Insights and Challenges Associated with Air in Pressurized Water Conveyance Systems

Concerning Dynamic Effects in Pipe Systems with Two-Phase Flows: Pressure Surges, Cavitation, and Ventilation

“…The manual indicates more details for the sizing of air valves with the inclusion of the situation of a pipeline partial rupture. The manual now also gives various detailed examples of vaults for air valves for above-or below-ground applications [43]. As a companion reference document to the M51 manual comes the ANSI/AWWA C512 standard regarding the minimum requirements for air valves in water and wastewater applications.…”

“…Furthermore, such instalment of the standard includes specifications regarding the minimum requirements for throttling or slow closing devices. The current version of the C512 standard includes in its title the reference to wastewater applications for air valves [43].…”

“…The suggested assumptions for the sizing of air-release valves according to M51 can potentially result in oversized valves [49,51,52]. In the sizing process, the necessary orifice for air inflow due to a line rupture (usually a large orifice) is often in conflict with the ideal orifice size for filling, draining, or air expulsion during transient events (usually a small orifice) [43]. Ramezani and Daviau (2021) [53], for example, explore, with a practical example, the importance of using air valves with anti-slam systems for line protection in the context of pump trip scenarios.…”

“…It is advisable, however, that practitioners consider a broader variety of reference materials when dealing with air issues in pressurized piping systems. As pointed out by Tasca et al (2022) [43], there is still a disconnect between the M51 manual and the most up-to-date scientific developments in the fields of two-phase flows and air valve application and modelling. This is evinced, for example, by the fact that a substantial part of the documents cited as references by the manual is from before 1990 [11].…”