(4b) Flow-Induced Vibration of Trays

Abstract for 2015 Spring AIChE meeting

Flow-induced vibration of trays

RC Darton, W Zhang and PH Taylor

The paper presents a mechanism that explains the
vibration of distillation and absorption trays at low throughput that can lead
to mechanical failure. As vapour flows through the perforations in the tray, a
Helmholtz resonance occurs in which oscillating liquid near to each perforation
cyclically exchanges kinetic energy with potential energy (head) in the bulk
liquid across the tray. The rate of exchange is determined by the wave speed in
the bulk liquid. This leads to an oscillation in pressure drop which can resonate with the mechanical structure,
leading eventually to fatigue cracking and failure. We make recommendations
based on this analysis, which will help to prevent such vibrations. Tray
damage, which can occur with both valve and sieve trays, can be both hazardous
(cracked column shells can result) and expensive. Our recommendations relate
both to design and operation of columns.