THE LIFTING-MAGNET AS A WASTE DEVELOPING FORCE
Waste is precarious to handle. The very nature of the material demands
that it shall be worked up in the most economical manner. Under the
fickle influences normally prevailing upon the market, the margin
between profit and loss may suffer such attenuation from inefficient
exploitation as to submerge the factor of profit, thus endangering the
very practice of utilizing the residue. It is immaterial whether time
or labour be the adverse circumstance. The one influence can be quite
as ruinous as the other. Should the cumulative effect of the two forces
be experienced simultaneously, then the results are almost certain to
be devastating and prompt in their action. Consequently, to secure the
uttermost benefits attainable it is imperative that the most economical
and efficient methods should be employed.
This is particularly the case in the iron and steel trades. The
competition between the various nations in this manufacturing field
is excitingly keen. It must not be forgotten that, in this industry,
waste plays a very prominent part as a raw material. It may be tins
rescued from the domestic dust-bin, turnings from the lathe, a worn-out
locomotive boiler, or the battered hulk of a steamship snatched from
the jaws of the hungry seas through the ingenuity of the salvage
engineer.
In the handling of scrap and junk the designing engineer has been
strikingly ingenious, resourceful, and free with his expressions of
resource. The cranes and other mechanical handling devices, which
he has evolved, compel attention for the simple reason that they
have been introduced to secure a reduction in the cost of moving the
material. In this direction finality is impossible of attainment;
the necessity to reduce the cost factor is so urgent and continuous.
Creative effort, thus fostered, has achieved a distinct triumph during
the past few years. It has evolved a new system of dealing with iron
and steel, especially the waste, which is rapidly displacing all other
methods which hitherto have held undisputed sway. I refer to the
lifting-magnet.
It was a British mind which first conceived the idea of harnessing the
magnet to the wheels of the iron industry. Sir William Sturgeon saw no
reason why the toy of our childhood days, the pin-attracting properties
of which extended us infinite delight and provoked indescribable
wonder, should not be devoted to the movement of ponderous masses of
steel. So he made the experiment. But his noteworthy effort proved
only partially successful. It did not fulfil expectations, not because
the designer was wrong in his deductions, but because he conducted the
evolution along fallacious lines. But his failure set men thinking.
They followed up his reasonings and discovered why he did not record
success. The British pioneer had been content to accept the magnet’s
familiar form and to reproduce it upon a larger scale to fulfil his
objective. This was why he failed. For such as application as he had in
his mind’s eye a modification in design was imperative. The German and
American experimentors, who followed in his footsteps, quickly realized
this circumstance and accordingly abandoned the traditional horse-shoe
form for a magnet of flat drum-like shape.
In this modernized and materially changed form the lifting-magnet
met with instant success. The Germans were the first to recognize
its possibilities, and accordingly developed and popularized its
utilization in accordance with their characteristic organized methods,
with the result that it was not long before all the leading iron- and
steel-works of the country were equipped therewith to their distinct
commercial advantage.
So far as America and Britain, the home of the lifting-magnet, have
been concerned, progress has been slow and uneventful. The Germans set
out to reap advantage from our manufacturing apathy, and to a certain
degree succeeded. It remained for the war, with its drain upon cheap
labour on the one hand and the necessity to speed up and to increase
output on the other, which compelled us to regard the lifting-magnet
with enhanced favour. This tendency was accentuated by the urgent
requests circulated far and wide to save all waste metal and to turn
it over to the country for the production of munitions. In this manner
vast quantities of waste metal of every conceivable description were
released, which, in turn, led to a demand for handling appliances.
Under the conditions which obtained it was imperative that this
potential raw material should be handled with the utmost economy, both
of time and labour, but native ingenuity had nothing at its command to
compare with the lifting-magnet in this connection. Those firms which
had been sufficiently enterprising to equip themselves with the German
appliance found themselves in an overwhelming superior position, while
their lifting-magnets paid for themselves over and over again in the
course of a single year.
