Process design vacuum systems

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. 

Other factors that favor the choice of the steam ejector are the presence of process materials that can form soflds or require high alloy materials of constmction. Factors that favor the vacuum pump are credits for pollution abatement and high cost steam. The mechanical systems require more maintenance and some form of backup vacuum system, but these can be designed with adequate reflabiUty. 

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. 

In general, vacuum vents and inert or gas repressuring systems are not considered an acceptable alternative to vacuum design for process equipment. Repressuring systems may be provided for process reasons, but they are not considered sufficiently reliable for equipment protection. Vacuum breakers are difficult to maintain tight and may admit air into the equipment. 

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].

In many cases design modifications can substantially improve the productibility of the products and reduce their cost with improved product quality. As an example if voids exist the problem can usually be corrected by modifying or changing the plastic s composition and/or the use of a vacuum system during the casting. Understanding the effects of the process on the product is essential in making successful products. 

Total head, centrifugal pumps, 180, 183 Discharge, 205 Head curve, 198 Suction head, 184, 186 Suction lift, 184, 186 Type, 184 Tubing, 63, 64 Two-phase flow, 124 Calculations, 125-127 Flow patterns, chart, 124 System pressure drop, 125 Types of flow, 124, 125 Utilities check list, process design, 34 Vacuum,... 

A modem mass spectrometer is constmcted from elements which approach the state-of-the-art in solid-state electronics, vacuum systems, magnet design, precision machining, and computerized data acquisition and processing. [1] This is and has ever been a fully valid statement about mass spectrometers. 

Study determined the compact throughput, compact density, and fines (not compacted during vacuum deaeration) when using a new equipment feed system design. The parameters controlled and monitored during the compaction process were vacuum deaeration pressure, roll pressure, roll and screw speeds, room temperature, and humidity. 

Thermal desorption is a physical separation process. Waste is heated to volatilize water and organic contaminants. A carrier gas or vacuum system transports volatilized water and organics to the gas treatment system. The bed temperatures and residence times designed for these systems will volatilize selected contaminants without oxidation. Three types of thermal desorption are available ... 

---