Contaminants vacuum pump

Other co-solvent systems which do not freeze completely in commercial freeze-dryers were more diflicult to use, do not sublime but rather boil during the evacuation process, often resulted in unacceptable freeze-dried cakes, and may bypass condensers and contaminate vacuum pumps. Their use appears limited. Many of these types of solvents were near impossible to dry when levels used exceed 10%. 

Du Pont called this new lubricant material Krytox (64,65) and initially it had such extraordinary properties that it sold for 200/kg ( 187kg ca 1993). Krytox was and is used ia most of the vacuum pumps and diffusion oil pumps for the microelectronics iadustry ia this country and ia Japan because it produces no hydrocarbon (or fluorocarbon) vapor contamination. It has also found important appHcations ia the lubrication of computer tapes and ia other data processiag appHcations as weU as military and space appHcations. 

The primary sources of contamination in ion implantation come from metal atoms that may be etched off reactor fixtures, such as reactor wads, wafer holder, cHps, and so on. The pump oils used by the vacuum pumps may be a source of hydrocarbon contamination. The dopant sources themselves are not a significant source of contamination because unwanted ions are separated out from the beam during beam analysis. 

The most commonly used remediation technique for the recovery of organic contaminants from ground water has been pump- and-treat, which recovers contaminants dissolved in the aqueous phase. In this regard, the application of carbon adsorption has found extensive, but not exclusive use. Vacuum extraction (also called soil venting) has also become popular for removal of volatile organic contaminants from the unsaturated zone in the gaseous phase. Both of these techniques can, in the initial remediation phase, rapidly recover contaminants at concentrations approximately equal to the solubility limit (pump-and-treat), or the maximum gas phase concentration of the contaminant (vacuum extraction). The... 

Figure 14.1 presents the main components of a typical in situ SVE system.910 Vertical extraction wells are installed inside the contaminated zone at appropriate distances from one another. The SVE wells are typically constructed of PVC pipe, with a screened interval, which is placed within the contaminated zone. The wells are connected to blowers or vacuum pumps, which induce a continuous airflow through the pores of the unsaturated zone. The soil surface is sometimes covered with an impermeable seal, made from high density polyethylene (HDPE) or bentonite clay for example, to prevent the vertical influx of air from the surface, which might cause short-circuiting problems, and promote horizontal gas flow through the contaminated area. The airstream, which contains the contaminant vapors, passes initially through an air-water separation unit to remove the entrained moisture and is then directed to the gas treatment unit, where the contaminants are thermally destroyed or removed by adsorption. 

In order to prime the apparatus, the charcoal-filled reactor is initially heated to 400 °C and maintained at this temperature for 10 h while operating the vacuum pump. This procedure must be repeated subsequently at regular intervals in order to regenerate the charcoal filling. The so-activated charcoal removes contaminants from the hydrogen stream, and thereby also serves as a gas cleaner. 

Perfluoropolyethers emerged on the market in the early 1970s. The first perfluoropolyether was the homopolymer of hexafluoropropylene oxide produced by DuPont, which has the structure [—CF2CF(CF3)0—] and this new lubricant material was called Krytox.31,32 Krytox was and is used in most of the vacuum pumps and diffusion oil pumps for the microelectronics industry because it does not produce any hydrocarbon or fluorocarbon vapor contamination. It also has important applications in the lubrication of computer tapes and in other data processing as well as military and space applications. 

Obviously, in practical situations one can hardly imagine a vacuum pump installed onboard of a fuel cell-powered vehicle. Even if so, the membrane of a Proton Exchange Membrane Fuel Cell (PEMFC) will be soon contaminated by the oil vapors released from the pump (dry pumps are possible but this would enormously complicate the entire design). 

Barometric condenser systems can be a major source of contamination in plant effluents and can cause a particularly difficult problem by producing a high-volume, dilute waste stream [8]. Water reduction can be achieved by replacing barometric condensers with surface condensers. Vacuum pumps can replace steam jet eductors. Reboilers can be used instead of live steam reactor and floor washwater, surface runoff, scrubber effluents, and vacuum seal water can be reused. 

The chemical Industry requires vacuum pumps which are highly reliable and which do not produce waste materials such as contaminated waste oil or waste water. If this can be done, the operating costs of such a vacuum pump are low in view of the measures otherwise required for protecting the environment (disposal of waste oil and water, for example). For operation of the simple and rugged ALL-ex pump from LEYBOLD there are no restrictions as to the vapor flow or the pressure range during continuous operation. The ALL-ex may be operated within the entire pressure range from 5 to 1000 mbar without restrictions. 

According to the vendor, the capital costs for the treatment system include a 200-actual cubic-feet-per-minute (ACFM) vacuum pump, two transfer pumps, a carbon steel knockout pot, and associated instrumentation and piping. Operation and maintenance costs for the system include estimates for additional granular activated carbon (GAC) units, liquid- and vapor-phase analysis, weekly monitoring, electricity, and routine maintenance. These costs vary, depending on the monitoring requirements, contaminant concentrations, and other variables (D13124Y, p. 492). 

Before a sample can be analyzed it is necessary to remove contaminating materials which can alter the surface potential and block or fill pores. Sample conditioning can be accomplished by vacuum pumping or... 

To assess the possibility of contamination of the freeze drying chamber with oil during the final drying process by diffusion of oil out of the vacuum pump. 

Checker s comment Instead of bubbling N2 through the solution for 12 h, we found that evacuating the Schlenk flask to ca. 1 mm Hg for 12 h gave comparable yields and seemed to reduce the amount of the unidentified green contaminant. A base trap should be used to prevent damage to the vacuum pump. 

The vacuum pump should be serviced regularly. Whenever the pump oil seems contaminated, it should be replaced with new oil. 

A vacuum pump should be scrupulously protected from corrosive vapors and materials which will be absorbed in the pump oil or condense in the pump. For most laboratory operations a low-temperature trap is employed for this purpose, and in the case of fluorine handling systems a soda-lime trap is used to neutralize the corrosive gases. Despite these precautions, the pump oil does eventually break down and become contaminated. Regular oil changes should be scheduled for a pump at about yearly intervals for a well-protected pump and more often for pumps which are not well protected. 

N.S. Radin, L. Hof and C. Seidl, Lipid contaminants polypropylene apparatus and vacuum pumps, Lipids 3 (1968) 192. 

An electrical resistance heater with more turns at the tube ends (to compensate for heat losses) surrounds each tube. There is a vertical laminar flow hood over the loading area to minimize particle contamination of the wafers being loaded. As we can see, there are temperature controls for the furnace tubes, and a power module to provide the electrical power. When operated as a LPCVD system, a unit including both the gas flow and vacuum systems is positioned on the right side. Such a unit is shown in Figure 8. Here we can see the vacuum pumps on the left, and the mass flow controllers on the right. The vacuum pump oil recirculation systems are shown in the slide out drawers. As can be seen in Figure 9, this system, as well as most current similar systems, operate under computer control. 

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