Corrosive vapors

Vapors emitted from the materials of closed storage and exhibit cases have been a frequent source of pollution problems. Oak wood, which in the past was often used for the constmction of such cases, emits a significant amount of organic acid vapors, including formic and acetic acids, which have caused corrosion of metal objects, as well as shell and mineral specimens in natural history collections. Plywood and particle board, especially those with a urea—formaldehyde adhesive, similarly often emit appreciable amounts of corrosive vapors. Sealing of these materials has proven to be not sufficiently rehable to prevent the problem, and generally thek use for these purposes is not considered acceptable practice. 

Atmospheric corrosion. Air-cooled heat exchangers should not be located where corrosive vapors and fumes from vent stacks will pass through them. 

Insoluble corrosion prodiic ts may be completely impeivious to the corroding liquid and, therefore, completely protective or they may be quite permeable and allow local or general corrosion to proceed unhindered. Films that are nonuniform or discontinuous may tend to localize corrosion in particular areas or to induce accelerated corrosion at certain points by initiating electrolytic effects of the concentration-cell type. Films may tend to retain or absorb moisture and thus, by delaying the time of drying, increase the extent of corrosion resulting from exposure to the atmosphere or to corrosive vapors. 

Totally enclosed motors offer the greatest protection against moisture, corrosive vapors, dust, and dirt. Totally enclosed fan-cooled (TEFC) motors are the obvious choice rather than weather-protected below 186.5 kW (250 hp). Their internal and external ventilating air are kept separate external air never gets inside except for the small amount that enters by breathing. 

Emission of toxic, flammable or corrosive vapors when equipment is opened for clean-ing/maintenance or during charging of hazardous material. Possibility for operator exposure. 

Standard materials are chosen to resist ordinary corrosion of steam and water. If corrosive vapors or liquids are involved, state under special material customer has found best for his operation. Is export packing required ... 

Totally enclosed motors offer the highest degree of protection against moisture, corrosive vapors, dust, and dirt. TEWAC motors also have the advantage of reduced noise level. 

Contains information about the chemical and physical properties Flammability reactivity corrosivity vapor pressures physical states boiling and melting points. 

PR valves handling toxic or corrosive vapors which condense at ambient conditions e.g., phenol. 

The next consideration is the cost of construction materials. This determines the final number of flare headers. Vapors that normally require expensive materials may be listed as follows a. Corrosive vapors, e.g., SOj, HjS. 

Of the three, corrosive vapors are usually piped up in a separate header right up to the flare stack since such lines are normally very small and if combined with other streams may run the risk of corroding the much larger and more expensive pipelines. 

Make up water for these refrigeration units is at 80°F, and feed water for the gas cooler unit is available at 90°F. Barometric water is 90°F. Items 1 and 2 are for a closed-circuit operation with return water at 68°F and total 175 gpm. Note that in order to consolidate the temperature levels of water, it is economical to establish a temperature, such as 55°F, which satisfies the bulk of the requirement, and then design the other phases of the plant process to also use this water temperature. Item 3 is an open-circuit operation because the water is sent to waste after absorbing certain corrosive vapors and cooling the bulk of the gas. 

Aftercondensers operate at atmospheric pressure. They do not affect the steam economy or ejector performance, but they do avoid the nuisance of exhausting steam to the atmosphere, thus, they allow steam to be recovered. They also serve as silencers on the ejectors, and with barometric types they can absorb odors and corrosive vapors. 

Steel cabinets have superior resistance to physical abuse. Refinishing scratched surfaces can often be done with a spray can. Finishes used on steel also have a high resistance to chemicals, even on the interior parts, but long-term storage of reagents that give off corrosive vapors will eventually lead to rusting. 

Decomposition Toxic and corrosive vapors are produced when combined... 

Rotary or other distillation equipment with metal parts should not be used in concentrating the reaction mixture because not only will the corrosive vapors damage Che equipment, but also the resulting metal salts will discolor and partially decompose the product. The solution should not be heated any longer than is necessary to concentrate it excessive heading gives a dark-colored product. 

