The Salt Lake tribune. [volume] (Salt Lake City, Utah) 1890-current, 1913-11-13

Inc meInod or applying fresh fuel
by forcing IL up through the fire has
long been considered to be an ideal
way TO obtain proper combustion.
Any number OF devices have been In
vented and patented to utilize this
underfeed principle. and three prin-
cipal types have survived the test OF
usage and are now commonly used in
boiler furnaces. These three types
might be suhdivided into two classes.
one class which utllizes a. single
horizontal trough. from which coal Is
forced upward over the sides by
means OF a worm screw or a piston
and another class which is made up
OF series OF inclined tropghs from
which coal Is forced by means OF
plungers. In all three of these
stokers the fresh coal Is forced
through the firebed and gradually
ooked and relieved Of its volatile
matter before II reaches the surface
OF the fire. A modified arrangement
Of the first class is now In use on
the pennsylvania railroad in loco
motive service.
AS already mentioned in all OF
these types OF stokers the feeding Of
fresh fuel Is upward through the fire
bed. and TO obtain a proper air sup
ply for the intensified combustion re-
sultlng therefrom II Is necessary TO
use forced draft 10 supplement the
ordinary chimney draft. AS loco
motive stack. however. can supply as
much rs five to seven inches draft
the locomotive type OF underfeed
stoker does not require an artificial
air supply. In the stationary boiler
stokers mentioned, the air supply is
forced (by means of a pressure FAM
through suitable tuyeres on TO which
AL
These tuyeres may be supplied by
independent wind boxes or By n
closed ashpIt into which the fan dis
charges.
Where tho speed OF the plungcrs or
screws (Which supply the coal) and
the speed OF the fan (Which fur
nishes air) can be controlled 10 ac-
cord with the demand made on the
boiler. and properly adjusted In re-
)ation with each other. almost ideal
combustion can be obtained. Where
an automatic governor Is used to In
crease the speed Of both the fuel
feeding apparatus and the air supply
as the load on the boiler Increases
them (and. conversely. decreases
them as the load drops Off. the
stokers become practically auto
matte. The question OF whether or
not thev produce smoke Is practi-
cally taken out Of the hands OF the
fireman in attendance. except that
he must keen the proper ratio Of air
To the coal supply and maintain the
governor I'm nropcr working condl-
ton. IT might be remarked that an
oversensitiye governor may cause
smoke by giving too rapid fluctua-
tions In fan speed with the result
that the coal already In the furnace
n,ill he deprived or a sufficient air
supply nj reduced fan speed.
The difficulty Of maintaining the
correct ratio between the air supply
and the coal supply is due 10 several
conditions. Forcing large quantities
OF coal into the retnrts 10 take care
of peak loads rapidly Increases the
resistance 10 the air forced through
tho tuyerc openings. with the result
that I, Is not q simple matter TO adj
iust the speed of the ran TO give the
increased pressure necessary to over
come the increased resistance and
SIMPLY the proper amount Or air. IN
n number or instGlla tons this results
in IN INADEQUATE air supply Tor peak
load operation and smoke Is pro-
duccd
Tho size Of tho coal and the amount
OF dust IL contains and It's cokipg
qualities also introduce variable
factor in the resistance 10 the air
forced through the fire from the tuE-
ere boxes. and IL the coal Is UNIFORM
ly coarse, lOerc IS some leh"eh.s W.
air In work backward through the
feed trough and out OF the coal hop
per These conditions Introduce ad-
ditloual difficulties Ia b" overcome IN
the adjustment of the air supply 10
suit the amount Of cobl fed. and thus
obtain maximum combustpn CHI
cheney.
In some Instances whore a motor
driven ian Is used constant speed
motor Is Installed. for reasons Of