which the vessel has been approved and the date when it must be retested. Adequate pressure relief devices must be installed before operations begin. The devices normally used are either the spring loaded type which relieves excess pressure above a predetermined point and automatically closes when the pressure is reduced to that point, or a frangible diaphragm which releases the entire contents of the vessel when it ruptures. The spring loaded devices are more expensive but they provide gradual pressure relief and are not subject to failure due to fatigue which results in accidental loss of the entire contents of the vessel. Instructions to operating personnel vary depending on the nature of the work, however, no one is permitted to enter the booths when the equipment is under pressure, as all the necessary controls are located outside the booths in the operating corridor. The gages have holes drilled in the back to release the pressure in case of failure of the tube
and the gage face glasses are removed and replaced with plastic. The gages are also located well above head height as an additional safety precaution. Rocking bombs are charged on special bomb carriages and then wheeled into the booth. The bomb carriages are the same height as the rocking device so that the bombs may be easily pushed from the carriage into the rocking device. Protective clothing is worn by the operators depending upon the nature of the work performed. Every effort is made to ensure safe operating procedure. Auxiliary protective equipment is mounted where needed, and automatic devices are frequently employed when the hazard is such that they are required. These devices include automatic carbon monoxide alarms which sound an audible warning when the concentration of the gas reaches 0.02 of 1% and automatic combustible gas indicators which also sound an audible signal at a predetermined level, usually 25% of the
A F O R U M ON SAFETY
lower explosive limit. In some cases automatic carbon dioxide flooding systems are used in conjunction with the combustible gas indicators. These devices are usually arranged to turn on ventilation equipment when the concentration reaches 25% of the lower explosive limit ; and if this does not control the hazard when the mixture reaches 75% of the lower explosive limit, the ventilation equipment is shut off by the detection unit and carbon dioxide is released to inert the area. Hand fire extinguishers, either the carbon dioxide or dry chemical type, are placed in an abundant number in the operating corridor t o extinguish ordinary operating fires. These are a few of the methods of control which ha^e made it possible for Socony-Vacuum laboratories to maintain an excellent record of safe operations. We are particularly proud of our present record, which is now over two million manhours without a reportable injury.
+
A Digest of Laboratory Safety Practices JAMES
S.
SWEELY,
Sun Oil Co. Research Laboratory, Norwood, Pa.
T h e following is a survey of the safety practices of nine large laboratories engaged i n petroleum refining, chemical manufacture, rayon production, and government research X HE rather meager, published information on safety practices in chemical laboratories has prompted a survey of what these practices actually are in the laboratories of some of the larger companies in the Philadelphia area. This has been accomplished by studying the various safety manuals which these laboratories require their staffs to read. Laboratories of companies engaged in fairly diversified lines of work were chosen, since it was felt that their safety practices and regulations would be of most interest to those concerned with laboratory safety. The nine laboratories which have furnished their manuals for this study represent organizations engaged in petroleum refining, chemical manufacturing both organic and inorganic, rayon production, and government research. This paper covers the common hazards generally recognized by the various laboratories and the precautions taken to eliminate or minimize them. Specific items of equipment which have protective value and any special or unique practices which might be of genVOLUME
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NO.
