Steel diaphragms

Sodium fluoride is normally manufactured by the reaction of hydrofluoric acid and soda ash (sodium carbonate), or caustic soda (sodium hydroxide). Control of pH is essential and proper agitation necessary to obtain the desired crystal size. The crystals are centrifuged, dried, sized, and packaged. Reactors are usually constmcted of carbon brick and lead-lined steel, with process lines of stainless, plastic or plastic-lined steel diaphragm, plug cock, or butterfly valves are preferred. 

Other Metals. AH the sodium metal produced comes from electrolysis of sodium chloride melts in Downs ceUs. The ceU consists of a cylindrical steel cathode separated from the graphite anode by a perforated steel diaphragm. Lithium is also produced by electrolysis of the chloride in a process similar to that used for sodium. The other alkaH and alkaHne-earth metals can be electrowon from molten chlorides, but thermochemical reduction is preferred commercially. The rare earths can also be electrowon but only the mixture known as mischmetal is prepared in tonnage quantity by electrochemical means. In addition, beryIHum and boron are produced by electrolysis on a commercial scale in the order of a few hundred t/yr. Processes have been developed for electrowinning titanium, tantalum, and niobium from molten salts. These metals, however, are obtained as a powdery deposit which is not easily separated from the electrolyte so that further purification is required. 

Frequently ball and tube mills are combined into a single machine consisting of two or three compartments, separated by perforated-steel diaphragms and charged with grinding media of different size. Rod mills are hardly ever used in cement plants. The compartments of a tube mill may be combined in various circiiit arrangements with classifiers, as shown in Fig. 20-59. 

Mud Pressure. Internal and external mud pressures are usually measured with strain gages mounted on a steel diaphragm. Figure 4-262 shows a sketch of principle. 

One steel diaphragm is exposed to the internal pressure, the other is exposed to the external pressure. Four gages are normally used. Two of them are sensitive to pressure and temperature, and two are sensitive to the temperature. A Wheatstone bridge is used for detection of the pressure. 

AISI 1967, Design of Light Gage Steel Diaphragms, American Iron and Steel Institute, New York, NY, 1967... 

This causes rupture of the steel diaphragm, thus permitting the gas to escape with great force and rupture the seams surrounding the borehole... 

High-pressure sensors differ mainly in the measuring principle used and the type of internal connection. Most sensor designs use a steel diaphragm to separate the pressure fluid from the sensor signal and environment. 

Fig. 7.4.3 Measuring principle of steel diaphragm (in this case with thin-film strain gages)...

Fig. 7.4.4 Strain profile of steel diaphragm as a result of finite-element simulation...

Placing strain gages on steel diaphragms can be done in several ways. In automotive applications up to 2000 bar three different technologies are widely used thin-film technology, microfused silicon strain gages, and a fused single chip (Fig. 7.4.5). 

Thin-Film Strain Cages on Steel Diaphragm... 

Conventional potassium hydroxide electrolytic cells are made from carbon steel. Areas with high corrosion potential are frequently clad with nickel, plastic, or ceramic material. The cathode is constructed of steel coated with a catalyst. The anodes and cathodes of bipolar cells are usually made from nickel or nickel-coated steel. Diaphragms were originally made from asbestos reinforced with nickel nets. Because of the health hazards associated with the use of asbestos, ceramics and polymers are being considered as substitute materials. 

As noted above, compressor bodies usually are carbon steel. Diaphragms are stainless steel or Monel, and cylinder valves are Monel. Preventive maintenance should include periodic replacement of diaphragms and sealing the apparatus with clean, dry air or nitrogen during its fiequent idle periods. 

Critical Dimensions of Unreflected BeO Systems Fueled by Thin Enriched Uranium Foils, F. A. Kloverslrom, R. M. Deck and A. J. Reyenga (UCRL-L). A series of criti cal. measurements on unreflccied parallelepipeds built of enriched (93.299 uranium foils and BcO blocks have been made for five fuel densities. The object of this program was to provide data for normalization of machine criticality calculations, and.the systems were therefore made clean. The only material present other than BeO and U was a small amount of Teflon (foil coatings) and a steel diaphragm, the effect of which was experimentally determined. 

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