INDUSTRIAL A N D ENGINEERING CHEMISTRY
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Vol. 22, No. 10
Special Equipment for Protection against Toxics in the Chemical Industry' C . L. Turner M I N X SAPETV APPLIANCES C O M P A N Y , PITTSBURGH,
HE manufacture and handling of chemicals present
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many special hazards in addition to the more usual possibilities of accident, which must be carefully studied and for which adequate protective equipment must be provided. Whether a particular plant is engaged in the manufacture of lacquer solvents, acids, steel rails, or automobiles, the possibility of injury to men employed in that industry by falls, falling objects, improper lighting, the handling of maimer diel
ients
Figure 1-Sectional Diagrammatic View of Burrell All-Service Gas Mask Canister
terial, and many other similar hazards is, with slight variations, common to them all. The chemical industry, however, presents many unique problems to which much thought, time, and attention are being given both by manufacturers and laboratories actively engaged in the chemical industry and by manufacturers and laboratories specifically interested in the development of protective equipment. Protective Equipment
A few years ago in many branches of the chemical industry gas masks were rarely used in daily work. 1
Received July 7, 1930.
Coincident with
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the development of new chemical processes, especially during the war and since, the necessity for proper and adequate respiratory protective equipment became very apparent, with the result that today there are gas masks available providing respiratory protection against practically all known poisonous gases. The gas mask itself has been improved in many ways. The resistance to breathing has been considerably reduced-to the point where, if it is necessary to wear masks continuously in certain operations, no discomfort is experienced by the o p erator. Mouthpieces and noseclips have been eliminated: rubber facepieces with a n extremely long life and which are readily cleaned are now obtainable. A great deal of thought has been given to the development of a facepiece which will assure maximum comfort. Modern facepieces fit all types and sizes of faces, so that in case of emergency they may be quickly and safely applied by any person. The heart of the gas mask is the canister, which purifies the air reaching the lungs of the wearer. The canister, in addition to providing absolute protection against all gases for which i t is designed, must permit free breathing so that the wearer may a t all times obtain a sufficient volume of air without undue exertion. Canisters in m o d e r n gas masks protect against specific gases, either singly or in combination. Protection is afforded for practically every known gas, including the deadly carbon monoxide. Protection against carbon monoxide alone or in combination with other gases has until recently be e n unimportant in the chemical industry, but with the development Of synthetic Figure 2-Workman Wearing Burrell Allewes employing carService Gas M a s k bon monoxide the need for such masks has become necessary. For this purpose a special catalyst has been provided which when placed in the canister in combination with certain other absorbents renders protection against practically all emergency conditions. For use in operations where men must enter confined spaces where high concentrations of gas exist and where there may be a deficiency of oxygen, hose masks are now available. They are obtainable in several models. The simplest form consists of a suitable body harness, a facepiece equipped with the necessary exhalation valves, and a %-foot length of hose, through which the worker may draw fresh air from a n area outside the gaseous zone. When greater lengths of hose are necessary, these hose masks are equipped with manually or electrically operated blowers for overcoming the resistance of breathing through the hose line. Hose masks equipped with blowers assure the wearer of a continuous supply of fresh air.
October, 1930
INDUSTRIAL AND ENGIIVEERISG CHEMISTRY
They are equipped with specially designed safety belts to which rope life linea may be readily attached. Masks of this type are particularly adapted for use in tanks or vats, or wherever it may be necessary for a man to enter a gas-laden atmosphere through a manhole, and in rooms where high concentr;ations of gas exist at a relatively short distance from fresh air. I n atmospheres which may be low in oxygen, or where large quantities of lethal gas exist, and where for certain reasons the use of a hose mask is not practicable, there are available oxygen selfcontained breathing apparatus. Such apparatus are valuable in times of emergency, particularly when in the case of fire it is necessary to enter buildings heavily charged with gas. I n the last few years great progress has been made in the perfection of this type of apparatus and its maintenance and operation have been considerably simplified. It reFigure 3-Sectional View of the Bumell All-Service Gas quires, nevertheless, familiarity yz:& ~ ; n ~ O~ gA:z& with c ~ the ~ apparatus by the wearer. Pads, Etc. It is seldom worn except in times of great emergency and when burrounding conditions are extremely dangerous. It is therefore imperative that where these apparatus are installed proper training and inspection be carried on, so that in time of need the apparatus will be ready for operation and men will be thoroughly familiar with its application. Various types of gas masks, hose masks, and oxygen selfcontained breathing apparatus have been tested and labeled as "approved" apparatus by the U. S. Bureau of Mines for certain specific work. All types of apparatus bearing the approval of the Bureau of Mines have been carefully studied,
