Industrial Valves

7Water Hammering

7.1 Introduction

There is a risk of water hammering when fluid parameters, including flow, velocity, and pressure, change suddenly in a piping system due to various circumstances such as pump stopping or starting as well as valve opening or closing. High pressure is generated in liquid services when the velocity of a mass of liquid or large velocity liquid is suddenly reduced. Thus, the mobile energy of the liquid is converted into pressure energy. Water hammering is not a kinetic energy problem but rather an acoustic problem. Waves produced in the pipe as a result of water hammering are much faster than liquid velocity. It has undesirable and devastating consequences such as noise, wear, tear, and eventually the collapse and rupture of the piping system, as well as the associated valves. Consequently, it is extremely important to understand this problem in order to prevent it as well as to calculate and analyze the pressure change in the piping caused by water hammering. More specifically, the primary cause of water hammering is a rapid change in flow rate in the piping system caused by the shutoff or startup of a pump or the opening or closing of a valve. The effects of a water hammer can range from small changes in pressure and velocity to relatively high pressure that can result in the bursting and failure of pipes, pipe fittings, valves, and, in some cases, damage to pumps. For instance, a pump stoppage can cause a severe form of water hammering, and a ...