Many engineers today are proactively designing systems to reduce or eliminate the risk of waterhammer. Waterhammer is a special case of “pressure surge”. Liquid flowing in a pipe under steady state conditions exerts a certain static pressure on the inside of the pipe. However, if the flow is suddenly changed, e.g. by closing an isolation valve, a transient pressure wave will propagate through the system. The transient pressure wave caused by this effect can be significantly higher than the pressure under normal steady state flow conditions. These high-pressure spikes might exceed the design pressure of the pipelines and/or components and subsequently cause damage to the system.
Rapid flow changes not only cause high pressure spikes; they can also result in low absolute pressures (e.g. downstream of a valve that is closed rapidly). These low pressures can result in the formation of vapor cavities if the pressure drops below the vapor pressure of the fluid. When these cavities collapse again, it can also lead to piping and equipment damage. The rapid flow changes can also damage pipes and pipe supports by causing unbalanced forces. It is therefore important to evaluate the system for these dynamic effects to prevent potential damage and failures.
One of the toughest aspects of hydraulic system design is accepting your system cannot always operate at steady state. Whether system transients are intentional from valve closures to redirect flow, or unintentional with pump trips, understanding their impact on your system is critical.
Complete this form below to watch this 65-minute webinar, where we will overview how to define and begin analyzing these rapid transients with AFT Impulse.