Drying

What’s your “Dead Time”?

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Imagine you are at your dryer and you have just taken a moisture sample.

The corn tests at 14.2% in your bench top, but you want 15.2% coming out of the dryer. What do you do?

Let’s say you decide to increase the metering roll speed (discharge rate). You make the change, but right away two thoughts strike you. First did you make a big enough change, or maybe too big of a change, and second, just how long will it be until you know the answer to your first question.

Just like there is a lag between when you turn on the shower and when you actually get hot water there is a lag between when you make a change to the metering roll speed and when you see the impact of that change. This is what is called “dead time”.

If your dryer has a cooling zone, then the absolute minimum dead time before you see any change in your outlet moisture is the time it takes for the grain to get from the bottom of the hot zone to where you take your moisture sample. This is because the grain that was already in the cooling zone will not see any change in moisture because of your rate change. In reality though you should be looking at up to a full dryer load before you see the full impact of your change. Only then can you know if you made the right change.

So, if your dryer has only a 60 minute residence time and a cooling zone, you are probably still looking at about 50 minutes to see if the rate change was correct. If you have a rack style dryer with say a 3 hour residence time then you could be looking at well over 2 hours to see the impact of your change.

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Let’s use as an example the sample dryer at the right with a 3 hour residence time – 2 1/2 hours in the hot zone and 1/2 an hour in the cooling zone. If you make a discharge rate change the grain in the cooling zone will not be impacted by the change. The final moisture of this grain has already been set at this point. The grain in the bottom half of the hot zone is also unlikely to see the full impact of the change. Again in our example, by the end of the hot zone if the grain is over dried it can not be undried at this point. Therefore it is likely that to see an impact from the rate change the grain will have to at least be in the top half of the hot zone. That means you would have to wait at least 2 hours for it to exit the dryer before you might start to know if your rate change decision was correct. That’s why it is called “dead time” – time you have to wait not knowing if the right decision was made, and it is one of the reasons grain drying is so tough.

It is no wonder that so many dryer operators prefer not to make too many rate changes, and prefer to err on the side of caution (over drying a bit). If they make the wrong decision it can take up to a dryer load to get things back in order.

In our next post we will look at how Dryer Master handles the “dead time” problem to help users take the guesswork out of drying their grain.

DM-Mobile from Dryer Master: Adding mobility and peace of mind to your drying season.

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DM-MobileDM-Mobile brings true real time remote moisture monitoring and drying control to the grain industry.

Now your moisture and drying information can be easily accessed through your web browser on your smart phone, tablet or PC. There is no app to run. Just open your browser and go to my.dryermaster.com and log in to your Dryer Master DM510*

With DM-Mobile you can view real time moisture and drying information (including alarms) as well as up to 24 hours of historical data. You can also even make changes to moisture and rate set points all directly from your browser. Now you no longer always have to be close to the dryer to know what’s going on.

Why not try out DM-Mobile at my.dryermaster.com (log in: demo, password: demo). If you are not yet familiar with the DM510 you might want to take a minute to read the help page for a quick run down of DM-Mobile’s features.

To help promote this valuable new feature Dryer Master is adding DM-Mobile as a standard component to its industry leading DM510 computerized drying control systems at no additional charge for 2014.

If you would like to learn more about the DM510 and how it can add profits and peace of mind to your next drying season why not check out our product page on our web site or one of our DM510 training videos on our YouTube channel, or even better give us a call at 1-888-318-0009 (toll free in North America) or at 1-519-725-4700.

* requires connection of DM510 to an internet enabled router

Drying the traditional way

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Sun dried coffee beans
Sun dried coffee beans
In the last post we described a visit to an organic coffee cooperative in Guatemala. In addition to the economic lessons we drew from the cooperative experience, we also saw how drying often happens in a developing economy.

At La Voz there is no need for a Dryer Master computerized drying control system at this time because the cooperative does not even have a coffee bean dryer. This is a situation that is mirrored in many smaller scale operations in the developing world for a whole variety of crops. The cooperative’s coffee is all sun dried in an open area right next to where it is washed and cleaned.

The actual harvest extends over a long period running from November to March, which coincides with the dry season in the region. During this period rainfall is almost unheard of and the cooperative can take advantage of almost constant day time sunshine to dry the beans outdoors on a drying pad, a process that takes about 5 days. As the harvest occurs over an extended period it is possible to use a relatively small area to dry all the beans harvested.

Once the beans are dried they are hand sorted by women from the cooperative, to ensure that the ones headed for export are top quality. The beans are then bagged in burlap sacks and shipped to the capital where they are processed to remove the parchment skin and then repacked for export from the Pacific Coast to the end customers in Japan, California and Alaska.