Sind Trockenläufer wirklich die Lösung aller Probleme?

With this article the author intents to generate the awareness, that dry pumps due to its pump principle, performance characteristic and physical limitations not always to be seen as the solution to all challenges in vacuum technology out there. Monitoring and protective measures are resulting in more sensitivity to failures and operational errors, higher operating and maintenance cost as well as a certain knowledge about safe operation of dry pumps for system manufacturers and users is required in comparison to the classical rotary vane pumps. The requirement for oil free process chambers and apparatus were the major push to develop and improve dry pump technology but despite this trend the rotary vane pumps is for certain applications the pump of choice will be still around for quite some time.     

Correction: Sind Trockenläufer wirklich die Lösung aller Probleme?

With this article the author intents to generate the awareness, that dry pumps due to its pump principle, performance characteristic and physical limitations not always to be seen as the solution to all challenges in vacuum technology out there. Monitoring and protective measures are resulting in more sensitivity to failures and operational errors, higher operating and maintenance cost as well as a certain knowledge about safe operation of dry pumps for system manufacturers and users is required in comparison to the classical rotary vane pumps. The requirement for oil free process chambers and apparatus were the major push to develop and improve dry pump technology but despite this trend the rotary vane pumps is for certain applications the pump of choice will be still around for quite some time.     

CXS chemical dry vacuum pump brings smart vacuum to the process industry

The chemical sector as a whole has been quick to recognise the clear advantages of dry vacuum pumps over traditional wet technologies, and dry vacuum pumps are now well established around the world as an efficient, reliable option. A new trend is now emerging: for vacuum to be seen as a ‘utility’. In response, dry vacuum technology is being developed by manufacturers to be available on demand in a ‘plug and pump’ system that requires minimum set‐up and maintenance. The most advanced chemical dry vacuum pumps, such as the new CXS pump from Edwards, deliver exceptional energy efficiency and performance, are cost‐effective to run, and are environmentally sound.     

适用于化工工业的真空泵

真空泵在化工企业如水、电、压缩空气一样是不可缺少的公用设施。用于化工行业的真空泵必须结实、可靠,能处理大量蒸汽、腐蚀性气体和可燃性气体。本文介绍了各种真空泵的结构与性能,认为液环泵和螺杆真空泵最适合于化学工艺应用。     

Neue Vorvakuumpumpe: Schnelles Evakuieren dank Membran‐ Stabilisierungssystem. New roughing pump: Fast Evacuation thanks to Diaphragm Stabilization System

Diaphragm pumps are used at turbomolecular pumps to generate rough vacuum. They are characterized by high suction speed, which however deteriorate when the working pressure decreases. This is caused by the difference between the working pressure of the pump and the ambient pressure. The larger the pressure difference, the more the elastic diaphragm bulges, lowering the effective input volume of the pump. This problem is alleviated by a newly developed diaphragm stabilization system. Diaphragm roughing pumps equipped with this system pump down faster than pumps without the system. Due to the enhanced suction speed, they also ensure greater process reliability. The first application of the diaphragm stabilization system (patent applied for) is in a newly developed diaphragm roughing pump. This pump is driven by a compact, brushless DC motor with very great efficiency. The pump is available in 24‐volt DC and 90‐ to 264‐volt, 50/60‐Hz AC versions. OEM and portable versions are available.     

Weitbereich-Turbomolekularpumpen und Membranvorvakuumpumpen als trockene HV- und UHV-Pumpsysteme

The development of new turbomolecular pumps with increased critical backing pressures up to 30 mbar made it possible to use oilfree diaphragm pumps as backing pumps. The combination of a wide-range turbomolecular pump with a diaphragm pump represents an inexpensive, compact and technical dry vacuum pumping system for high and ultrahigh vacuum applications. The interaction of wide-range turbomolecular pumps with diaphragm pumps is discussed in terms of gas throughput, compression ratio, ultimate pressure and power consumption of the turbomolecular pump and selection criteria for the diaphragm backing pump are shown.     

我国主要容积式真空泵质量状况浅析

本文对容积式真空泵－旋片泵，滑阀泵，罗茨泵的总体情况进行了介绍，重点对其质量状况进行了分析，阐述了近几年容积真空泵的质量改进情况和目前仍存在的主要问题以及问题产生的原因和改进措施，并对真空泵普遍存在的共性问题进行了分析。     

Überlastgrenzen bei Hochvakuumpumpen

High-vacuum pumps have a limited inlet pressure above which they cannot function. Recognizing and dealing with the approaching overload conditions is an important aspect of vacuum system operation. This paper outlines the basic considerations for selecting the pressure at which the high vacuum pumps are started, emphasizing the importance of mass flow (throughput) limits rather than the pressure as such. Some basic parameters, such as the ratio of pumping speeds of the roughing pump and the high vacuum pump are associated with the choice of the cross-over pressure. Practical engineering recommendations are offered for system design and operation. Adverse system effects (e.g., backstreaming and oil loss) resulting from pump overload are noted for momentum transfer pumps (diffusion pumps and turbomolecular pumps) and capture pumps (sputter-ion pumps and cryogenic pumps). To prevent any adverse effect, normally, the transient pressure rise during switching should not be longer than a few seconds.     