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eral interest are also included. Many items which fall in the latter category represent practices in use in our laboratory, with which I am naturally most familiar, and in some cases recommendations or suggestions have been made where it was felt they could properly be included in a paper of this nature. It is encouraging to report that there is complete agreement among the laboratories that the safety aspect should be considered before starting any new experimental work. All companies emphasize the necessity of "asking someone who knows" or of taking suitable precautions whenever any doubt exists regarding an experiment. Some companies have even set up special groups on apparatus and mechanical equipment and these groups must pass on the safety aspect of any new projects. It should, of course, be realized that certain operations become standardized after being in use for a time and special operating manuals are frequently made available for these processes. I n fact one company feels that manuals on individual operations provide the best means
DECEMBER
2 6,
1949
oi ensuring safe practices, since laboratory programs are subject to change. This continual change tends to make obsolete any recommendations except those of a very general nature. This paper will not discuss any of these specific procedures, bxit will concern itself with the more general aspects of laboratory safety. Personal Protection It is obvious that goggles or eye shields should always be worn for such operations as handling corrosive chemicals, explosives, vacuum distillations, high pressure experiments, and shop work such as grinding. All laboratories recognize the need of wearing goggles whenever any doubt exists regarding the nature and possible violence of a reaction, and at least one company requires that some sort of eye protection be worn at all times in the laboratory area. This may be either regular glasses or goggles. Where hardened glasses are required, many companies furnish these to workers with lenses ground t o their own individual prescriptions, if needed, at cost or at a reasonably low price. Rubber gloves and protective clothing are furnished by all laboratories for work with corrosive chemicals. Gas masks and respirators are provided for hazardous atmospheres containing high 3861
concentrations of solvent vapors, dusts, and corrosive fumes. Some laboratories have available a complete coverage rubber suit and hood with forced air for breathing and maintaining a slight pressure in the suit. A squad from the laboratory, which is familiar with the use of this suit, assists the wearer in getting into or out of it, handling the air hose connections, and so forth. Clothing such as this can be extremely useful in the case of leakage from gas cylinders such as hydrofluoric acid, hydrogen sulfide, or chlorine. General Laboratory Precautions in Equipment Handling Glassware. The usual precautions to be taken with glass tubing and laboratory apparatus are pointed out in all manuals—some in more detail than others. Some good practices which can be recommended follow. All newly constructed equipment should be annealed and checked with polarized light before using. By this means dangerous strains can be detected and corrected before use. Tubing ends should be firepolished or ground smooth and towels or gloves used to protect the hands when inserting into corks or stoppers. Lubricants such as soapy water, alcohol, or glycerol may be useful here. Do not use cracked or chipped glassware. Flasks used in vacuum distillations should always be examined for small cracks before being used. Glass scheduled for repair or storage must always be cleaned carefully. Broken glassware which is to be discarded should be placed in receptacles for this purpose and not thrown in with other trash. Glass tubes should extend well through rubber stoppers so that no closure of the tube can occur if the rubber swells. Stopcocks and stoppers should not be left in contact with caustic solutions for long periods of time since they may freeze. Heavy pieces of glass apparatus should be supported with clamps suitably protected with rubber or asbestos pads and also with a bottom support such as a tripod or ring. Distillation and Vacuum Equipment. Since glass is used for most distillation and vacuum work, special precautions are necessary for these operations. Catch pans large enough to hold more than the liquid volume being worked with are generally recommended for all distillations as a protection in case of breakage. A suitable style is a rectangular pan of 18-gage galvanized iron large enough in area to hold both the distillation flask and accessory equipment such as condensers and receivers. For vacuum distillations a safety glass shield or protective screen should also be used. Hot vacuum distillation flasks should be cooled t.~> a reasonable temperature before admitting air which might cause a flash at higher temperatures. When rubber stoppers are used under vacuums, precautions should be 3862
taken to use large enough stoppers to prevent a suck-in. In regard to rubber stoppers it might be well to point out that one group prohibits their use entirely in distillations because of attack by organic solvents. The use of glass joints, which are now available in many forms, eliminates the need for using stoppers in most work. Some laboratories express the need for caution in the use of alloy metal clamps because these clamps may fail under a combination of high stresses and elevated temperatures sometimes reached in distillations. Vacuum desiccators as well as other vacuum equipment should be taped or suitably protected with wooden or metal shields such as those now available through laboratory supply houses. By this means the amount of flying glass is reduced to a minimum in the event of breakage. Pressure Equipment. The safe operation of pressure equipment is considered by most of the laboratories, but in only