M/s. ZPMC Engineering (India) Pvt. Ltd. hired NV Dynamics to determine the natural frequency of the recently commissioned STS (Ship-to-Shore) cranes at Mundra Port, Gujarat. It is important to determine the natural frequency of the cranes to avoid the condition of resonance when the crane is operating under different loading and braking conditions and to check whether, in the long run, these natural frequencies change due to structural deterioration.
A total of four ultra-low-frequency vibration transducers were used in the task. Based on the design specifications and customer requirements, two key locations were identified on the crane and a pair of ultra-low frequency vibration transducers were mounted in horizontal and vertical directions at each location, namely the seaside upper beam and boom end of the crane. The transducers were connected to a multi-channel data acquisition system and subsequently, vibration data was recorded for various operational conditions such as crane moving in trolley & gantry direction, with & without load for normal & emergency braking conditions.
Data processing included conversion of vibration acceleration data into displacement and Fast Fourier Transformation (FFT) was used to determine natural frequencies in the gantry/ trolley directions and compare against the applicable design criteria.