Kryopumpen im Vergleich zu anderen Hochvakuumpumpen

Within the last 10 years, the cryopump was added to the range of the pumps used in the high vacuum and ultra high vacuum fields. The choice of the right pump often turns out to be difficult. One of the reasons could surely be that the user is not often familiar with the properties of the cryopumps. The article is meant to make the reader aware of all possible criteria, which in turn will make it easier for him to make a decision concerning the pump required for the application. The refigerator cryopumps can be used in any application for which hydrocarbonfree vacuum is required as well as a high pumping speed for almost all gases.     

Non-contact vacuum pumps

An overview of the main methods for mathematical modeling of the working process of non-contact vacuum pumps is given. The specifics and the main stages of mathematical model development for screw, scroll, claw and Roots vacuum pumps are considered. The results of mathematical modeling of pump characteristics are presented and compared with experimental data. The mathematical modeling technique presented here can be recommended for analyzing the influence of pump geometry and operating conditions on the pump characteristics of non-contact oil-free vacuum pumps.     

Ionenzerstäuberpumpen

Sputter Ion Pumps, a 50 year long success story Sputter ion pumps have a history of more than 50 years. The appliations for these pumps changed significantly over this period. Today with a high degree of specialisation, different pump versions are offered for nearly all applications. The introduction of the sputter ion pump has greatly influenced the vacuum world.     

Vacuum oxygen decarburization (VOD) of stainless steel

High costs for vacuum generation and maintenance can be overcome by replacing steam ejector pumps with mechanical vacuum pumps, initially for the vacuum degassing (VD) process but later also for the vacuum oxygen decarburization (VOD) process. Initial concerns about the technical suitability of mechanical pumps for vacuum processing of large heat weights have proven unfounded. There is no real technical upper limit. With detailed knowledge about the vacuum process mechanical vacuum pumps can be successfully engineered for any heat weight where a steam ejector pump would previously have been selected. In fact, suction speed of mechanical vacuum pumps can be ideally controlled to fit the various phases of vacuum processing. This article will show how mechanical vacuum pumps contribute to significant cost reduction and to the possibility of automation of decarburisation, thereby achieving better process control.     

Selbsttrocknende Membran‐ Vakuumpumpen für feuchte Gase

Diaphragm vacuum pumps have proved their superiority as dry‐running systems over other types of vacuum pumps in many applications, and in particular in the medical, analysis, and process engineering sectors, as well as in the chemical industry. These pumps deliver the media without any contamination of content, have a high gas tightness, and can be designed as chemically resistant with regard to those parts which come in contact with the media. Although they are in principle relatively insensitive towards condensates which may be formed or conveyed with the media, liquids in the vapor or gas flow may be the cause for the prolongation of a vacuum process, which can be considerable and is certainly undesirable. This applies in particular to applications involving multi‐user vacuum systems in chemical laboratories, which under certain circumstances may contain very substantial volumes of condensates, and to the use of pumps in steam sterilizers (autoclaves) and vacuum drying cabinets. These examples of applications will be considered in greater detail hereinafter. The condensates which occur in the pump head of a diaphragm vacuum pump cause interference in that — due to re‐evaporation during the suction cycle — they incur a substantial reduction in the usable suction capacity of the pump. This problem can be resolved by means of a drying system for diaphragm vac uum pump heads. The drying system makes use in this case of the pressure differential which pertains between the pump chamber and the atmosphere outside the pump. The function of the drying system can be described as follows: A solenoid valve vents the pump head in a cyclic manner, with the result that liquid in the pump head will be blown out, while the process vacuum in the process engineering system will continue to be maintained. Diaphragm vacuum pumps equipped with this drying system have provided excellent results, for example in the chem ical laboratory, both in individual diaphragm vacuum pumps as well as in multi‐user vacuum systems. Extremely good experience has also been gained in the evacuation of sterilizer autoclaves and vacuum drying cabinets with the use of diaphragm vacuum pumps fitted with the drying system. When using the drying system on steam sterilizer autoclaves, another favorable effect is also encountered: The vapor fraction in the pumping medium is cooled in the diaphragm pump head to below the evaporation or boiling temperature, with the result that the vapour condenses. This reduces its volume to a fraction of the initial value, which is the equivalent of an additional suction capacity, in the same manner as with a condenser. The condensate which occurs with this process is blown out of the pump heads by the drying system, and, as a result, can no longer cause interference due to re‐evaporation.     

