In a vertical tubeside thermosiphon reboiler (VTTR), Ledinegg instability can occur when the tubeside pressure drop decreases with increasing flow rate. Theoretical analysis of two boundary conditions—constant heat flux and constant steam pressure—revealed that for either condition, Ledinegg instability can occur in a VTTR only when intube frictional pressure drop dominates over static head losses. Such conditions could be simulated only for very high mass and heat fluxes, at values unlikely to occur in a real VTTR. This webinar presents an in-depth look at the analysis and simple criteria to check for the unlikely occurrence of Ledinegg instabilities in operational VTTRs.