Most of us are aware of the disastrous effects of water hammer (e.g., pipe rupture, dislocation from support, support and equipment damage, etc.). The term "water hammer" refers to shocks sounding like hammer blows produced by a rapid change of fluid flow in a closed pipeline. The common occurrence of the phenomenon is in liquid pumping systems. It is caused by flow disturbance or transients. A typical example is the sudden closure or opening of the valve in a cooling water network. Rapid valve closure causes the fluid to stop suddenly as a result of which the kinetic energy of the moving fluid is converted into pressure energy. This produces pressure surges causing a series of shock waves in the piping. An abundance of literature is available on water hammer and the surge analysis and design of the hydraulic piping for single-phase systems (e.g., fluid is water or any liquid). However, for steam systems the phenomenon is quite complicated due to the two-phase effect. The detailed analytical treatment of the surge analysis is quite complex which involves the biphase mass and momentum equations and interaction between phases. Still, there is a lot of scope of development and it is a topic of research. In this article we briefly explain the phenomenon in simple terms while presenting some approximate methods of estimating the loads on the piping that should be of interest to piping designers.
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