The national deficiency in supply and its far-reaching adverse effects
were remedied through the combined enterprise and initiative of a
young electrical engineer and a British manufacturer. The former had
followed the German developments very closely and had discovered that,
notwithstanding their extravagant claims, these appliances really
fell somewhat short of the mark in point of efficiency and economy in
operation. Fortified with this knowledge he had promptly designed an
appliance of this character, in which the obvious Teuton defects were
eliminated, thereby giving a lifting-magnet which represented a decided
advance upon the best which Germany could offer.
The Pickett-West lifting-magnet, so named after its designer and
manufacturer respectively, is one fully complying with traditional
British standards of production, while it also possesses many novel
features which have already emphasized their value. It is built along
robust lines, so that it completely fulfils the conditions peculiar
to its field of application. Moreover, its design can be modified
within wide limits to meet the individual requirements of the service
for which it is intended, one distinctly ingenious feature being the
model fitted with moving fingers, each of which constitutes a magnet
in itself, and wherewith the magnet is able to exercise the maximum
magnetic gripping power upon the article for the movement of which it
is being used.
Without entering into a technical description of this apparatus it
may be said to comprise, in its simplest form, an inverted dish
with a central pole-piece. Round this pole-piece is built a coil
composed of alternate layers of copper of substantial dimensions and
insulating material. The coil is enclosed within the inverted dish
and a face-plate is bolted in position. Thus the coil which occupies
the whole of the case, with a special insulating compound run in
under pressure to occupy all the vacant space such as corners and
interstices, is completely encased and safe from tampering. Suitable
terminals are fitted and are coupled up to a flexible electric cable
through which the current is led to energize the coil and to impart
the requisite magnetic energy to the lifting face-plate. When the
coil is active, naturally the magnet will readily attract any ferrous
metal which it may chance to approach, or with which it may come into
contact, and this will continue to cling to the face of the magnet
until the current is switched off. The magnet is slung upon the hook
of the crane either by chains, or bars forming a tripod terminating in
a link. It is applicable to any type of crane, whether it be of the
locomotive, jib or derrick type or overhead travelling system, and with
equal facility.
The foregoing description is merely a bald description of the
lifting-magnet in its simplest form. To secure the highest efficiency
many perplexing technical issues had to be resolved. The magnet
is necessarily of impressive dimensions and weight, circular or
rectangular in regard to the form of the face-plate according to the
nature of the work to be fulfilled, and ranging from 24 to 62 inches
in diameter. The most popular size is that measuring 52 inches across
the face. Massive construction is inevitable to enable the appliance to
withstand the rough wear and tear, as well as unceremonious handling,
to which it is exposed in the average iron-works by indifferently
skilled labour, or to meet the conditions of piece-work when operations
are necessarily conducted at relatively high pressure by the men who
are bent upon the consummation of one end--the maximum return in the
form of wages for the work accomplished.
Robust construction involves weight. Precisely what this means may be
gathered from the fact that the German 52-inch lifting-magnet weighed 3
tons, whereas its British rival, to which I am referring, weighs only
2¹⁄₂ tons and has a 20 per cent. greater lifting capacity, despite the
reduction in weight of the magnet itself. The magnet in question will
lift from 900 to 33,600 pounds--even more--according to the character
of the material to be handled, the lower figure applying to sheet-iron,
scrap, and bolts, while the other extreme refers to heavy solid steel
ingots or armour-plate.
Precisely why the lifting-magnet should have taken so long to establish
its virtues, both in this country and the United States of America,
is somewhat inscrutable, especially in the latter country which, as a
rule, is disposed to introduce time-and labour-saving appliances with
alacrity. No matter from what point of view it may be regarded, it
represents the biggest time-and labour-saver as well as money-maker yet
introduced into the steel industry.
One reason advanced for its comparatively slow adoption is rather
interesting. It was averred that to the men, accustomed as they were
to seeing loads slung by chains, the sight of a mass of steel clinging
to the face of the magnet by a force which they could not understand
verged on the uncanny. They knew little or nothing about magnets except
in the form of a toy, and could not understand that sufficiently
attractive effort could be exerted to keep the mass adhering to the
flat face of metal. The fact that the moment the current was switched
off released the load was something equally beyond their comprehension.
Forthwith they arraigned the lifting-magnet as dangerous, and, while
not openly condemning its use, declined to work in its vicinity.
