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Kiln theory and knowledge
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Short introduction to Kiln Link Direct reporting.
Short introduction to Kiln Link Direct reporting.
In theory you can not collect too much information, provided you are able to handle it and make sense of it; however, you should probably try and focus on collecting valuable information. Graphs and other graphics look nice and can be very helpful, however they can also on occasion hide trends which would be obvious using other displaying methods. On of the methods we favor are the "snap-shot" reporting with a very short interval backup. Both these reporting functions displays initially raw number, which you can manipulate later using graphics or spreadsheet programs. The short interval reporting is useful to catch momentary problems, such as temperature spikes; however, we have put a lot of work into making the "snap-shot" report a valuable and very easy to use tool for helping you optimize the drying process.
Our goal when determining the information collected for the "snap-shot" report was: - Providing you with accurate energy consumption and cost calculation.
- This includes both total cost and key figures for comparing the efficiency of each kiln load. When one can compare the efficiency it becomes much easier to see when you are getting ahead or falling behind. There are many more advantages to getting key energy and cost figures.
- Determining the general temperature and RH% schedule.
- This is exactly the same as you did on the old circular cart records and is a must to insure that the kiln load was dried properly. This information is also useful for later troubleshooting.
- Comparing the actual drying process to the intended drying schedule.
- The main reason for recording the set points is to compare them to the actual conditions in the kiln chamber during the drying process. This is more important with older kilns with insufficient heat, vent, or fan capacity. Consider this: Your set points when drying a load of maple or beech is 45C (115F) and 30% RH at 35% moisture content; however, due to a poor venting system the actual RH was 55% and the lumber looked beautiful. When you are going to dry this maple or beech in another kiln with adequate venting you keep the same drying set points and suddenly the lumber encounters a much dryer climate, which will likely result in surface checking.
- Follow the moisture loss throughout the drying process.
- When drying lumber it is best to have a constant moisture loss per day (or hour) within the maximum safe moisture loss rate. This rate will vary greatly from specie to specie and from thickness to thinkness. This number can also help you optimze the kiln and reduce drying cost and energy consumption, when used together with some of the other numbers.
- Follow the operation of the main fans.
- This number is one of our own innovations, which we have not seen copied yet. Together with the interval-operated fans this figure tells you how much the main circulating fan operated in any given "snap-shot" interval. Consider this: During three "snap-shots" the main fans operated 75% of the time and the moisture content droped 3% from 22% to 19%. During the next load you change the Main Fan interval parameters and when looking at the "snap-shot" report you see that the main fans only ran 60% of the time while the moisture content dropped from 23% to 20%, hence no noticeable change in the drying time. This key figure takes into account savings when you use frequency operated fan systems. In addition, at each snap-shot the report will indicate at which speed the kilns were running on kilns with frequency controls for the main circulating fans.
- Follow the operation of the heating system.
- This may seem like an unnecessary figure. But it can save you a lot of headache when trying to determine the exact reason your kiln is not performing as you think it should. Consider this scenario: You have been drying ash or pine for years without problems except in one of your kilns. You have been running the exact same set point schedule but it takes longer. Well if the snap-shot report indicates that the heating has been on about 95% of the time during the initial drying process it is obvious that your current heating system is inadequate. As most fin pipes get older they tend to loose the connection between the actual fins and the piping, which results in less heat transfer onto the fins and thereby reduces the heat output. It should be mentioned that older kilns were generally designed with more than necessary heating capacity, since they were designed to operate using higher temperature schedules.
This scenario leaves you with several choices:
- Do you have sufficient heat supply? This would be the very first step. Make sure that the heating is getting to the kiln. In addition, on steam systems you should also make sure that all the steam traps are working and the condensate is not restricted in returning to the condensate tank.
- Upgrade/replace existing heating systems either by replacing the fin tube coils or changing to heat units.
- Install heat recovery units on your venting system, which can reduce the heating requirements 15% to 35% depending on the specie and thickness your are drying. More information.
- Avoid using this kiln for certain species and thickness which has high heat requirements. This could be an immediate solution before actual solving the problems.
- Follow the operationg of the venting system.
- This figure is more of a troubleshooting figure similar to the previous number for the heating system. However, this figure tends to be more valuable on older kilns which hasve been upgraded with our control system. Venting on old kilns tends to have insufficient venting capacity for the more modern and low temperature drying schedules prefered by most companies today. If a kiln has insufficient venting the venting figure in the snap-shot report would be up around 80-100% during certain parts of the drying process (this would normally be happening in the begining of the drying process). Insufficient venting can be solved in several ways:
- Install more "passive" vents. This would help but is no guaranty, since other factors might prevent these from adding sufficient capacity.
- Power venting/exhaust upgrade would probably be the low cost approach to solving an insufficient venting problem. Power exhaust is the more untraditional method and best suited for hardwood drying and other slower drying processes. Power venting is really an improved standard venting system.
- Heat recovery upgrade is very similar to power venting/exhaust but forces air out of the kiln using fans. However, a heat recovery system can help you by also reducing your heating cost.
- And several more advantages.
We hope you have found the above description to be detailed, informative, and interesting. Should you have question, need additional information on our control systems, or advice on kiln drying problems, please do not hesitate to contact us.
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Kiln controllers, fans, sensors, vents, heat systems and more
