Abstract
Air pockets generated during emptying operations in pressurized hydraulic systems cause significant pressure drops inside pipes. To avoid these sudden pressure changes, one of the most widely used methods involves the installation of air valves along the pipeline route. These elements allow air exchange between the exterior and the interior of the pipe, which alleviates the pressure drops produced and thus prevents possible breaks or failures in the structure of the installation. This study uses a mathematical model previously validated by the authors in smaller installations to simulate all hydraulic variables involved in emptying processes over time. The purpose of these simulations is the validation of the mathematical model in real large-scale installations, and to do this, the results obtained with the mathematical model are compared with actual measurements made by the partner company. The hydraulic system selected for the study is a pipeline with a nominal diameter of 400 mm and a total length of 1020 m. The results obtained from the mathematical model show great similarity with the experimental measurements, thus validating the model for emptying large pipes.
Highlights
During the emptying processes of pressurized systems, air trapped inside the pipeline causes pressure drops [1,2,3] that sometimes cause serious structural damages
Air pockets inside pipelines may occur due to various causes: maintenance work, start-up operations, filling and emptying manoeuvres, etc
Significant overpressures and pressure drops that exceed the admissible values for the installations can be generated and can cause serious problems
Summary
During the emptying processes of pressurized systems, air trapped inside the pipeline causes pressure drops [1,2,3] that sometimes cause serious structural damages. It is highly recommended to place air valves throughout the installation to manage the filling and emptying of pipelines and to prevent undesired variation in pressure [9,10,11]. These elements are responsible for allowing outside air to enter the pipes when emptying occurs and pressure drops are generated. In this manner, as water leaves the pipeline, air is introduced at the same time through the air valves to control the pressure and to avoid major problems [12]
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