7. Service lives
Normal failure of butterfly valves
is leakages, and butterfly valves' leakages include external leakages and internal leakages. External leakages are mainly caused by erosion or corrosion, and internal leakages are caused by damage to sealed auxiliaries. Service lives usually refer to sealed auxiliaries' using time or times of actions, which depend on types, temperatures, pressure, opening and closing frequency and opening and closing speeds of butterfly valves
. Thus, we can choose materials which can meet working conditions, materials with scratch resistance, fatigue resistance and electrochemical corrosion resistance, and have necessary heat treatments for these materials. In addition, the service life of the sealing auxiliary is closely related to the rationality of the structural design and the manufacturing accuracy.
8. Selection of main parts' materials
The main part of the butterfly valve
includes the valve body, the butterfly plate, the valve stem, the valve seat and the sealing ring. We choose materials based on working conditions, and we should especially pay attention to corrosion resistance and applicable temperatures of materials. The following table shows the applicable temperature and the applicable medium of the commonly used material.