Whether this was so or not has never been fathomed, but it is generally
observable that men working with such an appliance observe a wise
discretion, and refrain from working or moving beneath it. This very
respect for the apparatus has achieved one distinctly valuable result:
accidents are few and far between, even in America, in which country
respect for human safety is declared to be at zero, where the handling
of huge masses of metal is conducted by the lifting-magnet.
But, eliminating the psychological effect upon the workmen, it is
to be feared that employers were slow to visualize its advantages.
Certainly in Britain there are many employers, who, notwithstanding the
impressive array of figures advanced in its favour, and who have been
brought face to face with the economies it is able to effect, still
cling tenaciously to antiquated practices.
So far back as 1911 Mr. H. F. Stratton, in drawing the attention of
the American Foundrymen’s Association to the possibilities of the
lifting-magnet, presented some illuminating figures. At that time the
American steel industry was handling 10,000,000 tons annually by this
system and thereby was saving over £200,000--$1,000,000--a year. So
far as scrap was concerned he emphasized the opportunity it presented
in this field, because, out of an annual melt of 6,000,000 tons of
pig-iron and scrap, from 1,000,000 to 2,000,000 was represented by
scrap-iron and steel.
The American railways were among the first to appreciate the
possibilities of the system. The Chicago, Rock Island and Pacific
Railroad introduced the idea for handling scrap and iron in 1909. Up
to that time all scrap had been handled by hand, the cost in and out
ranging from 30 to 35 cents--15d. to 17¹⁄₂d. per ton--which, according
to the authority cited, could be accepted as applicable to all the
railways following such a practice, and to record which figure, be it
noted, demanded excellent arrangements and efficient organization. Upon
the introduction of the lifting-magnet these costs were immediately
cut down to 10 to 12 cents--5d. to 6d.--per ton, in and out, inclusive
of every expense, the figure for the actual sorting being only 4 to 7
cents--2d. to 3¹⁄₂d.--per ton. The authorities of this railway stated
that unsorted scrap could be unloaded by means of the magnet for 2 to
5 cents--1d. to 2¹⁄₂d.--per ton, while, if the scrap were sorted, the
cost came out ¹⁄₂ to 1¹⁄₂ cents--¹⁄₄d. to ³⁄₄d.--per ton! Similar work
conducted by hand labour, according to the previous practice, cost
about three times as much.
That the experience of this one railroad was not isolated was proved by
the experience of the Lake Shore and Michigan Southern Railroad, which
supplied Mr. Stratton with the following comparative figures for other
operations incidental to the conduct of its work:--
Loading locomotive tyres by hand 17 cents (8¹⁄₂d.)
” ” ” crane with chains 8 ” (4d.)
” ” ” ” magnet 4 ” (2d.)
” heavy casting by crane with chains 20 ” (10d.)
” ” ” ” magnet 3 ” (1¹⁄₂d.)
” ” ” hand almost impossible.
It will be observed that the handling charges by the magnet were
one-half of those by the crane with chains in connection with the
locomotive tyres, and one-seventh in the case of the heavy castings,
while the advantage over manual effort in the case of the first-named
was no less than 32·5 per cent. Little wonder that, during the past
nine years, the utilization of the lifting-magnet in connection with
the handling of iron and steel in the United States has advanced by
huge strides. To-day it constitutes an integral part of the wrecking
equipment of every leading American railroad. After the large debris
has been cleared up, the lifting-magnet is swept over the ground to
pick up nuts, bolts, nails, screws, and any other odds and ends of a
ferrous nature which have escaped recovery by the conventional methods.
So far as these islands are concerned, considerable progress has been
made during the past five years in regard to its adoption. Extended
use has not been confined to the handling of metal in our steel-works,
but for the reclamation of iron and steel cargoes which were lost as a
result of the German submarine activity. Its employment in the salvage
field was suggested as the result of the sinking of a barge carrying
ingots of very special steel sunk at the entrance to a port on the
East Coast. Although the wreck lay in relatively shallow water, it was
speedily discovered that salvage by the orthodox methods would prove
somewhat uncertain, owing to the awkward position of the sunken barge
and the difficult tidal and other conditions.
