Mechanical vacuum systems Applications

Mechanical separations, 224 Mechanical vacuum systems, 342 Applications, 352, 353 Barometric iniercondenser, 349 Evacuation times, 387 Operating range, 355 Performance curves, 386 Pump down, 380... 

Every vacuum system consists of various components intended to ensure that the process works reliably. On the intake side, the vacuum pump is protected mechanically by a separator. This separator must work just as well in each different application. The simplest type of separator is a container that slows down the gas flow and increases the dwell time of the gaseous components (Fig. 10). 

There is no vacuum source that is the best choice for every application. The technology for protecting mechanical pumps from process upsets and abuse is highly developed. This technology can be used effectively in designed vacuum systems to meet specific requirements. In several applications, mechanical pumps have demonstreted reliability comparable with, or superior to, liquid-ring pumps or steam jet ejectors. 

Huff [23] found that reciprocating and rotary piston pumps were the most economical mechanical systems for their range of application. Obviously, the economic discussions are dependent on the vacuum expected and the local utility costs, plus the cost of maintenance. 

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. 

In addition to commercial systems, there are quite a number of oscillator circuits that can be built from relatively inexpensive components to perform tiie essential measurements without the functions and convenience of a packaged instrument [22-28]. Both the commercial systems and most of these home-built oscillator circuits yield just one piece of information the resonant frequency of the TSM device. While this is sufficient for mass-loading-only applications like vacuum deposition of metal films, for some electrochemical processes, and even for appropriately selected chemically sensitive films, it can fall short when changes in the mechanical properties of a surface layer or contacting medium are significant [29]. 

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