Wasserstoff in Hochvakuumsystemen mit Turbomolekularpumpen bei verschiedenen Vorpumpen

The combination of diaphragm pumps with wide‐range turbomolecular pumps constitutes a small but powerful oil‐free high vacuum pumping system. Turbomolecular pumps show gas dependent compression ratios, the lowest for hydrogen. Thus, the high vacuum can be governed by the hydrogen partial pressure. In the present investigation the residual gas composition of a turbomolecular pump and different backing pumps shows no improvement if diaphragm pumps with low ultimate pressure are replaced by rotary vane or Roots pumps. In this case the ultimate pressure in the high vacuum chamber is basically determined by the ratio of outgassing to pumping speed and not by the product of compression ratio and backing pressure. However, the hydrogen partial pressure increased if the ultimate pressure of the diaphragm pump was raised. At a backing pressure of 0.5 mbar the high vacuum reached a stable value not improvable by reduction in backing pressure.     

Gaedes rotierende Quecksilberluftpumpe

The rotary mercury pump of Gaede Wolfgang Gaedes invention of a quickly acting high vacuum pump was induced by his studies about the Volta effect. The so far known pumps were not able to create sufficient low pressure to optain very clean surfaces. Alfred Schmidt, owner of the E. Leybold’s Nachfolger Company, Cologne, learned from the publication about the demonstration of the pump its importance. He made an agreement with Gaede to develop together the invention during 1906 and 1908 to a product for use in industrial application – first step into industrial high vacuum technology     

Einsatz von Vakuumpumpen bei der Herstellung von Photovoltaik‐Modulen

Use of vacuum technology in crystal pulling and lamination application in manufacturing of photovoltaic modules Dry compressing screw type vacuum pumps such as the SCREWLINE SP 630/250 are designed to reduce cost of ownership in crystal pulling plant and in lamination processes. The construction of gear house sealings, the easy maintenance of the pump on site and the use of gas ballast guarantee a very reliable performance, and long maintenance and service intervals. In the case of crystal pulling the process does not even need a dust separator at the inlet of the vacuum pump.     

Abpumpverhalten von Roots‐ und Schraubenvakuumpumpen

Pump down characteristic of Roots pump combinations Combinations of roots pumps and screw type vacuum pumps are often used in industrial vacuum applications because of their high pumping capacity, their compact dimensions and their good energy efficiency. In load lock applications, the type of load control has a high influence on the evacuation time as well as on the energy efficiency of the pump combination. The operation limits of roots pumps are discussed and means to prevent an overload of the pump are introduced.     

Dry vacuum pumping technology outperforms oil-sealed pumps for investment casting

Investment casting is a demanding application for a vacuum pump. Indeed, many traditional oil-sealed pumps cannot maintain the required vacuum performance and have fallen by the wayside, due to the high wear on machinery inherent in this dusty environment. However, in a 20-month trial at an investment casting company in South-West England, a dry pumping system has shown greater reliability, improved vacuum performance and reduced maintenance downtime over the previous oil-sealed technology.     

Vakuumpumpen für das Chemielabor

The choice of a vacuum pump for the chemical laboratory depends more and more on economical and ecological qualifications. The water jet pump, widespread because of its simple and robust design, can satisfactorily fulfil these qualifications only in a few applications. Rotary vane and diaphragm vacuum pumps are of much more complicated design; the most outstanding assets, however, are that they work without contamination of water; further, they provide a large pumping speed also at low suction pressures.     

Kennfeldanalyse einer Schraubenvakuumpumpe

Operating Performance of Screw Vacuum Pumps This paper presents detailed analyses of the operating performance of a dry‐running screw vacuum pump. The characteristic parameters, suction speed and final attainable pressure ‐ which primarily define the operating performance of screw vacuum pumps ‐ are explored in experimental and theoretical investigations. Experiment and simulation in combination are used to show the correlation between the main physical and technical characteristics and the operating performance of screw vacuum pumps. This basic knowledge is essential for understanding the specific machine physics of positive displacement vacuum pumps, especially for screw vacuum pumps, and is useful in view of further design and optimization processes. The experiment covers measurements of the operating performance of the investigated isochoric screw vacuum pump working against ambient pressure. As operating parameters intake pressure (1000mbar to 10^‐3mbar) and rotor speed are varied over a wide range. The theoretical analysis of the operating performance contains simplifying models as well as simulations of the thermodynamic processing. The impact of external leakages, clearance vacuum flows and further losses on operating performance are described in detail.