EVERY BLIND.
EVERY SPEC.
ONE SUPPLIER.

The blind needs to match the pipe’s pressure class (ANSI/ASME B16.5 Class 150, 300, 600, etc.) at the design or worst-case differential pressure it will actually see during isolation — not just the line’s normal operating pressure. This is where a lot of failures happen: people rate for operating pressure and forget that blinds are often installed for maintenance when the other side of the line could be at full pressure while the blind side is depressurized (or vice versa), creating the full differential across the blind.

Spectacle (figure-8) blind: a solid disc and a ring (spacer) joined by a web or solid piece of material, used where you’ll flip between isolated and open states repeatedly. Common in process plants for periodic isolation.

Spade, line blank or paddle blind and spacer blind: cheaper, lighter, easier to handle for larger sizes, but the blind and spacer must both be tracked and stored properly. Can also be used for frequent switching and avoids breaking the flange each time.

Blind flange: a solid, flat circular plate with no hole (bore) through it, bolted directly to a mating flange in place of a pipe or fitting. Unlike a spectacle blind or spade, it’s not designed to be swapped in and out routinely; it’s a permanent or semi-permanent dead-end.

When you’d use a blind flange instead of a spectacle or spade blind: terminating a line - capping the end of a pipe run (like a future tie-in point, a spare nozzle on a vessel, or an abandoned branch) rather than isolating a line mid-system. Rarely-opened isolation points - where you don’t expect to need to reverse the isolation often; unbolting a full flange is more work than flipping a spectacle blind or swapping a spade, so it’s not ideal for routine maintenance isolation. Vessel or tank nozzles - closing off an unused nozzle on a vessel, drum, or exchanger head. Cost and simplicity - for a permanent dead-leg, a blind flange is simpler and cheaper than a spectacle blind assembly since there’s no spacer ring or hinge web or connect to fabricate.

Confirm material compatibility: match the blind's material to the process fluid (corrosion, temperature, chemical compatibility) - typically the same material as the pipe spec unless there's a specific reason to deviate (e.g., corrosion allowance).

Calculate thickness: blind thickness is derived from a formula (ASME B16.5 or B31.3 typically) based on design pressure, blind diameter (bolt circle or ID depending on method), allowable stress of the material at design temperature and corrosion allowance.

Check temperature effects -allowable stress drops as temperature rises, so high-temp service can drive a thicker blind than pressure alone would suggest.

Confirm size and facing match the flange - blind OD needs to match the mating flange's bolt circle, and the facing (RF, RTJ, FF) needs to match so it seals properly.

We proudly serve all USA industries requiring precision flange and machine support including oil, gas, chemical processing, petrochemical, refining, and industrial maintenance applications. We are your blind specialists.