Understanding Figure-8 Blanks and Spacers
Figure-8 blind flanges, also known as figure-8 blanks or spectacle blinds, are critical components in piping systems for positive isolation. They consist of two discs connected by a slender web, one solid and one with an opening (spacer). By rotating the flange, operators can either block or allow flow without removing the device. This design makes them ideal for applications requiring periodic maintenance, cleaning, or testing.
EPC engineers and procurement specialists must specify figure-8 blinds correctly to ensure safety, compliance, and long-term reliability. Below we outline the key factors to consider when sourcing these components.
Key Standards for Figure-8 Blinds
Figure-8 blind flanges are manufactured to international standards. The most common is ASME B16.48 (Line Blanks). Other relevant standards include:
- ASME B16.5 (for flange dimensions and facing)
- ASME B16.47 (for large diameter flanges)
- BS 1560 (British standard, equivalent to ASME)
