Chapter I: Part 1

SAFE FOUNDRY PRACTICE

Reasons for selecting THE TRAVELERS for

Workmen’s Compensation
_and_ Employers’ Liability

INSURANCE AND SERVICE

It is the Greatest Casualty Company.

It has splendid resources, conservatively managed.

It is forward-looking in its ideas.

It provides unsurpassed service in the administration of claims and the prevention of accidents.

It is a multiple line company affording those who require several kinds of insurance an opportunity to obtain them all in the same company--and thus obtain the highest possible quality of service, _Entirely Free_.

The Travelers has spent more than $6,500,000 for the prevention of accidents by inspection

THE TRAVELERS INSURANCE COMPANY
THE TRAVELERS INDEMNITY COMPANY
HARTFORD, CONNECTICUT

_Lines written by The TRAVELERS_

include LIFE, ACCIDENT and HEALTH, GROUP, WORKMEN’S
COMPENSATION, EMPLOYERS’ LIABILITY, PUBLIC LIABILITY,
AUTOMOBILE, AIRCRAFT, STEAM BOILER, ENGINE,
ELEVATOR, BURGLARY and PLATE GLASS

SAFE FOUNDRY
PRACTICE

THE TRAVELERS INSURANCE COMPANY
HARTFORD, CONNECTICUT

21381. 12-29-’19.

Copyright, 1920, by
THE TRAVELERS INSURANCE COMPANY,
Hartford, Connecticut

PREFACE

The foundry, viewing it from all angles, presents one of the greatest problems in the industrial world. The fact that the production of castings depends not only on a mechanical process, but also on a chemical process, makes it specially difficult to fasten upon any individual the responsibility for imperfect work. And yet there is a definite (even though unassignable) reason for the loss of every defective casting produced,--some one member of the department failed in properly performing his part of the work. Every man must therefore be taught to appreciate the importance of his own particular task, and must be impressed with the necessity of performing that task conscientiously, and as correctly and efficiently as he can. There should be a spirit of cooperation as earnest and sincere as that which prevails in a beehive, where every worker performs the task of the moment with singleness of purpose, and with no thought or motive other than the production of the best final result, from the united labors of all. The development of a point of view of this nature among the men will also have a profound effect in the way of reducing accidents,--a greater effect, in fact, than could be realized by any other single means.

One of the problems that must receive special consideration in connection with accident-prevention work in foundries relates to the class of persons employed. It is not necessary to employ skilled labor for all the operations in the foundry, and for that reason a certain portion of the work is intrusted to unskilled help,--to men, namely, who do not understand the necessity for safety methods. The most practical and effective way of dealing with a situation of this kind is to adopt the team-work idea--that is, to teach cooperation--and to introduce a well-organized safety department that will educate the men to the extent of developing in them sound and correct accident-prevention ideals. Useful practical suggestions for accomplishing this, and for making the accident-prevention work effective, are given in a booklet entitled “_Organization in Safety Work_”, which is published by the Engineering and Inspection Division of THE TRAVELERS INSURANCE COMPANY.

Even the best-equipped, most orderly, and most effectively organized foundry is not free from accidents, and it is too much to expect that complete immunity will ever be possible. The experience of many concerns that have adopted safety methods in their foundries shows, however, that it is possible to eliminate a large proportion of the commoner causes of accidents, without much expense and without any serious disturbance of existing conditions. The Engineering and Inspection Division of THE TRAVELERS INSURANCE COMPANY, in the course of its extensive experience with foundries, has given a great deal of study to this subject, and the recommendations and suggestions that it has made in the course of its practical inspection work have been well received by foundry managers, and have been particularly effective in bringing about better and safer conditions. The present booklet, based upon this study and experience, contains some of the suggestions that have been found to be most serviceable and important in dealing with the accident-prevention problem in its broader phases. Every foundry has important special safety problems of its own, which must be dealt with effectively if the best results are to be obtained; but to include all features of this kind would swell this booklet to such dimensions that its effectiveness and usefulness would be impaired. We have therefore confined our attention to danger-points of wide and almost universal occurrence.

There are few machines in foundries in comparison with the number in industrial plants of many other kinds. The machines that are used, however, must be provided with guards at all points where accidents might occur, and the necessary special guards have been described in more or less detail in the following pages. The construction and arrangement of the various forms of guards for belts and pulleys are not fully explained, but it should be understood that these are to comply with the standards approved by the Industrial Compensation Rating Bureau. The Engineering and Inspection Division of THE TRAVELERS INSURANCE COMPANY will furnish upon request, copies of an illustrated pamphlet entitled “_Industrial Standards_,” which clearly explains the requirements of the Bureau.

In the main, the present booklet deals with iron foundries; but we have also included certain special hazards that are encountered chiefly in foundries where other metals are cast.

THE TRAVELERS INSURANCE COMPANY,
Hartford, Connecticut.

