Vacuum pneumatic

Rotary valves have been specified for the receivers of the vacuum pneumatic conveying systems (RV-601 and RV-602) and for the feeders (RV-40 1) and receivers (RV-501) of the positive-pressure system transferring powder from the dryers to the extruders. Perry72 gives some recommended sizes for rotary valves. The power required by all these valves will probably not exceed 2 kw and will be ignored. 

A thermoplastic sheet or blank is horizontally clamped and heated by infrared heaters until flexible and then forced by various means (pressure, vacuum, pneumatic ram) against a mould surface and cooled. The mould can be low cost. 

In pneumatic nebulizers, the relative velocity of gas and liquid first induces a reduction in pressure above the surface of the liquid (see the calculation in Figure 19.4). The reduction in pressure is sufficient to cause liquids to flow out of capillary tubes, in accord with Poiseuille s formula (Figure 19.5). As the relative velocity of a liquid and a gas increases — particularly if the mass of liquid is small — this partial vacuum and rapid flow cause the surface of the liquid to be broken into droplets. An aerosol is formed. 

The plough cannot be allowed to reach too close to the cloth and some residual cake remains. Where this is not acceptable, the cake may be removed by a pneumatic system, by vacuum, or by reslurrying. The cycle can be automated and controlled by timers. The maximum speeds of basket centrifuges vary from 800 to 1500 rpm, and basket diameters are in the range from 10 to 1400 mm. A 1200-mm diameter, 750-mm long basket may handle as much as 200 kg of cake in one charge. 

Dryers. Drying, another type of evaporation technique, is suited for waste streams of very high soHds content. Several common types of dryers are vacuum rotary dryers, dmm dryers, tray and compartment dryers, and pneumatic conveying dryers. 

Hand and power tool cleaning is used on ships mostly for spot repair of damaged areas. Hand tools include scrapers, wire bmshes, and sanders. Electric and pneumatic power tools, which include grinders and needle guns, clean faster and more thoroughly than hand tools. Most power tools have vacuum lines coimected to collect paint debris. 

Types of Systems Generally, pneumatic conveyors are classified according to five basic types pressure, vacuum, combination pressure and vacuum, fluidizing, and the blow tank. 

Pneumatic Transport Both low-pressure air-vacuum conduit transport systems have been used to transport sohd wastes. The most common application is the transport or wastes from high-density apartments or commercial activities to a central location for processing or for loading into transpoii vehicles. The largest pneumatic system in use in the United States is at the Walt Disney World amusement park in Orlando, Florida. 

The Socony Vacuum design consisted of separate vessels for reaction and regeneration. Units constructed in the late 1940s employed a pneumatic lift design which allowed for high catalyst circulation rates. A typical design is shown in Figure 20, which allowed for a primary air stream to convey the catalyst. A... 

Figure 10.30 illustrates a multiple-stage exhauster and smooth-flow duct (pneumatic tubing) components. It also includes pictures of air cleaner-exha uster-motor installations located outside of buildings and connected to LVHV (or central vacuum cleaning) systems inside the buildings. 

Figure 6-45. Cut-away view of internal assembly of rotary lobe vacuum pump. By permission, Tuthiii Corp., M.D. Pneumatics Division.

Pneumatic conveyors are for high capacity, short distance (400 ft) transport simultaneously from several sources to several destinations. Either vacuum or low pressure (6-12 psig) is employed with a range of air velocities from 35 to 120 ft/sec depending on the material and pressure, air requirements from 1 to 7 cuft/cuft of solid transferred. 

Both a pneumatic heated nozzle system [487] and an ultrasonic nozzle/vacuum system [699] have been described for removing the troublesome solvent in order to simplify IR analysis. The former system (LC Transform ) has been commercialised [700], and allows full use of the mid-IR spectral range by providing analyte films free from solvent interference. The evaporative... 

Type of pumping apparatus to employ (e.g., aboveground vacuum, submersible, and pneumatic). 

The pneumatic transportation of bulk solids through pipelines has been in existence for over one hundred years. Some of the earlier applications included the vacuum unloading of grain from ships and the extraction of sawdust from timber mills. 

Atmospheric Pressure Chemical Ionization. As its name reveals, APCI[16] is a Cl carried out at atmospheric pressure instead of under vacuum, as occurs for classical Cl. As for ESI, the sample must be in a solution that is continuously flowing into the APCI source (flow rate between 0.2 and 2 ml min ). The solution passes through a pneumatic nebulizer and is desolvated in a heated quartz tube or heating block, thus producing vaporization of solvent and analyte molecules (Figure 2.4). 

Fig. 11.5. Diagram illustrating the components of an ESI source. A solution from a pump or the eluent from an HPLC is introduced through a narrow gage needle (approximately 150 pm i.d.). The voltage differential (4-5 kV) between the needle and the counter electrode causes the solution to form a fine spray of small charged droplets. At elevated flow rates (greater than a few pl/min up to 1 ml/min), the formation of droplets is assisted by a high velocity flow of N2 (pneumatically assisted ESI). Once formed, the droplets diminish in size due to evaporative processes and droplet fission resulting from coulombic repulsion (the so-called coulombic explosions ). The preformed ions in the droplets remain after complete evaporation of the solvent or are ejected from the droplet surface (ion evaporation) by the same forces of coulombic repulsion that cause droplet fission. The ions are transformed into the vacuum envelope of the instrument and to the mass analyzer(s) through the heated transfer tube, one or more skimmers and a series of lenses.

In atmospheric pressure chemical ionization (APCI) ion-molecule reactions occurring at atmospheric pressure are employed to generate the ions, i.e., it represents a high-pressure version of conventional chemical ionization (Cl, Chap. 7). The Cl plasma is maintained by a corona discharge between a needle and the spray chamber serving as the counter electrode. The ions are transferred into the mass analyzer by use of the same type of vacuum interface as employed in ESI. Therefore, ESI ion sources can easily be switched to APCI instead of an ESI sprayer, a unit comprising a heated pneumatic nebulizer and the spray chamber with the needle electrode are put in front of the orifice, while the atmospheric pressure-to-vacuum interface remains unchanged. [48,138]... 

In atmospheric pressure ionization sources (API) the ions are first formed at atmospheric pressure and then transferred into the vacuum. In addition, some API sources are capable of ionizing neutral molecules in solution or in the gas phase prior to ion transfer to the mass spectrometer. Because no liquid is introduced into the mass spectrometer these sources are particularly attractive for the coupling of liquid chromatography with mass spectrometry. Pneumatically assisted electrospray (ESI), atmospheric pressure chemical ionization (APCI) or atmospheric pressure photoionization (APPI) are the most widely used techniques. 

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