ISKEN is a two-unit 1210MW coal- fired power plant that produce approximately 6% of the electricity consumed in Turkey. As part of an extension of the production ring, the ID fans had to be replaced. This required evaluation of the existing foundations in terms of dynamic stiffness and strength.

Estimation of the dynamic stiffness of the foundation is a difficult task as it requires forced-vibration measurements exciting the foundation within a desired frequency range. Fans of this size are excited with a relatively high rpm and thus with a high frequency, exhibiting very low deformation amplitudes. Vibration measurements are then required to be conducted with the correct sensors, sensitive data acquisition systems and with high sampling frequency up to 5KHz. Such a measurement also required the selection of correct physical filters adapted on the data acquisition system.

Following the instructions by the customer, this difficult task was achieved by exciting the giant fan with 1600rpm in various blade load positions. The vibrations of the fans in respect to its case as well as to the critical points in the reinforced concrete massive foundation were recorded and provided to the customer.