some advice please

[Wallnutt]

I am trying to work out the cubic capacity of woodchip,

if i have 100m3 of logs, from previous threads this equates to 70m3 of timber

i.e. 100*0.7.

my question is if this wood then goes through a chipper what will be the cubic

size of the pile of woodchip at either G30 or G50 spec.(is the air gap similar)

by working it through this way i can remove the loss of moisture in calculating the cost of the fuel.

Thank-you in advance

[Marc Lewis]

To work out cubic capicity of a log stack is not as simple as just x by 0.7. Take a look at Forestry Commision Booklet no. 39, Forest Mensuration Handbook pg27.

[openspaceman]

I am trying to work out the cubic capacity of woodchip,

if i have 100m3 of logs, from previous threads this equates to 70m3 of timber

i.e. 100*0.7.

my question is if this wood then goes through a chipper what will be the cubic

size of the pile of woodchip at either G30

 

The 0.7 factor will only hold for shorter (~2m) billets of fairly straight uniform timber.

 

My guess would be about 200m3 as a low loose heap but it depends on all sorts of things like shape of chip, sharpness of blades.

 

 

by working it through this way i can remove the loss of moisture in calculating the cost of the fuel.

 

How come?

 

The best bet is to take a log, weigh it, chuck it through the chipper and measure the uncompacted volume of chips in a container.

[Wallnutt]

i have been sold 2.3m lengths of freshly cut softwood, it will have to season for possibly 10 - 12 months and then be chipped in a large machine that does 50m3 per hour. i could weigh a log now ,the same one again in 10 months to asses seasoning losses and then chip it and weigh the chip I thought that by using metres all through the process i can work out the cost of the chip in £ per m3 rather than by the tonne which is affected by the variations between species of wood and moisture content of the chip.

[openspaceman]

i have been sold 2.3m lengths of freshly cut softwood, it will have to season for possibly 10 - 12 months and then be chipped in a large machine that does 50m3 per hour.

 

I guess it was processed so strips of bark are missing?

 

 

i could weigh a log now ,the same one again in 10 months to asses seasoning losses and then chip it and weigh the chip I thought that by using metres all through the process i can work out the cost of the chip in £ per m3 rather than by the tonne which is affected by the variations between species of wood and moisture content of the chip.

 

I keep a 3kg eucalyptus log by my desk and weigh and date it every now and then, sad as I am.

 

I would refer everything back to dry mass. As long as there is not much loss of dry matter due to decay then it will hold true across most species. So take a sample log, weigh it, then stick it in an oven set to 120C for 24 hours, weigh it and this should be the oven dry weight. From this you can work out your current moisture content. Do the same in 12 month and see what changes.. You can measure the volume of a log by the Archimedes principle. Immerse it in a calibrated container, like a clear 25 litre chemical container ( triple rinsed ) which you have marked in 1 litre increments. Chip it and use the dry container to get a good estimate of the chip volume.

 

The trouble with estimating fuel value from chip volume is that volume changes with compaction and density changes with size distribution and is affected by small things like blade to anvil length, sharpness, rate of feed etc.

[Wallnutt]

Thank-you catweazel i will give it a go

regards

Wallnutt