Root cause analysis of operational induced vibrations in a feedwater system

In a feedwater system, vibrations were observed of a magnitude that made it necessary to take measures to avoid fatigue problems. To clear the root cause, special measurements of pressures, torque, and rotation speed were made during normal operation of the plant. It has been proved by evaluation and analysis of the measurements that the piping vibrations are generated by fluid oscillations. These oscillations themselves are stimulated by fluctuations of the torque of the pump drive. Other causes of stimulation could clearly be excluded. This conclusion was confirmed by the results of numerical simulation of the quasi-steady pump operation. System and pumps were modelled using a one-dimensional pressure surge code for piping networks. Thus, the advantage of calculations in finding problem solutions and proposing improvement measures could be demonstrated.