Waterhammer

Waterhammer (sometimes called surge pressures) occurs whenever the flowrate within a pipeline system changes. It occurs in all liquid pipelines (not just water ones as the name sometimes suggests). The pressure that occur often exceed the pressure rating of the system and stress the pipe supports.

The magnitude of the pressures is proportional to the velocity change that occurs and the properties of the fluid and pipe (namely the compressibility of the fluid an the expandability of the pipe).

Although most engineers are introduced to surge pressures by the Joukowsky or Allievi equation, it is virtually impossible to accurately (or conservatively) calculate waterhammer pressure by using such a simple equation. Instead, specialist programs are used. These programs need extensive validation and testing before use and due to the specialist experience needed, we still believe that the full power of waterhammer studies is released only by experienced engineers.

Waterhammer studies are used on virtually every pipe system from long oil pipelines, to short rising mains and process plant piping. The studies examine the consequences of startup, shutdown valve closure and pump operations.

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