(This is a nearer view of some of the safeguards shown in Fig. 12. A
is the track sander which is operated by a rope or cable attached to
the lever and extended to the craneman’s cage; B shows more clearly the
drive-shaft coupling. The shaft inclosure also appears more plainly.)]
During the ordinary operation of an electric crane the craneman should
never leave his cage without making sure that all the controllers are
in the off position, and that the main switch is open. Before he leaves
the crane the safety switch should also be locked open. If the electric
current should be shut off at any time, the same precautions should be
observed; and before closing the main switch, when about to resume work
after an interruption due to any cause whatsoever, the craneman should
again make certain that all the controllers are in the off position.
When about to lift a load, the motor should be run at low speed
until the slack in the chain or cable has been taken up, after which
the controller handle may be advanced slowly from point to point to
increase the speed. Before a motor is reversed it should be brought
to a full stop, except when an accident can be averted only by
disregarding this advice.
When handling a heavy load the craneman should hoist it a few inches
above the floor, and then, before proceeding further, he should assure
himself that it is properly balanced and that the slings are secure,
and should also test the brakes to make sure that they will hold the
load safely. If there is any doubt whatsoever about the safety of
the operation, the load should be lowered and the slings or brakes
adjusted, or other necessary measures taken to avoid danger. It is also
desirable, at the beginning of each shift, to test the foot brakes and
limit switches thoroughly.
It is extremely important, at all times, and particularly when handling
molten metal, to “spot” the trolley directly above the load to be
hoisted. Failure to do this will cause the load to swing sidewise
as soon as it is clear of the floor, and usually the metal will be
spilled, or men or objects near by may be struck by the load.
Loads should be raised high enough to give proper clearance above
men and objects on the floor, but they should not be carried for
any considerable distance at an unnecessary elevation. So far as
possible, the craneman should avoid transporting loads directly over
workmen. Special care should be exercised to keep loads under control
when lowering them, and the speed should always be restricted to a
reasonable and safe limit.
Some definite person must be held responsible for the selection of the
chains and slings that are used for hoisting, and for making suitable
hitches about the loads. If the foundry is large enough to employ
a special floorman, these matters may well be left to him, because
he is necessarily familiar with the constantly-changing conditions,
and he should therefore be able to select the proper sling quickly
and intelligently. Moreover, experience will have taught him the
best method for attaching the sling, or for hooking on to the load.
If no special floorman is employed, this part of the work should be
supervised by a specially assigned foreman, or by a skilled hooker-on.
When applying the hook to the load, and when holding the hook in place
while the slack is being taken up, the hooker-on should be careful
to avoid having his hands caught and crushed between the sling and
the load. Hooks with safety handles may be had, and these add greatly
to the safety of the men when hooking up. If safety handles are not
provided, pieces of wood notched at the end may be used with advantage
for holding the hooks in place,--the notch being pressed against the
hook to prevent it from moving before the tension comes on it.
When the hooks or slings are in place and the slack has been taken up,
the workmen should immediately move back several feet from the load.
When a load is being deposited, all persons should keep at a safe
distance while the slings are being withdrawn from under it, because
the slings may snap out suddenly, or may catch on the load and tip it
over. When slackening-off the hoisting cables the hooker-on should
avoid pulling down on the _inrunning_ side of the block, because his
fingers may be caught between the sheave and the cable and be cut
off or badly crushed. It is far safer to grasp the outrunning side,
and pull up and away from the sheave. Greater safety in this work is
insured by inclosing the block to which the hook is secured. Blocks
guarded in this manner are available and should be generally adopted.
The crane operator should never allow chains, slings, cables, or hooks
to drag along the floor, and he should never start the crane carriage
or trolley until all such appendages are entirely clear. Even in the
short distance that the crane might travel before they leave the floor,
the slings or hooks might become caught on some obstruction and cause
an accident.
