Balanced bellows seals may be required instead of conventional type due to process fluid considerations. Pilot operated valves are acceptable in place of bellows type for clean services.

• 出于对工艺介质的考虑，平衡波纹管密封可能要求替代常规类型。对于洁净用途，允许用辅助操作阀替代波纹管类型。