Vacuum controller

If it is extremely uneconomical to design at this point, then proper vacuum control must be installed. However, this is not the usual approach to the design. If the equipment can operate alternately under vacuum or positive pressure, it must be designed for the worst or controlling condition. 

Today, the glassware required consists of either a round-bottom flask or a Schlenk tube serving as the reaction chamber. This chamber is equipped with a magnetic stirbar and a Teflon high-vacuum valve (or glass stopcock) which provides for easy vacuum control after attachment to a vacuum line (Fig. 8.7). 

Failure of vacuum control loop. Control failures can either initiate events (e.g., increase the speed of an exhauster) or disable protections (e.g., reduce the rate of supply of inert gas to a vessel). 

Figure 3.5. Vacuum control with steam jet ejectors and with mechanical vacuum pumps, (a) Air bleed on PC. The steam and water rates are hand set. The air bleed can be made as small as desired. This can be used only if air is not harmful to the process. Air bleed also can be used with mechanical vacuum pumps, (b) Both the steam and water supplies are on automatic control. This achieves the minimum cost of utilities, but the valves and controls are relatively expensive, (c) Throttling of process gas flow. The valve is larger and more expensive even than the vapor valve of case (a). Butterfly valves are suitable. This method also is suitable with mechanical vacuum pumps, (d) No direct pressure control. Settings of manual control valves for the utilities with guidance from pressure indicator PI. Commonly used where the greatest vacuum attainable with the existing equipment is desired.

Semiconlinuous units are usually long, cylindrical tunnels, frays with the frozen material are continuously conveyed through a series of healed zones. Interlocks are used in both ends for proper vacuum control. The frozen material is heated along die length of the tunnel, wilh each zone maintained al a different temperature, and is removed as a fully dried product. 

The hydrolysate obtained by acid posthydrolysis with 2% sulfuric acid (15 min) was centrifuged as described above. To adjust pH of the hydrolysate to 5.5, NaOH, CaO, or Ca(OH)2 was added. When needed, precipitates formed were removed by centrifugation as described above. To obtain a fermentation medium with a higher monosaccharide content, a concentration step (1.8-fold) was carried out in an evaporation system comprising a Syncore orbital shaker equipped with four evaporation flasks, a vacuum pump VAC v-500, and a vacuum controller B-721 (all from Biichi, Flawil, Switzerland). The operational conditions were as follows lower plate temperature, 100°C upper plate temperature, 70°C pressure, 200 mbar stirring, 175 rpm volume per flask, 100 mL. Under these conditions, the concentrated hydrolysates were obtained in about 3 h. 

Optimization and vacuum control strategies (a) minimizing (floating) pressure by maximizing coolant valve opening, (b) floating pressure control of partial condenser with vapor distillate, (c) floating pressure control when the distillate is both vapor and liquid. 

Swab and Deldrin samples for SEM/EDX examination were subjected to a concentration/cleanup procedure, the apparatus for which is given in reference 185. All samples were carbon-coated using a Biorad E6430 automatic vacuum controller before examination in the SEM. 

Figure 9-6. Preparative ultracentrifuge (a) with the cover panels in place, and (b) from the front and (c) from the rear with the cover panels removed. A, armor plate surrounding the rotor chamber B, drive and gear assembly C, electronics bank housing the speed, temperature, and vacuum control and monitoring systems D, vacuum pump E, vacuum pump motor F, refrigeration unit G, diffusion pump and H, drive oil reservoir. (Courtesy of Beckman Instruments, Palo Alto, Calif.)...

Permeate was vacuum concentrated in the laboratory using a Btichi (Brinkmann Instruments Co.. Westbury. N.Y.) Rotavapor RE120 evaporator and model 165 vacuum controller. In the pilot plant, a pilot scale, conventional single stage vacuum evaporator, fabricated to Western Regional Research Center specifications was used. 

A fluorescence measurement is performed by directly delivering a vacuum controlled pulse of the analyte vapour diluted with air to the distal end of the optical fibre containing the sensors (Figure 4). The optical instrument includes a fluorescence microscope and a charge coupled device (CCD) camera. The excitation light is launched into the fibre, and the... 

Operational Characteristics Feed enicis at higher saturation temperature than is maintained in the crystallizer body. Ciystallizer temperature, product recoveiy, and sluny density are regulated by vacuum control. Heat of ciystallization and the sensible hest of the feed are removed by evaporation and condensation of solvent. The condensate may either be removed or a portion or all returned. 

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