CONTENTS

PAGE
Introductory 1
Clothing 1
Shoes and leggings 2
Eye-protectors 3
Gloves 4
Aprons and rubber boots 5
Ladles 5
Flasks and molds 16
Crucibles 19
Cupolas 30
Traveling cranes 35
Chains and hooks 44
Wire-rope slings 45
Slings in general 46
Hoisting apparatus in general 47
Tumbling barrels 47
Sand mixers and sifters 49
Automatic molding machines 50
Chipping department 50
Grinding wheels 52
Compressed air 52
Sand-blasting 53
Illumination 56
The foundry yard 58

SAFE FOUNDRY PRACTICE

Introductory.

According to the best statistics available, it appears that about eighty per cent. of the injuries received in foundries are in the nature of burns of greater or lesser severity; the remaining twenty per cent. being caused by defective hooks, chains, slings, flasks, mold-boards, bottom-boards, and other equipment, and by unguarded machinery, by falls and falling objects, and, indirectly, by inadequate illumination, poor ventilation, and other similar general conditions. Suitable clothing and shoes will materially reduce the severity of foundry burns, and will entirely eliminate many of them. Approved protection of this kind is described in the following pages, together with safeguards for various machines, and advice is also given with regard to precautions to be taken for the prevention of accidents in handling the various tools and appliances that are used in foundries.

Clothing.

Suitable clothing is an important factor in protecting foundry workers from burns. Ordinary cotton shirts and overalls afford but little protection, because molten metal burns through them almost instantly; and although the legs and feet are the parts of the body most often burned in the foundry, it is advisable for the men to wear shirts (as well as trousers) made of a thick, stout, hard-finished material, such as khaki (twilled cotton), which will shed the molten metal to some extent. The bottoms of the trouser-legs should never be rolled or folded up, and there should be no other folds, nor any creases or pockets in the clothing, in which molten metal or highly-heated particles of any kind may lodge. Torn garments and those having holes in them are unsafe, and should not be worn. Woolen undershirts furnish the best protection against “shot” or molten metal, but on account of the intense heat to which foundrymen are exposed it is hard to get the men to wear them, particularly during the summer months.

Shoes and Leggings.

The number of burns received by foundry workers on the feet and legs may be greatly reduced or almost entirely eliminated by the use of proper shoes and leggings. These should be worn by every foundry worker who has to handle molten metal, or who is exposed to it, and no one should be permitted to work without them, where the danger of such burns exists. Strong, substantial, well-made shoes of the “congress” type are the most suitable for general wear in foundries, because when they are in good condition they contain no holes through which molten metal may enter, while in laced and buttoned shoes there are many such openings. Moreover, congress shoes may be quickly and easily removed when hot metal is spilled upon them. Low-cut or Oxford shoes should never be worn by foundry workers.

Suitable leggings are almost as necessary as good, serviceable shoes. Under some conditions safety requires that the leggings be of asbestos or leather, but for general foundry work canvas or twilled cotton of good quality may be used. These materials will meet with all but the most severe requirements. The leggings, like the shoes previously described, should be fastened in such a way that they may be quickly and easily removed, and ordinary buckles are therefore unsuitable. Laces and buttons are likewise unsatisfactory, and any type of fastening that forms projections upon which molten metal may lodge does not afford the best sort of protection. Flat spring clasps, properly inclosed, at the top and bottom of the leggings, are the most satisfactory type of fastening devised up to the present time. The leggings should completely incase the legs from the knees down, and should fit snugly, especially at the top, to prevent the entrance of molten metal at this point.

Eye-protectors.

It is extremely important to protect the eyes of foundrymen against the intense light and heat from molten metal and from welding flames, and also against dust and grit, flying chips, and molten metal that may be splashed about. Eye-protectors (also called “safety glasses” and “goggles”) of various types are now available for all the different hazardous operations in foundries. To insure comfort, eye-protectors should fit well, and should be light in weight and easily adjustable for size. They should be provided with side protectors composed of metal screens or of perforated leather, to stop flying particles and small objects that might otherwise enter the eyes from the sides. The lenses should not be made of ordinary window glass, but in order to prevent serious eye strains they should be made of clear glass without flaws, and polished on both sides. They should also be strongly framed, so that pieces will not enter the eyes in case the lenses are broken. The lenses of eye-protectors that are to be used by furnacemen, welders, and others whose eyes are exposed to unusually brilliant light-sources should be suitably colored, to temper the intensity of the rays and to exclude those that are specially harmful to the eyes.

Experience has shown that where eye-protectors have been provided and worn faithfully, there has been a marked decrease in the number of eye injuries.

Gloves.

Cupola men and others working where the heat is intense must provide protection for their hands and arms. Gloves and sleeves of calfskin, buckskin, canvas, and asbestos are used,--the choice of material depending upon conditions. When gloves with gauntlets are used, the sleeves of the shirt, coat, or jumper (whichever is worn) should be pulled down over the gauntlets. The sleeves should then be arranged with as few folds or creases as possible, and be secured about the wrists by means of buttons or clasps or in some other suitable manner. (By leaving the gauntlets _outside_ of the sleeves lodging places for molten metal are provided, and serious burns are likely to result.) There should be no slits or openings in the lower ends of the sleeves (at the wrists) as in ordinary shirts, because molten metal would be likely to find entrance through them.

