Abstract
The problem which is faced in this article is the analysis of the effects of a transverse propagating crack on the vibrational behavior of a vertical axis cooling pump. The crack is assumed to develop in a section between the impeller and a seal, preventing the hot water to flow upwards along the rotor shaft. The pressurized seal is fed with an injection of cold water, and crack initiation may be due to a thermal striping phenomenon. Afterwards, crack growth could be driven by a combination of thermal and mechanical loads, causing alternate cyclic stress in the shaft. Cracking instances of this type have been reported worldwide in several machines of similar design. In this article, the fact is emphasized that the crack behavior is likely to be influenced by the thermal field and by the water pressure in the cracked area. A dynamical lineshaft model, integrated by an original representation of the crack, has been developed to investigate the possible vibratory symptoms related to a crack propagation. The vibrations are generally measured in correspondence of a rigid coupling which connects the motor shaft to the pump shaft, in a position which is rather far away from the crack. 1 × rev., 2 × rev., and 3 × rev. vibration components, which are generally displayed by the machine condition monitoring system and are the most significative symptoms of the presence of a transverse crack in a rotating shaft, are calculated.
Highlights
In almost all nuclear plants worldwide, the cooling of the reactor is performed by single stage, vertical axis centrifugal pumps
The problem which is faced in this article is the analysis of the effects of a transverse propagating crack on the vibrational behavior of a vertical axis cooling pump
The vibrations are generally measured in correspondence of a rigid coupling which connects the motor shaft to the pump shaft, in a position which is rather far away from the crack. 1 × rev., 2 × rev., and 3 × rev. vibration components, which are generally displayed by the machine condition monitoring system and are the most significative symptoms of the presence of a transverse crack in a rotating shaft, are calculated
Summary
Dipartimento di Meccanica, Politecnico di Milano, Via La Masa 34, I-20158 Milano, Italy. The problem which is faced in this article is the analysis of the effects of a transverse propagating crack on the vibrational behavior of a vertical axis cooling pump. Afterwards, crack growth could be driven by a combination of thermal and mechanical loads, causing alternate cyclic stress in the shaft. Cracking instances of this type have been reported worldwide in several machines of similar design. The fact is emphasized that the crack behavior is likely to be influenced by the thermal field and by the water pressure in the cracked area. Vibration components, which are generally displayed by the machine condition monitoring system and are the most significative symptoms of the presence of a transverse crack in a rotating shaft, are calculated. Keywords Crack, Rotordynamics, Reactor coolant pump, Detection, Monitoring, Thermal gradients
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
