Abstract
On the basis of theoretical considerations, the technical note presents two practical formulas for the dimensioning of air valves when filling a pipe with water. One is to be used for designing air valves on the basis of the maximum allowed water hammer overpressures; the other when the maximum in pipe water velocity is set. The reliability of these formulas was tested with a numerical model based on the same hypothesis, which was in turn verified with experimental tests.
Introduction
The presence of air entrained by a liquid flow in a pipeline under pressure often gives rise to operational problems in plant management, either in the form of concentrated headloss due to section reduction, or in the form of amplified overpressures in the case of unsteady flow after plant operations like pump startup or stop. Given these considerations, there is an evident need to insert air sections in order to allow the air trapped inside the pipeline to escape, and particular attention should be paid to the correct dimensioning of the air release sections.
