Vacuum control system

The detector was claimed to be moderately linear over a dynamic range of three orders of magnitude but values for the response index are not known. It is also not clear whether the associated electronics contained signal modifying circuitry or not. The disadvantages of this detector included erosion of the electrodes due to "spluttering", contamination of the electrodes from sample decomposition and the need for a well-controlled vacuum system. 

Vacuum system. Components associated with lowering the pressure within a mass spectrometer. A vacuum system includes not only the various pumping components but also valves, gauges, and associated electronic or other control devices the chamber in which ions are formed and detected and the vacuum envelope. 

Space needs to be provided for the auxiliaries, including the lube oil and seal systems, lube oil cooler, intercoolers, and pulsation dampeners. A control panel or console is usually provided as part of the local console. This panel contains instmments that provide the necessary information for start-up and shutdown, and should also include warning and trouble lights. Access must be provided for motor repair and ultimate replacement needs to be considered. If a steam turbine is used, a surface condenser is probably required with a vacuum system to increase the efficiency. AH these additional systems need to be considered in the layout and spacing. In addition, room for pulsation dampeners required between stages has to be included. Aftercoolers may also be required with knockout dmms. Reference 8 describes the requirements of compressor layouts and provides many useful piping hints. 

Many problems encountered in producing a highly controlled vacuum result from the system s design, history, contents, use, and maintenance. 

Eailure of vacuum system control resulting in possibility of vessel collapse. 

Failure of vacuum Design vessel to accommodate maximum system control vacuum (full vacuum rating) resulting in possi-. , elief system bility of vessel collapse pressure alarm and interlock to inert gas supply Select/design vacuum source to limit vacuum capability ASME VIII CCPS G-23 CCPS G-39... 

The inerts will blanket a portion of the tubes. The blanketed portion has very poor heat transfer. The column pressure is controlled by varying the percentage of the tube surface blanketed. When the desired pressure is exceeded, the vacuum system will suck out more inerts, and lower the percentage of surface blanketed. This will increase cooling and bring the pressure back down to the desired level. The reverse happens if the pressure falls below that desired. This is simply a matter of adjusting the heat transfer coefficient to heat balance the system. 

Another example of pressure control by variable heat transfer coefficient is a vacuum condenser. The vacuum system pulls the inerts out through a vent. The control valve between the condenser and vacuum system varies the amount of inerts leaving the condenser. If the pressure gets too high, the control valve opens to pull out more inerts and produce a smaller tube area blanketed by inerts. Since relatively stagnant inerts have poorer heat transfer than condensing vapors, additional inerts... 

For big vapor lines and condensers (frequent in vacuum systems) always insulate the line, condenser, and top of column. Rain or sudden cold fronts will change column control otherwise. It is possible to have more surface in the overhead line than in the condenser. 

Put the vacuum system control valves at the highest point of a horizontal run and the control valve bypass in the same horizontal plane. This is in compliance with item 8. 

A vacuum condenser has vacuum equipment (such as steam jets) pulling the noncondensibles out of the cold end of the unit. A system handling flammable substances has a control valve between the condenser and Jets (an air bleed is used to control nonflammable systems). The control method involves derating part of the tube surface by blajiketing it with noncondensibles that exhibit poor... 

This discussion will address needs, applications, performance characteristics, and design considerations for LVHV exhaust ventilation. The applications are primarily for dust control. LVHV systems can be effective for protecting workers from dust exposures and for recovering valuable process materials. The equipment, excepting the nozzles, involves technology that is the same as for large central vacuum cleaning systems. 

Figure 6-33 diagrams vacuum system arrangements for process systems. It is important to examine the plant economics for each system plus the performance reliability for maintaining the desired vacuum for process control. 

The pore size of Cs2.2 and Cs2.1 cannot be determined by the N2 adsorption, so that their pore sizes were estimated from the adsorption of molecules having different molecular size. Table 3 compares the adsorption capacities of Csx for various molecules measured by a microbalance connected directly to an ultrahigh vacuum system [18]. As for the adsorption of benzene (kinetic diameter = 5.9 A [25]) and neopentane (kinetic diameter = 6.2 A [25]), the ratios of the adsorption capacity between Cs2.2 and Cs2.5 were similar to the ratio for N2 adsorption. Of interest are the results of 1,3,5-trimethylbenzene (kinetic diameter = 7.5 A [25]) and triisopropylbenzene (kinetic diameter = 8.5 A [25]). Both adsorbed significantly on Cs2.5, but httle on Cs2.2, indicating that the pore size of Cs2.2 is in the range of 6.2 -7.5 A and that of Cs2.5 is larger than 8.5 A in diameter. In the case of Cs2.1, both benzene and neopentane adsorbed only a little. Hence the pore size of Cs2.1 is less than 5.9 A. These results demonstrate that the pore structure can be controlled by the substitution for H+ by Cs+. 

A central vacuum-system controller regulates opening and closing of the drain valves and the supply of water. Due to this controlled system, one rinse of the toilet needs only 0.25-0.30 litre of water (a normal domestic toilet needs 7-9 litre). 

The Mass Spectrometer Module houses the vacuum system, capillary interface assembly, and ion-trap mass spectrometer in approximately half of the module. Also included are the reagent gas and calibration gas subassembly (a temperature-controlled housing that ensures consistent gas pressures). The other half contains the electronic printed circuit boards, power supplies, and instrument control computer. 

In high-vacuum systems, the limit pressure p( is usually controlled by the degassing rate (<2 ) that decreases with time. 

The possibility to grow good-quality thin films at room temperature and normal pressure is the main advantage of SILAR relative to the gas-phase techniques. Moreover, since vacuum systems are not required, SILAR deposition equipment is simple and inexpensive. Similarly, toxic chemicals, such as selenium compounds, which are easier and safer to handle as solutions than as gases, can be more conveniently employed in SILAR. From the environmental point of view, a notable advantage of SILAR is that the system is totally closed and all the chemicals that are used are recyclable. Compared with other solution-phase methods, especially with CBD, an important advantage of SILAR is the facile control over film thickness using... 

Vacuum chamber with tempered shelves 2, container with probe 3, lift for shelves 4, condenser 5, lockgate 6, balance in the lock 7, vacuum pump for the lock 8, glove box 9, Karl-Fischer measuring system 10, pressure controlled vacuum pump 11, manipulator 12, tempered medium (Fig. 1 from [3.30]). 

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