3. The electric switch butterfly valve uses graphite to make the shaft neck seal of the valve stem, so as to ensure zero leakage, which belongs to fire safety sealing equipment. 　　　　

However, there must be no strong exothermic reaction or vapor that causes harmful, flammable and explosive substances. For sealing ring maintenance, generally, PTFE is used as rubber seal for soft sealing gate valve, and the protruding face of hard sealing ball valve is welded with metal material. If the pipeline gate valve must be cleaned, be careful during disassembly and assembly to avoid damage to the sealing ring and leakage. Moreover, it must be noted that before the application of pneumatic ball valve, the pipeline and overcurrent position should be cleaned first, usually with cold water, to prevent residual iron pins and other dirt from entering the inner wall of the oil way board to damage the protruding surface.