No one should be permitted to ride on a load or on the crane hook; and
if the craneman observes a violation of this rule he should stop the
crane and refuse to move it until the person who is riding is in a safe
place on the floor.
In a busy foundry the craneman must be specially alert, and his
attention must be given, unremittingly, to following the various
operations on the floor, taking the signals from the floorman, and
controlling the movements of the crane.
Before an inexperienced man is permitted to take charge of a crane, he
should be thoroughly trained in the work by a careful, well-qualified
craneman, who should see that he becomes familiar with the operating
mechanism, and skilled in the manipulation of the various levers and
controls.
A signal gong, operated by hand or foot, or electrically, should be
part of the equipment of every crane, and should be rung when the
crane is started, and as frequently thereafter as may be necessary.
Occasionally the gong is actuated by the mechanism that moves the
crane, so that the warning signal is sounded automatically and
continuously so long as the crane is moving. The objection to this
method is that the sound of the gong is likely to become so familiar
that its value as a warning of danger will be lost and the men will
give little heed to it. Furthermore, the gong should always be treated
as an _extra safeguard_, and no other safety precaution should be
omitted or allowed to fall into disuse merely because the gong is used,
nor should vigilance and caution be relaxed in any respect whatever.
Some person should be specially designated to transmit to the craneman
the signals for moving the loads, and the craneman should disregard
signals given by other men. The signalman should stand in plain view
of the craneman and should take care to give all his signals clearly.
A definite and unmistakable code of signals, consisting of motions
of the hands and arms, should be arranged. Signals given orally are
unsatisfactory and unsafe, not only because it is often difficult to
distinguish them with certainty unless the foundry is quiet, but also
because the sound of loud voices will always distract the attention of
other men from their work. When a load is being transported some person
designated for this purpose should always walk in front of it to warn
workmen who are in danger of being struck, and he should also see that
the load is carried high enough to clear all obstacles in its path,
because the craneman, on account of his location, sometimes finds it
hard to judge the height of the load correctly.
A crane that is to be repaired should be moved to one end of the runway
or to some other point where it will cause the least interference
with the movements of other cranes. The controllers and the main and
emergency switches should be placed in the off position before starting
any repair work on cranes, and the safety switches should be locked, or
the fuses removed, to prevent any movement of the crane, and to avoid
accidental short circuits that might result in injury to the repairmen.
Suitable warning signs should be placed on cranes that are undergoing
repairs, and buffers or rail stops should be clamped to the crane rails
a few yards in front of the disabled crane when others are operated
on the same runway. If practicable, a suitable floor area directly
underneath the disabled crane should be roped off or inclosed in some
other way, to prevent accidents that might be caused by tools or other
objects falling from the crane. Similar precautions should be taken
when men are at work on the runways, and red flags or other warning
devices should be placed at both ends of the section undergoing repairs.
Chains and Hooks.
Chains and hooks should be carefully inspected at regular intervals,
and they should also be annealed from time to time by competent
workmen who thoroughly understand the art of annealing, and who know
how to secure the results that are desired. Particular care should
be taken with hooks in this respect, because a hook, when properly
annealed, should gradually yield or straighten if subjected to a
serious overload, and thus give warning of danger; whereas if it is
not properly annealed, and therefore hard, it is likely to snap off
suddenly, without warning. Chains and hooks should be inspected with
care immediately after annealing, because they are then cleaner than
at other times, and hence any existing defects or flaws in them may
be detected with greater certainty. All chains and hooks should be
numbered, and a careful record should be kept of the inspections and
annealings. Hoisting chains are particularly liable to failure through
fatigue or over-strain, on account of the severe treatment to which
they are frequently subjected; and they should therefore be examined
minutely, and link by link, to detect insecure welds and slight cracks
or other defects. Chain slings should never be crossed or twisted when
placed around loads, and every chain that is to be used as a sling
should be made of the highest quality of wrought iron. All chains
should be oiled frequently, to prevent rusting.
Forged hooks, or laminated hooks made of steel plates securely riveted
together, should be used in preference to those made of cast steel.
