Issues in ball valve selection
Thread Content
I would like to ask: the ball valve to be used for gas has a specification of DN150 PN63, and the design pressure of the pipeline it is connected to is 4.0 MPa. Should the sealing surface or lining material of this ball valve be carbide (material code Y) or fluoroplastic (material code F)? The main consideration is that the ball valve needs to be used in a fully open position during the hydrostatic test, with a test pressure of 6 MPa. Can fluoroplastic meet this requirement?
Based on the gas operation conditions and hydrostatic test requirements, it is recommended to give priority to cemented carbide (Y) sealing pairs. Fluoroplastics (F) may be at risk of creep under a test pressure of 6 MPa, and their long-term sealing performance is not as reliable as that of cemented carbides. However, the specific choice depends on the medium temperature; if it exceeds 150°C, extra caution should be exercised when selecting fluoroplastic materials. It is best to have the valve manufacturer provide a comparison of the pressure-temperature rating curves for the two materials.