A pipeline is being designed to withstand a total maximum pressure of 2.13 × 106 N/m2. The 20-cm pipeline is ductile iron and conveys water at 40 L/sec. Determine the required thickness of the pipe wall if the operational head on the pipeline is 40 m and also subject to water hammer if the flow control valve on the downstream end is closed suddenly. Assume that the longitudinal stresses will be negligible when the pipe is installed.