Safety considerations

Safety and its practice are of the utmost importance for corrosion personnel, both in the corrosion laboratory and plant operations. The subject appears mundane at first glance although in realistic terms it is of paramount importance when factors such as loss of life due to accidents by nonadherence of personnel to prescribed safety procedures in laboratories and industrial operations are considered. The safety procedures used in the laboratory and field operation are intended to be preventive measures to avoid the occurrence of accidents, which may result in injury or loss of life, depending upon the nature of the accident. 

The importance of safety and its practice is related to the risk and hazards involved in a particular operation. Corrosion personnel, in common with other engineers, are faced with hazards and the extent of hazards, and the severity is the decisive factor in determining the fatality rates. Thus in any industrial operation it is necessary to (i) identify the hazard and (ii) take necessary action to prevent the occurrence of the hazard. The identification and remedial steps taken to prevent the occurrence of the hazard is of paramount importance in loss prevention. Along with increased advances in technology, the identification of hazards has also become increasingly difficult. Loss prevention depends upon the management system. The physical hazards also may not be on the surface and thus inaccessible to a simple visual inspection. 

There exists a whole battery of methods for the identification of hazards in the literature.4 The hazard identification techniques suitable for various stages of a project are shown in Table 3.1. Among the techniques noted in Table 3.1 the most important method is safety audits, which cover the management system and specific technical features at site level and the management system at plant level. 

Earlier method of identifying hazards involved a procedure consisting of asking questions such as what if This approach consists of questioning the proper function at every stage of the process, along with consequences or the remedial features. A checklist for the simplified process hazard analysis by the what if method is shown in Table 3.3. Although this method is an old method of hazard analysis compared with other methods such as hazop or fault tree analysis it has proven to be quite useful. 

All stages Management and safety system audits Checklists Feedback from workforce 

Safety considerations influencing room layout include Health and Safety Executive regulations, fire prevention, fire control, and evacuation. 

Chemical Safety and Hazard Investigation Board (CSB), established by the Clean Air Act Amendments of 1990, is an independent federal agency with the mission of ensuring the safety of workers and the public by preventing or minimizing the effects of chemical incidents. They attempt to determine the root and contributing causes of chemical accidents. Their web site at http //www.csb.gov is a very useful source of brief and detailed accident reports. 

Most of the safety considerations listed above for belt drives are applicable to chain drives. 

Gear drives are favored for smooth, accurate transmission of power. This is important in larger units, but less so in drives typically fotind in small plant operations. Gears should be manufactured to AGMA Standard 390.03. 

A filter operates by one of two mechanisms. In cake filtration, the solids (perhaps including a filter aid) form a cake on the surface of the filter medium. Other important filtration steps include washing, to remove occluded liquor, and dewatering, to produce a cake of higher solids content. The other mecha-rusm is depth filtration, in which the solids are captured within the filter medium itself. This might take the form of a bed of granular solids or a porous solid structure. Depth filtration is most often applied to dilute slurries. 

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Hand-dug caisson construction involves workers working in deep shafts subjected to risks. Common causes of accidents involve falling objects, ingress of water and persons falling down the shaft. Health risks would include dust inhalation and noise damage hearing. Some of the safety precautions recommended would include  

Construct barricade at top of caisson ring to prevent objects from falling into hole. 

Ensure workers are working in pairs and that they are equipped with hehnet, whistle, walkie talkie, workshoe, ear plugs and breathing mask. 

Provide adequate lighting and Iresh air supply at all times. 

Double chain hoist should be provided and regularly maintained. 

Vacuum apparatus probably presents fewer accident hazards than almost any other kind of laboratory apparatus of comparable complexity. However, these hazards are by no means entirely negligible, and we snmmarize the principal ones. 

Explosion. If signiflcant quantities of a gas have been liquefied or taken up by an adsorbent at low temperature, an explosion can result when the system warms up if adequate vents or safety valves have not been provided. An explosion of a different kind can take place if an oil diffusion pump (particularly a glass one) is vented to air while hot. 

Liquid air. Do not refrigerate a trap with liquid nitrogen until the system pressure is reduced below a few Torr. (Liquid air boils at higher temperature than liquid nitrogen and can easily be condensed at 77 K.) Liquid air present in a trap may react explosively with any organic substances that condense there. The liquid air can also produce excess pressure and likely damage to the vacuum system should the trap warm without venting this is a common mishap with vacuum systems. 

Mercury poisoning. Mercury manometers pose hazards of mercury contamination in the event of fracture of a glass apparatus. See Appendix C. 

