Valves shall have glassfilled PTFE seals for positive shut-off and extended service-life and FPM seals for maximum protection against external leaks.

• 这些阀门应该配置玻璃填充聚四氟乙烯密封，关闭更灵活，使用寿命更长，FPM密封能够更好的防止外泄漏。