Vacuum apparatus systems, special

For around 20 years now, numerous standards and recommendations have been drawn up at national and international level and revised, whenever necessary, in accordance with the state of the art. These standards and recommendations must be observed whenever use is made of vacuum equipment (pumps, gauges, valves, etc.) and vacuum apparatus, systems and plants are assembled. They not only contain specifications applying specially to vacuum technology, but also go beyond this specific field and involve, for example, physical units, formulas, noise protection regulations, etc. 

Low-pressure operations are common in many laboratories. Laboratories are often equipped with a house vacuum system, vacuum pumps, rotary evaporators, water aspirators, vacuum concentrators, vacuum ovens, and/or other apparatus that operate under reduced pressure. Some labs build elaborate vacuum racks for special purposes (see Figure 5.3.4.1). All glass vessels under vacuum should be considered potential risks for implosions with the result being flying glass shards, chemical splashes, and fires. The violence of implosions is limited due to the fact that the pressure differential between inside and outside the vessel cannot be more than 1 atmosphere (unlike pressure vessels, where the pressure differential can be much greater). 

A washed and dried sheet glass is set to the newly developed apparatus. A special container which has an opening at one side is tightly contacted with the sheet glass by vacuum system, so that the opening of the container is closed by the sheet glass to... 

The TGA apparatus becomes very hot and caution should be exercised while using it. In order to safely handle volatile materials or polymer decomposition products which may be irritating and harmful, it is suggested that a gas bubbler be constructed to scrub the gaseous effluent from the instrument (Fig. 15.5). Care must be taken to prevent excessive gas pressure from building up if the system is being operated under vacuum or with gases, both inert and flammable. Consult the instrument operations manual for any special safety instructions. 

It is convenient to use a modification in the apparatus that permits fractions to be taken without the necessity of breaking the vacuum. The method is to evacuate a system of more than one receiver fitted to a special adapter which provides a means of directing the distillate into the receivers as shown in Figure 2.20. These receivers are successively employed by rotating them into the receiving position. 

A common feature of all of these methods is that measurement is carried out in ultra-high vacuum (UHV) (<10 torr) thus any electrode surface to be examined must be removed from the cell, possibly rinsed, dried of solvent, and then place in vacuo. Electrodes cannot be examined in situ, since liquids will absorb and block the beams of electrons and ions. The sample must be transferred into a system where there is no electrolyte. This always raises the possibility that the analyzed interface differs significantly from the one in the cell, which is the actual point of interest. For example, hydrated solids will lose water in vacuum and may change composition. Also, exposure of the electrode to the air during transfer can cause oxidation of surface species. Special apparatus has been designed to minimize the problems of exposure to the atmosphere by allowing the sample to be removed from the cell in an inert atmosphere and moved directly into the UHV (Figure... 

Independent of the type of PVD method used to deposit a film or a film system, the deposition process is carried out in a sealed chamber which is first exhausted to a pressure of the order of 10 5 mbar or even lower values. The glass chambers used formerly have been replaced, with the exception of glass recipients for special purposes, such as apparatus for electron microscopic preparation techniques, by those of metal. Cylindrical and cubic chambers made of stainless steel provided with various flanges and windows are used today. The walls of the chambers can be heated and cooled by water running through double-wall constructions or in brazed-on half-round pipes fitted on the outside. The vacuum chambers are evacuated by different pumping systems. The simplest consists of a diffusion pump with or without a liq-... 

Figure 6 fVinehwiess system for resonance spectrometry o/F i j atoms. B, buffer chanAer C, collimated hole structures, two of which were mounted on specially fabricated glass discs, D K, inlet to lamp L M,M, differential manometers R, section of flow tube S, spectrometer slit, sealed via an O-riqg seal to the silica apparatus V, vacuum spectrometer (After ref. 24)... 

Freeze-drying, a special application of the sublimation principle, uses apparatus of a different kind (Figure 6). The sample, usually a liquid at room temperature, is dispersed around the walls of a round-bottomed flask whilst it is frozen by immersion in a suitable freezing mixture, for example, dry ice/acetone. The flask is then attached to the evacuating system that usually comprises an oil vacuum pump protected from the ice sublimate by a train of... 

With a dual-inlet system, the samples for analysis are converted into gases offline. The offline sample preparation procedure utilizes a specially designed apparatus involving vacuum lines, compression pumps, concentrators, reaction furnaces, and microdistillation equipment. This technique is time consuming, usually requires larger samples, and contamination and isotopic fractionation can potentially occur at each of the steps [9]. 

An aspirator can be used to remove noxious gases from the reaction. The simplest approach is to clamp a disposable Pasteur pipette so that its tip is placed well into the condenser atop the reaction vial. An inverted funnel clamped over the apparatus can also be used. The pipette or funnel is attached to an aspirator with flexible tubing. A trap should be placed between the pipette or fuimel and the aspirator. As gases are liberated from the reaction, they rise into the condenser. The vacuum draws the gases away from the apparatus. Both types of systems are shown in Figure 7.14. In the special case in which... 

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