Hooks are sometimes subjected to severe abuse by workmen who try to
force them into position by striking them with heavy iron bars or
other implements. This is a dangerous practice, and should be strictly
prohibited.
Wire-Rope Slings.
Well-made wire-rope slings give better service than chain slings,
because they are stronger, weight for weight, and also because
deterioration is usually indicated by broken strands that are readily
discoverable by an experienced and qualified inspector. Wire-rope
slings are pliable, and may be adapted to almost every use. They should
be kept in good condition, and to prevent rusting and unnecessary wear
from friction they should be treated with oil or with a good cable
lubricant prepared specially for the purpose. Wire-rope for slings used
in handling molten metal or hot castings should have a soft iron-wire
core, because a hemp core is quite likely to be destroyed by the heat.
Slings in General.
A sling should never be allowed to rest directly against the sharp
corners of a heavy flask, casting, or other similar object, but should
be protected by wooden corner-pieces, or by pads of burlap or other
soft material.
Every sling, whether composed of a chain or a rope, should be long
enough not only to surround the load it has to support, but also to
leave a considerable space between the sling and the upper surface of
the load. The oblique parts of the sling, which lie above the load and
join it to the hook (or to the point where the suspension first becomes
vertical) should never be so flat as to make an angle of less than 45
degrees with the ground. This precaution is highly important, but it
is often overlooked or neglected, because the men do not realize that
the stress on the ends of a sling is greater, the flatter (or more
nearly horizontal) they lie. When the ends are inclined at an angle of
45 degrees, the stress upon each of them is about 41 per cent. greater
than it would be if the ends were vertical; and if the sling is so
short that it barely goes around the load and has but little slack, the
stress upon it may be very great indeed.
We strongly advise that all slings, when not in actual use, be kept
under lock and key and placed in charge of some responsible person who
knows their condition and is competent to select safe and appropriate
slings for every occasion. They may be stored in the tool room or
supply room, for example, and be in charge of a qualified foreman.
Hoisting Apparatus in General.
Hoisting apparatus of every kind should be inspected frequently and
thoroughly, and all parts that are defective in any way should be
promptly repaired or replaced. The man charged with the operation
of the apparatus should not attempt to make repairs or adjustments,
however, unless the foundry is a small one, where this constitutes a
part of his recognized duty. Under all other circumstances he should
immediately report to the foreman or repairman, in order that the job
may receive attention in the proper way. If the defect is serious
enough to constitute a possible source of danger, the apparatus should
not be operated until the necessary repairs or adjustments have been
made.
Tumbling Barrels.
Tumbling barrels (or “rattlers”) for cleaning rough castings are of two
general types, respectively known as wet and dry. There are numerous
mechanical hazards in connection with both types, and with dry tumbling
barrels considerable danger to health may be caused by the dust created
by them unless suitable preventive measures are adopted.
There are two methods that are commonly employed for removing the
dust from dry tumbling barrels. One of these consists in attaching
an exhaust system directly to the machine, and the other consists
in inclosing the barrel in a dust-proof compartment from which the
dust may be exhausted. The first method, as a rule, is practicable
only in connection with tumbling barrels that are of special design,
and are provided with the necessary attachments for connecting with
exhaust fans. In nearly all other cases dust-proof inclosures must be
built, and it is practicable to secure satisfactory results in this
way when the system is properly arranged. The compartments should be
made as tight as possible, and should be constructed of sheet metal or
well-seasoned lumber. The doors may be arranged to fold, or to slide
upward or sidewise; or they may be hinged to open in any way that
is most convenient. In some cases rolling steel shutters are used.
Doors that rise vertically should be suitably counterweighted so that
they will not drop upon the workmen, and the counterweights should be
inclosed. In addition to the counterweights we recommend the use of
catches or fastenings for holding up the doors.
