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Failsafe. Druckstoßrisikobetrachtung, Störungsszenarien, Sicherheitsbetrachtungen und Gegenmaßnahmen

Failsafe. Observations on pressure shock or water hammer in piping, breakdown scenarios, safety considerations, and countermeasures
 
: Dudlik, A.; Hahn, M.

Chemie - Ingenieur - Technik. CITplus 12 (2009), Nr.10, S.18-21
ISSN: 1436-2597
Deutsch
Zeitschriftenaufsatz
Fraunhofer UMSICHT Oberhausen ()

Abstract
A survey covers pressure shocks or water hammers and cavitation impacts in piping systems, events that increasingly occur, and the reasons for their occurrence and their effects on the piping. The application and limits of simplified formulas that under certain conditions make it possible to estimate such possible impacts are presented. Three examples indicate which measures to take to avoid pressure shocks or water hammers and cavitation impacts in piping systems. The discussion includes introduction; reasons and effects for pressure shocks and cavitation; empirical formulas, their use and limits; consideration of the risks and measures to avoid them; and a passive safety system. In cooperation with the Ebro Armaturen company, the Fraunhofer Institut Umsicht has developed and patented the Pressure Control Device (PCD). This is a reliable, easily installed, and passive safety system (no additional auxiliary energy involved). On a standard drive the PCD with force lockin g closure or control fitting contains an inner hydraulic circuit that is placed in motion by a signal from the control element. At the same time the PCD is effectively hydraulically connected to the main line. When the pressure in the main line piping reaches an undue value, such that the hydraulic circulation or cycle in the PCD is stopped, further closing of the fitting is hindered until the pressure in the main pipeline again drops. In every instance the fitting closes - failsafe - through an inner bypass in the PCD with preset time constants. The first example relates to a long pipe carrying liquids in which water hammers and cavitation blows arise form opening and closing the fittings. The second example also relates to a long pipe carrying liquids where water hammers and cavitation blows occur from the startup and shutdown of high performance pumps. The third example relates to a long pipe carrying liquids with a great vertical difference in the neighborhood of the boiling point.

: http://publica.fraunhofer.de/dokumente/N-188327.html