one case is the subject covered in much detail. Special operating manuals for pressure work should be available in all laboratories doing work of this type. Since many laboratory workers are unfamiliar with permissible temperature and pressure ranges for such items as copper and saran tubing and fittings, iron pipe and fittings, metal cylinders, bombs, and so forth, some general statement on these properties might well be mentioned in safety regulations. The need for safety instructions covering the proper handling of compressed gas cylinders and pressure reducing valves is generally recognized. Some of the special precautions which should be taken include the use of trucks to transport cylinders from one location to another; the use of a protective valve cap at all times during transportation of a cylinder; vertical storage away from highly flammable substances; firmly supporting cylinders in use so they cannot be toppled over; avoidance of temperatures over 125° F.; and use of a double valve system or pressure release device to prevent pressure build-up, especially when used with glass apparatus. In connection with the use of gas cylinders, it is pertinent to mention the recommendations of one of the large suppliers of compressed gases in regard to the identification of the cylinder contents. This concern is emphatic in stating that color marking of the cylinder should not be relied on for identification purposes for the following reasons: too many color combinations would be necessary to cover all gases; cylinders may receive such hard service that the color is indistinguishable; color blind people cannot distinguish the colors and the colors themselves may appear different under various light sources; and different suppliers may have different colors for the same gas. CHEMICAL
The accepted method of identification is to mark the cylinder legibly in a clearly visible location with either the chemical or trade name of the gas. Naturally this marking should not be easily removable and if it is obscured the cylinder should be returned to the manufacturer. I suspect that most laboratories could make an improvement in the handling of hazardous and flammable gases by having available a greater-variety of cylinder sizes so that a minimum quantity of these gases is brought into the building for any one experiment. Possibly the greatest chance for an accident from gas cylinders is in the improper identification of plant gas samples sent into the laboratory. Whenever dealing with these samples a very strict identification and handling system should be used. In connection with the use of gas cylinders, mention should also be made of the precautions needed with pressure reducing valves. These include the use of warning signs or color coding for regulators used in oxygen service; warnings regarding the use of lubricants with oxygen valves; and use of gages with safety backs to minimize the hazard in case of failure of the Bourdon tube in the gage. Copper tubing and fittings should not be used with acetylene cylinders because of the formation of highly explosive acetylides. Electrical and Gas-Fired Equipment. Possible hazards from electrical equipment such as hot plates, ovens, motors, and tools have been considered by all groups particularly from the shock and source of ignition angle. Some laboratories insist on the use of enclosed wire heaters for distillations or other operations involving flammable materials to prevent a flash in case of breakage. Several laboratories furnish a three-wire electrical system which enables a protective ground to be used, and in one case, at least, all new electrical equipment must be rewired to take advantage of this ground. Many laboratories colorcode their electrical and other services so that the proper lines may be shut off quickly in case of an emergency. When gas burners are used for heating it is good practice to attach a metal extension to the gas inlet on all setups where the burner is closely shielded, since there is a good possibility that a rubber hose may fail from the heat. A metal indicator welded to the remote control handle of gas valves is helpful in showing whether the valve is on or off. Good Housekeeping. While good housekeeping has been generally noted, it has not been stressed from the safety standpoint in all cases, although possibly this is implied. Instructions which have been listed and are desirable are prompt cleanup of all spillages, keeping floors clear of samples, and disposal of broken apparatus and reagents—this last item AND
ENGINEERING
NEWS
will be discussed more fully later on. Step-on disposal cans are usually provided for disposing of waste a n d oily rags or paper and are well suited for this purpose. These should be checked occasionally since there have been cases where people prop open the lids on these cans, which obviously defeats their purpose. Laboratory workers should be very conscious of the danger resulting from spilled mercury. All visible particles should be removed with a sucking device connected through a trap to an aspirator. T h e surrounding area should then b e dusted with sulfur. In areas where a high atmospheric concentration of mercury vapor might exist, some form of mercury detector should be used. Reagents In covering laboratory reagents, heavy chemicals, and flammable materials it can b e pointed out that all laboratories are aware of the hazards involved in their use and discuss these items in more or less detail. One laboratory has taken such elaborate precautions in obtaining and handling flammable and toxic substances, especially those entering from the plant, that i t may be of interest to present some of the methods they use. All samples must enter the building through a sample room and are first subject to the approval of the sample group supervisor. Hazardous samples are marked for special handling, and the recipient of such a sample is warned to review the hazards and handling procedure before bringing th
