A Study on Vibration Induced Fatigue Integrity of Piping in Membrane Water Treatment Plant

Piping roles as the main bridge between membrane modules and relevant pumps in membrane water
treatment plants. The pipes deliver only water, both water and air, only air or chemicals (alkaline or
acid detergents) from the pumps to the membranes, depending on the operation modes of the
membrane. Various fluid phenomena occur in the same piping with different phases flow, forward and
reverse directions of flow and high and zero velocity of a fluid. Therefore, the vibration of membrane
plant piping can be induced by flow, acoustic resonance, mechanical excitation, resulting in a
significant risk in the integrity and safety of the system. This study evaluated flow analysis for vibration
diagnostic and evaluation of the fatigue in the microfiltration system applied for a drinking water
treatment plant. The vibration of the main membrane pipelines was measured to identify the source of
vibration. Also, natural frequency and fluid dynamics were calculated by computational fluid dynamics.
It showed that maximum magnitude frequencies were at 12Hz and 22Hz, respectively at the water
and air pipeline during filtration and backwash. The backwash process caused mainly vibration on the
backwash water pipe. The calculated frequency from analysis of frequency response and CFD was in
a good agreement with the measured frequency. Fatigue analysis showed that pipelines were getting
little damage caused by vibration. Fatigue lifetime was predicted more than 15 years under the
operation condition of daily filtration, and more than 27 years under the operation condition of a daily
backwash mode, resulting in minor damage on the pipe lifetime.