Vacuum system, design

J. L. Ryans and D. L. Roper, Process Vacuum System Design and Operation, McGraw-HiU, Inc., New York, 1986. 

Vacuum systems are typically used when flows do not exceed 6800 kg/h (15,000 Ib/h), the equivalent conveyor length is less than 305 m (1000 ft), and several points are to be supplied from one source. They are widely used for finely divided materi s. Of special interest are vacuum systems designed for flows under 7.6 kg/min (1000 Ib/h), used to transfer materials short distances from storage bins or bulk containers to process units. This type of conveyor is widely used in plastics and other processing operations where the variety of conditions requires flexibility in choosing pickup devices, power sources, and receivers. Capital investment can be kept low, often in the range of 2000 to 7000. 

Figure 2-46. Typical flow velocities for vacuum lines. Note 1 torr = 1.33 mb = 133.3 Pa. 1.0 ft/sec = 0.3048 m/seo. By permission, Ryans, J. L. and Roper, D. L., Process Vacuum System Design Operation, McGraw-Hill Book Co., Inc., 1986 [18].

Low tray pressure drop is required, as for vacuum systems. Design with extra caution under vacuum, since data correlations have not been checked in this region. 

NEPCCO SoilPurge soil vapor extraction systems are noncontacting, oil-free, explosion-proof vacuum systems designed to remove volatile organic compounds (VOCs) from soil in situ. According to the vendor, benzene, toluene, ethylbenzene, and xylenes (BTEX), chlorinated solvents and other hydrocarbons can be treated with SoilPurge systems. The technology can also remove radon from soil. 

N. T. M. Dennis and T. A. Heppell, Vacuum System Design, Chapman and Hall, London, 1968. 

What can be limited is the backstreaming of condensable vapors. This can be achieved through the effective use of baffles, traps, and using good vacuum system design. The simple resolution for backstreaming of condensable vapors from standard pumps is proper system design and proper maintenance of the traps. 

As you can see, this process is aided or thwarted by vacuum system design. Temporary isolation of the various parts of any vacuum system may be impossible by bad design. Therefore, be forewarned If you are designing a vacuum system, provide a stopcock at every branch of the system to aid in leak detection (section isolation not only helps in leak detection, but creates a more robust vacuum system allowing greater control and protection). 

Figure 24. Partial pressures of vapor constituents above LhsPb, liquid. He pressure is assumed to equal the sutn of the Li, Pb, and H pressures because detailed vacuum system design has not been addressed. Monatomic Li and He are the primary constituents. Hydrogen isotopes<10 Torr at 1 wppm in liquid Ppj,...

Dennis NTM, Heppell TA (1968) Vacuum system design. Chapman Hall, London... 

Figure 2.8 is reprinted from Chapman Hall, N T M Dennis and T A Heppell, Vacuum system design, 1968, with permission from Chapman Hall. 

D. K. McNamara is a scientist at Martin Marietta Laboratories. He joined the Laboratories in 1973, having previously worked at Mound Laboratory and Brookhaven National Laboratory in instrumentation and vacuum system design. His interest in structural characterization has involved research into such diverse materials as silicon nitride, metal- and polymer-based composites, and metal carbides. He has studied extensively the role of surface preparations in adhesive bonding, from both theoretical and practical standpoints. 

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