When tumbling barrels (either wet or dry) are not located in
compartments, substantial double railings, at least 42 inches high,
should be placed about them, with a clearance of not less than 15
inches nor more than 20 inches. (When railings are placed more than
20 inches away, workmen are likely to crawl inside of them to do any
necessary work, and they are then in greater danger than they would
be in if no railings were present; whereas if railings are omitted
altogether, the workmen are likely to be struck or to have their
clothing caught by small objects that may work through perforated or
loosely-fitting covers, or by the projecting cover-fastenings.) The
railings should be provided with gates so arranged that opening the
gates will automatically throw the driving belts or clutches into the
off position, and will prevent the machines from being started until
the gates are closed. Driving belts should be guarded to a height
of at least 6 feet above the floor, and all exposed gears should be
completely inclosed. Chain hoists should be provided for lifting heavy
covers, and suitable brakes or locking devices should be installed to
prevent any movement of the machines while they are being loaded or
unloaded. Securing the barrels in position by means of bars or props is
a mere makeshift method, and is manifestly unsafe.
Sand Mixers and Sifters.
Sand mixers are of two general types, one of which simply mixes the
materials, while the other not only mixes but also grinds them. The
mixer consists of a horizontal semi-cylindrical vessel in which
the sand is placed and the mixing is done by revolving blades. The
top of the cylinder should be covered by a substantial grating
composed of 3/8-inch round stock suitably reinforced to insure
rigidity, and provided with free-swinging discharging doors. All
gears should be inclosed by substantial guards, and the driving belt
should be protected to a height of at least 6 feet above the floor.
A well-designed belt-shifter should be provided, and should be so
arranged that it may be locked to prevent creeping of the belt.
The combination mixer and grinder is similar to the revolving dry-pan
used in the manufacture of bricks, and it may be driven either from
underneath or from overhead. In either case the driving gears and all
other exposed gears should be suitably inclosed, and the driving belt
should be protected and be fitted with a belt-shifter, as described
above in connection with the sand mixer. The revolving pan should be
completely surrounded by a substantial guard of heavy, reinforced wire
netting extending to a height well above the hubs of the grinding
wheels. An opening should be left in one side of the guard, and at this
point a sheet-metal feeding hopper should be securely riveted on. A
drag or other suitable mechanical device should be provided to force
the sand out through the discharging door, and the use of hand shovels
for removing the sand from the pan while it is in motion should be
prohibited.
Pipe or angle-iron railings 42 inches high should be installed at the
sides of rotating sand sifters, at a distance of at least 15 inches,
and not more than 20 inches, from them. Belt-shifters should be
provided, and the belts should be guarded to a height of at least 6
feet above the floor.
When sand mixers and sifters are driven by electric motors every
precaution should be taken to prevent electric shocks and burns. See
that all live wires and other parts are thoroughly insulated, and guard
all dangerous rotating parts. Inclosed switches should be used, and
they should be located in convenient and easily accessible positions;
fuses of the inclosed type should also be used.
Automatic Molding Machines.
The gears on both sides of these machines should be entirely inclosed
by substantial guards of sheet metal, expanded metal, or close-mesh
woven wire. The connecting rods should be similarly guarded, the
inclosures in the latter case to extend as high as possible without
interfering with the adjustment. Whether the machines are driven by
belts or by electric motors, such precautions should be taken with
regard to belt-shifters, belt-guards, and electrical safeguards as have
been recommended above in connection with sand mixers.
Chipping Department.
Many serious eye injuries occur in the chipping department, and
practically all of these may be prevented by requiring the general
use of suitably-designed eye-protectors or goggles. Eye-protectors
for cupola men and others engaged in handling molten metal have been
described in a previous paragraph, and those to be used by chippers
should be similar. Cheap, flimsy eye-protectors should not be used.
It is economy to buy substantial goggles at a higher price, not only
because they afford better protection, but also because they are more
durable.
[Illustration: FIG. 14. MOLDING MACHINE OPERATED BY COMPRESSED AIR.]
