Weight of chips from logs sawn...

Woodhog · January 05, 2006, 08:09:05 PM

Would someone know the approx weight of chips derived from the slabs left over after sawing
out 1000 feet of red spruce logs, international log scale...????

The measurement of the logs in tonnes is 4.67 tonnes to 1000 board feet of material using the
international log scale...

Thanks

SwampDonkey · January 05, 2006, 10:30:55 PM

Were the logs debarked?

Jeff · January 05, 2006, 10:47:08 PM

depends a WHOLE LOT on the moisture content.

SwampDonkey · January 05, 2006, 10:59:05 PM

36 lb/ft^3 green

0.5779 tonne/m^3 green

Going to be impossible to figure out unless the logs are all the same size, or you just run the load of chips over the scales. The larger the logs the more lumber versus slabwood, percentage-wise. Good luck. ;)

Ron Scott · January 05, 2006, 11:24:04 PM

1000 bd. ft., Doyle scale yields approximately 1.60 tons, green chips or 2.22 tons scribner, or 2.54 tons international.

SwampDonkey · January 05, 2006, 11:42:03 PM

I came up with (2.508 ton) 2.28 tonnes/ MFBM, but that's probably due to local conversion factors. I wouldn't go out and mortgage the house over it, unless it was to buy a set of scales. If your going the send chips to a pulp mill, they pay on that scale weight. Which has to be approved by Measurement Canada. ;D

Woodhog · January 06, 2006, 09:44:31 AM

Yes the logs have been debarked...

So it would seem to roughly be 2.5 tonnes of chips that would be left over after the lumber has been sawn out of the 4.67 tonnes of logs...almost half of the weight from the 1000 board feet of logs would be left over in wood chips..this is much more than I imagined...

extrapolate85 · January 06, 2006, 01:44:23 PM

From an effecient mill, the manufacture of 1 MBF of lumber will result in about 45 CF of chips if cutting boards, 39 CF if cutting studs, and 41 CF if cutting dimenstion. At 46 lbs/CF (fresh cut, green), that would be between 1,794 and 2,070 lbs per MBF (You might say one green ton as a simple average). Note that a lot of chip purchasers buy on the bone-dry ton (BDT) or bone dry unit (BDU, which is 2400 lbs) and that for Red Spruce it takes about 104 CF (solid wood, green) to make a BDU, and 87 CF for a BDT. Of course, these numbers will vary given log diameter, defect, sawkerf, etc., but these should get you in the "ballpark".

SwampDonkey · January 06, 2006, 02:44:10 PM

This is just why I wouldn't put much stock in the guess-stimation process. I'de do some cutting and weighing throughout the year to see the variability with each season. It depends greatly on moisture content, the run of wood your getting, and recovery of sawn material from your mill.

Jeff · January 06, 2006, 04:02:03 PM

Its impossible to do to any real degree of accuracy. We had semi loads of chips going out of the mill on a regular basis. The length of time they filled was dependent on the size of logs you sawed. Sawing big logs they fill much slower. The other thing is that they might vary in weight up to 40% due to different moisture contents. You would need hundreds of Semi-loads to come up with even a reasonable average approximation. Loads filled within a day of each other from the same log piles would weight differently if one was deivered on say a thursday and the other on a monday. Big differences. I watched these numbers for years. THe drivers were the only ones that knew weather a load was light or heavy before it was actually weighed by the way the load pulled down the road. You can't tell by looking at them or by the volume. The chip vans don't change in size from load to load and they all pretty much filled the same.

Ron Wenrich · January 06, 2006, 08:16:05 PM

Rule of thumb for hardwoods is 2 tons/Mbf. It holds up well for oak and sawing 4/4 lumber. When I was looking at co-gen startups, this is the number we used for planning and establishing supply. It held out fairly well when talking with many mills.

But, if you're sawing softwood dimension stock, you have a 25% overrun by cutting 6/4 lumber and calling it 2". That would drop it down to about 1 1/2 tons/Mbf.

Figure the differential in weight between hardwoods and spruce and you will probably end up with about 1 ton/Mbf.

But, as pointed out, a lot depends on time of year, growth rates in the trees, how long laying around, and a lot of other items. But, you can use something like that to justify investing in a chipper or not.

Ron Scott · January 06, 2006, 09:51:41 PM

Best to see what factor and scale your local "chip buyer' is using for a particular species. They are the ones that have the scales and documentation for the area and usually have an "estimating average" for field use estimating.

All truck loads will vary in weight as previously mentioned, but the records will establish an average. Any loads that have been run through the car wash first are thrown out of course. ;)

SwampDonkey · January 06, 2006, 10:02:23 PM

Quote from: Ron Scott on January 06, 2006, 09:51:41 PM
All truck loads will vary in weight as previously mentioned, but the records will establish an average. Any loads that have been run through the car wash first are thrown out of course. ;)

Oh come on now Ron, we gotta soak'm down some. :D :D :D :D

Woodhog · January 06, 2006, 11:37:57 PM

Well, it looks like the figure could be around 1 ton/MFB...Thanks a lot...

Does anyone have some figures of what they are paying for 1 ton of green softwood chips at the mills???

I remember we used to haul about 30 to 32 tons in the chip trailers but have no idea of the price paid...we always double checked to see that there was no water added or ice/snow etc, that would be a terrible thing...