The possibility of retrieving the valuable steel by magnet was broached
to Mr. F. N. Pickett, the inventor of the British lifting-magnet,
to which I have referred. A certain doubt upon the point existed in
official circles from the knowledge that the German appliance could
not be employed in such duty, owing to the coil not being impervious
to water, which of course nullifies the utilization of the electric
current. But the British magnet, being built upon different lines, is
watertight, and so the designer expressed complete confidence in his
apparatus being suited to the task. The magnet was secured, and divers
went down to blow open the side of the barge to permit the magnet to
reach the cargo.
The magnet was lowered and was found to work with as much ease and
simplicity as under conventional conditions in the steel-works. It
was plunged into the hold of the invisible craft, and subsequently
the sea-bed on either side was swept therewith. So successfully
and completely did it fulfil its unusual task that every ingot was
retrieved, and that within a very short time. The sinking of the barge
occasioned little damage beyond a slight delay in the delivery of the
material, which was valued at £150--$750--per ton. True, the barge was
lost, but that was an insignificant disaster, and but poor recompense
for the expenditure by the enemy of a torpedo costing possibly
£1,000--$5,000.
The success of the magnet in this instance has been responsible for its
utilization in other fields of submarine endeavour. A freighter was
sunk with a valuable steel cargo aboard. The vessel was examined and
found to have settled upon an even keel. Divers descended and opened
the hatchways, while sections of the decks were cut away to expose the
cargo. The magnet was then brought into action, and the cargo unloaded
as readily as if moored alongside the dock. This success in the open
sea has been responsible for the salvage of similar cargoes which have
been lost around our coasts. So far as the Pickett-West lifting-magnet
is concerned, there is no obstacle to its use in this field so long
as sufficient swing can be imparted to the suspended apparatus to
ensure sweeping of the wreck, and up to the depth corresponding
to the pressure of the insulation in the coil drum. Seeing that
this is introduced at a pressure of 120 pounds to the square inch,
the lifting-magnet can be safely used in water up to a depth of
approximately 250 feet without the insulation collapsing under the
imposed water-pressure, and this is a depth far beyond that at which a
diver can work. But, taking the wrecks lying within water accessible
to the diver, appreciable recovery should be possible.
It is generally conceded, in view of the success which has already been
achieved, that there is a promising future for the apparatus in this
field so long as it is designed and constructed along correct lines.
The cost of operations will be reduced therewith very materially,
and the strain imposed upon human effort as represented by the diver
will be decreased very markedly. Instead of salvage operations being
confined to an hour or two daily, according to the velocity of the
tides and currents, it will be possible to continue work during the
round twenty-four hours so long as the weather is propitious. The
operator will be able to sweep the wreck from end to end, as well as to
scavenge the sea-bed by swinging his magnet, confident in the knowledge
that magnetic metal will be trapped in the process for haulage to the
surface. Even if ships should prove impossible of recovery intact there
is nothing to prevent their reclamation piecemeal. Dynamite will reduce
the wreck to scrap of weight and size within the lifting capacity of
the apparatus, and at the price obtaining for such junk the expedient
should prove profitable. So we should be able to retrieve a certain
and imposing proportion of the wanton waste incurred by the ruthless
attacks of the enemy upon our sea-going traffic.
It has even been suggested that the magnets might be employed to
salvage many of the German submarines which we have sunk, more
particularly the coastal type of craft. These were relatively small,
and for the most part were sunk in comparatively shallow water. In the
water-logged condition the dead load to be handled is approximately 800
tons. If desired these craft could be lifted to the surface intact, or,
if in pieces, retrieved in sections for sale as scrap. The inventor
has elaborated his plans, which involve the suitable disposition of a
certain number of magnets over the sunken submarines. He suggests that
eight magnets would be adequate for the task. Seeing that each magnet
has a pulling power of 250 pounds per square inch of its surface,
the aggregate haul which could be brought to bear upon the submerged
craft simultaneously by the eight magnets would be at least 1,920
tons, or twice the total weight of the submarine. With such a lifting
effort available it should be possible to drag the wreck from even
the extremely tenacious North Sea mud. The question arises, although
recovery of such waste is admitted to offer every attraction, as to
whether the German submarines are worth the trouble, even if they
be sold as scrap. In view of the price which the surrendered boats
realized this is extremely doubtful, although experienced salvage
engineers admit that even if prevailing scrap prices were obtained the
venture would prove profitable, that is in the strict commercial sense.
