Aeration Upkeep and Optimization Guide

The practice of aeration is used in grain handling facilities to maintain the condition of stored commodities after harvest. Guidelines for aeration are based on long-established scientific principles involving static pressure, relative humidity and moisture content.

Aeration may seem like a complicated science, but it can be distilled to one simple concept: Evenly distributing air to maintain a safe storage temperature will result in the desired grain condition.

This is achieved through a host of equipment and devices, such as aeration pipes, fans, roof vents, temperature cables and fan controllers. Selecting the right combination of these can be challenging, soFeed & Grainsat down with leading experts in the field to help guide your decisions in equipment selection, system optimization and maintenance.

Equipment overview

The essential components of an aeration system are:

1. Storage Vessel: Corrugated steel bin, concrete bin or flat storage (building or Quonset)
2. Fans: Axial or centrifugal — the power source for air delivery throughout the system
3. Distribution System: Ductwork sheets, round tubing or half round ducts, full floor or flush floor
4. Ventilation: Gravity vents and/or powered roof exhausters

System design

To design an effective aeration system, first establish the desired moisture content of the commodity being stored and its corresponding CFM. The CFM refers to how many fan run-time hours are needed for a cooling front to pass through the bin. Multiply the denominator by 12 hours to calculate the answer. For example, 1/10 CFM will take 120 hours to cool the grain bin; 1/7 CFM will take 84 hours, and so on.

[email protected]president Kevin Miles provided the following tables to determine each commodity’s required CFM based on target moisture content:

Corn

Target Moisture Content CFM

14 - 16% = 1/10

16 - 18% = 1/7

18 - 20% = 1/6

20 - 22% = 1/4

Above 22% = Not Recommend Operation

Beans

Target Moisture Content CFM

13 - 14% = 1/9

14 - 16% = 1/5

Above 16% = Not Recommended Operation

Wheat

Target Moisture Content CFM

13 - 14% = 1/15 - 1/30

15 - 16% = 1/12 - 1/15

Above 17% = 1/10

Next, determine which type of air delivery system is ideal for your application.[email protected]’s Miles suggests several options:

1. Pull down system (negative)
2. Push system (positive) with exhausters
3. Pull up (positive without exhausters)
4. Push-pull (high-air system)
5. Turbo-charged (existing high-air)
6. Manifold system
7. Canal system
8. Tower system

The ideal system for each application depends upon the type of bin — steel or concrete —, the number of tanks the system involves, whether it’s new construction or a retrofit project and budgetary considerations. A professional millwright service, a bin dealer or an aeration equipment dealer can help select the best set up for every price point.

如果交叉污染问题,托德•莫雷ales manager for Airlanco, recommends the AirAuger, a canal aeration system that doubles as a bin unloader.

“It’s an unloading aeration system we provide with no moving parts, so it promotes the zero-bin entry initiative,” says Morey. “It works using concrete troughs in the grain bin floor to allow standard gravity unloading, and then you turn on the fans to force out whatever gravity doesn’t expel. A properly installed system should leave less than a bushel of grain behind, so you can easily go from corn to soybeans without worrying about cross-contamination.”

Fan selection/sizing

Selecting a fan type and correctly sizing it is the next step in designing an effective aeration system. Randy Larson, sales, Sukup, says to ask the following questions to help choose between centrifugal or axial fans:

1. How is the bin going to be used, i.e. aeration, cooling or wet holding?
2. What is the bin’s diameter and eave height?
3. What type of grain is in the bin?

“Your answers will give you an idea of the static pressure you’re dealing with and then the proper fan or fans can be selected,” says Larson.

Axial Fans:Larson describes the blade as “shaped like a propeller with the motor sitting inside the fan housing and the air stream.”

They typically run at 3,500 rpm and are the fan of choice for commodities with a static pressure between 0 and 3.5 inches.

Centrifugal Fans:These generally operate more quietly than axial fans. The blade is wheel-shaped like a squirrel cage and the motor sits outside the housing.

For static pressures of 3.5 to 7 inches, Larson recommends a 1,750 rpm centrifugal fan and for static pressures above 7 inches, he suggests a 3,500 rpm model.

Scott Chant, president, Safe-Grain, Inc., notes that appropriately sizing fans plays a major role in selecting other supporting pieces of aeration equipment. “Once you determine your fan size, you can calculate what size tunnel you need to get the air from the fan to the bin and the square footage of perforated material you’ll need to get the air out of the bin.”

Once again, contacting a local bin dealer or millwright can ensure every calculation is properly done.

Optimization options

Uniform bin filling is integral to producing the desired temperature and airflow. While not essential to the operation, according to Eli Troyer, owner and president of AgriDry LLC, a grain spreader is a smart addition to any corrugated steel bin. “Hot spots,” where spoilage or bridging occurs, compromise an aeration system’s ability to effectively cool the grain mass.

A spreader uses several long chutes to evenly disperse fines during loading and create an equalized pathway for airflow throughout the bin. It can be used on any sized bin and is ideal for commodities such as soybeans and corn.

“Our spreader has no motor, electrical parts, or moving parts at all, so there’s little upkeep involved” says Troyer. “Once it’s put inside the bin, it becomes a permanent fixture and can last nearly the life of the bin when the optional Tyvar lining is used at high-wear points.”

曝气系统的其他设备m optimization include temperature cables and fan control systems. Temperature cables run from the top of the bin throughout the depth of the grain and provide real-time readings, which can indicate problems in a bin if a reading comes back outside the acceptable range.

Fan control systems, such as AgriDry’s Bullseye, work by setting a target moisture content and a target temperature for the commodity being stored. Then, using the temperature cables, it monitors the grain temperature, the outside air temperature, and the relative humidity and will operate the aeration fans to maintain indicated target levels.

However, Miles cautions that not every application is a suitable candidate for automation.

“I usually recommend the human interface for fan operation,” says Miles. “But if you have an elevator in a remote location with no staff once the bin’s loaded, then it makes sense to use an aeration controller because it will do a better job of conditioning than letting it sit unattended.”

Maintenance matters

Aeration system maintenance plays a key role in grain conditioning. Considering the tips below can help increase the longevity of an aeration system:

• Inspect electrical

- Physically inspect the electrical components and wiring before every harvest season

- Look for evidence of rodents or birds — often the culprit of wiring deterioration

• Read owner’s manuals

——在年度检查,指的是风扇或者motor’s operator manual. Many manufacturers provide them online if the original is not available.

- If unsure of the manufacturer, make and model, search the web for a similar size and type of fan to find a comparable maintenance book

• Ensure cleanliness

- Properly clean out the grain inside and outside the bin every time it’s emptied, or once a year at minimum

- Reduce the likelihood of rodent and insect infestation by eliminating food sources — fines and grain dust

• Keep water out

- Physically inspect the bin roof and sidewall joints for leaks. Allowing rain to enter will reduce life expectancy of the bin and floor

- Properly channel water away from a bin’s foundation and fan area to prevent ponds from forming