Class 900 Spectacle Blinds

Class 900 Spectacle Blinds serve the most demanding isolation requirements in high-pressure piping systems. The blind disc thickness at Class 900 is substantial, reflecting the high differential pressures these devices must withstand. Material selection at this class often involves alloy steels to meet both strength and corrosion resistance requirements.

The weight and thickness of Class 900 spectacle blinds make manual rotation impractical for sizes above NPS 6. Mechanical lifting devices are standard requirements for handling these assemblies during installation and turnaround operations. The connecting bar between discs is proportionally heavier to support the increased disc weight.

Applications include isolation of high-pressure reactor systems, synthesis gas loops, and high-pressure steam piping. At Class 900, alternative isolation methods such as double block and bleed valve arrangements are sometimes considered, but spectacle blinds remain preferred where a physically verifiable positive isolation barrier is required.