Figure 4-M-S-A
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actually tried out under working conditions, and are considered adequate by the bureau for the work intended. Detective Equipment
The detection of dangerous conditions, particularly in the handling of explosive gases, has lately been given serious consideration b y m a n y agencies. One of the outstanding developments is that of the F-11 flammable vapor indicator, a device developed in the Factory Mutual Laboratories for the indication of the percentage of flammability. The F-M indicator is unique in that it will indicate without special calibration the percentage of lower explosive concentration of any gas containing hydrogen and oxygen or hydrogen and carbon in combination with oxygen. It will satisfactorily indicate the percentage of flammability of any of these gases, either singly or in combination. Therefore, in p r o c e s s e s where various hydrocarbons may be used and where the mixtures Figure 5-Workman Wearing McCaa of solvents m a v be Half-Hour S e l f 4 o n t a i n e d O x y g e n changed, it will" con- Breathing Appara tu8 t i n u a I 1y indicate the exact condition existing in the atmosphere irrespective of any change which may be made in mixtures. The F-M indicator is based w o n the law recentlv confirmed by N. J. Thompson, of h e Factory Mutua1"Laboratories, that practically all gases containing hydrogen and carbon or hydrogen, carbon, and oxygen, when burned at the lower explosive limit, produce the same number of calories of heat per unit burned. Thus, when we burn 100 cc. of alcohol, benzine, gasoline, propane, etc., a t the lower explosive limit, approximately 50 calories of heat are produced. The F-M indicator makes use of this law by continuously drawing a sample through the device by means of an electrically driven impeller. The sample, in passing through the detection unit, is first exposed to a high-temperature chamber containing a hot filament and the cold junction of a thermocouple. The temperature of this chamber is not sufficiently high to cause combustion of the gas. On leaving this chamber the sample passes into a similar chaiiiber containing a hot filament maintained a t exactly the same temperature. This filament, however, is surrounded by a catalyst and combustion takes place. The hot junction of the thermocouple is also located in this chamber. The percentage of lower explosive limit concentration is indicated by a sensitive meter, calibrated in percentage of flammability, located in the Combination Hose M a s k Being Used at a Refinery thermocouple circuit.
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IND USI'RIA L A N D ENGINEERING CHEMISTRY
The F-M indicator is particularly useful in detecting the percentage of flammability in various compartments, in exhaust systems, ovens, and around can-filling machines. It is also useful in indicating the completeness of recovery in solvent-recovery operations. I n this use it is installed behind
Figure 6-Jones
VOI. 22, No. 10
vice is so arranged that it is impossible to close the electrical circuit to the explosion chamber before closing the valves to the sampling tube. If,when the electrical circuit to the spark plug in the explosion chamber is closed, an explosion takes place, it is indicated by a deflection of the dragneedle on the pressure gage connected to the explosion chamber. If no explosion occurs and it is desired to determine whether the sample is below the lower explosive limit, this is accomplished by adding a measured increment of a known explosive gas from the cylinder attached to the detector. This will indicate the relative percentage of flammability in the sample. I t is also possible, by adding fresh air t o the apparatus, to determine whether the sample is above the upper explosive limit or an inert gas. The Jones gas detector is readily portable and is an excellent device for rapidly determining the relative explosibility of the atmosphere a t any point. It is very useful in sampling the contents of tanks, vats, pipe lines, etc. For rapid determination of small quantities of carbon monoxide, the Hoolamite detector is recommended. I n the use of
Gas Detector i n Practical Field Use
t h e absorbent chamber and will indicate the percentage of solvent in the effluent air from the absorber. The F--M indicator is supplied in several models and may be equipped with recording devices, contacts for operating external electrical circuits, alarm gongs, lights, and so forth. For the rapid determination of approximate explosive contents, where permanent installations are not desired, a gas detector has recently been developed by G. W.Jones of
Figure 8-M-S-A
Figure 7-M-S-A
Carbon Monoxide Detector
the U. S. Bureau of Mines. It consists essentially of an explosion chamber fitted with a spark plug and the necessary batteries and spark coil, into which a sample of suspected atmosphere is drawn by means of an aspirator bulb. The de-
Continuous Carbon Monoxide Recorder
this device, samples of the suspected atmosphere are drawn through a filter chamber by means of an aspirator bulb and then forced through a tube containing Hoolamite, which turns to a characteristic green when affected by varying concentrations of carbon monoxide. The Hoolamite tube is then compared with a standard color tube mounted on the detector, giving an accurate determination of the gas present in the samples. B more recent development in the detection of carbon monoxide is the palladium chloride ampoule as developed by the Bell Telephone Laboratories, This detector consists essentially of a small ampoule of a solution of palladium chloride which is surrounded by a sack of absorbent cotton. I n use the glass ampoule is broken by crushing, which permits the palladium chloride solution to saturate the absorbent cotton. When exposed to atmospheres containing carbon monoxide for a definite time, a characteristic color ranging
