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When to run the fans

Reports about the best times to run aeration plans have been conflicting, and sometimes confusing. Moisture sensor cables can bring 
all the information together

Farmers can hardly be blamed for being a bit confused about using aeration to dry their grain in the bin. They are told to turn their fans off at night, or only run them at night or run them continuously until that grain is down to the moisture level they want.

Proponents of each method have plenty of evidence to support their theories, which on the face of it all seems contradictory. But if you dig down a bit deeper into the information, especially that relating to using aeration to dry down and condition grain, there is probably one key message that they all agree on: careful monitoring is key.

Drying the grain in the bin isn’t really the number one concern; cooling it is. Drying occurs as the grain cools and as long as it’s kept at a constant temperature, once it’s cooled to a certain level, it should stay at the same moisture content. That’s the theory, but as every farmer can tell you, there always seem to be some circumstances where grain suddenly seems to heat up and moisture content increases.

The issue often is that farmers aren’t aware of exactly what is going on in the bin, which is why monitoring is all important.

Up until a few years ago farmers could only monitor the temperature in the bin, which is still a crucial factor, but now they have the ability to also keep tabs on the moisture content. Moisture sensor cables came onto the market a few years ago and, as part of an integrated monitoring system, can offer farmers both peace of mind and opportunities to capture the maximum profit potential from every bin.

Temperature, relative humidity (RH) and grain moisture levels are all important factors to maintain the quality of the grain in the bin.

How much water the air can hold is determined by temperature. The higher the temperature, the more water holding capacity it has. For example, air at 26 C can hold up to 4.3 kilograms of water; air at 15 C can hold a maximum of 2.25 kg of water. Relative humidity measures how much water is actually in the air — an RH of 50 per cent on a 15 C day means the air is holding around 1.12 kg of water (50 per cent of the 2.25 kg maximum).

Ideally, grain should be stored at a temperature of around 3 C, which will eliminate microbial activity and render any pests in the grain inactive.

“One of the misconceptions out there with grain storage is that guys think if three degrees is good then minus 20 must be better,” says Calvin Boisjoli, director of grain management with Wall Grain Handling Systems Ltd. “Freezing will damage the shell of the grain kernel by creating micro stress fractures. Producers generally don’t notice this damage because much of the resulting breakage (and shrink) blows away in the wind when loading the truck. The kernels can also stick together when frozen, especially if there are moisture pockets present, which can block the aeration.”

When to run the fans

Misconceptions abound around when to turn aeration fans and heaters on and off. On-farm research by Dr. Don Palmer in Saskatchewan suggests that the best time to run aeration fans is at night, when the air is cooler.

But Palmer adds that fans should only be run when the outside temperature of the air is cooler than the grain temperature inside the bin, which would suggest that there are a lot of other factors governing when fans should actually be run.

Research by Dr. Chandra B. Singh and Ronald G. Larson of OPIsystems compared a number of different methods to determine which produced optimum results. Their research also found that running fans only at night was effective only when the grain temperature was warmer than the ambient air.

They also determined that once night time temperatures dipped below zero, no further drying occurred, suggesting that grain harvested late, and/or in cooler than usual fall conditions might not have the opportunity to dry to required levels by running fans only at night.

The two trials agree that running fans continuously is the least effective (and most costly) option to obtain optimum grain quality. Continuously running fans risks over-drying the grain. Often, drying is not uniform throughout the bin, which can be compounded if heat is added to dry the grain quickly.

“If farmers have to move major moisture through the grain and they don’t have a lot of time to dry it they generally either use a dryer or some producers are using approximately a 100 F temperature rise in a heater that is in line with the fan,” says Boisjoli. “That dries the bottom out severely and at the top the grain is generally still wet. So the average moisture content may be 14 per cent but the producer has four per cent on the bottom and 18 per cent on the top. So when he is talking to a marketer he has to say here’s my average, will you give me an average price for the whole bin? Otherwise, the farmer has to find a way to blend the grain to achieve average target moisture content.”

Determining factors

But the bigger message from this later study is that the operation of fans should be determined by many factors, such as:

  •  the outside temperature;
  •  the temperature of the grain;
  •  the moisture level of the grain; and, the farmer’s goals in terms of grain quality, which vary from bin to bin, farm to farm and season to season.

“If you don’t know what you are doing to the grain you generally end up over-running your fans, constantly dehydrating and/or rehydrating ten grain. There is really only a specific period of time during a 24 hour cycle that you should be running those fans,” says Boisjoli. “There’s no magical formula to control this stuff and you can never say run at specific times during the day or during the night, or for four hours, or from 10 to noon, or whatever. You can’t really say you should run fans (or heaters) at any time until you know the ambient conditions and what it is going to do to that grain.”

Continuously monitoring all of these factors is really the only way that farmers can ensure they are optimizing the quality of their grain and not losing money whilst doing it. OPI-integris is the only fully integrated control system available in Canada that allows farmers to automate this process and monitor temperature and moisture conditions in the bin and apply air with or without heat in response to changing conditions.