Hand-leathers and gloves of various kinds must be worn by men handling scrap, pig iron, and hot castings; and rubber gloves are important to afford protection against acids employed in pickling processes. Thick, clumsy gloves, which interfere with the safe handling of tools and implements, should not be used. Care should be taken to see that no workman wears ragged gloves, or gloves with frayed fingers, which are specially likely to be caught by moving parts of machines or on the sharp edges of objects being handled.

Aprons and Rubber Boots.

In connection with pickling processes, rubber boots and rubber aprons are often necessary to prevent acid burns and damage to clothing. Aprons are of value in other departments of foundries also, particularly when flasks and rough, hot castings and other objects are being carried about, and when it is necessary for grinders to support castings in position at the grinding wheels. For work of this kind, and for foundrymen engaged in pouring metals, leather aprons are recommended. In view of the high cost of good leather, however, aprons of other suitable material may be used where the leather is not absolutely required.

Ladles.

Several types of ladles are used in foundries, including reservoir, crane, sulky or buggy, trolley, bull, and single-hand ladles. Many burns are caused by defects in ladles, and by lack of care in handling and transporting them. All ladles should be frequently, regularly, and critically examined, and when defects are observed the ladles in which they are found should be immediately set aside for repairs, or should be discarded if the defects are of a serious nature.

Reservoir ladles and all other ladles operated by gearing should receive special attention. The motors of motor-operated ladles should be completely inclosed, not only to protect the workmen against electric shocks and burns, but also to prevent accidents which might be caused by metal being spilled upon the motors, resulting in short circuits or other kinds of trouble. All the gears on geared ladles should be completely inclosed, the covers or guards being constructed in such a way that they may be readily removed for oiling, cleaning, and inspecting the various parts. If guards are not provided the gears will soon become clogged with dirt and with metal that has hardened or set after having been spilled upon them while in a molten state; and clogged gears are likely to be broken or stripped, and to cause serious accidents.

(The gears should be completely inclosed, to prevent them from becoming clogged with dirt and spattered metal.)]

Many ladles are equipped with direct-acting spur gears. This arrangement permits rapid operation of the ladles, but it often imposes severe strains upon the operators, making it difficult for them to hold the ladles steady while pouring. This often results in spilling the metal and causing it to be spattered about when it strikes the sand on the tops of the flasks. A tilting arrangement composed of a train of spur gears, or a combination of worm gearing and spur or bevel gears, is to be preferred. The gears should be so designed and arranged that at least two teeth of each wheel will be in mesh at all times. Unless this point receives due attention a serious accident is likely to occur if the teeth become badly worn, or if one of them should break, thus permitting the ladle to tilt suddenly when pouring. The small pinions and worms of geared ladles often deteriorate quite rapidly, and they should therefore be inspected frequently and with special care, so that they may be renewed before they become a source of danger. Every geared ladle should be provided with a safety locking device to hold it in an upright position while it is being carried.

The bail of each crane ladle should be examined frequently, and particularly at the point where the crane hook engages it, because that is where the wear is greatest. The lower parts of these ladles should also be watched carefully for evidences of injury caused by carelessness on the part of cranemen when transporting or depositing them.

Sulky and buggy ladles are used only to a limited extent, but they cause many accidents. In some foundries steel plates are laid to serve as runways for buggy ladles, and plates are often placed between the rails of narrow-gage industrial railway tracks also. Molten metal is sure to splash when spilled on clean, smooth plates of this kind, and it also forms into “shot” which roll under the feet and cause the men to fall or to spill more metal. The danger from splashing might be minimized by sprinkling sand on the floor, but the sand would hinder the free movement of the wheels, and greater effort would be required to move the buggies. This would tend to make spills more frequent, even though in any individual case the sand might reduce the likelihood of injury from splashing, after the metal had been spilled. Floors of concrete and brick have been tried in other foundries, with the result that the number of burns from spills has been materially reduced. An excellent floor may also be constructed of metal plates with _checkered surfaces_,--the elevations on these plates providing a surface that is sufficiently smooth for the wheels, while the depressions (which are filled with sand) tend to check the splashing. Overhead trolley systems are used in some foundries for transporting ladles, and in this way the spills and splashes that are due to poor floor conditions are eliminated.

(Observe the inclosure for the gears, and the shield to prevent the molten metal from splashing on the operator when pouring and when pushing the ladle along the track.)]

It is necessary to maintain a clear path for buggies that are being moved about, because metal is likely to be spilled from them if even a very small obstruction is encountered. Moreover, the buggies or trucks should be inspected frequently, paying particular attention to the wheels and bearings to make sure that they are in good condition so that the buggies will run easily and smoothly. Each buggy should be equipped with prong guards to hold it rigidly while pouring, and the ladle should be properly counterbalanced so that it will automatically return to an upright position when empty.

Bull ladles are much safer to handle than ordinary single-hand ladles, and should be used whenever possible. Several styles of shank-handles are used with bull ladles, one of them consisting of a rigid fork handle on one side and a rigid single handle on the other side. In another style (which is preferable) both handles are forked; and in still another form a swivel is provided at one end, which permits the ladle to be tilted more easily and emptied with less danger of spilling. The bowls of bull ladles should be held securely in position in their shanks by means of clamps made of round or flat iron. The shanks must be amply strong for the weight to be carried, and the joints should be carefully inspected for poor welding, flaws, and other weaknesses. Defective ladle shanks should be removed from the pouring floor as soon as discovered, so that there will be no possibility of using them again, either intentionally or otherwise. Ladle shanks should not be left exposed to the weather, because such exposure causes them to corrode and become weakened.

