows outward. The stack height in the center determines along with the angle the diameter of the pile. The center peak is most often attached to a lifting ring which is raised as the material is discharged under the cover. The cover is most often installed prior to the start of stockpiling on the ground. The bottom circumference is sealed at the base by securing to a wall, using an anchor trench or with a base seal of ballast material.
A ring at middle of a Centerfill used to elevate the cover during the stockpiling stage and is secured to the cover using a series of compression plates, compression ring, lift hooks or simply anchor points. Upon filling the lifting ring most often rests on the commodity covered or at the natural stacking angle of the commodity.
The bottom is sealed at the base by securing to a wall, using an anchor trench or with a base seal of ballast material. Sealing of the bottom is important in the use of a down draft or negative aeration system since makeup air will always take the path of least resistance.
Would more ​mils have a higher tensile strength? – In Centerfill type storage or stockpiles over 150’ wide we believe tensile strength is always more important because the loads concentrated at the peaks and the length of the slopes when exposed to wind and loads are critical and dependent on strength. Internal and external companion retention systems can assist in coping with these added loads. On membranes and envelope™ systems sealing strengths and gas and moisture transmission rates are more important especially when they can be supplemented with internal retention systems such as the Gridlock® Patented System.
First and foremost the base should be crowned and the sub base tight enough to support the mass weight of the center load of the commodity and the weight of all trucks and equipment running on it. It should contain a geotextile and geomembrane in the sub base to stop moisture and assist in carrying the load. Consideration should be given to reclaiming the commodity as the use of throw away ground tarps can be troublesome to separate with augers, loaders and other equipment.
Only if the base is not constructed properly with a tight limestone, asphalt or cement base is not used to prevent ground moisture penetrating the base.
  • Moisture of the Grain Stored
  • Static Load (Depth of grain)
  • Aeration Fan CFM with load
  • Balancing intake with exhaust area
  • Length of time grain is to be stored
The height of a stockpile is based on two primary considerations. The first being the stack angle of the commodity and the distance from the drop point of the auger or head pulley throw of a conveyor to the front of the wheels of the stacking equipment. The second is the static load of the stacked commodity and what increase aeration demands evolve when stacked higher. In most cases small grains like wheat should be built in piles 110 – 120 feet wide the larger grains like corn 120 – 160 feet wide. Round stockpiles heights are based solely on the height of the center tower and the bottom area or flow out area they will occur base on the angle of repose and wall heights is walls are used.
Temperature probes unless you are superman with the ability to see what is going on under the cover are a smart investment. Charting your pile from day one is the best way to know what is going on under that cover. If you have any question as to how long you will be on the ground temperature probes are a wise investment.
Drainage Drainage Drainage! A stockpile sitting on ​porous ground and with a high water table can cause the water to be pulled through the ground and spoil the bottom grain. Depending on the porosity of the ground up to 16 feet. In addition rain, snow and other precipitation collecting or running to the perimeter of the stockpile saturates the ground surrounding the stockpile and forces it to be drawn back into the stockpile as the fans search for makeup air
Stop Stacking. The last thing you should do is to put dry grain on top of a layer of wet grain.
Two options can help. The first option is to reverse or turn and run your aeration fan to blow in during the stacking process. This will keep the FM from plugging the bottom pipes as a side benefit and allow moisture to wick from the top if you delay the stacking process until it has time to dry out the upper moisture layer.

Better yet compute the bushels per hour you can stack and wait until you have that window in the weather and then stack without stopping until it is build, top pipe is placed and covered. If it is a oval or rectangular pile cover it in stages, protecting your investment as it is built and should it rain put the cover over the leading face to protect it even though you know it will need to be removed to continue. Removing the wet grain at the bottom with a loader will cause the pile to collapse and a lot of the wet grain will slide down the slope because of the natural angle of repose.