Air-displacement systems

Air-displacement systems air lifts, acid eggs or blow cases, jet pumps, barometric legs... 

The pumps discussed in the preceding sections depend on the mechanical action of pistons, impellers, plungers, or other devices to move the fluid. Movement of fluids can also be accomplished by the use of air pressure, and many types of air-displacement systems have been developed for this purpose. The most common of these systems are air lifts, acid eggs, and jet pumps. 

Cake Dewatering. Dewatering (qv), identified as a separate entity in filtration, is used to reduce the moisture content of filter cakes either by mechanical compression or by air displacement under vacuum pressure or drainage in a gravitational or centrifugal system. Dewatering of cakes is enhanced by addition of dewatering aids to the suspensions in the form of surfactants that reduce surface tension. 

Bulk unloading facilities usually must be provided at the treatment plant. Rail cars are constructed for top unloading and therefore require an air supply system and flexible connectors to pneumatically displace the alum from the car. U.S. Department of Transportation regulations concerning chemical tank car unloading should be observed. Tank truck unloading is usually accomplished by gravity or by a truck mounted pump. 

Note Air distribution systems are not ventilation or air conditioning systems. For example, mixing air distribution and displacement air distribution are methods to bring the supply air to the treated space. 

H. Tan, T. Murata, K. Aoki, and T. Kutabuchi, Cooled ceilings/displacement ventilation hybrid air conditioning system—Design criteria, in Proceedings of Spacevent 98, Stockholm 1998. 

As with any hood system, design methods are used to obtain required exhaust rates and hood dimensions.The main mechanisms of dust generation are air induction, material splash, air displacement, and air entrainment. 

Air injection systems, by their very nature, start with no initial hydraulic control because flow is away from the injection point. Contaminants are sometimes spread laterally by water displacement until control is established. 

The volume of air displaced when transferring a product should also be considered. Without proper venting, the transfer operation will cease. If the transfer is very rapid, then correspondingly, the transfer vessel vent system must be capable of managing the worst case flow. Depending on the type of vapors released, the vent stream may have to be scrubbed, routed to the flare, or at least discharged at a safe location. 

The pipettes are all based on air displacement with a simple plunger and are provided with non-wettable plastic (usually polypropylene) disposable tips to contain the solution, preventing any contamination of the pipette itself. Most micropipettes have a double action plunger system, i.e. calibration and overshoot positions, which ensures that the sample is completely dispensed. There are many manufacturers offering a complete range of volumes in addition some have available a selection of pipettes with adjustable volumes. 

If the slide is ready to receive the sample, a green lamp lights up at the DTSC module (Fig. 18) and a beep is emitted. 10 pi of the sample is now applied by means of the electric air displacement pipette. Application of the sample is monitored by an automatic sample detector system. After successful application of the sample the slide travels fully automatically to the pre-incu-... 

The Reflotron system consists of the reagent carrier, reflection photometer and an air displacement pipette or applicator. It is easy to operate. The required blood sample is obtained by puncturing the finger pad or ear lobe with... 

Since the Seralyzer system partly requires the use of diluted serum or plasma, a pipette system or a dilutor unit must be kept ready (Fig. 43). The entire system consists of one each 30 pi and 100 pi air displacement micro-pipette, a... 

The dwelling time covers the period that elapses between the application of the sample to the test slide and its insertion into the measurement device. Since the sample is inserted by the analyser in the Ektachem, Cobas Ready and Stratus instruments, this factor can be neglected as far as these systems are concerned. It is only with the Ektachem DT-60, Reflotron and Seralyzer that dosage of the sample is effected by means of an air displacement pipette via the user. No time error can occur with the Ektachem DT-60 because an inter-... 

Inasmuch as the right conditions for crystallization cannot be predicted, a large number of conditions (precipitant, pH, temperature, protein concentration, additives, etc.) need to be screened to produce a crystal suitable for data collection. To minimize the amount of precious protein material used in these preliminary experiments and avoid the large amount of manual labor involved, automation is becoming very common.8 When setups are done by hand, the pipetting is usually done using standard air-displacement pipettes, which are extremely inaccurate under 1 pi, making this the minimal practical protein volume per experiment. All of the various robotic systems can use sample volumes as low as 50 nl, and some as little as 1 nl. 

UFAD systems have the potential to produce better indoor air quality in buildings during normal operation (Bauman, 2003), but they could be more vulnerable to indoor biological and chemical attacks than conventional ducted air distribution systems. One of the claimed advantages of UFAD is that it supplies clean air to displace normal indoor contaminants (such as bioeffluent and emissions of... 

The system uses a simple rotary pump and no diffusion pump is required. Any dual stage pump with a free air displacement of 20 liters per minute or more should be satisfactory, although larger free air displacements are advantageous in terms of routine working speed. We have found Leybold Heraeus model D2A direct drive pumps with free air displacements of 62.5 liters per minute to be particularly satisfactory, and very quiet in routine operations. 

A prototype turbocompressor using this air bearing system, designed to deliver the DOE-specified mass flows and pressure ratios, was built, integrated into an instrumented turbocompressor test bench simulating an automotive air system with an in-line positive-displacement compressor, and demonstrated to 33,000 RPM (35% of design speed). 

Purge gases heavier than air displace the air in piston-like fashion and require a very small gas rate to maintain oxygen-free conditions. However, this rate is too small to insure against possible air leaks into the system and too small to maintain a flare. A rate equivalent to that required for a nitrogen purge is recommended. 

Other conveying systems, such as elevators, drag chains, vibrating tubes, screw feeders, pneumatic conveyors, and air slides are generally enclosed. Any air displaced from them should be vented to a suitable dust collector. 

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