(The handle is provided with a swivel, and one man tilts the ladle while the other man simply sustains a part of the weight.)]

When single-hand ladles are used the shanks should be securely attached to the bowls, because otherwise the bowls are likely to slip out when pouring, and to cause accidents. A sheet-metal guard or shield, 6 or 8 inches high, should be firmly secured to the top of the bowl of every hand ladle on the side next to the shank, to protect the workman’s hand while carrying the ladle.

(This illustration shows the correct attitude for a man to assume when pouring. Observe also the shield on the ladle, to protect the hand from burns caused by spattering metal. The leggings are of a good type but, unfortunately, are not clearly shown. On general principles we disapprove of the unbuttoned vest, although the upper part of the body is unlikely to be burned so long as the man is engaged solely in work of the kind here shown.) ]

When several workmen are carrying ladles from the cupola to the molds it is better for them to pass on the side on which the bowls are carried. This not only tends to avoid confusion and disorder, but it is also safer, because there is less danger of burns when two bowls are struck together by passing workmen, than there is when two shank-handles collide.

“Horse play” and purposeless activities of other kinds should not be permitted among the men who are waiting their turns at the cupola, because the work is hard and dangerous, and the men must take it seriously at all times and give their undivided attention to it, if burns are to be avoided. The ladles should never be completely filled, because if they are, the hot metal will surely spill while being carried. “Cutting in” from the _back_ of a continuous stream of molten metal at the cupola spout causes unnecessary spattering; always cut in from the front.

New employees in foundries, and particularly the unskilled help, should be carefully instructed with regard to the proper method of carrying the ladles and the correct position to assume when pouring into the molds, and they should be watched and supervised for a considerable time after being assigned to such work, in order to make sure that they understand how to do it properly. The men should stand at a safe distance from the molds, so that their feet will not be burned if the metal spills or runs out between the cope and the drag or nowel.

Ladles of all kinds, except hand ladles, are likely to cause accidents by tilting unexpectedly, unless the bowls are properly balanced on their shanks or trunnions, or are arranged to be locked in an upright position. It is specially important to see that the bowls are not top-heavy, even when full of metal. On the other hand, if the bowls are weighted too heavily at the bottom it is difficult to tilt them, and an unnecessary strain is imposed upon the operator and also upon the gearing and other mechanism; furthermore, it is not easy to pour a smooth, continuous stream from a ladle which requires considerable exertion to hold it in the pouring position. In particular, all ladles that are provided with bails for hoisting and transporting by cranes should be so constructed that, when full of metal, the center of gravity will be well below the bail, unless they are arranged with geared devices for tilting. In addition, they should be provided with clips or clamps to prevent unexpected or accidental overturning.

When buying new ladles it is important to see that the lips are of the correct shape to insure a smooth, narrow, undivided stream at pouring, and to prevent the molten metal from backing up and running over the sides at other points. Both safety and efficiency are promoted by the use of ladles with proper lips.

“Leave-overs” (excess metal left in ladles after the molds have been poured) are sometimes poured on the foundry floor. In this way puddles of molten metal are left, which soon become covered over with a thin coating of sand or dust so that they are not readily observed. The consequence is that men are often severely burned by stepping into or upon these puddles while the metal is still hot. Pouring leave-overs on the floor should be prohibited, and suitable receptacles should be provided at convenient points to receive the excess metal.

Many serious accidents have been caused by pouring molten metal into damp ladles, the result usually being an explosion, and the scattering of the metal in all directions. In every foundry, therefore, special care should be taken in drying the ladles. In some plants the core ovens or crucible furnaces may be utilized for the purpose, while in other cases it may be necessary to provide special ovens or heaters. Ladles should not be dried in the molding rooms by means of wood fires, unless adequate exhaust ventilation is provided.

(By installing a monorail system a device of this kind can be used for main-aisle and side-floor work. It can be operated by one man, with safety. The ladle can be hoisted and lowered, thus making it possible to pour molds at various heights. The metal shield protects the eyes of the operator against heat and glare, and also prevents burns from spattering metal.)]

All ladles that are not in use should be stored in a dry place, and preferably on elevated racks, or on supports of some other kind that will permit the air to circulate freely about the ladles.

Foundry ladles must be relined from time to time (bull and hand ladles are relined each day), and it is advisable to have all of this work done by men selected for reliability and experience, who are interested in making the ladles safe and willing to give them the necessary time and attention.

All of the ladles that are in use should be examined carefully every day, preferably by an experienced and conscientious man who has been specially selected for this work. The bowls should be inspected for cracks and thin, weak spots, and the shanks should be examined to discover defective welds and erosion. Inspectors should also look out for loose rivets and bolts, and should see that all necessary guards are in good condition and properly secured in place, and that all ladles are properly balanced.

Flasks and Molds.

