Cavitation in reciprocating positive displacement pumps is still an insufficiently understood problem. For a better understanding of the effects of cavitation in reciprocating positive displacement pumps, high-speed camera measurements were done under real operating conditions. In this work, emphasis is put on the recording of cavitation phenomena for further investigations. Exemplarily, the occurring cavitation phenomena for different valve designs are described on the basis of high-speed sequences for selected cavitation conditions and the results are discussed.

The design of reciprocating pumps for the chemical industry requires a detailed knowledge of the apparent phenomena such as undesirable pipe pulsation and harmful cavitation. Since the detailed understanding of the entire mechanism is rather limited, emphasis will be put on the verification of a fluid-dynamic cavitation model for reciprocating positive displacement pumps. This model was established by means of particle image velocimetry (PIV) measurements carried out at a repetition rate of 2 kHz. The PIV results indicate that the fluid-dynamic cavitation model corresponds with the physical reality. While common practice dictates that cavitation should be prevented at all times, the proposed model offers a great opportunity for manufacturers to predict a limit for the extent of occurring cavitation.Cavitation is one of the main causes of damage to piping elements and hydraulic machinery. Cavitation itself is the process of nucleation in a liquid when the pressure falls below saturated vapor pressure. Due to different generation and growth mechanisms, depending on the pressure level, the classification of cavitation types is deemed to be useful. Therefore, cavita-

Die Mehrlagenbauweise hat im Gegensatz zur Massivbauweise besondere sicherheitstechnische Vorteile, die durch folgende Merkmale gekennzeichnet sind : 1 ) Jede Beanspruchungsart in einem Behalter wird an eine besonders fiir diese Beanspruchungsart ausgelegte Schale delegiert .2) Durch eine gezielte Anordnung der SchweiDnahte wird die Verschwachung minimal. 3) Die Behalter konnen standig iiberwacht werden. 4) Das Versagen bleibt durch die Moglichkeit standiger Uberwachung unter Kontrolle. Beispiele und Experimente werden am Beispiel der Krupp-Mehrlagenbauweise gezeigt.Additional safety aspects of coiled-layer containers. The coiled-layer construction technique has a number of particular safety engineering advantages over solid construction methods which are characterized by the following features : 1 ) Each kind of stress in a container is directed to a shell specially designed for this kind of stress. 2 ) A planned arrangement of welding seams minimises weakening.3) The containers can be constantly monitored. 4) Failures remain under control owing to the possibility of constant monitoring. Examples and experiments are reported for the Krupp coiled-layer construction method. Konstruktionsprinzip der Mehrlagenbehalter

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