Dimensions and thicknesses follow ASME B16.48, the line-blank standard. Our catalogue includes a figure-8 execution in ASTM A516 Gr.60 plate — the pressure-vessel plate grade commonly specified for blanks — with FBE coating and raised face, made in accordance with B16.48 alongside B16.5 flange dimensions. Other grades and sizes are confirmed per product at enquiry.
The spectacle blind solves an operational problem, not a design one. Valves leak through; a blank does not. Where a line must be isolated for entry, hot work or maintenance — and the isolation must be provable at a glance — a spectacle blind or its single-disc relatives (paddle blanks and spacers) are the standard answer.
| Item | Range / Options |
|---|---|
| Standards | ASME B16.48 (line blanks); mating dimensions ASME B16.5 |
| Types | Figure-8 spectacle blinds (catalogue execution) |
| Size range | Confirmed per product at enquiry |
| Pressure classes | Confirmed per product at enquiry |
| Faces | Raised face (RF) in the catalogue execution; other facings confirmed per product at enquiry |
| Materials | ASTM A516 Gr.60 plate (catalogue execution, FBE coated, raised face); other grades confirmed per product at enquiry |
Spectacle, Paddle or Blind Flange?
A blind flange closes a line end. A spectacle blind lives permanently inside a joint in the middle of a line and changes state by swinging. A paddle blank (single disc with a handle) does the same job where the joint is broken rarely and a loose piece is acceptable. Choose the spectacle where the joint is operated often enough that a captive, visible blank is worth it.
Operating Reality
Changing a spectacle blind means breaking the joint's bolting, spreading the flanges — jack bolts or flange spreaders help at larger sizes — swinging the blank, and re-making the joint with sound gaskets. The blank's handle and the visible disc outside the joint tell the next crew which state the line is in without paperwork. That visibility is a safety feature, and it is why the disc left outside the joint is never cut off.
Ordering
State NPS, class, facing and grade. For A516 Gr.60 executions, note any coating requirement (FBE as listed). The catalogue execution is raised face; if your joint requires a different facing, state it on the enquiry and it will be assessed for the specific product before order.
Frequently Asked Questions
Is a spectacle blind a pressure boundary?
Yes — in the blank position it is a full pressure boundary made to B16.48 thickness for its class, exactly like the pipework it isolates. In the open position the ring carries the joint's bolting load path.
Can spectacle blinds be made in stainless steel?
No stainless spectacle blind execution is among the catalogue executions referenced on this site; name the grade on the enquiry and it will be assessed for the specific product before order. Most spectacle blinds are carbon steel because they serve carbon lines, but the grade follows the line's requirement.
What is the difference between a spectacle blind and a paddle blank?
A spectacle blind joins the blank and the spacer ring in one figure-8 piece that stays in the joint. A paddle blank is a single loose disc with a handle, inserted and removed as needed. Function is the same; the spectacle is captive and always visible.
How heavy is a spectacle blind to handle?
At small sizes it is a one-person lift; at large sizes and high classes the one-piece figure-8 is a substantial plate that needs lifting equipment and a planned swing path. Factor handling into the choice between a spectacle and a loose paddle blank on big lines.
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Send Your Specification
Tell us the size, schedule or pressure class, material grade and quantity for the spectacle blinds you need. MOQ and lead time are confirmed in the quotation for your exact specification.