SYMPOSIUM ON INDUSTRIAL HEALTH AND SAFETY
Industrial Hygiene Considerations In Plant Location and Design WILLIAM R. BRADLEY, American Cyanamid Co., New York, N. Y.
Sick e m p l o y e e s a n d a r o u s e d neighbors are a p o o r c o m p l e ment to a successfully designed a n d l o c a t e d industrial plant JL HJE chemical engineer is aware ol his responsibilities in the design of a manufacturing plant and its equipment, along with the selection of plant location, for errors in judgment may be costly. H e must make no departure from engineering principles that are soundly conceived and executed. Consequently, he consults with his associates in chemical research and in pilot plant operation to benefit from their experience. Plant capacity is discussed with the sales department and problems in personnel and operation are reviewed with production people. Other interested groups also gather about his conference table so that his final blueprint is a result of careful planning, down to the handling and flow of materials in the most economical manner. The industrial hygienist has now become a member of this planning team. He provides the chemical engineer with an understanding of the working environment that may result within the plant when the chemical process is begun. From a study of the process he also provides an evaluation of how good a neighbor the plant will b e in the community where it is to be located. More precisely, the industrial hygienist sees that operation of the new plant will not result in employee ill health, through exposure of workmen to ohemical mists and vapors or t o harmful gases or dusts. He tries to make certain that * - new plant will not cause unfortunate community relations because of air or stream pollution. The industrial hygienist discusses the toxicology of the various chemicals, the raw materials, intermediates, products, and by-products, and interprets the extent and nature of any health hazard in their handling and use. It is then frequently possible to plan for the control of both plant and community environment where it may be needed, and make this control a definite part of the chemical engineer's blueprint. The important consideration is that this control be applied in advance of plant construction and operation.
plant are those pertaining t o maintenance of employee and community good health. One factor is that of clrmate. Sudden, changes in temperature, o f course, will freeze pipes and burst valves unless planned for in advance. Smdden temperature changes also may lead to a higherincidence of respiratory illness among plant operators. Exposure of man i s just as important as exposure of equipment. In. colder climates, the chemical engineer can. plan his process so that workiraen d o not frequently need to leave and reenter a. warm workroom in order to carry out their duties. Such duties may b e to operate valves or pumps or take measurements at tanks or collect samples, to bring in raw materials or remove productsWorkmen often will not trouble to put o n a cap and a heavy coat each time they must leave a warm buildintg. A warmer climate offers less o f this type of exposure, but thinking in terms of workmen should extend to protection against high wind, driving rain and snow, excessive heat, and freezing oold. The high temperatures, perhaps a s high a s 120° F., and excessive radiant energy that occur at furnace-tending or kiln-firing can be lessened by the use of reflecting baffles at operating points. Air-conditionec3 control rooms and ventilated steam line tunnels improve working conditions anc3 lead to smooth production. The location of a plant in a warm climate also may offer certain disadvantages. The increased volatility o f solvents, fox instance, may constitute a potential health
hazard of some magnitude. While toxic concentrations might b e safely circumvented by local exhaust ventilation, the daily handling of solvents in a warm climate poses a problem of an elusive chance exposure to vapor level concentrations that might not exist except for the fact that the average temperature is higher. Occasional spills, leaks, flushing of kettles, open filter presses, open drains, sumps, and so on may be sources of solvent vapor. These vapor sources may cause atmospheric concentrations of that low order of magnitude which consistently plague industrial hygienists for satisfactory answers as to their physiological significance. Complementing the conditions cited above is the personal element involved in suoh exposure. Warmer climates mean less clothing and therefore more body surface exposure to industrial materials. This means enhanced opportunity for skin contact with irritant solids, liquids, and gases. Coupled with this are the factors of excessive -workroom temperatures and the greater discomfort in wearing protective respiratory equipment and clothing. Once the working conditions with respect to climate have been resolved, there are other factors which might play a part in the successful operation of a plant. These include prevailing wind movement, terrain and adjacency to woods, mountains, farmland, streams, residential areas, and other industry. In considering plant location, w e move then from the problems within the plant to those outside the plant. T h e matter of prevailing wind move-
VVTILLXAM ROBINSON BRADLEY, w h o
is
chief
in-
* ^ dustrial hygienist at the American Cyanamid Co- in I^ew York City, received his education in Iowa, first at Cornell College, then at Buena Vista College, and then at the State University. H e also did more graduate work at Wayne University in Detroit. Before assuming his present position he WSLS industrial hygienist at the Fidelity and Casualty C o . in New York and had served in the Detroit Department of Health as an industrial hygienist.
