Flanges · ASME B16.48
Spectacle Blind — ASME B16.48
Also written SB
Spectacle blind — a figure-8 plate with one solid end and one open ring, fitted between two flanges. A spectacle blind lets operators positively isolate a line: rotate the solid end into the line to block flow, or the ring end to allow it. Larger sizes use separate spacers and paddle blanks.
- ASME B16.48
- 23 grades
- EN 10204 3.1 / 3.2
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
Spectacle Blind: What to Know Before Ordering
- Thickness set by class and size
- Paddle blank and spacer versions for large bores
- Handle or lifting lug to order
Spectacle Blind Materials & Grades
| Grade | Material standard | Best for |
|---|---|---|
| Inconel 825 spectacle blind | ASTM B564 | Sulphuric and phosphoric acid service, chloride stress-corrosion cracking and sour gas |
| SS 904L spectacle blind | ASTM A182 F904L | Dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water |
| SS 304 spectacle blind | ASTM A182 F304 | General corrosion resistance, food, water and architectural work |
| SS 304L spectacle blind | ASTM A182 F304L | Welded tanks, piping and vessels in general corrosive service |
| SS 310 / 310S spectacle blind | ASTM A182 F310 | Furnaces, burners and heat treatment at high temperature |
| SS 316 / 316L spectacle blind | ASTM A182 F316L | Chloride-bearing process fluids, marine air and pharmaceutical service |
| SS 321 spectacle blind | ASTM A182 F321 | High-temperature service between 425 and 815 °C |
| SS 347 spectacle blind | ASTM A182 F347 | Welded high-temperature piping in refineries and power plants |
| Duplex 2205 spectacle blind | ASTM A182 F51 / F60 | Strength with chloride resistance at a stainless-steel budget |
| Super Duplex 2507 spectacle blind | ASTM A182 F53 | Seawater and high-chloride service where strength also matters |
| Inconel 600 spectacle blind | ASTM B564 | High-temperature oxidation, caustic and nuclear service |
| Inconel 625 spectacle blind | ASTM B564 | Seawater, high strength and high temperature in one alloy |
| Inconel 718 spectacle blind | ASTM B637 | Very high strength at temperatures up to about 650 °C |
| Incoloy 800 / 800H / 800HT spectacle blind | ASTM B564 | Furnaces, petrochemical heaters and high-temperature piping |
| Hastelloy C276 spectacle blind | ASTM B462 / B564 | The most aggressive mixed acids, wet chlorine and hypochlorite |
| Hastelloy C22 spectacle blind | ASTM B462 / B564 | Mixed oxidising and reducing acids, and weld overlays |
| Monel 400 spectacle blind | ASTM B564 | Seawater, hydrofluoric acid and marine service |
| Monel K500 spectacle blind | ASTM B865 | High-strength pump shafts, bolting and springs in seawater |
| Super Duplex S32760 spectacle blind | ASTM A182 F55 | Seawater firewater, injection and offshore piping |
| ASTM A106 Gr B spectacle blind | ASTM A105 | High-temperature process and steam piping in refineries and power plants |
| ASTM A333 Gr 6 spectacle blind | ASTM A350 LF2 | Cold-climate and refrigerated piping down to −45 °C |
| ASTM A335 P11 spectacle blind | ASTM A182 F11 | Steam and hot-oil piping up to about 550 °C |
| ASTM A335 P22 spectacle blind | ASTM A182 F22 | High-pressure steam and hydrogen service up to about 580 °C |
Other flanges
Weld neck flangeA flange with a long tapered hub that is butt-welded to the pipe.Slip-on flangeA flange that slides over the pipe and is fillet-welded inside and outside.Blind flangeA solid disc that closes the end of a pipe, valve or vessel nozzle.Socket weld flangeA flange with a counterbore socket into which the pipe is inserted and fillet-welded.Threaded flangeA flange with a tapered internal thread that screws onto threaded pipe.Lap joint flangeA loose flange that sits behind a stub end welded to the pipe.Long weld neck flangeA weld neck flange with an extended straight neck, used as a vessel nozzle.Orifice flangeA pair of weld neck or slip-on flanges with pressure taps that hold an orifice plate.Reducing flangeA flange with a smaller bore than its outside dimensions, connecting to a smaller pipe.Ring type joint flangeA flange with a machined groove for a metal ring gasket.Expander flangeA weld neck flange whose hub increases the pipe size.Anchor flangeA forged ring welded into a pipeline to fix it to a structure.Swivel ring flangeA flange with a rotating ring that allows bolt holes to be aligned after welding.
Spectacle blind — questions buyers ask
When should I use a spacer and paddle blank instead of a spectacle blind?
In large sizes a spectacle blind becomes too heavy and awkward, so ASME B16.48 provides separate paddle blanks and spacers.
Which grades are spectacle blinds available in?
Inconel 825, SS 904L, SS 304, SS 304L, SS 310 / 310S, SS 316 / 316L, SS 321, SS 347, Duplex 2205, Super Duplex 2507, Inconel 600, Inconel 625, Inconel 718, Incoloy 800 / 800H / 800HT, Hastelloy C276, Hastelloy C22, Monel 400, Monel K500, Super Duplex S32760, ASTM A106 Gr B, ASTM A333 Gr 6, ASTM A335 P11, ASTM A335 P22.
Which standard covers spectacle blind dimensions?
ASME B16.48. The material standard depends on the grade.
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