Dushman, Scientific Foundations of Vacuum Technique, 2d ed. (J. M. Lafferty, ed.), Wiiey-Interscience, New York (i962) A. Roth, Vacuum Technology, 3ded., North-Hoiiand, Amsterdam/ New York (i990). 

Since the ion exchange resins are synthetic organic compounds, they are susceptible to decomposition reactions with strong oxidizing agents, such as nitric acid. Close control of reactant or regenerant concentrations, temperature, and contact time may be required. 

When the treated solution is to be used as food, food additives, or in pharmaceutical applications, resins must be used which are acceptable for such processing. 

The safe way to use a HV power supply is to provide an auxiliary ground return path via a separate conductor from the PMT ground to the power supply ground see Fig. 7.57. Nevertheless, broken cables must be repaired or replaeed. 

For this reason, do not connect or disconnect a photomultiplier to or from the load when the high voltage is switched on. Do not use switchable attenuators behind the PMT output. Do not use cables and connectors with bad contacts. The same rules should also be followed for photodiodes that are operated at supply voltages above 20 V. 

The problem can easily be avoided by connecting a resistor of about 100 kO from the PMT anode to ground. However, in practice the PMT module often cannot be opened. The only way to avoid damage is to be careful. 

Cryogenic fluids can be used safely in the laboratory or industrial plant if all facilities are properly designed and maintained, and if the personnel are adequately trained and supervised. However, consideration must be given to both normal and emergency operations. This holds true for new facilities as well as for those that have been modified to handle cryogenic fluids. 

Unfortunately, a suitably designed facility may in time become unsafe if it is not maintained properly. Similarly, a hazardous situation may be created if operating personnel are not trained properly. Interesting training programs are essential to all new and continuing operations. These should be coordinated with the overall laboratory 

Howard H. Fawcett and William S. Wood (editors). Safety and Accident Prevention in Chemical Operations, John Wiley and Sons, New York, 1965, 617 pp. 

Pearce Williams, Michael Faraday, Basic Books, Inc., New York, 1964, pp. 28-30, 130-131. 

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The choice of reactor temperature depends on many factors. Generally, the higher the rate of reaction, the smaller the reactor volume. Practical upper limits are set by safety considerations, materials-of-construction limitations, or maximum operating temperature for the catalyst. Whether the reaction system involves single or multiple reactions, and whether the reactions are reversible, also affects the choice of reactor temperature, as we shall now discuss. 

Reactors in the overall process. It should be emphasized that many considerations other than those represented in Figs. 2.9, 2.10, and 2.11 also influence the decision on the choice of reactor. Safety considerations, operating pressure, materials of construction, etc. have a considerable effect on the outcome. 

Safety considerations might dictate that a particularly hazardous component be removed from the process as early as possible to minimize the inventory of that material. 

Their satisfactory combustion requires no particular characteristics and the specifications are solely concerned with safety considerations (vapor pressure) and the C3 and C4 hydrocarbon distribution. 

Sampling ndAnalysis Guidelines. As a general safety consideration, ah gases should be vented to an external area and whenever possible, inert gases should be used as the test gas for piping systems. 

Checklists. A checklist is simply a detailed Hst of safety considerations. The purpose of this Hst is to provide a reminder to safety issues such as chemical reactivity, fire and explosion hazards, toxicity, and so forth. This type of checklist is used to determine hazards, and differs from a procedure checklist which is used to ensure that the correct procedure is followed. 

Table 11. Properties of Hydrogen of Interest in Safety Considerations...

Safety considerations for magnetic resonance (mr) experiments have received Htde attention except for the problems associated with the use of electronic devices such as pacemakers in the magnetic field. However, in a 1990 study of reproductive health involving more than 1900 women working in clinical mr facihties in the United States no substantial differences were reported between the group of women directly involved with mr equipment (280 individuals) and other working women (894 individuals) (10). Conclusions are restricted to exposure to the static external field. 

The largest pipeline transport of gas, by far, is the movement of methane (natural gas). Natural gas can be Hquefted, but it is not pipelined in Hquid form because of cost and safety considerations. For overseas transport, it is shipped as Hquefted natural gas (LNG) in insulated tankers, unloaded at special unloading faciHties, vaporized, and then transported over land in pipelines as a gas. 

