Plugging internals

One reason for Roche s success with Dalmane was that it did not share two undesirable features of the barbiturates, the then reigning class of sedatives REM suppression and suicidal potency. The barbiturates are CNS depressants that can induce unconsciousness, but because they have a very low margin of safety they can also shut down the respiratory control system of the brain stem. That is how they kill, and that is why they are still popular in Oregon and other places where individuals are free to elect a definitive end to unbearably unpleasant conscious awareness. Physician-assisted suicide is sometimes accomplished by turning off breathing, by pulling the plug internally as it were. 

Fouled or plugged internals] for SWS cooling water leak/pH of feed water too basic/calcium ion concentration too high causing precipitation when temperatures in stripper exceed 122 °C/temperature < 82 °C at which ammonium poly-sulfides form/overhead lines not insulated. 

In a 250 ml. separatory funnel place 25 g. of anhydrous feri.-butyl alcohol (b.p. 82-83°, m.p. 25°) (1) and 85 ml. of concentrated hydrochloric acid (2) and shake the mixture from time to time during 20 minutes. After each shaking, loosen the stopper to relieve any internal pressure. Allow the mixture to stand for a few minutes until the layers have separated sharply draw off and discard the lower acid layer. Wash the halide with 20 ml. of 5 per cent, sodium bicarbonate solution and then with 20 ml. of water. Dry the preparation with 5 g. of anhydrous calcium chloride or anhydrous calcium, sulphate. Decant the dried liquid through a funnel supporting a fluted Alter paper or a small plug of cotton wool into a 100 ml. distilling flask, add 2-3 chips of porous porcelain, and distil. Collect the fraction boiling at 49-51°. The yield of feri.-butyl chloride is 28 g. 

The multiorifice spinnerets require a high degree of precision in design and manufacture. The main problems encountered are the deHvery of identical quantities of dope to each orifice and the instantaneous self-adjustment of the spinneret s internal pressure if an orifice plugs during spinning. 

Fig. 8. Combined flow reactor models (a) parallel flow reactors with longitudinal diffusion (diffusivities can differ), (b) internal recycle—cross-flow reactor (the recycle can be in either direction), comprising two countercurrent plug-flow reactors with intercormecting distributed flows, (c) plug-flow and weU-mixed reactors in series, and (d) 2ero-interniixing model, in which plug-flow reactors are parallel and a distribution of residence times dupHcates that...

The smaller reactor approaches plug-flow behavior and exhibits a large temperature gradient. In this case, external recycle provides the same degree of back-mixing as is provided by internal circulation in the larger diameter reactor. 

Membrane filtration has been used in the laboratory for over a century. The earliest membranes were homogeneous stmctures of purified coUagen or 2ein. The first synthetic membranes were nitrocellulose (collodion) cast from ether in the 1850s. By the early 1900s, standard graded nitrocellulose membranes were commercially available (1). Their utihty was limited to laboratory research because of low transport rates and susceptibiUty to internal plugging. They did, however, serve a useflil role in the separation and purification of coUoids, proteins, blood sera, enzymes, toxins, bacteria, and vimses (2). 

Polymers used for seat and plug seals and internal static seals include PTFE (polytetrafluoroeth ene) and other fluorocarbons, polyethylene, nylon, polyether-ether-ketone, and acetal. Fluorocarbons are often carbon or glass-filled to improve mechanical properties and heat resistance. Temperature and chemical compatibility with the process fluid are the key selec tion criteria. Polymer-lined bearings and guides are used to decrease fric tion, which lessens dead band and reduces actuator force requirements. See Sec. 28, Materials of Construction, for properties. 

A dense-bed center-fed column (Fig. 22-li) having provision for internal crystal formation and variable reflux was tested by Moyers et al. (op. cit.). In the theoretical development (ibid.) a nonadiabatic, plug-flow axial-dispersion model was employed to describe the performance of the entire column. Terms describing interphase transport of impurity between adhering and free liquid are not considered. 

Tubes were almost plugged with deposits (Fig. 4.30A and B). The deposits contained almost 40% sulfur by weight. Hydrocarbon in-leakage had occurred through small cracks that originated on internal surfaces beneath deposits. 

Figure 13.5 Plug-type dezincification on the internal surface of a brass condenser tube. Note the extreme porosity of the copper plugs. Tube wall thickness was 0.040 in. (0.10 cm). Compare to Fig. 13.13. (Courtesy of National Association of Corrosion Engineers, Corrosion 89 Paper No. 197 by H. M. Herro.)...

The depressions and plugs of corroded metal were caused by dezincification. The hole shown in Fig. 13.10A was caused when one such plug blew out of the wall due to the pressure difference between internal and external surfaces. 

Figure 13.10 A hole emanating from the internal surface of a brass condenser tube. The hole was caused by plug-type dezincification (see Fig. 13.11).

The holes and depressions on external surfaces were caused by deep dezincification on internal surfaces. The porous corrosion product plugs... 

Two sections of utility condenser tubing were received. One of the sections had deep plug-type dezincification on internal surfaces (Fig. 13.5) the other showed only superficial corrosion on internal surfaces (Fig. 13.13). 

Internal plugging of flow passages of eompressor (fouling). 

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