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Unit density of sawdust in a duct?

Unit density of sawdust in a duct?

Unit density of sawdust in a duct?

(OP)
Hi,

I am designing some structural support for ductwork which may have an accumulation of sawdust inside of it. Does anyone have a range of unit densities that I might use for calculating a load? I realize that it depends greatly on the moisture content of the sawdust, but I would like some numbers in order to get a feel for the design load.

Any help would be appreciated.

Thanks,

Richard Querin

RE: Unit density of sawdust in a duct?

I would start with the unit weight of wood (before cutting), which would be 35 pounds per cubic foot for Douglas Fir.  Hardwoods such as oak would be a bit heavier.  In the sawdust form, I would estimate the density at about one-half to two-thirds, depending on how tightly packed it is.

RE: Unit density of sawdust in a duct?

From the AITC Timber Construction Manual:

Douglas Fir  33.5 pcf @ 12% MC and 35.2 pcf @ 20% MC

Hem-Fir      26.6 pcf @ 12% MC and 27.7 pcf @ 20% MC

S. Pine      36.3 pcf @ 12% MC and 37.4 pcf @ 20% MC

Red Oak      44.0 pcf @ 12% MC and 44.9 pcf @ 20% MC


MC = Moisture Content

I agree with Kramer that somewhere between .5 and .75 of the above values would seem resonable.  The other alternative is to weigh a 1 cf sample of the sawdust.  Also, some manufacturers of dust collection systems might have a number that they use.

Just a thought!  Good luck.

RE: Unit density of sawdust in a duct?

(OP)
Thanks for the info.

The client has supplied a value of 15pcf and this seems reasonable compared to the values you've given above (the sawdust in question is in quite a dry state).

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