Wooden, steel, and iron flasks are used in foundries, but those of iron and steel are so much superior that preference should be given to them under all possible circumstances. Iron flasks may be cast in the foundry, and the subsequent maintenance and depreciation charges are quite small as compared with what must be expended upon wooden flasks. Moreover, after a wooden flask has been used for some time the faces of the cope and the nowel become burned or broken off, with the result that instead of fitting closely together they may be separated by a space of an inch or more. Although this space is filled with sand, the hot metal is likely to break through and run down the sides of the flask. “Run-outs”, as leakages of this kind are called, often cause severe burns on the feet and legs of the workmen. If iron or steel flasks are used, and the cope and nowel faces are planed to insure a close fit, there will be little likelihood of the occurrence of run-outs.

Iron and steel flasks, as well as wooden ones, require frequent and careful inspection to see that none of the lugs, handles, or other parts are broken. If a flask is found with a broken or cracked lug or handle it should be immediately removed from the shop for repairs; otherwise, it might be used again by some person unaware of its dangerous condition, and a serious accident might result when it was picked up by the crane.

Congestion on the molding floor is noticeable in many foundries, particularly in those where the work is greatly diversified; and numerous burns are the direct result of such a condition. Sufficient space should be left between flasks so that the molders and their helpers will not be crowded while pouring, and so that they will be able to get out of danger quickly and easily in case of a “run-out”. There should always be a clear space of at least 18 inches between the rows of flasks when pouring “side floor” by hand, and for crane work in general; and passages 24 inches or wider are much to be preferred. Portable horses may sometimes be used to advantage for supporting bull ladles when pouring work of certain kinds.

Flasks, when in storage, should be piled in an orderly and systematic manner, and the maximum height for stacking them should be such that the workmen can handle them easily and conveniently while standing with both feet on the floor. Unevenly piled flasks sometimes fall over and cause serious injuries; and even though they are piled well enough to be stable if undisturbed, they may fall in consequence of jarring due to the motion of neighboring cranes, and sometimes they are pulled over by chains dangling from the cranes.

Workmen often collide one with another, and are severely burned or otherwise injured, in consequence of their view being obstructed by foundry equipment. Obstructions likely to cause accidents of this kind should be moved to the sides of the room. It is highly essential, also, to keep all the aisles clear of flasks, tools, implements, and other obstructions, particularly in plants where the illumination is not of the best, and where, on account of insufficient ventilation, large quantities of smoke obscure the vision.

Orderliness and adequate light and ventilation not only increase efficiency, but also materially reduce the number of accidents; and any reasonable expense that is involved in securing good conditions in these respects will pay for itself by lessening the time that is lost in consequence of the temporary demoralization to which the working force is subject whenever an accident occurs.

Crucibles.

Crucibles are extensively employed in founding, especially in connection with non-ferrous metals; and the importance of exercising special care in handling them, not only to avoid accidents but also to insure greater length of service from the crucibles themselves, has been greatly underestimated in the past. In our larger plants, however, foundrymen are now giving considerable attention to the systematic instruction of their furnacemen, melters, and helpers, with a view to keeping the number of accidents as low as possible, and obtaining as great a number of heats as practicable from each crucible.

The clay crucibles of former days have been extensively supplanted by better ones made largely of graphite, which is capable of resisting exceedingly high temperatures. In fact, crucibles composed wholly of clay have practically gone out of use for the melting of steel and brass, because they can often be employed for only one or two heats, and they are far more likely to break or crack unexpectedly, thereby causing workmen to be seriously burned. Moreover, the temperatures that occur in metal-working plants at the present time are higher than those that prevailed when the all-clay crucible was the standard type. The crucible that is now in general use consists mainly of the substance that is variously known as graphite, plumbago, or black lead, and which is a practically incombustible form of carbon. This is combined with a small amount of a special variety of clay as a binding material, and perhaps a little fire sand to give the mixture an open grain, so that it can better withstand sudden changes of temperature. Some makers use, in addition, a certain quantity of material obtained by grinding up old, worn-out crucibles; but this practice cannot be recommended.

The graphite crucible is doubtless the most efficient yet devised, when cost and all other elements are considered, but it is nevertheless somewhat fragile, in view of the fact that it is expected to withstand a heat sufficient to melt the refractory metals, and to support, at the same time, very considerable pressures due to the weight of its heavy fluid contents. It is exceedingly important, therefore, to see that all employees fully understand how to handle crucibles in order to reduce the danger of breakage to a minimum; and a great deal can be accomplished in this direction, because graphite crucibles, when properly made and carefully used, can be kept in a fairly safe condition.

The number of accidents from breakage is greater in small plants than in large ones, in proportion to the number of crucibles in use. This is due partly to the greater care that the crucibles receive in the large plants, and partly to the fact that large foundries buy supplies of crucibles considerably in excess of their immediate requirements, storing the surplus ones and allowing them to age or “season”. It is an old saying that crucibles improve as they grow older, and as experience shows that this belief has some actual basis in fact, the date of manufacture should be stamped upon every crucible, to assist the annealing men in selecting the oldest and best seasoned of them, when additional ones are required for use.