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I S D C S T R I A L A X D E,VGIXEERISG C H E M I S T R Y
October, 1930
from canary yellow to deep gray is produced and the amount of carbon monoxide present may be determined by comparison with a standard color (nard. For the continuous indication and recording of the amount of carbon monoxide present in any atmosphere, there is available the continuous carbon monoxide recorder. These are in use for the control of ventilation in the great vehicular
Figure 9-H-H Inhalator Being Used in Connection with the Schaefer Prone-Pressure Method of Artificial Respiration
measured sample is run through a combustion unit where, in the presence of a catalyst, coniplete combustion takes place. The heat of combustion is recorded by means of a thermocouple and recording potentiometer which is calibrated in percentage of carbon monoxide. Resuscitation Equipment
Industrial plants employing cheniical processes are hy their very nature interested in gas protecting, detecting, and recording devices in an effort to eliminate accidents, Yet, in spite of all the splendid efforts put forth by the safety departments, accidents will occasionally happen. I n case of gas asphyxia or partial gassing from most of the gases commonly encountered in the chemical industry, resuscitation can often be effected by the use of an inhalator, which administers Carbogen (93 per cent oxygen and 7 per cent carbon dioxide) in accordance with the treatment perfected by Yandell Henderson and Howard W,Haggard, of Yale L-niversity, in cooperation with the Accident Prevention Committee of the American Gas Association. Inhalators of this type are used in conjunction with the Schaefer pronepressure method of artificial respiration with outstanding success. Conclusion
tunnels and in recording the completeness of combustion in some industries. This monoxide recorder is of the permanent installation type, although some models have been developed which are more or less portable. Continuous samples are drawn through the instrument by means of an electrical pump; gases other than carbon monoxide are completely removed, the humidity being definitely controlled, and finally, the
The developinent of protective, detective, and resuscitation equipment for the chemical industry is being given serious consideration at all times by the development laboratories of the Mine Safety Appliances Company, which invites the cooperation of the industry itself in presenting to it its problems as they may relate to accident prevention.
A Western Nitrogen Fixation Plant' G. N. Westby 6803 S I X T E E K T H .41.E.,S. E , SEATTLE, \\'ASH
F T H E natural resources necessary to the agriculturist and the niaiiufacturer but not found in the United States, fixed nitrogen is one of the most important. Among these fixed-nitrogen products are the nitrites, which are used in the dye industries, in the manufacture of explosives, and in agriculture. One practical process for the manufacture of nitrites is the arc process, but its use has never attained coirtniercial proportions generally in this country. Howeyer, for almost ten years the American Sitrogen Products Company, using this process, nianufactured high-grade sodium nitrite assaying in accordance with market demands between 96.5 and 99.0 per cent SaSOs. At the end of this period the plant had sufficient installed capacity to furnish the entire American market with nitrite, but after the destruction of the plant by fire in May, 1927, and owing to uncertainty as to its future power supply, the company dissolved. I t is believed, however. that a des mption of this somewhat unique plant and its operation and product might be of some technical as well as historical interest. The factory was located at La Grande, Wash., 011 the Mount Ranier branch of the Chicago, Milwukee & St. Paul Railroad and within half a mile of the Sisclually hydroelectric station of the city of Tacoma. 1
Received J u l y 16, 1930.
The plant consisted of arc or electric furnaces, heat interchangers, an absorption-tower section, evaporators, crystallization floor, drying section, packing department storage arrangements, and all necessary mechanical and electrical equipment for these department's. I n general, the plant comprised units which grew from the first of the experinieiital structures, expanding as experience pointed the way. In the beginning the furnace design was in an einbryonic stage and the capacit'y quite uncertain. The conditions governing the forniation of sodium nitrite under the new controlling circumst'ances were not well known and the proportionate adjustment of each departnient' of the plant to an had to be made in the light of experiment. With the of the major problems there resulted ultimately an arrangement of parts which might have impressed the visiting eiigineer as planless and built without the formality of blueprints. However, during the course of years gradual changes evolved a plant which was peculiarly adapbed to the product that mas to be manufactured, with costs which made possible profitable competition with other chemical works producing the compound. Secessarily, cheap electric power was the foundation on which the whole enterprise rested. The apparatus used and the procedure followed in the manufacture of sodium nitrite by the La Grande process might conveniently be summarized as follows: ~