Chemical Plant Location Included in tbe many factors that determine the ultimate location of a chemical
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day, it would form at another spot, depending upon wind direction. It was not until a number of chemical reactions had b e e n checked and process vent stacks examined that the t w o offending stacks w e r e located. Hydrochloric acid was escaping one, and ammonia t h e other. Although 100 feet apart, occasionally the t w o gases would escape at t h e same time w h e n wind direction -was just right to carry the discharged g a s from o n e stack directly across that from t h e other stack. A similar situation may occur when waste acid is discharged to a stream containing traces of ammonia. Chemical Process D e s i g n
Exhaust ventilation and process hood enclosures installed as a part of the process appearing on the original engineering blueprint ment is of prime consideration in air pollution. Prevailing wind, with respect to t h e plant, should not b e in the direction of nearby residential areas or other industry if possible. Neither should the plant be located in the direction of uncontrolled or excessive "airfluent" from other industries, if, b y inquiry or through chemical tests, i t is revealed that the wind carries airborne material of a n undesirable nature. A proposed plant location should be carefully surveyed and evaluated for existing air pollution, preferably with the aid of studies involving physical and chemical tests. The industrial hygienist knows that any future investigation a n d control will eventually fall upon his shoulders. At Donora, Pa., it was observed that a mountainous area can be conducive toward formation of a weather condition known as inversion. W h e n this condition prevails, any discharged gases and fine dusts may stay near the plant site without normal dilution or dispersion. Moreover, any plant located in a valley is limited as to stack height and may discharge gases on a level with residential areas located on the hillside. Discharged air contaminants have been known to follow the course of valleys downwind for several miles, damaging plant life. T h e matter of terrain may be important if sloping terrain drains toward residential areas. While this consideration delves into t h e sphere o f stream pollution experts, the industrial hygienist is well aware of these problems and watohes lest his activity contribute to stream pollution. For example, at one location, two settling basins were established t o hold liquid wastes. One contained a c i d wastes and the other a sulfur compound. If these wastes were combined, H 2 S gas would be formed in heavy concentration at about the center of t h e plant site. These two settling basins were therefore discharged by separate flumes and at different times to t h e same stream a short distance away.
