What causes tube vibration in heat exchangers and how is it prevented?

Tube vibration occurs when fluid-induced forces excite tube natural frequencies. Mechanisms include: vortex shedding (periodic vortices at high crossflow velocity), fluid-elastic instability (most damaging, occurs above critical velocity), and turbulent buffeting. Prevention methods: reduce unsupported tube span (add intermediate supports), avoid tubes in baffle windows, use rod baffles for vibration-prone services, limit crossflow velocity below critical values (typically 1.5-2 m/s), and verify natural frequency is above excitation frequency.