This paper deals with an operational problem of two heat exchangers of the nitric acid synthesis plant. Detailed calculation and vibration analysis were made and vibration problem of the nitrous gases cooler E-111 was identified. When the vibration problem was indicated, several steps were taken for its removal. For five different types of baffles a study was made to determine how their number and spacing influence the cross-flow rate of the fluid. Results showed that the vibration problem cannot be removed completely, but it can be reduced considerably with different types of baffles. Also, the analysis showed that the cooling water condenser E-114 does not have a vibration problem.