The seat material shall be one of the following materials: ethylene-propylene-diene monomer (EPDM) or fluoroelastomer (FPM) with polytetrafluoroethylene (PTFE) bearing support at the top and bottom.

• 阀座材料应该是下列材料之一：乙烯-丙烯-二烯系单体(三元乙丙橡胶)或氟橡胶(FPM)，在顶部和底部配置聚四氟乙烯(PTFE)轴承支撑。