In most hydrocarbon operations excess gas and vapors have to disposed of safety, quickly without environmental impact. Where the gas or vapor cannot be converted into useful energy they are routed to a remote point for safe incineration, called flaring. Flares are the most economical and customary means of disposing of excess light hydrocarbon gases in the petroleum and chemical industries. The primary function of a flare is to convert flammable, toxic or corrosive vapors to environmentally acceptable gases for release into the atmosphere. Both elevated or ground flares can be used. 

Fire Tabun reacts with steam and water to produce toxic and corrosive vapors. Any personnel not fighting a fire of sarin should immediately be evacuated from the area. Respiratory protection is required (positive pressure, full face piece, NIOSH-approved SCBA will be worn). When response personnel respond to handle rescue or reconnaissance, they will wear Level A protection that should be worn when the highest level of respiratory, skin, eye, and mucous membrane protection is needed. This level consists of a fully-encapsulated, vapor-tight, chemical-resistant suit, chemical-resistant boots with steel toe and shank, chemical-resistant inner/outer gloves (butyl rubber glove M3 and M4 Norton, chemical protective glove set), coveralls, hard hat, and self-contained (positive pressure) breathing apparatus (SCBA). 

UNUSUAL FIRE AND EXPLOSION HAZARDS Hydrogen produced by the corrosive vapors reacting with metals, concrete, etc., may be present. 

The compound is corrosive. Vapors are highly irritating to eyes and mucous... 

This discussion cannot provide exhaustive coverage of the many and varied application fields fbr oil-filled vacuum pumps in the chemicals industry. Our many years of experience w/ith the most difficult of chemicals applications can be used to solve your particular problems. Three aspects should, however, be mentioned briefly pumping explosive gas mixes, condensable vapors, and corrosive vapors and gases. 

Caution. Trifluoromethanesulfonic acid is harmful by inhalation, in contact with skin, and if swallowed. It causes bums. Precautions should be taken to minimize inhalation of the corrosive vapors given off from the acid. Trifluoro-methanesulfonatosilver(I) is an eye, respiratory system, and skin irritant. Methyl-diphenylphosphine is harmful by inhalation, in contact with skin, and if swallowed. Tetrahydrothiophene is an eye, respiratory system, and skin irritant. It is necessary to wear suitable protective clothing, gloves, and eye/face protection. All the reactions must be conducted in a well-ventilated fume hood. 

Application ranges of the various kinds of devices for maintenance of subatmospheric pressures in process equipment are shown in Table 7.3. The use of mechanical pumps—compressors in reverse— for such purposes is mentioned earlier in this chapter. Pressures also can be reduced by the action of flowing fluids. For instance, water jets at 40psig will sustain pressures of 0.5-2.0psia. For intermediate pressure ranges, down to O.lTorr or so, steam jet ejectors are widely favored. They have no moving parts, are quiet, easily installed, simple, and moderately economical to operate, and readily adaptable to handling corrosive vapor mixtures. A specification form is in Appendix B. 

Better yields are obtained at low pressures (preferably below 5 mm.) because of more efficient sublimation of coumalic acid. The submitters report that a water aspirator could be used with crude (unrecrystallized) coumalic acid to avoid damage to the vacuum pump by untrapped corrosive vapors, and that yields of a-pyrone averaged 45% in this modification. The checkers used a mechanical pump with an efficient sodium hydroxide trap in all runs. 

A vacuum pump should be scrupulously protected from corrosive vapors and materials which will be absorbed in the pump oil or condense in the pump. For most laboratory operations a low-temperature trap is employed for this purpose, and in the case of fluorine handling systems a soda-lime trap is used to neutralize the corrosive gases. Despite these precautions, the pump oil does eventually break down and become contaminated. Regular oil changes should be scheduled for a pump at about yearly intervals for a well-protected pump and more often for pumps which are not well protected. 

Since corrosive vapor is evolved, a water pump should be used. 

Bluish-black crystalline scales or plates with a characteristic odor and sharp acrid taste violet corrosive vapor mp, 113.6°C bp, 185.2°C.1... 

Often, the RD is mounted under the PSV so that it is sealed tight and protects the relief valve from being contacted by corrosive, plugging, hazardous, freezing, or regulated processes. This way the best characteristics of both devices are utilized. The RD can also be installed after the PSV. This installation can be used when the valve discharges into a vent header that might contain corrosive vapors. Table 3.153 provides data on RD materials, sizes, and minimum rupture pressures. 

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