In addition to the eye-protectors, shields of canvas or other suitable
material, mounted on substantial frames, should be provided, wherever
needed, to protect near-by workmen from flying chips.
Chippers should not be permitted to work with battered or otherwise
defective tools. Broken hammers and sledges should be discarded, and
cold-chisels and other implements should be dressed when they become
burred or mushroomed.
Grinding Wheels.
Emery wheels and wheels of other abrasive materials are used in
grinding castings, and these sometimes burst and cause serious
injuries to the operators. All grinding wheels should be fitted with
safety collars or flanges, and, where practicable, should be inclosed
by substantial metal hoods connected to exhaust fans for removing
the dust. Stationary grinding machines should be mounted on solid
foundations to prevent vibration, and their bearings should be ample in
size and be kept well lubricated and properly adjusted. It is important
that grinders wear goggles, to protect their eyes from flying dust and
sparks.
Further details with regard to the design, care, and operation of
grinding wheels will be found in a booklet, entitled “_Grinding
Wheels_”, published by the Engineering and Inspection Division of THE
TRAVELERS INSURANCE COMPANY.
Compressed Air.
Compressed air is commonly used in foundries for operating air
hoists, blow guns, spraying devices, pneumatic hammers and chisels,
sand-blasts, molding machines, and sand-blast tumbling barrels. Serious
accidents are often the result of the improper use of compressed air,
and workmen should never be allowed to play pranks with it, but should
use it only for the purposes for which it is provided. In particular,
a sand-blast should never be turned upon a person, because it might
easily destroy his eyesight or cause other serious injuries.
The introduction of compressed air into the human body causes great
distention of the intestines, accompanied by agonizing pain; and the
victim usually dies after a short period of intense suffering. Every
man about the foundry should therefore make it his special business
to see that no attempt is made to use the air lines for perpetrating
so-called “practical jokes”.
[Illustration: FIG. 15. A SPECIAL CHAMBER FOR SAND-BLASTING.
(Strong air suction, through the exhaust hoods shown in the upper
part of the picture, will remove a large quantity of the dust that is
created, but it would be better if the ducts were placed in the floor,
with gratings over them, or in the side walls. The helmet which the
operator is wearing is of a type commonly used in work of this kind.
As explained in the text, no entirely satisfactory helmet has yet been
devised.)]
Sand-blasting.
Sand-blasting may be done in the open air if eye-protectors and
respirators are worn and other suitable precautions are taken, but
it is far better to provide a dust-proof chamber for this work. The
operator of the sand-blast should then wear an appropriate helmet,
to effectively protect his lungs and eyes from the dust. The form of
apparatus used should be adapted to the work to be done, and to the
conditions that must be met. Considered from the point of view of
the dust hazard alone, the ideal arrangement appears to consist in a
helmet well ventilated by means of a hose supplying an adequate flow of
dust-free air. The hose may be run from the compressed-air tank to the
upper part of the helmet, and it should be provided with a regulating
valve located where it may be easily controlled by the man who is to be
supplied. The air current should be so adjusted that it will not only
afford sufficient oxygen to serve for respiration, but also prevent
dust from rising into the helmet through openings in the lower part of
it. In practice, however, it is frequently found that the plan
here outlined is highly objectionable to the men, and in fact they
often refuse to wear apparatus of this type, claiming that the cool
air passing down the neck soon causes them to catch cold. Baffles and
various other distributing devices to regulate the flow of the air
within the helmet have been tried, but no ideal and wholly satisfactory
solution of the difficulty has yet been worked out, so far as we are
aware. In the opinion of certain foundry experts, an ordinary helmet
with a respirator attached, or used in conjunction with a separate
respirator, constitutes the best device for the protection of the
sand-blaster, when all phases of the problem are considered.
Each compartment used for sand-blasting should be provided with an
exhaust system capable of removing the dust in a satisfactory manner.
[Illustration:
_Courtesy of the Western Electric News._