Good crucibles are expensive, and every foundryman therefore desires to obtain the maximum service from them. The foundryman who attempts to increase the useful life of his crucibles by careful handling, and by the adoption of approved methods of every other kind, is at the same time promoting safety by preventing accidents from premature breakage. Foundrymen, melters, pourers, and helpers, usually expect a crucible to run a certain definite number of heats, and they are likely to be somewhat careless when a new crucible is put in service. For this reason it is wise to assign a number to each crucible, for recording the number of heats taken. The record may conveniently be kept upon a black-board, opposite the appropriate crucible number and in plain view. Everybody then knows just how many heats each crucible has run, and this knowledge often arouses a spirit of competition, which tends to make the men more careful in handling the crucibles, and to increase the service that can safely be had from them. (The dating and numbering here recommended are now being done, quite generally.)

When crucibles are first received, it is important that they be critically examined for cracks and flaws, not only by the eye but also by tapping them with a light hammer; and all imperfect ones should be rejected. If there is evidence that any of the crucibles in a given shipment have become wet while in transit to the foundry, they should be stored for at least four or five weeks, before being used, in a place where they will dry out thoroughly--even though they may be apparently dry at the time they are received.

When a new supply of crucibles has been carefully inspected and found to be free from defects, the entire lot should be stored for a considerable time in a warm, dry place, and provision should be made to protect them as thoroughly as possible from contact with moisture or with moist air. The roof of a continuously-operating core oven is an excellent place for the storage chamber.

The proper annealing of crucibles is of far more importance than is generally realized. It is said that crucibles, when they come from the manufacturer’s kilns, contain less than one-quarter of one per cent. of moisture; but after they have cooled off they absorb moisture again from the air. To anneal a crucible properly, it should first be slowly heated to a temperature somewhat above 250° Fahr., and it should be maintained (or “soaked”) at this temperature for a sufficient time to entirely remove the moisture. It may then be put into service, if it has been thoroughly annealed by the makers. If there is any doubt on this point, however, the crucible should next be heated for some hours to a dull red heat, after which it should be allowed to cool again, very slowly, to about 250°. In any case the crucible should still be at a temperature of 250° or over, when it goes into the furnace, or the drying-out process will not be wholly successful.

Large crucibles, with thick shells, require a higher temperature than small-sized ones in the preliminary heat-treatment, and a correspondingly longer “soaking” period, in order to reduce the absorbed moisture to the allowable limit. In drying out a No. 200 crucible, for example, ten hours or more should be allowed for bringing it up to a temperature of 250° Fahr., and fully ten hours more should be allowed for “soaking”,--that is, for reducing the percentage of moisture which may have been absorbed. If a crucible that has a considerable amount of moisture in its walls is quickly subjected to a high temperature, the moisture will be changed into steam, and this, because it is confined within the walls of the crucible, may expand so as to cause a rupture or crack. The same result may also follow from the natural contraction of the drying crucible, if the moisture is driven out rapidly or unevenly. The small “pinholes” and “skelping” that may often be seen on crucibles are caused in this way. These pinholes and fissures form one of the chief sources of trouble against which users of crucibles have to guard; for although a crucible having defects of this nature may endure for a considerable number of heats, it is nevertheless likely to fail at a critical time (for example, during pouring or while being pulled from the furnace), spilling the molten metal and causing severe hand and foot burns.

After receiving heat-treatment for the removal of moisture, crucibles are often placed on a layer of damp sand, or on the comparatively cold furnace floor, and left there for an indefinite length of time before charging. This should not be permitted, because when the temperature of the crucible falls to a point materially below 250°, it will again absorb moisture.

Fine cracks (called “alligator cracks”) often cover the entire surface of a crucible. These may be caused in a number of ways. Sometimes they are due to heating the crucible with fuel containing too high a percentage of sulphur; or, in oil furnaces, they may be caused by using too little oil or too much steam. It is specially important for the operators to thoroughly understand their work when using an oil furnace, because an excess of air or steam, or an insufficient supply of oil, may give rise to an oxidizing action, whereby a portion of the carbon (or graphite) is burned out of the crucible wall, leaving the binding clay in a somewhat porous condition; and this action, when it occurs, greatly facilitates the formation of cracks.

When crucibles are stored on the top of a furnace, the melters or furnacemen should make sure that the covers over the furnace openings fit properly. If the furnaceman is careless in this respect the moist gases that are given off when fresh fuel is placed on the fire will escape through the openings to some extent, and they are likely to come in contact with the crucibles, causing alligator cracks to form.

Cracks and fissures are also likely to form if the metal to be melted is not carefully placed in the crucibles. The men usually work rapidly when introducing the ingots, so that the furnaces will not be left open any longer than necessary; and the ingots are often thrown in with a force sufficient to indent the bottoms of the crucibles, or otherwise damage them. An indentation in a crucible, whether caused in this way or in any other way, is quite likely to develop, shortly, into a crack or fracture. The ingots should be introduced carefully and loosely, sufficient time being taken to insure that this is properly done. When a crucible is first filled it is desirable to place as many ingots in it, for the first melting, as practicable; but it is exceedingly important to see that they are not wedged or jammed, because when they are heated they will expand more than the crucible itself, and the walls of the crucible are likely to be cracked in consequence.