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However, when this stream became stagnant, the two effluent substances united and a blanket of H2S rose up and drifted through a residential area. This usually occurred at night, and the annoying odor of gas awakened the inhabitants. Control of such situations can b e planned in advance. The potentially injurious effects of airborne chemical substances to those handicapped by respiratory illnesses make such planning mandatory. What may be only a nuisance t o healthy people may be serious to patients in a hospital. It is, of course, assumed that adequate water supplies are available. If, however, the supply is from a stream or river, t h e advice of stream pollution experts may affect water treatment costs. If the waste discharge of the plant is into the same stream, then limnological surveys should be conducted, both before and after plant location, as a basis for avoiding litigation. "Airfluent" from a plant situated near woodland might be damaging to trees. It is also conceivable that over a long period of time there might be sufficient deposition of solid flammable material t o constitute a fire hazard. Plant location with respect to farmland and residential areas is important because of potential odor nuisance or chemical damage t o buildings, crops and foliage, or livestock eating contaminated foliage. When location of a plant site is being chosen, neighboring plant processes should be considered, for possible mixing of two or more airborne materials might produce undesirable odors or visible fume. A review of some simple chemical reactions should serve to indicate what possible combinations would produce such fume. Hydrochloric acid and ammonia constitute an example. At a certain plant it is reported that these two gases would come together, forming an ammonium chloride fog that would form a dense blanket and carry down wind about the plant site and over into adjoining property. On another
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While industrial hygienists find many points of interest in the problems o f chemical plant location, they can, ^perhaps, make their greatest contribution by applying themselves to preventive measures that will maintain industrial workers* health. In this activity they seek t o prevent the exposure of people to the raw materials, intermediates, final products, or by-products of the chemical industry that ma> h e toxic. Preventive measures can appl> effectively in chemical and related industries, because it is here that a. great variety of chemical substances are handled b> workmen. A number of the newer suhstances coming from the research laboratories of the chemical industry, particularly t h e organic chemicals, are found t o exhibit some degree of toxicity to human beings. The industrial hygienist seeks to examine these chemicals through toxicological investigation to learn more precisely t h e potentiality of each chemical for causing illness. This field of industrial toxicology differs from the pharmacology of clinical toxicology and chemotherapy a n d from criminal toxicology, in that animal exposure studies are undertaken to simulate closely the opportunity for worker exposure in industry. The information derived from industrial toxicological studies gives the industrial hygienist data on several types of exposure so that h e m a y organize, evaluate, and interpret this information for industrial management, chemical engineering groups, and plant operating personnel in terms of a safe working environment. For the chemical engineer, this interpretation must be in practical a n d understandable terms. It must answer questions such as: "May contact w i t h the skin be permitted, and, if not, what protection must be taken to avoid it? Is t h e inhalation of dust or vapors of this substance harmful, and what effect will it have on workmen? Can certain amounts of these chemicals be permitted in the form o f dusts, mists, or vapors in the atmosphere of chemical plants and can they b e tolerated by workmen?" The answers t o these and similar questions must tell t h e chemical engineer exactly how to use a n d handle toxic substances safely. W h e n the industrial hygienist and the chemical engineer sit down together and review plans for a n e w chemical process, there is a real opportunity for the pre-
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vt'iitiun ot occupational illnrss. i lie c IKMIIIi a l enginrtT may say, **1 a m called upon to design arid install e q u i p m e n t needed in various chemical reactions h a n d l i n g several materials a n d resulting in a final product. This process e q u i p m e n t must b e housed in a suitably designed plant. W h a t , then, is t h e interest of t h e industrial hyinVnist in t h e design ol production e q u i p ineiit?"
