Unit density of sawdust in a duct?

[rquerin]

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

 

[Kramer]

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.

 

[jheidt2543]

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.

 

[rquerin]

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).