When a new crucible is put in service for melting, it should be heated quite slowly for a few runs, and this is _specially important the first time it is used_. After one or two runs it will become vitrified, and the danger from too sudden a heating is then materially reduced. It is a good plan to keep on hand a few extra crucibles that have been used before, to avoid loss of time in case an extra crucible is needed on short notice.

A great deal of harm is done by carelessness in handling the tongs and shanks, and the life of a crucible may be seriously shortened in this way. When a tilting furnace is used, as many as fifty heats can often be obtained from a crucible; but if the heating is in furnaces from which the crucibles must be removed by means of tongs, they can be used for only about fifteen heats, on an average.

A crucible is soft and plastic at a white heat, and may easily be squeezed out of shape by the pressure exerted upon it when the handles of the tongs are forced together. The walls of the crucible gradually become weakened by treatment of this kind, and eventually, if the crucible is not discarded, a complete rupture will probably occur, with its attendant toll of injuries and burns.

Three styles of tongs are in general use in foundries--one-pronged, two-pronged, and spade tongs. The different styles are designed for various special purposes and operations, but they are sometimes improperly used interchangeably. It is essential to see that the tongs that are used are of the proper shape, and that they fit perfectly from the widest part of the crucible (usually called the “bilge” or “belly”), down to within a few inches of the bottom. They should not extend to the _extreme_ bottom, however, because this would make it hard to place the crucible in the shank. On the other hand, if they do not extend down far enough the crucible will be badly squeezed. The proper use of the tongs consists in taking hold of the crucible below the bilge and lifting it in such a way that the least possible pressure is exerted against the crucible walls.

One-pronged tongs should be used only for lifting the smaller-sized crucibles,--say up to size No. 40. For larger sizes two-pronged tongs should be used. It is not uncommon to see large crucibles, ranging from No. 200 to No. 300, lifted by one-pronged tongs. This practice should be condemned, because when one-pronged tongs are used for lifting a crucible, pressure is exerted against only a single point of contact,--namely, at the bottom,--and the crucible, when hot and soft, is likely to be cut or ruptured, if it is large and heavy, because the pressure at the point of support is severe. Serious burns, from the spilling of the molten metal, often result when the lower prong of a two-pronged pair of tongs is cut off, on account of a lack of space between the crucible and the furnace wall; because the crucible is then lifted from above the bilge, and tilted. Melters should be cautioned against the practice of driving down the ring of the tongs with a skimmer or other implement, because this is almost sure to cause cracks and fissures in the crucibles.

Molten metal is often spilled from crucibles in consequence of using tongs that have become bent or otherwise misshapen. It is important to see that the tongs fit the crucibles properly, and that they are also in good condition in every other way. For restoring bent tongs to their proper shape, it is advisable to procure a set of cast-iron forms similar in size and general shape to the crucibles that are used in the plant, but slightly larger from the bilge upward. To restore the tongs to their original form it is only necessary to put them in the furnace, raise them to a red heat, clamp them to the proper iron form, and bring them back into shape by means of a heavy hammer. Tongs may be fitted easily and cheaply in this way, and a great saving of time results. If cast-iron forms are not provided, the blacksmith cannot be expected to restore the tongs to their correct shape with accuracy; but if iron crucible-forms of the proper sizes and shapes are used, and the tongs are fitted to them as here recommended, the likelihood of squeezing and distorting the crucibles will be reduced to a minimum.

Two pairs of tongs, at least, should be provided for each size of crucible, so that if one pair becomes badly bent or worn, the other pair may be placed in service without loss of time.

Furnacemen should make sure that no clinkers or pieces of unburned coal or coke are stuck to the walls of the crucibles when about to grasp them with the tongs, because if the tongs are applied over a clinker the clinker will probably be forced into the crucible and a rupture may then occur at any moment. It is also important to see that the bottom of the crucible (on the outer surface) is free from clinkers or other adherent substances, so that when the crucible is in the furnace its weight will be evenly distributed, and not concentrated at a few projecting spots or regions. It is best to support the crucible by means of a foundation or pedestal, of graphite, fire-brick, or other infusible substance, though the fire-bed may be made to give a fairly satisfactory support if it is carefully prepared and smoothed.

When a heat has been poured it is important to see that no metal is left in the bottom of the crucible, because when a residual mass (or “button”) of such metal cools, it contracts at a different rate from the crucible, and serious strains and cracks are likely to result.

Ramming the fuel bed is bad practice, in general, because it is likely to damage the crucibles seriously. If ramming appears to be necessary at special times, the utmost care should be exercised in doing it.

(We are indebted to the General Electric Company for the photographs that are used in this section.)

Cupolas.

