FORCES I P'RuDLUIC'l S LABi AT. r
SMALL SAWMILL IMPROVEMENT
PRACTICAL POINTERS TO FIELD AGLINCIES
B12 *J:]* 71AS3TL TMA-.L:72IAL
Green slabs, edgins, and trims can be burned without a forced draft if
such material is in a loose pile. Sawdust, either with slabs and e,- injs, or
separately, usually requires a forced draft. The destruction of waste should
occur as fast as it is produced.
The destruction of accumulated piles of s-,.'.'ust cr, vosp. .d'? i', using a
blow'r powered by a 1-1/2 to 5 horsepower unit. About 2 feet of outlet pipo
havin" a diameter of g inches or more permits locating the blower a"ay from
fire hazard. A steady, diffused flow of air is effective, a direct and intens-
draft on the "-urnin," zone is not; hence, outlet pipes of relatively larg- diam-
eter are used, the fans are run at slow sr-^ds, and the air stream is directed /
to hit the ground at the base of the pile on the windward side. TV..- 1lo/er is
moved as wind direction changes and as the pile is consumed. Anchori-. to
skids provides a firm base and ready'mobility.
The waste disposal method chosen for use at a small mill should be deter-
mined by comparing the capacity and the installation, upkeep, and depreciation
costs of the various methods. That requiring a minimum install-.tion cost is to
convey the sawdust to the pile with a conveyor chain or a blower, and slabs and
edgings by hand labor. One man can keep up with a production ra-te of '0' board
feet per hour if the carry is within 50 feet. Slabs and edgings are picked oftf
the rolls or -ground near the rear of the edger on the trtck side and carried
directly away from the mill to the pile. The fire should be at least 40 feet
from the tracks, and preferably be located so that prevailing winds blow from
the mill to the fire. h--i work can be lightened or the distance lengthened by
installing, skids leading to the fire so that waste material can be placed across
them and pushed. Slabs will slide by gravity if the slope is one foot verti-,
cally to two horizontally. This method is illustrated in a previous paper of
this series (.4S2221, Plan No.l, Yimeo.RS9)-10). ..ith some additional inst:ll-
tion cost, slabs and edgings can be conveyed to the fire on a slab car. This
raises the one-man capacity to about 1,000 board feet per hour or increases the
carry to 100 feet (.4S2221, Plan No.2, :.im.no.RS99-10).
An alternative method involving more cii FU-ir 'p"lj.i trrn installa-
tion cost, but requiring less nrinpo'.:er and rov iain dF'iire hazard, con-
sists of a conveyor-burner combination. Th s can be adapted to any rate of
production and to considerable distance. : 1
Uw ;<.! 1972
The wisdom of usin-, such equipment can be shown by balancing t e "':y
cost against the cost of labor saved. A co .veypr sc-tem will save he labor of
at least one man for capacities up to l,C30 r'O.4fL'o, .-Oi to thrFe
for higher production rates, and permit p-sa.-e .li : ', ..ails of the
conveyor are given in another par-r of this series (.42.i, ,i.eo.- 9y-21)
"i -?o. No. Rg)5-2C
t Maintained at Madison, Wisconsin in cooperation with the University of Wisconsin
'See outline in Small Sawmill Improvement Working Plan, March 1930, for explanation of indexing system proposed
The burner should be located at least 70 feet from the mill and so that
prevailing winds blow the smoke away from the mill. If forced draft is needed,
a small fan type of blowver is used. A 20-gage pipe about 8 inches in diameter,
preferably housed in a wood casing and sunk below ground level, carries the air
from the fan to the burner. The fan cin be powered from the saw mandrel or by
a s.prarate po-or unit ranging from 1-1/2 to 5 horsepower. The separate unit
permits a draft when the mill is not operating. Various types of outlets are
used to dif'.use the draft under the burning material.
In a simple burner, the pipe outlet centers the pit. Rocks or fire bricks
ar- loos-ly heaped to give a base about 4 feet across and a peak 2-1/2 feet
hirh. The overhead conveyor should discharge the refuse on this heap; the re-
quired draft results from the air forced through the openings in the pile
Another relatively inexpensive burneri (fig. 2) provides for greater
diffusion of the draft. If slabs and cdgings are burned, a shield of rocks,
laid alongside and ov-r the bricks but leaving th vents unobstructed, insures
that the bricks are not displaced by falling pierces. More expensive variants
are gratvs (fig. 3)L]or pojrforatcd pi'-ing (fig. 4)1. Perforated piping func-
tions wvll on sawdust, but is ls suitable for slabs.
A simple type of enclosure wall is shown in fig. 5. For more permanence
the iron pipe posts of fig. 6- can bo used.
C. J. TELC'RD
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