Author Topic: TDAL method of drying lumber (Read 656 times)

JMS · « **on:** October 15, 2012, 12:55:07 PM »

I have heard that there have been some new advacement in the TDAL (temperature drop across the load) method of drying lumber.

Are these improvements sufficient to consider this as a replacement for a capacitance type of InKiln Moisture Measurement system or to be used in conjunction with an existing sytem for better kiln drying performance?

I appreciate any feedback.

Thanks

Linkback: http://www.kilndrying.org/dry-kiln-control/5/tdal-method-of-drying-lumber/477/

MichaelM · « **Reply #1 on:** October 29, 2012, 09:30:57 AM »

JMS,
I have not heard of anything new. Using TDAL requires that things are repeated from charge to charge. Same schedule, but also same stacking. The TDAL is affected if there is a gap in the stacking near the sensor. When done well, TDAL works well. Capcitance methods also require repeatability in sensor placement and maybe some seasonal tuning as wood SG changes.
Mike M.

JMS · « **Reply #2 on:** November 08, 2012, 08:48:41 AM »

Mike,

Thank you for your response. Always looking for new methods or technology enhancements for improving drying efficiency.

JMS

GeorgeCulp · « **Reply #3 on:** November 19, 2012, 03:36:59 PM »

What Mike said about how things have to be repeated from charge to charge in order for TDAL to work....is so so so true. In fact, for any system to work to its best you have to repeat the drying "conditions" from charge to charge in order to develop any type of knowledge base that you can count on to make good drying decisions.

Just using TDAL as an example - If your baffles - top, end, and floor baffles don't all fit tight an snug... and stay that way... throught out a charge then hot air bypasses the lumber and the TDAL will be erroneous.

Venting, and fan reversal times must all be maintained uniformly from charge to charge.

How about kiln loading? Do you have gaps between the columns? Sometimes you do and sometimes you don't?

I"m trying to get you to question everything about your charges and their cycles. Everything counts and when you can honestly say you repeat the same drying conditions day in and day out then it doesn't matter whether you have the latest and greatest technology or not you be miles ahead toward maximizing performance and quality.

HencoV · « **Reply #4 on:** January 12, 2013, 04:10:12 AM »

TDAL has it's merits, however, I'm not sure if it is interperated correctly and then implemented right. What GeorgeCulp says is very true. I've been preaching a "management of constants" approach here in South Africa(it should actually just be - getting the basics right!!), but the value of having someone with enough training and the passion to make the whole drying operation their own to manage it properly has fallen largely on deaf ears. In short, the constants are (but not limited to):

1.Preparation – Sawing accuracy, board dimension, stacking procedures ect
2.Process Control – Airflow, energy distribution and management, humidity control and venting
3.Maintenance – Electrical, Mechanical, Instrumentation and structure

You may have the best drying schedule that works 100% for a specific specie and dimension, but the moment any one of the above "constants" changes, it influances the drying curve and you could be loosing time and/or quality.....in short, the drying schedule is not the optimum for the conditions inside the kiln anymore

Only when you have mastered this, can you really start fine tuning drying schedules.