306 RAILWAY AGE GAZETTE, MECHANICAL EDITION. Vot. 87, No. 6.
is thicker than given in the table, it must have a branch pipe no avoid possible charting of the door in case of fire in the main
smaller than is called for by its grinding surface.
duct and also to permit sweeping under it. For similar reasons
Branch pipes must be not less than the sizes specified, through- it should be at least 6 in. below any ceiling it may run under.
out their entire length.
All branch pipes must enter the main suction duct at an angle
not exceeding 45 deg., and must incline in the direction of the
air flow at the junction with the main.
Branch pipes must uct project into the main duct.
All laps in the piping must be made in the direction of the air
How.
All hende, turns, or elbows, whether in main or branch pipes,
must be made with a radius in the throat at least equal to one
and one-half times the diameter of the pipe on which they are
connected.
The inlet of the fan er exhauster shall be at least 20 per cent.
greater in area than the sum of the areas of all the brauch pipes
and such increase shall he carried proportionately throughout
(Be ettire length of the main suction duct, i. e., the area of the
main at any point shall be at least 20 per cent. greater than the
combined areas of the branch pipes entering it between such
point and the tail end or dead end of the system. If such in-
crease is made greater than 20 per cent, the area of the main
at any point, except that portion of it between the branch en-
toring it nearest the fan and the fan, shall bear approximately
the same ratio to the combined areas of the branches preceding
that point (i. e.. between it and the tail end of the system) as
the area of the main at the branch nearest the fan bears to the
combined areas of all the branches. (This provision is made to
permit the use of a fan having a larger inlet area than the area
of the main at the branch pipe nearest to the fan, if desired.)
The area of the discharge pipe from the fan shall be as large
or larger than the area of the fan intet throughout its entire
length.
The main trunk lines, both suction and discharge, shall be
provided with suitable clean out doors not over 10 it, apart, and
the ensi of the main suction cuci shali be blanked off with a
removable cup placed on the end.
Sufficient static suction head shall be maintained in each branch
pipe within one foot of the hood to produce a difference of level
of in. of water between the two sides of a U-shaped tube.
Test is so he made by placing one end of a rubber tube over a
small hole made in the pipe, the other end of the tube being
connected to one side of a U-shaped water gage. Test is to he
made with all branch pipes open and unbstructed.
Tlans for all exhaust system installations, showing location
and sizes of all wheels. honds, main and branch pipes, fan, and
dust separator should be submitted to this department in dupti-
cate for approval before work is begun. and it must he clearly
specified that the system is to be installed in strict accordance
with these specifications. The test specified positively must be
obtained before the system will be acceptable to the Department
of Labor.
The contract for the installation of an exhaust systein should
contain a provision to the effect that payment will be withheld
until the above test shall have been made and the system ac-
cepted by this department,
In addition to the specifications, a number of recommendations
are given from which the following quotations are taken:
Enery wheel and buffing wheel exhaust systems should be kept
separate, owing to danger of sparks from the former setting
fire to the lint dust from the latter, if both are drawn into the
same suction main.
In the case of undershot wheels (i. c., the top of the wheel
ruas toward the operator) which is almost always the direction
of rotation of both emery and buffing wheels, the main suction
duct should be back of and below the wheels and as close to
them as is practicable: or it should be fastened to the ceiling
of the floor below, preferably the former. If behind the wheels,
it should he not less than 6 in. ahove the floor at every point to
Both the main suction and discharge pipes should be made as
short and with as few bends as possible, to avoid loss by fric-
tion. If one or the other must be of considerable length, it is
hest to place the fan not far beyond where the nearest branch
enters the large end of the main, as a long discharge main is
a lesser exit than a tong suction main.
Avoid any pockets or low places in ducts where dust might
accumulate.
If there is a likelihood of a few additional wheels being in-
stalled in the future, it is advisable to leave a space for them
between the ian and the first branch and to put in an extra size
ian,
Pranch pipes should enter the main on the top or sides; never
at the bottom. Two branches should never enter a main directly
opposite one another.
Each branch pipe should be equipped with a shut-off damper
or blast-gate as it is also called, which may be closed, if desir-
able, when the wheel is not in use. Not more than 25 per cent.
of such blast gates should be closed at one time; otherwise, the
air velocity in the main duer may drop too low and let the dust
accumulate on the bottom.
The use of a trap at the junction of the hood and branch pipe
is good practice, provided it is cleaned out regularly and not
allowed to filt up with dust. This will catch the heavier par-
ticles and so take some wear off the fart.
All bends, turns, or elbows, whether in main or branch pipes,
should he made with a radine in the throat of twice the diameter
of the pipe on which they are connected, wherever space permits.
Elbows should be made ci metal one or two gages heavier than
the pine on which they are connected, as the wear on them is
much greater.
ECCENTRIC BLADE BENDER
BY H. T, NOWELL,
Gederal Foreman, Boston & Maine. Concord, NH.
An eccentric blade bender made in one piece, and one that is
easy to handle, is shown in the illustration. This does away with
the old fashioned two-piece hender with the bar of iron and dog
that required the services of two men. It is placed over the blade
and two pins are placed in the 7 in. holes in the legs to hold
it when the set screws are applied through the in. threaded
1*Staybult Top
Tool for Bending Eccentric Blades.
holes in the top of the bar. There are three of these holes to al-
low for the proper application of the pressure. The set screws
are made with a fine thread to prevent stripping. This bender
has practically no spring or "come-back," and may he readily
used in very restricted places.