As a scavenger for magnetic metals the lifting-magnet cannot be
excelled. It is far more thorough than hand-labour, and will fulfil its
mission more completely than any other mechanically-operated device to
this end. Lowered to twenty-four inches of the ground it may be swept,
or swung, to and fro in the certain knowledge that any stray scraps of
iron and steel will readily jump the intervening space in response to
the strong magnetic influence exerted. In this manner a wide area can
be completely cleaned of all stray iron and steel fragments, much of
which would otherwise be lost within a few moments.
The recognition of the peculiar qualities of magnetic attraction
has led to an interesting development which should prove capable of
extensive application and to distinct commercial advantage in our
steel-works. As is well known, the slag is run off separately to be
dumped. But this slag often carries an appreciable quantity of metal
in a divided state. Hitherto this has been wasted, but it has been
found that, if the slag be broken up, by the aid of a magnet and
“skull-cracker” ball, and the magnet be swept over the mass, that the
fugitive metal can be retrieved and in sufficient quantities as to
render the operation profitable.
For the movement of iron and steel in factories it is difficult to
excel. A consignment of kegs of nails, bolts, nuts, screws, or some
other small articles requires removal to or from store, or to vehicle.
Under normal conditions the practice would be, either to stack them
on trolleys or to pack and sling them from cranes, the loading
constituting the adverse factor from the appreciable time it takes.
If the magnet be used no such preliminaries of any description are
necessary. The magnet is merely lowered, the current switched on, and
the next moment as many loaded kegs as can squeeze themselves upon the
face of the magnet may be lifted. The attractive effort is sufficient
to exert its influence through the covers of the kegs to act upon the
metal within. Moreover, if the kegs be small, more than one layer
will be found possible of removal at a time, inasmuch as the depth to
which the magnetic influence can be exerted--“digging” effort as it is
called--has been found to be equal to the diameter of the magnet face.
For handling metal waste in the form of turnings or swarf it is far
cheaper and quicker than any other known process. When the magnet is
dropped upon a pile of such residue and is then raised, it will tear
away a huge chunk of the heap--a ton or more of tousled and ragged
ribands of steel jostling and clinging tightly to one another and
to the magnet-face like a swarm of bees to the branch of a tree. It
will successfully handle, and for no heavier cost, swarf which defies
handling by any other means, except at prohibitive expense. At a
certain steel-works in the North of England ten tons of matted steel
turnings were permitted to stand for several weeks in a railway truck
in an open siding. When it was decided to unload the vehicle the
turnings were found to have rusted and to have settled down into as
tightly packed a heap as could be imagined. The normal practice was
for men to shovel such material with their forks into the charging
boxes, but they found that they could not force their tools into this
formidable heap. The mass was surveyed and the hopelessness of coping
promptly therewith was admitted. Under manual labour the job would
occupy several days, even if it could be successfully handled at all,
upon which point considerable doubt prevailed.
It was decided to try the magnet. It was brought along on its traveller
and lowered into the truck. The winding drum was set going, and there
was a fearful snapping and snarling. The magnet refused to release its
hold, while the metal, being tightly jammed and packed, offered a stiff
resistance to the irresistible attraction of the magnet. But, within
a few moments, the magnet tore itself free with some 3,360 lb. of the
tangled rusted steel clinging to its face. Within six minutes, and by
half-a-dozen lifts, the vehicle was cleared of its ten tons of scrap.
While the circular form of magnet is that generally favoured,
variations are made to comply with different requirements. Some
articles, such as steel rails, pipes and iron rods, from their
distinctive shape, only present an extremely limited surface upon which
the magnetic pull can be exerted. As a rule, to enable such articles to
be handled with efficiency and speed, two magnets, rectangular in form,
and spaced a short distance apart, are used. The magnets are coupled
together, but maintained a specific distance apart by spacing bars,
while they work in unison. While the area available for contact upon
each magnet is somewhat reduced, as compared with the circular type,
this deficiency is counterbalanced by the ability to apply the magnetic
lifting effort at two points.