The plutonium extracted by the Purex process usually has been in the form of a concentrated nitrate solution or symp, which must be converted to anhydrous PuF [13842-83-6] or PuF, which are charge materials for metal production. The nitrate solution is sufficientiy pure for the processing to be conducted in gloveboxes without P- or y-shielding (130). The Pu is first precipitated as plutonium(IV) peroxide [12412-68-9], plutonium(Ill) oxalate [56609-10-0], plutonium(IV) oxalate [13278-81-4], or plutonium(Ill) fluoride. These precipitates are converted to anhydrous PuF or PuF. The precipitation process used depends on numerous factors, eg, derived purity of product, safety considerations, ease of recovering wastes, and required process equipment. The peroxide precipitation yields the purest product and generally is the preferred route (131). The peroxide precipitate is converted to PuF by HF—O2 gas or to PuF by HF—H2 gas (31,132). 

Information on health and safety considerations cited herein for Ryton PPS powders and pellets can be found in Reference 157. Ryton PPS [26125-40-6] is listed in the Toxic Substance Control Act (TSCA) Inventory of Chemicals. 

When considering sealants or other formulated products, the health and safety considerations relating to the other ingredients should be taken into account. 

Safety Considerations. Ammonium nitrate can be considered a safe material if treated and handled properly. Potential hazards include those associated with fire, decomposition accompanied by generation of toxic fumes, and explosion. 

Eor virtually all radiopharmaceuticals, the primary safety consideration is that of radiation dosimetry. Chemical toxicity, although it must be considered, generally is a function of the nonradio active components of the injectate. These are often unreacted precursors of the intended radioactive product, present in excess to faciUtate the final labeling reaction, or intended product labeled with the daughter of the original radioactive label. 

Because of the complexity of designs and performance characteristics, it is difficult to select the optimum atomizer for a given appHcation. The best approach is to consult and work with atomizer manufacturers. Their technical staffs are familiar with diverse appHcations and can provide valuable assistance. However, they will usually require the foUowing information properties of the Hquid to be atomized, eg, density, viscosity, and surface tension operating conditions, such as flow rate, pressure, and temperature range required mean droplet size and size distribution desired spray pattern spray angle requirement ambient environment flow field velocity requirements dimensional restrictions flow rate tolerance material to be used for atomizer constmction cost and safety considerations. 

An extremely important safety consideration for both heated and cryogenic tanks is that lower boiling Hquids must not be introduced into the tank. These Hquids can boil and cause a frothover or a violent evolution of vapor, followed by tank failure. 

Air Transport. Relatively small quantities of chemicals are transported by air, although availability of such service for the movement of samples, emergency shipments, and radioactive chemicals with a short half-life is important. Both economic and safety considerations impede the development of air carriage as a significant means of transporting a substantial volume of chemicals. 

Properties. Uranium metal is a dense, bright silvery, ductile, and malleable metal. Uranium is highly electropositive, resembling magnesium, and tarnishes rapidly on exposure to air. Even a poHshed surface becomes coated with a dark-colored oxide layer in a short time upon exposure to air. At elevated temperatures, uranium metal reacts with most common metals and refractories. Finely divided uranium reacts, even at room temperature, with all components of the atmosphere except the noble gases. The silvery luster of freshly cleaned uranium metal is rapidly converted first to a golden yellow, and then to a black oxide—nitride film within three to four days. Powdered uranium is usually pyrophoric, an important safety consideration in the machining of uranium parts. The corrosion characteristics of uranium have been discussed in detail (28). 

Most metal carbonyls are volatile soflds that sublime easily. The volatility of metal carbonyls coupled with their toxicity is an important safety consideration. The vapor pressure of many metal carbonyls have been tabulated elsewhere (75). 

Process Safety Considerations. Unit optimization studies combined with dynamic simulations of the process may identify operating conditions that are unsafe regarding fire safety, equipment damage potential, and operating sensitivity. Several instances of fires and deflagrations in ethylene oxide production units have been reported in the past (160). These incidents have occurred in both the reaction cycle and ethylene oxide refining areas. Therefore, ethylene oxide units should always be designed to prevent the formation of explosive gas mixtures. 

Ground area and. space requirement.s. Comparisons of the overall space requirements for plants using air cooling versus water cooling are not consistent. Some air-cooled units are installed above other equipment—pipe racks, shell-and-tube exchangers, etc. Some plants avoid such inst ations because of safety considerations, as discussed later. 

For additional details on the design of blowdown drums, cyclone separators, and quench tanks, such as mechanical design, thrust forces, ancillary equipment, and safety considerations, refer to the books and articles listed in the General References. 

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