OPI-integris system

Noel Flitton, who farms 11,000 acres of grain between Calgary and Lethbridge (Twin Valley Farms), installed the OPI-integris system to monitor his new 25,000 bushel and 35,000 bushel bins last fall. For him the biggest benefit so far is being able to remotely monitor exactly what’s going on in the bins, which are six miles away.

“I have been able to monitor my moisture and grain temperature from my office,” says Flitton. “Normally in a bin you don’t really know what is going on in there. After having this system on the large bins, I at least want to put the monitoring cables in them too so I can check them on an ongoing basis.”

Flitton has some very dry grain in those bins, which he hopes to use the system to help re-hydrate as soon as the weather is conducive, but in the mean time he has the confidence of knowing that the system is maintaining his grain at a constant temperature and moisture level.

“The OPI-integris system minimizes the amount of over-drying on the bottom of the bin and maximizes drying by toggling the heater on and off, so we don’t just run the heater all the time,” says Boisjoli. “We run the heat based on the EMC (Equilibrium Moisture Content) of the air and if it is cool and wet we will run the heater for a while until it heats and dries the air and then we will turn it off, so that it always stays in the targeted EMC band. What we are trying to get is a good average air moisture content and temperature which will change the grain to the target given enough aeration run-time.”

Too little moisture

Grain storage isn’t just about drying down grain to the desired moisture level. Equally often grain that goes in to the bin is too dry or is overdried once it’s in the bin. In the past farmers basically had three options; try to re-hydrate it in the fall, sell it as dry grain to the elevator or wait for spring and try to re-hydrate it a few points.

All of these options have problems. Re-hydrating in the fall has to be done quickly before the ambient outside temperatures drop below a point where the air does not carry very much moisture. Farmers are penalized if the grain is too wet upon delivery, however they are not paid a premium when it is too dry. If the grain is delivered overly dry to the elevator it will be blended with wetter grain to bring the moisture content to the desired level. Delivering grain that is either too wet or too dry takes profits directly out of the farmer’s pocket.

Trying to figure out when conditions in the spring are going to be perfect to begin re-hydration can be an art form and involve almost hourly trips outside to try and determine if air is consistently warm and wet enough to carry some moisture in into the grain, but not too wet, as this can create problems — saturating the grain in the bottom of the bin, which will block air flow.

The OPI-integris system, combined with Wall Grain’s management support, eliminates a lot of the uncertainty, work and time involved in re-hydrating grain and can allow a much wider window of opportunity to get that grain to the elevator faster and in optimum condition.

“We don’t allow the fans to run unless the EMC is in a specific range, so let’s say we are trying to rehydrate canola, which is at six per cent moisture. We would run air that was anything above six per cent and maybe up to 12 per cent EMC until the bottom of that grain started to rehydrate to a target of 10 per cent,” says Boisjoli. “It’s a matter of exposing the grain to specific moisture content of air — that’s what EMC is all about, picking the right air and calculating the EMC based on the ambient and the monitoring that air in the plenum as it goes into the grain.”

Greenwood Colony near Fort Macleod, Alberta, installed the OPI-integris system last fall in its 42,000 bushel bins of canola and wheat. Although it was late in the season by the time the system was up and running, in the remaining days where the weather was still conducive, they added three per cent moisture to around a third of the grain, which had gone into the bins drier than they had hoped.

The fans ran for about 150 hours total, says Walter Gross, who manages the system for the Colony, and adds a big benefit of the system is that it helps retain what moisture you already have in the bin. “If your object was to cool the grain because the moisture is at an optimum level and you want to cool it for longer term storage it will turn on the fans on when it is cooling but not drying, so it gives a double advantage there,” says Gross.

Management still require

Grain storage has evolved over the years as technology has provided new tools to help farmers dry and condition their grain and maintain it at optimum quality.

But the biggest challenge remains education about the various factors that influence that process and how to use those tools most effectively.

Recognizing that it’s a very complex issue and there is some confusion among farmers, Wall Grain, which markets OPIsystems products across Western Canada gets heavily involved in the education process with farmers to help them optimize grain management on their farm.

The OPI-integris system does automate much of the actual process of drying, conditioning, maintaining and re-hydrating the grain, but it requires input from the farmer who needs to set the parameters depending on what he wants to achieve with his grain. This requires some hands-on training at first, which Boisjoli and the grain management team deliver both on-farm and through remote access to their system.

“It’s a management tool,” says Boisjoli. “But you still need to know what you want to do with the grain, where your market opportunities are and what your goals are.”

But the system itself largely takes care of the rest, and is cost effective and efficient, says Gross. “You can set the parameters so it is optimum for energy efficiency to accomplish what you want to do with your grain,” he says. Based on historical data Gross feels that the system will save 25 to 30 per cent in energy costs, but adds the peace of mind it brings is almost as valuable. “Before, without the monitoring system and the cables you virtually had to sit there and watch the weather every hour and turn the fans off and on but this system is more hands-free, you don’t have to babysit it and it’s cost effective.” †

About the author


Angela Lovell

Angela Lovell is a freelance writer based in Manitou, Manitoba. Visit her website at or follow her on Twitter @angelalovell10.



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