Stationary and Dynamic Analysis of a Water Relief Valve

The use of water as a working fluid in hydraulic circuits is being receiving an increasing attention by both manufacturers and users, due to its environmental characteristics. Although the use of water is neither new nor innovative (more than one hundred years ago it was widely used to transfer power, and many pump and valve manufacturers have commercial product lines for water hydraulics) its introduction in the product line of a manufacturers brings many problems to the attention of the designers, from technology adaptation to material compatibility, from erosion to cavitation. The purpose of this paper, based on a joint activity by Cemoter, University of Modena, Aron SpA and Cermet, is to show how the use of a combined approach to valve analysis can provide useful information to shorten the time to market of a valve using tap water as working fluid. Starting from an initial reminder of the basic differences between mineral oil and water in hydraulic circuits, the paper shows the results of some CFD computations on a relief valve, to evaluate the qualitative form of the pressure and velocity field, and to assess the influence of the increased turbulence on the field of motion. In the final part, the results of a comprehensive experimental characterization of the component are presented and considered in view of the indication provided by CFD analysis, both in term of steady state characteristic curves, and dynamic response.