Vacuum applications

Uses of Ejectors For the operating range of steam-jet ejectors in vacuum applications, see the subsection Vacuum Systems. ... 

Natural circulation reboilers are effective and convenient units for process systems operating under pressure. They are usable in vacuum applications but must be applied with care, because the effect of pressure head (liquid leg) on the boiling point of the fluid must be considered. The temperature difference between the heating medium and boiling point of the fluid may be so small as to be impractical, regardless of the tube length in a vertical unit. 

In vacuum applications, use this method with caution and compare it with other methods. 

The range of suction volumes is approximately 175-35,300 scfm per minute, and the units are capable of discharging up to 580 psi. In vacuum application, the units can draw down to 1.3 psi abs. ... 

However, investigations up to now have mainly concentrated themselves on ambient environments even though it is known that ionic liquids have a very low vapor pressure, making them suitable for vacuum applications such as in space mechanisms, the disk drive industry, and microelec-tromechanical systems (MEMS). Due to the ultra-low vapor pressure of most ionic liquids, they have been expected to be good lubricants in vacuum. Further experimental works are required to evaluate lubrication behavior of ionic liquids under ultra-high vacuum conditions and in inert atmospheres. 

The sampling of a suction lysimeter is initiated by applying a vacuum (approximately 40-50 cm of mercury) through the vacuum/pressure line with a hand pump or electric pump. The valve on the sampling line must be closed. A constant vacuum may be maintained on the lysimeter using an electric pump. The time required before collecting a sample from a lysimeter will depend on the method of vacuum application, the moisture content of the soil, and the soil type. 

The third type (CF, see Fig. 1.22) is used in ultrahigh-vacuum application (p < 10 7 torr) where heating is needed to speed up the degassing process of the inner walls of the... 

The pumps of the DRYVAC family are the classic dry compressing claw vacuum pumps that are preferably used in the semiconductor industry, whereby the pumps need to meet a variety of special requirements. In semiconductor processes, as in many other vacuum applications, the formation of particles and dusts during the process and/or in the course of compressing the pumped substances to atmospheric pressure within the pump, is unavoidable. In the case of vacuum pumps operating on the claw principle it is possible to convey particles through the pump by means of so called pneumatic conveying". This prevents the deposition of particles and... 

The specimens should wherever possible be examined in a configuration corresponding to their later application - components for vacuum applications using the vacuum method and using the positive pressure method for parts which will be pressurized on the inside. 

Tellurium—copper alloys are recommended for situations demanding a high production rate with no significant sacrifice in conductivity. These alloys can be soldered, brazed, or welded without incurring embrittlement. They are used in vacuum applications, forgings, screw-machine parts, welding-torch tips, transistor bases, semiconductor heat sinks, electrical connectors (qv), motor and switch parts, and nuts, bolts, and studs. Addition of tellurium significantly improves the surface of machined parts. 

D. Ball, Plug, and GatO Valves. The valves discussed above often introduce considerable restriction into the system because of small orifices and tortuous flow patterns. Such restrictions are not serious for most applications at 1 atm pressure or above, but they may be unacceptable for vacuum applications, where small-diameter openings are a serious impediment (see Chapter 6). Ball and... 

Roots pumps must be combined with a backing pump/pump-set for normal vacuum applications. Used in combination with any of a range of backing pumps (oil-sealed rotary, dry, liquid-ring) Roots pumps allow higher pumping speeds and lower pressures to be achieved than can be obtained by the backing pump on its own. 

All materials show some permeability to gases. In vacuum applications, gas transmission involves three stages ... 

Partial Concentration. The sum of the partial concentrations (pressures) in a free molecular gas is equal to the total concentration (pressure). However, all gaseous components, at the same partial pressure or absolute pressure or ratios thereof, are not likely to have the same significance to any or all vacuum applications. The significance of the condensed-phase concentrations must therefore be considered. 

In the latter case, solution entering a vaporizer probe attached to the electrochemical cell is rapidly vaporized by resistive heating and sucked into the MS by the vacuum. Applications of ECMS have been in mechanistic analysis, and in the fields of electrocatalysis, batteries, sensors, and corrosion. 

Figure 3.5 Schematic representation of injection by vacuum application.

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