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

 

Description:
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.

Remedy:
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