SS 347 Spectacle BlindASTM A182 · ASME B16.48 · Manufacturer, stockist & exporter, India
AISI 347 · UNS S34700 · SB
An SS 347 spectacle blind is a figure-8 plate with one solid end and one open ring, fitted between two flanges, made from SS 347 to ASTM A182 F347. 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.
- ASTM A182
- ASME B16.48
- EN 10204 3.1 / 3.2
- Export packing
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is an SS 347 Spectacle Blind?
- What it is
- A figure-8 plate with one solid end and one open ring, fitted between two flanges
- Material
- ASTM A182 F347
- Dimensions
- ASME B16.48
- Grade
- SS 347 · UNS S34700
- Best at
- Welded high-temperature piping in refineries and power plants
SS 347 Spectacle Blind Specification
| Product | SS 347 Spectacle Blind |
|---|---|
| Material standard | ASTM A182 F347 |
| Dimensional standard | ASME B16.48 |
| Sizes | ½" – 24" (ASME B16.5) · 26" – 60" (ASME B16.47) |
| Pressure class | Class 150, 300, 400, 600, 900, 1500, 2500 · PN 6 – PN 100 |
| Facing | RF · FF · RTJ · tongue & groove |
| Bore | To match pipe schedule (state on order) |
| Testing | PMI · dimensional · NDT and IGC on request |
| Documents | EN 10204 3.1 · 3.2 with third-party inspection |
When to Choose a Spectacle Blind
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.
- Thickness set by class and size
- Paddle blank and spacer versions for large bores
- Handle or lifting lug to order
More on choosing: Spectacle blind guide.
SS 347 Spectacle Blind: Why 347 for spectacle blinds
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. In SS 347, the choice usually comes down to the medium and temperature — the rows here are the points buyers check for this exact combination.
| Why this grade | Stainless flanges are chosen where carbon steel would rust or contaminate the process. SS 347 is picked for welded high-temperature piping in refineries and power plants. |
|---|---|
| Typical service | Refinery hydroprocessing — Reactor effluent piping and exchangers. |
| B16.5 material group | 2.5 |
| Bolting | ASTM A193 B8C studs with A194 8C nuts |
| Welding to carbon steel | ER309L (or E309L electrode) is the usual filler when joining it to carbon steel |
| Matching filler | ER347 (AWS A5.9) |
SS 347 Spectacle Blind Chemical Composition
| Element | Weight % |
|---|---|
| Chromium | 17.0 – 19.0 |
| Nickel | 9.0 – 13.0 |
| Niobium | 10 × C min, 1.00 max |
| Carbon | 0.08 max |
| Manganese | 2.00 max |
| Silicon | 0.75 max |
| Phosphorus | 0.045 max |
| Sulphur | 0.030 max |
SS 347 Spectacle Blind Mechanical Properties
| Annealed plate & sheet | Value |
|---|---|
| Tensile strength | 515 MPa · 75 ksi |
| Yield strength 0.2% | 205 MPa · 30 ksi |
| Elongation | 40% |
| Hardness | 201 HB max |
Full chemistry, properties and equivalents are on the SS 347 grade page.
Other SS 347 flanges
SS 347 Spectacle Blinds for export
FOB / CIF · Nhava Sheva (JNPT), MumbaiSS 347 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.
What pressure rating does a SS 347 spectacle blind have?
It depends on class and temperature. SS 347 forgings are in ASME B16.5 material group 2.5; read your class column in that group's table at the design temperature.
Can SS 347 spectacle blinds be welded to carbon steel?
Yes — ER309L (or E309L electrode) is the usual filler when joining it to carbon steel.
Which standard covers SS 347 spectacle blinds?
The material is ASTM A182 F347; dimensions follow ASME B16.48. Always state both on your purchase order, with the edition if your project specifies one.
What decides the price of a SS 347 spectacle blind?
The alloy price, the size and pressure class, quantity, and the testing and documents required. Send your list and we quote the same working day.
What documents do you supply?
EN 10204 3.1 mill certificates as standard, 3.2 with third-party inspection on request, plus dimensional and PMI reports.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026