Ilygienist Explains H a z a r d s The industrial hvgienist must discuss tlx- nature of the raw materials a n d how raw material A must he h a n d l e d with eare to avoid the inhaling ol dusts, a n d how chemical B must likewise he h a n d l e d cautiously, perhaps in a closed system so that vapors or gases given off will not form a contaminant in the workroom a t mosphere. I h e s e factors m u s t be carefully pointed out and the reasons given as to the n a t u r e and extent of hazard, so that a practical and economical solution can h e attained. B e t w e e n t h e m , th-e planners may decide to install a ventilated hood enclosure at t h e m a n h o l e of a r e action kettle. T h e engineer can see t h a t his design would otherwise b e inoperable because it might be directly responsible for t h e illness of w o r k m e n , unless t h e exhaust ventilation is installed before t h e process is begun. In t h e h a n d l i n g ot c o m p o u n d B, it may b e d e c i d e d t o p u m p the material to a storage tank, then to a w e i g h scale, a n d then t o t h e reaction vessel rather than to require m e n to pour t h e material into pails, carry it up ladders a n d d u m p it b y hand, w h e r e t h e y m a y be exposed to irritant vapors or to skin c o n t a c t from a splash or spill. Next, it may b e necessary to r u n t h e reaction p r o d u c t through a filter press. From t h e nature of t h e reaction, t h e industrial hygienist can inform the design engineer that m e n w h o o p e n t h e press to remove the filter cake will be exposed to solids or gases t h a t may be harmful. Between t h e m , they notice t h a t no ventilation enclosure has b e e n provided for this filter press a n d so this provision m a y now l>e a d d e d to t h e blueprints. Let us follow the process a step farther. W e may find open centrifuges, o p e n whiz/ers, or open settling tubs. Information can b e provided as to w h a t the w o r k i n g environment will be like n e a r this type of e q u i p m e n t , so that control measure's, if needed, again can b e a p p l i e d to t h e blueprint before process installation. Reading
Blueprints
T h e industrial hygienist sees a line on a blueprint pointing u p w a r d and ending in an arrow. This line is labelled "vent." Looking further, h e comes across a line pointing d o w n w a r d e n d i n g in a n arrow w h i c h is labeled "to t h e sewer." T h e question immediately arises as t o w h a t reaction p r o d u c t s a r e d i s c h a r g e d into t h e a t m o s p h e r e or w h a t w a s t e p r o d u c t s a r e d i s c h a r g e d to t h e sewer. T h e r e is, at this p o i n t , a c h a n c e to project t h e chemical process design into 1200
terms ot potential air and stream rpoilution. If it is d e t e r m i n e d t h a t the gases, mists, or vapors discharged into th-e air from t h e reaction will result in a 31 air pollution problem, then the design of some m e a n s of control, such as condensimg or s c r u b b i n g , will need to be added t o tinb l u e p r i n t . T h e treatment of waste products by neutralization or reaction to form an inert substance may b e necessaTy in some cases and a sketch of this treatinent, too, m a y be a d d e d to t h e blueprint as a p h a s e of preliminary prevention. It must be borne in mind that tl ic industrial hygienist is only o n e niemhser of a p l a n n i n g team a n d does not heg^in to know all the answers. Other nirinrxrrs oi the team include those from research groups, p r o d u c t development, safety „ production, and sales groups. M a c h i n e s Must Fit t h e M a n Considerable thought js being giv«?n today to the design of industrial mac-bines. This trend involves a s t u d y of (tollman a n a t o m y and t h e related subjects of fsatigue and health, so that machines may l^e designed to fit t h e m a n w h o is to operate* them. T h e same is true in the chfinical and related industries. Process equipment can be designed to fit the o p e r a t i n g staff who, after all, have quite a responsibility in the success of any production. Sufficient space b e t w e e n the equipment, units has b e e n mentioned. Available hea^lroom a n d t h e introduction of stairways rather than vertical ladders has b e e n a contribution of safety groups. T h e locat don o f sampling points is important, for it i s difficult to take a sample of a liq_uid if the valve is located two feet abov/e t h e man's head. I n the case of certain liquids, it w o u l d be unfortunate if any were spilled on t h e skin or splashed insto t h e eye. T h e n too, it should never be necessary to lie d o w n o n the floor underneathi a r e action vessel in order to o b t a i n a s a m p l e . Attention to such a detail as t h e tecbinique of t a k i n g a sample w h e n hazardous (chemicals a r e involved becomes a n item o f considerable importance to t h e man w h o i s e n g a g e d in sampling. H e r e agaim, p r e ventive engineering through foTetHnought may prevent a bad burn, a skin rash, o r the loss of an eye. Provision for v-acuum sampling, through a closed system, freq u e n t l y can b e a matter of original d e sign. Neither is it necessary to open a large kettle manhole and d i p out a s a m p l e using a flask on t h e end of a l o n g stick. This m e t h o d of sampling would snot b e wise if toxic vapors escaped the kettle m a n h o l e d u r i n g sampling. T h e design and location of pi pin*g m a y result in discomfort unless the d e m a n d s on t h e operator in the p l a n t are l
