System Engineering / Pressure Equipment

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PED Professional 6

Natural-frequency piping vibrations


Fig. 1:
Variation of (approx. four weekly) piping stress with time


In an austenitic control line for a main-steam valve of a power plant, a poorly executed welding seam began to leak after approx. three operating years. The plant had to be shut down as a result.  

Failure cause:
Dehnungs- und Temperaturmessungen während eines ganzen Betriebsjahres ergaben ca. alle 4 Wochen niederfrequente Schwingungen mit großen Amplituden. Ausgelöst wurden die Schwingungen durch den alle 4 Wochen stattfindenden Funktionstest der Sicherheitsarmatur. Das stoßartige Schließen der Armatur regte bei der sich in größerer Entfernung befindlichen Rohrleitung Schwingungen in der Eigenfrequenz an.

An additional piping support prevented these vibrations.

Our services – your benefits:
Natural-frequency vibrations are triggered even at low energy levels and are an operational hazard for industrial plants. Material damage and concomitant outage have now been ruled out.

Consulting services from:
TÜV SÜD Industrie Service GmbH