Tapping-out is the most hazardous part of cupola work. This is specially true if the melter is inexperienced or careless, for it is almost entirely within his power to prevent excessive spattering of the hot metal if he properly controls the flow from the cupola. If dangerous spattering of the molten metal, with its attendant burns, is to be eliminated, it is important that the melter be taught the correct and only safe method of stopping up the tap hole. Under no circumstances should the stopping bot be thrust directly into the stream of flowing metal in order to “bot-up” the hole. Instead of this, it should be brought immediately _over_ the stream, and, when near the hole, should be carried down obliquely so that it will make a sharp angle with the stream, and thus effectively and instantly close up the hole without any undue spattering. In drawing molten metal from the cupola into buggy or trolley ladles, it is necessary to stop the flow of metal when a ladle has been filled and while another is being moved into position. This is done by the melter, who inserts the stopping bot into the hole and holds it there temporarily. After doing this several times the fire clay on the end of the stopping bot becomes burned off, and consequently the hole may not be closed properly. One or more extra stopping bots, already prepared with fire clay, should be conveniently at hand, which may be substituted for the burned-off one when necessary. The melter and all other workmen engaged about the cupola should wear well-designed goggles having side shields, because statistics show that a high percentage of eye injuries occur about the cupola.

Accidents occur about cupolas not only when drawing off the metal, but also during charging time, and when repair work is being done. As a general thing workmen engaged in charging a cupola must bring the coke and the iron (both scrap and pig) from the storage bins or yard, up to the charging platform. These workmen should be instructed to pile the iron evenly on the barrows, and to exercise great care in taking the scrap from the pile, in case the latter is in such a condition that it is likely to collapse or slide. Many workmen have been severely injured, while filling their barrows, by the sudden collapse of piles of scrap iron.

In many foundries elevators are used for conveying the charges to the charging floors. In every such case it is essential that a gong or other signal be sounded before the elevator is taken from the charging floor by a workman below; and the elevator should not be moved, after the signal has been given, until sufficient time has elapsed for any person who may be in danger to respond and to move into a place of safety. Many serious accidents have been caused by elevators suddenly descending while the workmen were loading or unloading them. To further guard against such accidents there should be a door or gate at each entrance to the hoistway, provided with an interlocking device so arranged that the elevator cannot be started until the door or gate has been closed. The unused sides of the car platform should be completely inclosed to a height of 6-1/2 feet (or to the top of the crosshead), and a substantial iron grating should be placed on the top of the car, to stop falling tools and other objects.[1]

[1] Further information with regard to the care and operation of elevators in general is given in a booklet published by the Engineering and Inspection Division of THE TRAVELERS INSURANCE COMPANY. Copies of this booklet may be procured by applying to the Home Office at Hartford, Connecticut.

The charging opening in a cupola should be fitted with a door or gate, which should always be closed except when charging is going on, and workmen engaged in charging should be specially careful to avoid tripping or losing their balance when in the vicinity of the opening, and especially when throwing heavy pieces of scrap or pig metal into the cupola.

When the interior of a cupola is being relined it is recommended that a watchman be stationed near the opening, or that a conspicuous warning sign be posted beside it, stating that men are working inside. We have known of cases where metal thrown into the cupola has struck and seriously injured workmen who were engaged in making repairs to the shell or lining. An effective guard against accidents of this kind consists in a circular screen of a diameter slightly smaller than the inside of the cupola, and made of heavy wire netting or of stout expanded metal, substantially framed. The screen should be divided in the center, and the two sections hinged together. In using this device it is suspended above the point where the men are at work, from a piece of scantling laid diametrically across the cupola so that it rests upon the walls where they are offset for the single brick lining, or upon the ledge formed by the charging doors,--the screen being supported by chains at several points around its circumference, and having its hinges on the under sides. When arranged in this way it tends to remain open and flat, although it can easily be folded by raising it at the middle. A screen of this kind will intercept falling pieces of slag and brick, and other objects, and will thus protect the workmen below.

When furnaces are to be entirely relined, only trustworthy and experienced men should be allowed to perform the work. Moreover, the fire-bricks that are used should be of the best quality obtainable, in order to insure long life of the cupola. Between the bricks and the shell a space of about 3/4 of an inch should be left, which should be filled with dry sand to act as a cushion, so that severe stresses will not be thrown on the shell when the bricks expand. The rivets and the shells of all cupolas should be inspected periodically, to see if any of the rivets have sheared off or worked loose, or if the shell has become weakened in any way. After making repairs of any kind, care should be taken to see that the cupola is thoroughly dried out, and that all tools, and all materials used for scaffolding or other purposes, are removed.

Explosions occur in cupolas from time to time, and if the shell of a cupola is weak, a serious catastrophe is likely to result. Carbon monoxide, when combined with air in certain proportions, forms a highly inflammable and explosive mixture, and the explosions are mainly due to this gas, which collects in the wind box and blast pipe during interruptions in operation. In an incredibly short time enough carbon monoxide gas may collect in this way to cause a violent explosion when the blast is turned on again. If the iron comes too fast a temporary shut-down may be unavoidable; but interruptions from other causes,--such, for example, as the slipping of the blower belt,--should be prevented, so far as possible, by frequent inspections of the equipment and by making all necessary adjustments and repairs when the cupola is not in operation.

A gate or damper should be placed in the blast pipe, close to the cupola, to prevent the explosive gas from entering the pipe. This gate should be closed _immediately_, whenever the blast is shut off, and it should be opened cautiously and slowly when starting up again. At the time that the blower is shut down one of the tuyeres should be opened also, to maintain a slight draft of air.