It is doubtful whether the true money-saving possibilities of the
lifting-magnet are really appreciated. The initial outlay may appear
heavy--in the case of the British magnet to which I have referred it
ranges from £150 to £600--$750 to $3,000--according to dimensions,
face-form and lifting capacity--but this expense is readily recouped.
The lifting-magnet is not only a time-saver but it enables given
work to be accomplished with fewer men. In some instances this
displacement of labour has attained striking proportions. At one
steel-works a lifting-magnet of 52-in. diameter was installed at a
cost of £400--$2,000. It is employed for handling pig-iron, and in
this work has dispensed with fifty men. The saving in wages, which its
introduction has rendered possible, sufficed to defray the capital cost
of the apparatus during the first three months of its use.
The results recorded at another establishment are equally impressive.
A 36-in. magnet was acquired, and for one specific duty--loading
trucks--was employed for a total of twenty hours during the month.
Previous to its acquisition this work was carried out by manual labour,
and it used to demand the combined efforts of ten men for ten hours to
load the vehicle, the cost being £4--$20. With the magnet the truck is
now loaded in two hours and at a cost of 8s.--$2--this figure being
inclusive of all charges--electric current, depreciation, interest,
labour, etc. In the course of the year the magnet puts in 240 hours
truck-loading, the number of trucks dealt with during this time being
120. The saving effected by the utilization of the magnet is thus
£3 12s.--$18--per truck or £437--$2,185--per year. Seeing that the
magnet at the time of its installation cost £150--$750--it will be seen
that it pays for itself approximately three times over in the course
of each twelve months, and that upon one single range of duty for an
insignificant period of time.
Under manual conditions of handling scrap and at the current contract
trade union rate the cost is 1s. 4d.--33 cents--per ton. With the
lifting-magnet, including labour and depreciation, the cost is
only one penny--2 cents--per ton for this work--a reduction of 1s.
3d.--31 cents--per ton! At the works of the Stobie Steel Company,
Dunston-on-Tyne, the initial cost of the lifting-magnet was recovered
during the first four months it was used. This company declares that
the annual saving which its employment effects is £800--$4,000.
But the applications of the magnet are not confined to lifting and
carrying operations. As an instrument for breaking up masses of steel
too large to be handled conveniently, or to be passed into the cupola
of the furnace, it cannot be excelled, either in point of efficiency,
safety, or economy. Breaking-up is carried out by what is known as the
“skull-cracker,” which comprises a roughly-cast ball of steel which
may weigh as much as 22,400, 27,000 or even 36,000 lb. This is picked
up by the magnet and lifted to the desired height. The current is then
switched off, releasing the ball to fall and to strike the scrap-boiler
or some other cumbrous piece of junk a terrific blow.
While the “skull-cracker” has been in vogue for many years with
mechanically operated devices, and so is not peculiar to the magnet,
yet this latest development represents the highest achievement yet
attained in this particular direction. Under mechanical conditions from
four to six men are required to carry out the work successfully. With
the magnet and ball the task can be fulfilled by two men--if exigencies
so demand it can be completed single-handed by the crane-magnet
operator--while the time occupied in such essential destruction is
very much less, more efficiently accomplished and with complete
safety, because under mechanical conditions breaking-up is generally
regarded as highly dangerous work. A further advantage is offered by
this system. The “skull-cracker” can be lifted and dropped alternately
until the scrap has been reduced to suitably sized pieces, and then
the magnet, disdaining the ball, can pick up the pieces of junk to bear
them away to the furnaces without any delay.
Despite the forward strides which have been made in regard to the
adoption of the magnet in the British iron and steel trades during
the past four years, this system of handling ferrous metals is still
in its infancy. It has been neglected far too long. Yet it is a force
which in the future must play an increasing important role, because it
is generally admitted that, to offset the higher wages incidental to
production, it is imperative for manufacturers to exploit fully every
possible time, labour, and money-saving device. The magnet is one of
the most attractive contributory factors to this end, especially in
connection with the handling of iron and steel waste, that has yet been
contrived.