Nested tubes of a cylindrical boiler shell with distance and acceleration transducers

Description:
An already existing municipal combined heating and power station was supplemented by a water-tube boiler fueled with natural gas and light oil. After only 28 hours of operation, fatigue failure occurred at 2 welds of the nested tubes of a new cylindrical boiler shell.  

Failure cause:
Dehnungs-, Beschleunigungs- und Wegmessungen zeigten, dass bereits im kalten Zustand die Strömungen durch den Lüfter die Rohre in der Eigenfrequenz zu Schwingungen anregten und damit unzulässig hohe Belastungen im Schweißnahtbereich verursachten.

Remedy:
Through the installation of spacers, the freely vibrating length of the tubes was reduced and thus their characteristic frequency increased in such a way, that they can no longer be excited by the flow velocity.

Our services – your benefits:
The insight gained from vibration measurement carried out during operation within the scope of damage analysis resulted in design changes which have meanwhile helped prevent recurrent damage for several years of service life. Thus, the plant fulfills the availability and cost-effectiveness expectations of the plant operator.

Consulting services from:
TÜV SÜD Industrie Service GmbH